Electronic Effects in a Green Protocol for (Hetero)Aryl-S Coupling

Aryl and heteroaryl iodides have been efficiently converted into the corresponding thioacetates in cyclopentyl methyl ether (CPME), a green solvent, under Cu catalysis. The chemoselectivity of the reaction is mainly controlled by electronic factors, enabling the conversion of both electron-rich and electron-deficient substrates into the corresponding thioacetates in good to excellent yields. The products can be easily deprotected to the corresponding thiolates to carry out additional synthetic transformations in situ. Surprisingly, despite CPME's relatively low dielectric constant, the reaction rate significantly increased when conducted under microwave irradiation conditions. This synthetic methodology exhibits a remarkable tolerance to functional groups, mild reaction conditions, and a wide substrate scope, utilizing a safe and inexpensive CuI pre-catalyst in the green solvent CPME. A non-aqueous workup allowing for the complete recovery of both catalyst and solvent makes this approach an environmentally sustainable protocol for C(sp2) sulfur functionalization. Additionally, the reaction shows selective cross-coupling with iodides in competition with chlorides and bromides, allowing its use in multistep syntheses. To demonstrate the potential of this methodology, it was applied to the high-yield synthesis of a photochromic dithienylethene, where a selective synthesis had not been reported before.

Base-mediated homologative rearrangement of nitrogen-oxygen bonds of N-methyl-N-oxyamides

Due to the well known reactivity of C(O)-N functionalities towards canonical C1-homologating agents (e.g. carbenoids, diazomethane, ylides), resulting in the extrusion of the N-centered fragment en route to carbonyl compounds, formal C1-insertions within N-O bonds still remain obscure. Herein, we document the homologative transformation of N-methyl-N-oxyamides - with high tolerance for diverse O-substituents - into N-acyl-N,O-acetals. Under controlled basic conditions, the N-methyl group of the same starting materials acts as a competent precursor of the methylene synthon required for the homologation. The logic is levered on the formation of an electrophilic iminium ion (via N-O heterolysis) susceptible to nucleophilic attack by the alkoxide previously expulsed. The procedure documents genuine chemocontrol and flexibility, as judged by the diversity of substituents placed on both amide and nitrogen linchpins. The mechanistic rationale was validated through experiments conducted on D-labeled materials which unambiguously attributed the origin of the methylene fragment to the N-methyl group of the starting compounds.

Highly chemoselective homologative assembly of the α-substituted methylsulfinamide motif from N-sulfinylamines

α-Substituted methylsulfinamide are prepared through the homologation of electrophilic N-sulfinylamines with Li-CHXY reagents. The transformation takes place under full chemocontrol and exhibits good flexibility for preparing both N-aryl and N-alkyl analogues. Various sensitive functionalities can be accommodated on the starting materials, thus documenting a wide reaction scope.

Selective noncovalent proteasome inhibiting activity of trifluoromethyl-containing gem-quaternary aziridines

The ubiquitin-proteasome pathway (UPP) represents the principal proteolytic apparatus in the cytosol and nucleus of all eukaryotic cells. Nowadays, proteasome inhibitors (PIs) are well-known as anticancer agents. However, although three of them have been approved by the US Food and Drug Administration (FDA) for treating multiple myeloma and mantel cell lymphoma, they present several side effects and develop resistance. For these reasons, the development of new PIs with better pharmacological characteristics is needed. Recently, noncovalent inhibitors have gained much attention since they are less toxic as compared with covalent ones, providing an alternative mechanism for solid tumors. Herein, we describe a new class of bis-homologated chloromethyl(trifluoromethyl)aziridines as selective noncovalent PIs. In silico and in vitro studies were conducted to elucidate the mechanism of action of such compounds. Human gastrointestinal absorption (HIA) and blood-brain barrier (BBB) penetration were also considered together with absorption, distribution, metabolism, and excretion (ADMET) predictions.

Leveraging the 3-Chloro-4-fluorophenyl Motif to Identify Inhibitors of Tyrosinase from Agaricus bisporus

Tyrosinase (EC 1.14.18.1) is implicated in melanin production in various organisms. There is a growing body of evidence suggesting that the overproduction of melanin might be related to several skin pigmentation disorders as well as neurodegenerative processes in Parkinson's disease. Based on this consideration, the development of tyrosinase inhibitors represents a new challenge to identify new agents in pharmaceutical and cosmetic applications. With the goal of identifying tyrosinase inhibitors from a synthetic source, we employed a cheap and facile preliminary assay using tyrosinase from Agaricus bisporus (AbTYR). We have previously demonstrated that the 4-fluorobenzyl moiety might be effective in interactions with the catalytic site of AbTYR; moreover, the additional chlorine atom exerted beneficial effects in enhancing inhibitory activity. Therefore, we planned the synthesis of new small compounds in which we incorporated the 3-chloro-4-fluorophenyl fragment into distinct chemotypes that revealed the ability to establish profitable contact with the AbTYR catalytic site. Our results confirmed that the presence of this fragment is an important structural feature to improve the AbTYR inhibition in these new chemotypes as well. Furthermore, docking analysis supported the best activity of the selected studied compounds, possessing higher potency when compared with reference compounds.

Application of Biobased Solvents in Asymmetric Catalysis

The necessity of more sustainable conditions that follow the twelve principles of Green Chemistry have pushed researchers to the development of novel reagents, catalysts and solvents for greener asymmetric methodologies. Solvents are in general a fundamental part for developing organic processes, as well as for the separation and purification of the reaction products. By this reason, in the last years, the application of the so-called green solvents has emerged as a useful alternative to the classical organic solvents. These solvents must present some properties, such as a low vapor pressure and toxicity, high boiling point and biodegradability, and must be obtained from renewable sources. In the present revision, the recent application of these biobased solvents in the synthesis of optically active compounds employing different catalytic methodologies, including biocatalysis, organocatalysis and metal catalysis, will be analyzed to provide a novel tool for carrying out more ecofriendly organic processes.

Straightforward synthesis of bench-stable heteroatom-centered difluoromethylated entities via controlled nucleophilic transfer from activated TMSCHF2

The commercially available and experimentally convenient (bp 65 °C) difluoromethyltrimethylsilane (TMSCHF₂) is proposed as a valuable difluoromethylating transfer reagent for delivering the CHF₂ moiety to various heteroatom-based electrophiles. Upon activation with an alkoxide, a conceptually intuitive nucleophilic displacement directly furnishes in high yields the bench-stable analogues.

Synthesis, Computational Investigation and Biological Evaluation of α,α-Difluoromethyl Ketones Embodying Pyrazole and Isoxazole Nuclei as COX Inhibitors

α,α-Difluoromethyl ketones (DFMKs) emerged as currently investigated agents benefiting from the merging of chemico-physical features conferred by the constitutive elements (-CHF2 and carbonyl moietites). With vistas to biological applications, the...

Consecutive and Selective Double Methylene Insertion of Lithium Carbenoids to Isothiocyanates: A Direct Assembly of Four-Membered Sulfur-Containing Cycles

A formal CH₂−CH₂ homologation conducted with C1 carbenoids on a carbon electrophile for the obtainment of a four‐membered cycle is reported. The logic proposes the consecutive delivery of two single nucleophilic CH₂ units to an isothiocyanate—as competent electrophilic partner—resulting in the assembling of a rare imino‐thietane cluster. The single synthetic operation procedure documents genuine chemocontrol, as indicated by the tolerance to various reactive elements decorating the starting materials. Significantly, the double homologation protocol is accomplished directly on a carbon electrophile, thus not requiring the installation of heteroatom‐centered manifolds (e.g. boron).

166 Dual Mobility for Total Hip Arthroplasty Revision Surgery: A Systematic Review and Metanalysis

Dual Mobility (DM) implants provide greater stability especially in Revision Total Hip Arthroplasty (R-THA) when compared to primary THA. Aim: to identify the current evidence regarding outcomes of DM in R-THA when compared to fixed-bearing (FB) implants.

Review in accordance with PRISMA guidelines. Structured electronic searches. Primary outcome measure: dislocation rate following R-THA. Secondary outcome measures: implant survival, aseptic loosening, infection rate. Studies' methodology quality assessed using MINORS criteria.

All articles published from 2016 to December 2019 included. 1777 R-THAs were reported (49.9% with DM acetabular component, 50.1% with FB component). Sample size: 67-426 patients. Mean age: 57-73. Mean follow-up period: 12-60 months. Significant risk ratio of 1.08 [1.05, 1.12] (95% CI, I2 = 37%, P < 0.00001) with statistically significant difference between the two groups in favour of DM implant. Statistically significant difference in favour of DM group with respect to dislocation rate (risk ratio 0.22, 95% CI; P < 0.00001) and aseptic loosening (risk ratio 0.51, 95% CI; P < 0.05). No statistical difference between the groups on risk ratio for infection 0.94 (95% CI; P = 0.85).

DM implants are beneficial in R-THA when compared to FB implants. However, one needs to balance the benefits of using DM implant considering the patient’s clinical conditions and the costs involved.

169 Literature Review on Efficacy of Manual Therapy in The Conservative Treatment of Adolescent Idiopathic Scoliosis (AIS)

AIS is a common condition whose conservative options usually involve physical therapy. Manual therapy can be part of an adequate conservative strategy due to his ability to improve range of motion and decrease muscle tone and pain. However, his indications and efficacy remain controversial. What is the current evidence on indications and efficacy of manual therapy in the treatment of AIS?

Customized structured electronic searches: PubMed, Cochrane. Key terms: AIS manual therapy, AIS manipulative therapy, AIS mobilization exercises. 17 works included.

5 case reports, 3 case series, 2 group-control studies, 3 narrative reviews, 4 systematic reviews. Complications:0. Reviews suggested that manual therapy is a promising option if in adjunct to physical therapy exercises. Prevention of curve progression and better spine flexibility are often achieved. It remains unclear whether this should be attributed to physical therapy, manual therapy, or combination of both. Lacks in methodology leave room for uncertainty.

Only few papers analyse the indications and efficacy of manual therapy in treatment of AIS. The current evidence suggest that manual therapy is a promising beneficial treatment strategy for AIS with conservative indications, especially if in conjunction with physical therapy. This is further supported by absence of reported complications. Further research with better methodology is needed.

163 Audit cycle on the formal introduction of a standardised orthopaedic trauma patients’ admission pro-forma: the first Italian experience

An internationally recognised issue of general district hospitals is the accuracy and completeness of the admission documentation, particularly in a trauma setting. We built and formally introduced a Hospital Trust Wide admission pro-forma for orthopaedic trauma patients.

An Audit looking into the quality and completeness of the admission documentation for orthopaedic trauma patients was carried out at a single Hospital Trust in December 2017. This was followed by a second round Audit with formal implementation of our new clerking pro-forma.

Compliance was 94% overall. The documentation was incomplete in 7% of the cases. Delays of patients’ treatment caused by lack of documentation or written plan/instructions was recorded in only 3% of the cases. Satisfaction questionnaire: excellent 55%, good 42%, fair 7%, poor 1%.

The pro-forma provides all relevant information needed to fully assess orthopaedic trauma patients and plan the appropriate management. His utilisation facilitates completeness of documentation with a standardised approach. This is a unique work on the introduction of a standardised clerking pro-forma for the admission of orthopaedic trauma patients with excellent results in terms of compliance and improvement of patients’ care. Our study seems to be a quality improvement intervention with potentials of becoming a milestone for further improvements.

168 Interprosthetic Fractures of The Femur: A Literature Review

Increasing age expectations and number of joint replacement procedures have made interprosthetic femoral fractures (IFF) a progressively more common diagnosis and a challenge for surgeons. A gold standard and universally accepted classifications and guidelines do not exist yet.

Customized structured electronic searches performed in PubMed database. Relevant key terms: IFF, classification interprosthetic fracture, peri-implant femoral fracture, biomechanics interprosthetic femur fracture, radiographic femur fracture, risk factor IFF. 42 articles finally included (up to 2019).

High morbidity and mortality linked to IFF. Standardised classifications, management guidelines and surgical approaches are not available yet. Periprosthetic classification systems are still utilized even if not entirely appropriate. High rate of failure is related to thinner cortical bone, larger medullary canals and variable stresses depending on the distance among implants. High complication rates in all studies. Stress risers and implant stability based on fracture patterns and stress forces. Several surgical options with no uniformity. Less invasive surgical procedures are associated to reduction of metalwork failure rate, better preservation of vascularization and better functional-clinical outcomes.

Lack of specific classification systems and management guidelines. Several surgical options are available with no uniformity of results. Attention to stress risers and preservation of bone stock and vascularization are key aspects for better results.

165 A Review of The Current Literature on LMWH Administered at Different Times in Relation to MOS (Major Orthopaedic Surgery): Assessment of The Safety and Efficacy of The Different Proposed Strategies

Nowadays venous VTE represents an important perioperative and postoperative complication in patients undergoing elective Major Orthopedic Surgery (MOS). There are significant discrepancies between clinical practice, international recommendations, and published guidelines. Although thromboembolic events may be less common these days than in the past, they can still lead to serious medical complications. Therefore, most patients undergoing MOS procedures are provided with one of the thromboprophylactic treatments. The optimum timing of LMWH administrations remains debated.

Customized structured electronic searches in PubMed and Cochrane database. Meta-Analysis, Randomized Controlled Trials, Systematic Reviews on different strategies of the use of LMWH for MOS.

Studies on prophylactic regimens showed that subcutaneous LMWH plays a key role in the management of thromboprophylaxis in MOS. However, some controversies still stand. Among those most relevant, it remains unclear whether to start thromboprophylaxis before or after MOS to better balance the risks of clotting and bleeding.

With regards to different times of LMWH administration, there is no convincing evidence that starting prophylaxis 12 hours preoperatively is associated with lower risks of VTE compared to prophylaxis started 12 to 24 hours postoperatively. Furthermore, it seems that the most safe and efficient LMWH regimen is the one called “Just-in-time” (LMWH started 6 hours post-op).

Prevalence of fibrinous pericarditis in heavy pigs (170 kg) and its association with other pluck lesions at slaughter inspection

This study determined the prevalence of fibrinous pericarditis and its correlation with other pluck lesions in 658 batches of pigs from 236 intensive farms located in Northern Italy over a 12-month period. All pigs were slaughtered at 170 kg, and a total 57,943 plucks (approximately 90 pigs/batch) were individually assessed for the presence of fibrinous pericarditis, pneumonia, pleuritis, and liver milk spots. There was no seasonal variation in the prevalence of plucks with fibrinous pericarditis and annual mean prevalence was 5.6% (range, 0-26.3% at batch level; median, 4.71%). Farm of origin, evaluated as a random effect, accounted for 17.7% batch variation. Batches with a high prevalence of fibrinous pericarditis (≥7.7%) had higher prevalences of pleural, pulmonary, and liver lesions than those with low-middle prevalence of pericarditis; high prevalence of pericarditis was predictive of pluck lesions (P < 0.001). There was a highly significant association between fibrinous pericarditis and severe pleuritis, and 55% of plucks with the highest score for pleuritis also had ongoing fibrinous pericarditis, with a positive correlation at batch level (r² = 0.52; P < 0.001). The co-existence of pericarditis and pleuritis (73.5% of all pericarditis cases) suggests that pleuritis plays a role in the pathogenesis of pericarditis. Based on the prevalence fibrinous pericarditis, and the role of pleuritis as a potential comorbidity, abattoir data on pluck lesions with accompanying farm history, could aid the interpretation and management of on-farm health problems, and inform diagnostic protocols.

Neurolysis versus anterior transposition of the ulnar nerve in cubital tunnel syndrome: a 12 years single secondary specialist centre experience

BACKGROUND

Various conservative treatments and surgical techniques have been reported in the literature as efficient and feasible measures to treat the cubital tunnel syndrome. However, there has been no consensus on the best management of the syndrome, and uniform standardised guidelines have not yet been accepted or introduced. With our study, we present our experience on the clinical efficacies and outcomes of the surgical techniques of neurolysis alone and neurolysis associated with ulnar nerve anterior transposition at the elbow joint in patients with neuropathic symptoms due to cubital tunnel syndrome.

MATERIALS AND METHODS

A total of 107 patients with cubital tunnel syndrome were retrospectively enrolled, surgically treated and followed up in our study. The cohort was divided into two groups: 41 patients treated only with neurolysis of the ulnar nerve (Group 1), and 66 patients treated with neurolysis and anterior transposition (Group 2). Of the participants, 35 were women and 72 were men. The average age was 54 years. Significant comorbidities were preoperatively diagnosed in 26 patients. Conservative measures had been considered, followed by surgical management if appropriate. A pre-op electromyography was performed for all patients. All surgical procedures were performed by the same surgical team. A post-operative follow-up was carried out, and the findings were recorded. The "McGowan" and "Wilson and Krout" classifications and the DASH score were used. A satisfaction questionnaire was administered to all patients post-operatively at 2 weeks).

RESULTS

Ulnar nerve neurolysis and anterior transposition surgery were all successfully performed. Overall complications were post-operative haematoma (8%) and wound problems (5%). In 6% there was recurrence of symptoms. In 11% there was no improvement of symptoms. Pre-op McGowan classifications for groups 1 and 2 were 0% and 0% (grade 0), 21% and 24% (grade 1), 46% and 44% (grade 2), and 33% and 34% (grade 3), respectively. The post-op McGowan classifications were 34% and 37% (grade 0), 39% and 40% (grade 1), 23% and 20% (grade 2), and 4% and 3% (grade 3), respectively. The post-op Wilson and Krout classifications were 45% and 46% (excellent), 26% and 28% (good), 19% and 15% (fair), and 10% and 11% (poor), respectively. The DASH score means for groups 1 and 2 were 14.8 and 15.2, respectively. A negative Froment's sign was present in 73.2% and 71.2%, respectively. In Group 1, the post-op satisfaction questionnaire scores were 0 for one patient, 1 for four patients, 2 for seven patients, 3 for ten patients, 4 for twelve patients and 5 for seven patients. In Group 2, the post-op satisfaction questionnaire scores were 0 for three patients, 1 for nine patients, 2 for twelve patients, 3 for fifteen patients, 4 for eighteen patients and 5 for nine patients.

CONCLUSIONS

In our experience, the surgical technique to treat the cubital tunnel syndrome most efficiently and feasibly has not yet been established in terms of indications and outcomes. This is supported by the data present in the international literature. Good and similar results were obtained with neurolysis alone and neurolysis associated with anterior transposition of the ulnar nerve (in line with the international data). In conclusion, more high-quality studies of greater statistical power are needed to provide a consensus on the surgical indications and techniques to treat the cubital tunnel syndrome and to establish internationally standardised guidelines.

Direct and straightforward transfer of C1 functionalized synthons to phosphorous electrophiles for accessing gem-P-containing methanes

The direct transfer of different α-substituted methyllithium reagents to chlorinated phosphorous electrophiles of diverse oxidation state (phosphates, phosphine oxides and phosphines) is proposed as an effective strategy to synthesize geminal P-containing methanes. The methodology relies on the efficient nucleophilic substitution conducted on the P-chlorine linkage. Uniformly high yields are observed regardless the specific nature of the carbanion employed: once established the conditions for generating the competent nucleophile (LiCH₂Hal, LiCHHal₂, LiCH₂CN, LiCH₂SeR etc.) the homologated compounds are obtained via a single operation. Some P-containing formal carbanions have been evaluated in transferring processes, including the carbonyl-difluoromethylation of the opioid agent Hydrocodone.

Taking advantage of lithium monohalocarbenoid intrinsic α-elimination in 2-MeTHF: controlled epoxide ring-opening en route to halohydrins

The intrinsic degradative α-elimination of Li carbenoids somehow complicates their use in synthesis as C1-synthons. Nevertheless, we herein report how boosting such an α-elimination is a straightforward strategy for accomplishing controlled ring-opening of epoxides to furnish the corresponding β-halohydrins. Crucial for the development of the method is the use of the eco-friendly solvent 2-MeTHF, which forces the degradation of the incipient monohalolithium, due to the very limited stabilizing effect of this solvent on the chemical integrity of the carbenoid. With this approach, high yields of the targeted compounds are consistently obtained under very high regiocontrol and, despite the basic nature of the reagents, no racemization of enantiopure materials is observed.

(Difluoromethyl)trimethylsilane (TMSCHF2): A Useful Difluoromethylating Nucleophilic Source

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Electrophilicity Scale of Activated Amides: 17 O NMR and 15 N NMR Chemical Shifts of Acyclic Twisted Amides in N-C(O) Cross-Coupling

The structure and properties of amides are of tremendous interest in organic synthesis and biochemistry. Traditional amides are planar and the carbonyl group non-electrophilic due to n_N →π*_C=O conjugation. In this study, we report electrophilicity scale by exploiting ¹⁷ O NMR and ¹⁵ N NMR chemical shifts of acyclic twisted and destabilized acyclic amides that have recently received major attention as precursors in N-C(O) cross-coupling by selective oxidative addition as well as precursors in electrophilic activation of N-C(O) bonds. Most crucially, we demonstrate that acyclic twisted amides feature electrophilicity of the carbonyl group that ranges between that of acid anhydrides and acid chlorides. Furthermore, a wide range of electrophilic amides is possible with gradually varying carbonyl electrophilicity by steric and electronic tuning of amide bond properties. Overall, the study quantifies for the first time that steric and electronic destabilization of the amide bond in common acyclic amides renders the amide bond as electrophilic as acid anhydrides and chlorides. These findings should have major implications on the fundamental properties of amide bonds.

Chemoselective Homologation-Deoxygenation Strategy Enabling the Direct Conversion of Carbonyls into (n+1)-Halomethyl-Alkanes

The sequential installation of a carbenoid and a hydride into a carbonyl, furnishing halomethyl alkyl derivatives, is reported. Despite the employment of carbenoids as nucleophiles in reactions with carbon-centered electrophiles, sp³-type alkyl halides remain elusive materials for selective one-carbon homologations. Our tactic levers on using carbonyls as starting materials and enables uniformly high yields and chemocontrol. The tactic is flexible and is not limited to carbenoids. Also, diverse carbanion-like species can act as nucleophiles, thus making it of general applicability.

Carbenoid-Mediated Homologation Tactics for Assembling (Fluorinated) Epoxides and Aziridines

Homologation strategies provide highly versatile tools in organic synthesis for the introduction of a CH2 group into a given carbon skeleton. The operation can result in diverse structural motifs by tuning of the reaction conditions and the nature of the homologating agent. In this Account, concisely contextualizing our work with lithium carbenoids (LiCH2X, LiCHXY etc) for homologating carbon-centered electrophiles, we focus on the assembly of three-membered cycles featuring fluorinated substituents. Two illustrative case studies are considered: (1) the development and employment of fluorinated carbenoids en route to rare α-fluoroepoxides and aziridines, and (2) the installation of up to halomethylenic groups on trifluoroimidoylacetyl chlorides (TFAICs) for preparing CF3-containing halo- and halomethylaziridines. Collectively, we demonstrate that the initial homologation event generated by the installation of the carbenoid, upon modulation of the conditions, serves as a tool for creating fluorinated building blocks in a single operation.

Direct and Chemoselective Electrophilic Monofluoromethylation of Heteroatoms (O-, S-, N-, P-, Se-) with Fluoroiodomethane

The commercially available fluoroiodomethane represents a valuable and effective electrophilic source for transferring the CH₂F unit to a series of heteroatom-centered nucleophiles under mild basic conditions. The excellent manipulability offered by its liquid physical state (bp 53.4 °C) enables practical and straightforward one-step nucleophilic substitutions to retain the chiral information embodied, thus allowing it to overcome de facto the requirement for fluoromethylating agents with no immediate access. The high-yielding methodology was successfully applied to a variety of nucleophiles including a series of drugs currently in the market.

Straightforward chemoselective access to unsymmetrical dithioacetals through a thiosulfonate homologation-nucleophilic substitution sequence

A two-step electrophilic sulfur homologation strategy for building up unsymmetrical dithioacetals.

The synthetic versatility of the Tiffeneau–Demjanov chemistry in homologation tactics

Abstract

The Tiffeneau–Demjanov rearrangement can be regarded as an interesting alternative to the more common semi-pinacol transposition. It is usually employed for ring extension but, under specific conditions, it can also be used for ring contraction. Compared to other techniques, such as the Demjanov rearrangement or homologations with diazo compounds, the Tiffeneau–Demjanov pathway presents attractive features including high yielding and selective processes. Ring enlargements follow very strict and simple rules, such as the movement of the less substituted carbon and retention of the configuration. The rearrangement process is mainly affected by steric factors, due to presence of neighbouring groups, rather than electronic ones. The ring contraction may be achieved positioning the amine within the ring, thus achieving a high level of control. Unfortunately, applications of the reaction in modern homologation chemistry are rare; therefore, the aim of the review is re-proposing to the synthetic community the versatility of this venerable reaction and thus, spurring its employment for tackling challenging homologations processes.

Graphic abstract

Highly chemoselective difluoromethylative homologation of iso(thio)cyanates: expeditious access to unprecedented α,α-difluoro(thio)amides

The new motif - α,α-difluoromethyl thioamide - has been assembled starting from isothiocyanate (as thioamide precursor) and a formal difluoromethyl-carbanion generated from commercially available TMSCHF2. Upon proper activation of this reagent with potassium tert-amylate, the high-yielding transfer of the difluorinated nucleophile takes place under high chemocontrol. Various sensitive functionalities (e.g. ester, nitrile, nitro, azido groups) can be accommodated across the isothiocyanate core, thus allowing a wide scope. The methodology is highly flexible and adaptable to prepare analogous α,α-difluoromethyl oxoamides by conveniently using isocyanates as the electrophilic building-blocks.

Direct and Chemoselective Synthesis of Tertiary Difluoroketones via Weinreb Amide Homologation with a CHF2-Carbene Equivalent

The homologation of Weinreb amides into difluoromethylketones with a formal nucleophilic CHF₂ transfer agent is reported. Activating TMSCHF₂ with potassium tert-amylate enables a convenient access to the difluorinated homologation reagent, which adds to the acylating partners. The high chemoselectivity showcased in the presence of variously multifunctionalized Weinreb amides, jointly with uniformly high yields, enables the strategy of general applicability without requiring any stabilization element for the putative carbanion.

A Combination of Pharmacophore and Docking-based Virtual Screening to Discover new Tyrosinase Inhibitors

Melanogenesis controls the formation of melanin pigment whose overproduction is related to various hyperpigmentary disorders in humans. Tyrosinase is a type-3 copper enzyme involved in the rate limiting step of melanin synthesis, therefore its inhibition could represent an efficient way for the development of depigmenting agents. In this work, a combination of pharmacophore and docking-based studies has been employed to screen two in-house 3D compound databases containing about 2,000 molecules from natural and synthetic sources. As result we selected two "hit compounds" which proved to inhibit tyrosinase activity showing IC₅₀ values in the micromolar range.

Weinreb Amides as Privileged Acylating Agents for Accessing α-Substituted Ketones

The acylation of α-substituted carbanion-type reagents (MCR1R2X; X = halogen, OR, SR, NR3R4, SeR, etc.) with Weinreb amides constitutes a highly versatile and flexible approach for accessing α-functionalized ketones. In this short review we will present a series of transformations—from our own and the work of others—documenting the general applicability of the methodology. Chemoselectivity is uniformly manifested including for critical substrates featuring additional electrophilic functionalities or sterically demanding elements. Importantly, the stereochemical information contained in the Weinreb amides can be fully transferred to the targeted ketones without affecting the optical purity. The protocol is also applicable to chiral carbanions generated through sparteine-mediated asymmetric deprotonation: the careful design of the experimental procedure allows recycling of the sparteine and the Weinreb ‘amine’ (N,O-dimethylhydroxylamine), thus improving the sustainability perspective of the processes.

1 Introduction

1.1 The Problem of the Synthesis of α-Substituted Ketones

1.2 Weinreb Amides: General Features and Preparation

2 Synthesis of α-Substituted Ketones

2.1 α-Haloketones

2.2 Synthesis of α-Cyanoketones

2.3 Synthesis of α-Oxyketones

2.4 Synthesis of β-Oxo Thioethers (α-Thioketones)

2.5 Synthesis of Chiral α-Oxy and α-Nitrogen Ketones via the Sparteine-Mediated Generation of Optically Active Organolithiums

2.6 Synthesis of α-Selenomethyl Ketones

2.7 Reactivity of α-Phosphorus Carbanions with Weinreb Amides

2.8 Modification of the Weinreb Amide Core: The CLAmP Reagent

3 Competing Attack of Nucleophiles at More Reactive Electrophilic Sites than Weinreb Amides

4 Conclusions

Enhanced recovery after surgery (ERAS) in hip and knee replacement surgery: description of a multidisciplinary program to improve management of the patients undergoing major orthopedic surgery

PURPOSE

Enhanced recovery after surgery (ERAS) protocols aim to develop peri-operative multidisciplinary programs to shorten length of hospital stay (LOS) and reduce complications, readmissions and costs for patients undergoing major surgery. The aim of this study is to evaluate the effects of an ERAS pathway for total hip (THR) and knee (TKR) replacement surgery in terms of length of stay, incidence of complications and patient satisfaction.

METHODS

Patients scheduled for hip and knee replacement were included in the study. The main aspects of this program were preoperative education/physical therapy, rational choice of the anesthetic technique, optimization of multimodal analgesia, reduction of incidence of urinary retention and catheterization, active management of risk for blood loss and deep vein thrombosis, and early mobilization of the patients. All patients had 6 months predicted and planned follow-up appointments. Primary outcomes of the study were the mean LOS, readmission and complication rates. Secondary Outcomes were percentage of Knee Injury & Osteoarthritis Outcome Score (KOOS) and Hip disability and Osteoarthritis Outcome Score (HOOS) increase and patient's satisfaction.

RESULTS

We consecutively enrolled 207 patients who underwent total joint arthroplasty, 78 hip and 129 knee joint replacements. The mean length of stay (LOS) for patients of the two groups was 4.3 days for ASA 3-4 patients subjected to TKR and THR, in ASA 1-2 patients 3.6 days for TKR and 3.9 days for THR respectively. Postoperative satisfaction level was higher than 7 (very satisfied) in 94.4% of the cases. All patients were discharged home: 61.8% continued physical therapy in complete autonomy, 23.7% supported by a home-physiotherapist and only 14.5% needed the attendance to a physiotherapy center on a daily basis. The overall incidence of major complications was 3.4%.

CONCLUSIONS

The implementation of an ERAS program for hip and knee replacement surgery allows early patient's discharge and a quick return to independency in the daily activities.

LEVEL OF EVIDENCE

IV.

Palladium-Catalyzed Regioselective Syn-Chloropalladation-Olefin Insertion-Oxidative Chlorination Cascade: Synthesis of Dichlorinated Tetrahydroquinolines

A palladium catalyzed cascade process involving syn-chloropalladation, intramolecular olefin insertion, and oxidative C-Cl bond formation reactions was demonstrated for the synthesis of dichlorinated tetrahydroquinolines in high yields (up to 93%). The N-propargyl arylamines having a tethered α,β-unsaturated carbonyl moiety underwent a regioselective syn-chloropalladation followed by a Heck-type reaction to deliver the tetrahydroquinoline scaffold. The rare insertion of the second chlorine atom was rationalized comprising a Pd^II/IV catalytic cycle and oxidative cleavage of the C-Pd^II bond.

17O NMR and 15N NMR chemical shifts of sterically-hindered amides: ground-state destabilization in amide electrophilicity

The structure and spectroscopic properties of the amide bond are a topic of fundamental interest in chemistry and biology. Herein, we report 17O NMR and 15N NMR spectroscopic data for four series of sterically-hindered acyclic amides. Despite the utility of 17O NMR and 15N NMR spectroscopy, these methods are severely underutilized in the experimental determination of electronic properties of the amide bond. The data demonstrate that a combined use of 17O NMR and 15N NMR serves as a powerful tool in assessing electronic effects of the amide bond substitution as a measure of electrophilicity of the amide bond. Notably, we demonstrate that steric destabilization of the amide bond results in electronically-activated amides that are comparable in terms of electrophilicity to acyl fluorides and carboxylic acid anhydrides.

Sustainable Asymmetric Organolithium Chemistry: Enantio- and Chemoselective Acylations through Recycling of Solvent, Sparteine, and Weinreb "Amine"

The well-established Hoppe-Beak chemistry, which involves enantioselective generation of organolithium compounds in the presence of (-)-sparteine, was revisited and applied to unprecedented acylations with Weinreb amides to access highly enantioenriched α-oxyketones and cyclic α-aminoketones. Recycling of the sustainable solvent cyclopentyl methyl ether, sparteine, and the released Weinreb "amine" [HNMe(OMe)] was possible through a simple work-up procedure that enabled full recovery of these precious materials. The methodology features a robust scope and flexibility, thus allowing the enantioselective preparation of scaffolds amenable of further derivatization.

Telescoped, Divergent, Chemoselective C1 and C1-C1 Homologation of Imine Surrogates: Access to Quaternary Chloro- and Halomethyl-Trifluoromethyl Aziridines

A conceptually novel, high‐yielding, mono‐ or bis‐homologation was realized with lithium halocarbenoids and enables the one‐step, fully chemocontrolled assembly of a new class of quaternary trifluoromethyl aziridines. Trifluoroacetimidoyl chlorides (TFAICs) act as convenient electrophilic platforms, enabling the addition of either one or two homologating elements by simply controlling the stoichiometry of the process. Mechanistic studies highlighted that the homologation event, carried out with two different carbenoids (LiCH₂Cl and LiCH₂F), leads to fluoromethyl analogues in which the first nucleophile is employed for constructing the cycle and the second for decorating the resulting molecular architecture.

Cyclopentyl Methyl Ether: An Elective Ecofriendly Ethereal Solvent in Classical and Modern Organic Chemistry

Solvents represent one of the major contributions to the environmental impact of fine-chemical synthesis. As a result, the use of environmentally friendly solvents in widely employed reactions is a challenge of vast real interest in contemporary organic chemistry. Within this Review, a great variety of examples showing how cyclopentyl methyl ether has been established as particularly useful for this purpose are reported. Indeed, its low toxicity, high boiling point, low melting point, hydrophobicity, chemical stability towards a wide range of conditions, exceptional stability towards the abstraction of hydrogen atoms, relatively low latent heat of vaporization, and the ease with which it can be recovered and recycled enable its successful employment as a solvent in a wide range of synthetic applications, including organometallic chemistry, catalysis, biphasic reactions, oxidations, and radical reactions.

Modular and Chemoselective Strategy for the Direct Access to α-Fluoroepoxides and Aziridines via the Addition of Fluoroiodomethyllithium to Carbonyl-Like Compounds

An expeditious, high-yielding synthesis of rare α-fluoroepoxides and α-fluoroaziridines through the addition of the unkown fluoroiodomethyllithium (LiCHIF)-formed via deprotonation the commercially available fluoroiodomethane with a lithium amide base-to carbonyl-like compounds is documented. The ring-closure reactions, leading to α-fluorinated three-membered heterocycles, rely on the diversely reactive C-I and C-F bonds. Excellent chemoselectivity was observed in the presence of highly sensitive functionalities-aldehyde, ketone, nitrile, alkene-which remained untouched during the homologation sequence.

Chemoselective reduction of isothiocyanates to thioformamides mediated by the Schwartz reagent

Thioformamides are easily prepared – under full chemocontrol – through the partial reduction of isothiocyanates with the in situ generated Schwartz reagent.

Design, Synthesis, and Pharmacological Evaluation of Novel β2/3 Subunit-Selective γ-Aminobutyric Acid Type A (GABAA) Receptor Modulators

Subunit-selective modulation of γ-aminobutyric acid type A receptors (GABA_AR) is considered to exert fewer side effects compared to unselective clinically used drugs. Here, the β2/3 subunit-selective GABA_AR modulators valerenic acid (VA) and loreclezole (LOR) guided the synthesis of novel subunit-selective ligands with simplified structures. We studied their effects on GABA_ARs expressed in Xenopus laevis oocytes using two-microelectrode voltage clamp technique. Five compounds showed significantly more efficacious modulation of GABA-evoked currents than VA and LOR with retained potency and selectivity. Compound 18 [( E)-2-Cyano-3-(2,4-dichlorophenyl)but-2-enamide] induced the highest maximal modulation of GABA-induced chloride currents ( E_max: 3114 ± 242%), while 12 [( Z)-3-(2,4-dichlorophenyl)but-2-enenitrile] displayed the highest potency (EC₅₀: 13 ± 2 μM). Furthermore, in hippocampal neurons 12 facilitated phasic and tonic GABAergic inhibition, and in vivo studies revealed significantly more potent protection against pentylenetetrazole (PTZ)-induced seizures compared to VA and LOR. Collectively, compound 12 constitutes a novel, simplified, and subunit-selective GABA_AR modulator with low-dose anticonvulsant activity.