Metal- and base-free, aerobic photoredox catalysis with riboflavin to synthesize 2-substituted benzothiazoles

Sustainable approaches for the synthesis of 2-substituted benzothiazoles are sought after for their use in organic chemistry, bioorganic chemistry, and industrial applications. Here, we described a visible light-driven photoredox catalytic cyclization of thioanilides to afford 2-substituted benzothiazoles using riboflavin as a photocatalyst, where oxygen is used as a clean oxidant and ethanol as a greener solvent. These results provide a new photochemical route for environmentally benign synthesis.

Linker-Assisted CdS-TiO2 Nanohybrids as Reusable Visible Light Photocatalysts for the Oxidative Hydroxylation of Arylboronic Acids

A variety of phenols have been obtained in aqueous media with moderate to excellent chemical yields (≤100%) by using arylboronic acids and esters as substrates, a robust CdS-TiO₂ nanohybrid as a heterogeneous photocatalyst, visible light irradiation (467 nm), and an O₂-saturated atmosphere. The nanohybrid was prepared through a linker-assisted methodology that uses mercapto alkanoic acids as the organic linkers. The nanohybrid showed improved photocatalytic activity in the hydroxylation of substituted arylboronic acids and phenyl boronic esters compared with that of pristine CdS quantum dots. The nanohybrid can be reused in up to five photocatalytic cycles with ∼90% of its outstanding activity preserved.

Photochemical Csp2-H bond thiocyanation and selenocyanation of activated arenes, batch and continuous-flow approaches

Herein, we report an eco-friendly photochemical oxidative C_sp²-H thiocyanation and selenocyanation of activated arenes. The reaction proceeds under Violet LED irradiation in the presence of K₂S₂O₈, which quickly oxidizes KSCN and KSeCN, finally producing arylthio/selenocyanates. Using this benign, atom-economic protocol, the desired chalcogenide products were obtained regioselectively, with isolated yields that range from very good to excellent. Although, mechanistic study indicates that it is difficult to distinguish between a radical to a S_EAr reaction mechanism between the photo-induced formed ^•SCN, for the former, or NCSSCN, for the latter, to the aromatic heterocycles. The inhibition experiment together with the observed reactivity and regioselectivity, would be in agreement with the latter. The synthetic methodology designed could be successfully adapted to continuous-flow systems in a segmented-flow regime, employing the organic phase as the product reservoir. Using this setup, the advantage of the latter can be demonstrated by reducing the reaction time and improving the product yields. Similarly, the scaling up of the reaction to gram scale resulted in favorable outcomes by the flow setup, which installs the photo-flow chemistry as a powerful tool to be included into routine reaction procedures, which have great relevance for the pharmaceutical industry.

Highly Water-Stable Polymer-Perovskite Nanocomposites

The excellent performance of hybrid metal-halide perovskite nanocrystals (NCs) contrasts with their unsatisfactory stability in a high-humidity environment or water. Herein, polymer composite lead-halide perovskites (LHPs) NCs were prepared by casting or spin-coating to produce a high fluorescence yield and a fully water-resistant material. Poly(l-lactide) (PLla), polypropylene glycol (PPGly), and polysulfone (PSU) commercial polymers were used to prepare suspensions of MAPbBr₃-HDA NCs (MA: CH₃NH₃; HDA: hexadecylamine). The MAPbBr₃-HDA@PLla suspension exhibited a maximum fluorescence quantum yield of 93% compared to 43% for the pristine MAPbBr₃-HDA NCs. Strong emissions around 528 nm were also observed, with the same full width at half maximum value of 20 nm, demonstrating the successful fabrication of brightly luminescent LHP NCs@polymer combinations. Time-resolved photoluminescence measurements directly observed the enhanced spontaneous emission of the NCs induced by the polymeric environment. However, the cast films of MAPbBr₃-HDA NCs mixed with PLla or PPGly did not resist water immersion. On the contrary, MAPbBr₃-HDA@PPGly/PSU films containing well-dispersed ∼10 nm LHP NCs retained a bright green fluorescence emission even after 18 months under air conditions or water immersion up to 45 °C. From water contact angle measurements, profilometry, and X-ray photoelectron spectroscopy data, it could be assumed that the slightly hydrophobic PSU polymer is responsible for the high water stability of the fluorescent films, which avoids MAPbBr₃-HDA NC degradation. This work shows that the LHP NC dispersion in dissolved commodity polymers holds great promise toward the long-term stability of LHP NC composites for the future development of wearable electronic devices and other waterproof applications.

Mechanistic Insight into the Light-Triggered CuAAC Reaction: Does Any of the Photocatalyst Go?

The attainment of transition-metal catalysis and photoredox catalysis has represented a great challenge over the last years. Herein, we have been able to merge both catalytic processes into what we have called "the light-triggered CuAAC reaction". Particularly, the CuAAC reaction reveals opposite outcomes depending on the nature of the photocatalyst (eosin Y disodium salt and riboflavin tetraacetate) and additives (DABCO, Et₃N, and NaN₃) employed. To get a better insight into the operating processes, steady-state, time-resolved emission, and laser flash photolysis experiments have been performed to determine reactivity and kinetic data. These results, in agreement with thermodynamic estimations based on reported data, support the proposed mechanisms. While for eosin Y (EY), Cu(II) was reduced by its triplet excited state; for riboflavin tetraacetate (RFTA), mainly triplet excited RFTA state photoreductions by electron donors as additives are mandatory, affording RFTA^•- (from DABCO and NaN₃) or RFTAH^• (from Et₃N). Subsequently, these species are responsible for the reduction of Cu(II). For both photocatalysts, photogenerated Cu(I) finally renders 1,2,3-triazole as the final product. The determined kinetic rate constants allowed postulating plausible mechanisms in both cases, bringing to light the importance of kinetic studies to achieve a strong understanding of photoredox processes.

Diversity of variant alleles encoding Kidd, Duffy, and Kell antigens in individuals with sickle cell disease using whole genome sequencing data from the NHLBI TOPMed Program

BACKGROUND

Genetic variants in the SLC14A1, ACKR1, and KEL genes, which encode Kidd, Duffy, and Kell red blood cell antigens, respectively, may result in weakened expression of antigens or a null phenotype. These variants are of particular interest to individuals with sickle cell disease (SCD), who frequently undergo chronic transfusion therapy with antigen-matched units. The goal was to describe the diversity and the frequency of variants in SLC14A1, ACKR1, and KEL genes among individuals with SCD using whole genome sequencing (WGS) data.

STUDY DESIGN AND METHODS

Two large SCD cohorts were studied: the Recipient Epidemiology and Donor Evaluation Study III (REDS-III) (n = 2634) and the Outcome Modifying Gene in SCD (OMG) (n = 640). Most of the studied individuals were of mixed origin. WGS was performed as part of the National Heart, Lung, and Blood Institute's Trans-Omics for Precision Medicine (TOPMed) program.

RESULTS

In SLC14A1, variants included four encoding a weak Jka phenotype and five null alleles (JKnull ). JKA*01N.09 was the most common JKnull . One possible JKnull mutation was novel: c.812G>T. In ACKR1, identified variants included two that predicted Fyx (FY*X) and one corresponding to the c.-67T>C GATA mutation. The c.-67T>C mutation was associated with FY*A (FY*01N.01) in four participants. FY*X was identified in 49 individuals. In KEL, identified variants included three null alleles (KEL*02N.17, KEL*02N.26, and KEL*02N.04) and one allele predicting Kmod phenotype, all in heterozygosity.

CONCLUSIONS

We described the diversity and distribution of SLC14A1, ACKR1, and KEL variants in two large SCD cohorts, comprising mostly individuals of mixed ancestry. This information may be useful for planning the transfusion support of patients with SCD.

The screening of rare blood donors in a highly admixed population: A new approach for Holley and Diego genotyping and impact of genomic and self-reported ancestry

OBJECTIVES

The present study aimed to develop strategies for genotyping DO*HY (Dombrock system) and DI*A/DI*B (Diego system) alleles and to evaluate the impact of genomic and self-declared ancestry on rare donor screening in admixed populations.

BACKGROUND

The antigens Hy and Di^b demonstrate clinical importance. The lack of antisera for the serological evaluation of these antigens makes it necessary to develop molecular methods. In addition, considering that some rare red blood cell phenotypes present differences in frequency between ethnic groups, it is important to assess the applicability of self-declared ancestry in the search for rare donors in admixed populations.

METHODS

DO*HY and DI*A/DI*B genotyping based on real-time polymerase chain reaction (PCR) was standardised. A total of 457 blood donors clustered by self-defined skin colour/race categories were genotyped. Furthermore, individual genomic ancestry was used in the analyses.

RESULTS

The assays developed are reproducible and provide satisfactory results even at low concentrations of DNA, which make them useful in situations where the DNA is scarce, such as dried blood spots on filter paper, or when screening for pooled samples. No significant difference was observed in the frequencies of the DI*A, DI*B and DO*HY, comparing the self-declared White (branco) donors with those who are Black (preto) and Brown (pardo).

CONCLUSION

Real-time PCR, especially using pooled samples, is a promising strategy to screen rare blood donors. Although both self-reported race/colour and some blood group phenotypes are associated with ancestry, the results point to a greater complexity in the application of self-declared race/colour in the screening of rare donors in admixed populations.

Metal- and photocatalyst-free synthesis of 3-selenylindoles and asymmetric diarylselenides promoted by visible light

A novel and sustainable procedure was developed for the synthesis of 3-selenylindoles employing diorganyl diselenides and indoles or electron-rich arenes as starting materials. Visible blue light was used to promote the reaction without employing transition metal complexes or organic photocatalysts as sensitizers. Additives such as strong oxidants or bases were not required. Moreover, ethanol was employed as a benign solvent under mild reaction conditions. Through this easy and eco-friendly approach, several 3-selenylindoles and a number of asymmetric diarylselenides were obtained in good to excellent isolated yields.

A novel and sustainable procedure for the synthesis of 3-selenylindoles employing diorganyl diselenides and indoles or electron-rich arenes and promoted by visible light was developed.

Colloids of Naked CH3NH3PbBr3 Perovskite Nanoparticles: Synthesis, Stability, and Thin Solid Film Deposition

A novel preparation of lead halide, CH₃NH₃PbBr₃, perovskite nanoparticle solid films from colloidal "naked" nanoparticles, that is, dispersible nanoparticles without any surfactant, is reported. The colloids are obtained by simply adding potassium ions, whose counterions are both more lipophilic and less coordinating than bromide ions, to the perovskite precursor solutions (CH₃NH₃Br/PbBr₂ in dimethylformamide) following the reprecipitation strategy. The naked nanoparticles exhibit a low tendency to aggregate in solution, and they effectively self-assembled on a substrate by centrifugation of the colloid, leading to homogeneous nanoparticle solid films with arbitrary thickness. These results are expected to spur further the interest in lead halide perovskites due to the new opportunities offered by these films.

A straightforward and sustainable synthesis of 1,4-disubstituted 1,2,3-triazoles via visible-light-promoted copper-catalyzed azide–alkyne cycloaddition (CuAAC)

A simple and environmentally friendly synthesis of triazoles through the effective reduction of copper(ii) assisted by organic dyes and promoted by visible light was developed.

Unexpected formation of 4,4-dimethyl-1,2-disubstituted-dicarbonyl cyclopentanes from ketone enolate anions and 1,3-diiodo-2,2-dimethylpropane

Novel access to 1,2-dicarbonyl cyclopentane compounds by tandem dimerization–cyclization reactions under transition-metal-free conditions.

Nature of the Chain Propagation in the Photostimulated Reaction of 1-Bromonaphthalene with Sulfur-Centered Nucleophiles

The reactivity of -SC(NH)NH2 (1), MeCOS- (2), and PhCOS- (3) toward 1-naphthyl radicals was studied in DMSO. The photostimulated reaction of anions 1, 2, and 3 with 1-bromonaphthalene (4) after quenching with MeI renders 1-(methylthio)naphthalene (6) as a main product together with bis(1-naphthyl) sulfide (7) and naphthalene (5). The thioacetate ion (2) and thiobenzoate ion (3) were unreactive toward 4 as electron-donor under photostimulation; however, in the presence of potassium tert-butoxide anion (entrainment conditions), they gave the mentioned products 5, 6, and 7, after the addition of MeI. Quenching of the triplet state of 4 was assigned as the photoinduced initiation step, with a rate constant value of (4.6+/-0.5)x10(8) M-1 s-1 for tert-butoxide anion and a rough estimated value of (8+/-7)x10(7) M-1 s-1 for anion 1. By using hydrogen abstraction from DMSO as the competitive reaction, the absolute rate constants for the addition of anions 1, 2, and 3 to 1-naphthyl radicals have been determined to be 1.0x10(9), 1.2x10(9), and 3.5x10(9) M-1 s-1, respectively. This reactivity order is in agreement with the stability of the resulting radical anions (ArNu)*- (10-12)*-. The inhibition experiments of the photoinduced substitution reaction in the presence of radical scavengers and the global quantum yield higher than the unity are evidence of a radical chain mechanism for these substitution reactions by anions 1 and 2. Anion 3 adds to the 1-naphthyl radical, but is neither able to initiate nor to keep the propagation cycle. Evaluation of the electron-transfer driving forces for the reaction between (ArNu)*- and 4 together with the absence of a chain reaction for the anion 3 indicate that the propagation in the proposed mechanism is given by an acid-base reaction between the radical .C(O)Me or .C(NH)NH2 (13) and a base.

“One-Pot” Two-Step Synthesis of Aryl Sulfur Compounds by Photoinduced Reactions of Thiourea Anion with Aryl Halides

[reaction: see text]. The photoinduced reactions of aryl halides with the thiourea anion afford arene thiolate ions in DMSO. These species without isolation, and by a subsequent aliphatic nucleophilic substitution, S(RN)1 reaction, oxidation, or protonation, yield aryl methyl sulfides, diaryl sulfides, diaryl disulfides, and aryl thiols with good yields (50-80%). This is a simple and convenient approach which involves the use of the commercially available and inexpensive thiourea in a "one-pot" two-step process for the synthesis of aromatic sulfur compounds.

Stability of family interaction from ages 6 to 18

Research has demonstrated the stability of juvenile offending during childhood and adolescence but generally has not focused on the continuity of family interactions associated with juvenile offending. The present report focused on the stability of several family interaction events and attributes (i.e., physical punishment, communication, supervision, positive parenting, and parent-child relationship) for a large sample of male adolescents and their primary caretakers, drawn from a multiyear longitudinal study that represented middle childhood through late adolescence (ages 6-18). We also assessed the impact of ethnicity, family composition, teenage motherhood, and youth delinquency on these interactions. Test-retest correlations and growth-curve analyses were used to assess relative and absolute stability of the interactions, respectively. As predicted, relative stability of family interaction was high. There was an absolute change in scores of physical punishment (decreased) compared to poor supervision and low positive parenting (both increased), whereas poor communication and bad relationship with the caretaker did not measurably change with age. Single-parent families and families with teenage mothers experienced significantly worse interactions over time than did families consisting of two biological parents present in the household. These findings are discussed in relation to the development of juvenile offending.