Palladium-Catalyzed Carbonylative Synthesis of Isoindolinones from Benzylamines with TFBen as the CO Source

Pd-Catalyzed cascade Heck cyclization/carbonylation of indoles with aryl formates: enantioselective construction of indolo[2,1-a]isoquinolines

An efficient palladium-catalyzed cascade cyclization/carbonylation of indoles with aryl formates to access ester-functionalized indolo[2,1-a]isoquinoline scaffolds has been developed. In addition, an asymmetric variant is also achieved using a chiral phosphine ligand, affording the indolo[2,1-a]isoquinoline products in good yields and enantioselectivities.

New Analogues of the Nicotinamide Phosphoribosyltransferase Inhibitor FK866 as Potential Anti-Pancreatic Cancer Agents

BACKGROUND

During the past two decades, many nicotinamide phosphoribosyltransferase (NAMPT) inhibitors were prepared and tested because this enzyme is overexpressed in pancreatic cancer. Although FK866 is a well-known, strong NAMPT inhibitor, it suffers severe drawbacks.

OBJECTIVE

Our work aimed to synthesize efficient NAMPT inhibitors featuring better pharmacokinetic properties than the pyridine-containing FK866. To this aim, the new anticancer agents were based on benzene, pyridazine, or benzothiazole moieties as a cap group instead of the pyridine unit found in FK866 and other NAMPT inhibitors.

METHODS

The new compounds, prepared exploiting standard heterocycle chemistry and coupling reactions (e.g., formation of amides, ureas, and cyanoguanidines, copper-mediated azide-alkyne cycloaddition), have been fully characterized using NMR and HRMS analyses. Their activity has been evaluated using cytotoxicity and intracellular NAD depletion assays in the human pancreatic cancer cell line MiaPaCa-2.

RESULTS

Among the 14 products obtained, compound 28, bearing a pyridazine unit as the cap group and a thiophene moiety as the tail group, showed 6.7 nanomolar inhibition activity in the intracellular NAD depletion assay and 43 nanomolar inhibition in the MiaPaCa-2 cells cytotoxicity assay, comparable to that observed for FK866.

CONCLUSION

The positive results observed for some newly synthesized molecules, particularly those carrying a thiophene unit as a tail group, indicate that they could act as in vivo anti-pancreatic cancer agents.

Ultrasound-assisted-one-pot synthesis and antiplasmodium evaluation of 3-substituted-isoindolin-1-ones

As the attempts to control malaria through chemotherapy strategies are restricted, we have prepared a small library of 3-substituted-isoindolinones from (Z)-3-benzylideneisobenzofuran-1(3H)-ones in one-pot fashion under ultrasound irradiation. The one-pot reaction was scalable and efficiently produced the desired products (1a-m) in high yields in a short reaction time. Evaluation of their in vitro antiplasmodium assay against the 3D7 (chloroquine-sensitive) and FCR3 (chloroquine-resistant) strains of Plasmodium falciparum demonstrated that they displayed moderate to strong antiplasmodium activities (the IC50 values ranging from 4.21-34.80 μM) and low resistance indices. The in silico prediction of ADME and physicochemical properties showed that the synthesized compounds met the drug-likeliness requirements and featured low toxicity effects. Based on the evaluation of the antiplasmodium profiles, 3-substituted-isoindolinone derivatives of 1a, 1d, 1h, and 1l may become potential antiplasmodium candidates.

Divergent Synthesis of Pentacyclic Isoindolinones Enabled by Sequential Insertion of Two Different Isocyanides and Acid Promoted Cyclization of Ketenimines

A palladium-catalyzed multicomponent reaction involving o-bromobenzaldehydes and two different isocyanides was developed to assemble series of isoindolinones with spiroindolenine or azepinoindole skeletons. This sequential insertion reaction features mild conditions, a wide substrate scope, and high efficiency. Preliminary mechanistic study indicated that the difference in steric hindrance between isocyanide components is crucial when regulating the reaction sequence, whereas the ligand also played an important role during the whole process.

Palladium- and nickel-catalyzed cascade enantioselective ring-opening/coupling reactions of cyclobutanones

The chemistry of small ring compounds is an intriguing subject in organic chemistry. As the smallest stable cyclic aliphatic ketones, cyclobutanones have garnered tremendous attention owing to their intrinsic high reactivity such as transition-metal catalyzed C-C bond cleavage. In this context, transition-metal catalyzed formal cycloaddition of cyclobutanones via a "cut and sew" strategy has gained marvelous advances. In contrast, an alternative reaction paradigm, i.e., transition-metal catalyzed ring-opening reactions of cyclobutanones, is still underdeveloped. This feature article aims to summarize our efforts in developing enantioselective palladium-catalyzed ring-opening/coupling reactions and recently emerging nickel-catalyzed ring-opening/reductive coupling reactions of cyclobutanones with a tethered aryl halide. The possible mechanisms are briefly showcased and the advantages and limitations of each strategy as well as their synthetic applications in the synthesis of natural products or bioactive compounds are presented.

Convenient synthesis of benzothiazinoisoindol-11-ones and benzoindenothiazin-11-ones, and antimicrobial testing thereof

Benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t and benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones 6a-e were synthesized conveniently via cyclocondensation of 2-bromo-2-(2/3-substitutedphenyl)-1H-indene-1,3(2H)-diones and 2-aminobenzenethiols in freshly dried ethanol with 70-85% yields. The synthesized derivatives were well characterized by employing different spectral techniques (FTIR, ¹H & ¹³C NMR and HRMS) and X-ray crystallographic analysis. Further, all the reported compounds were tested for their antibacterial and antifungal activities using Ciprofloxacin and Fluconazole as standard drugs, respectively. The results of antimicrobial evaluation revealed that compounds 5o and 5t displayed remarkable inhibitory activity against B. subtilis, S. aureus, P. aeruginosa and A. niger with MIC values in the range of 0.0141-0.0283 µmol/mL, whereas 5j was found active against E. coli and C. albicans with MIC values of 0.0286 µmol/mL and 0.0143 µmol/mL, respectively. Additionally, among all the benzo[b]indeno[1,2-e][1,4]thiazin-11(10aH)-ones, 6c exhibited excellent inhibition against all the tested bacterial and fungal strains with MIC values ranging from 0.0143 to 0.1145 µmol/mL. Structure activity relationships were also established for all the tested benzo[5,6][1,4]thiazino[3,4-a]isoindol-11-ones 5a-t.

Base-Promoted 5-exo-dig Cyclization of o-Alkynylamides or 2-En-4-ynamides with CO2 toward Fully Substituted Acrylates

A base-promoted sequential cyclization and carboxylation of o-alkynylamides or 2-en-4-ynamides with CO₂ has been achieved with high efficiency, stereoselectivity, and regioselectivity. This approach begins with 5-exo-dig cyclization followed by trapping the resulting vinyl anion with CO₂ and MeI, which provides a convenient access to diverse cyclic and fully substituted acrylates with CO₂ as the carboxylic source.

Ring-Opening 1,3-Carbothiolation of Donor-Acceptor Cyclopropanes Using Alkyl Halides and In Situ Generated Dithiocarbamates

Two-step, ring-opening 1,3-carbothiolation of donor-acceptor (D-A) cyclopropanes employing alkyl halides and in situ generated dithiocarbamates (from amines and CS2) has been demonstrated under mild conditions. The reaction is operationally simple and works with good functional group compatibility. Three new bonds including C-N, C-S, and C-C are formed in this 1,3-bifunctionalization strategy. Electron-poor olefins can also be used as electrophiles instead of alkyl halides. The use of enantiomerically pure D-A cyclopropane afforded enantiopure 1,3-carbothiolated product, thus demonstrating the stereospecificity of the reaction.

Polyoxometalate-Driven Ease Conversion of Valuable Furfural to trans-N,N-4,5-Diaminocyclopenten-2-ones

We investigated the catalytic efficacy of silicotungstic acid (H₄SiW₁₂O₄₀) polyoxometalate (POM) toward the reaction between furfural and amines that selectively yields trans-N,N-4,5-substituted-diaminocyclopenten-2-ones (trans-DACPs). H₄SiW₁₂O₄₀ facilitates the synthesis of a library of trans-DACPs with loadings as low as 0.05 mol %, in open air, without additives, in short times and good to high isolated yields. The protocol was applied to secondary amines as well as to aromatic primary amines with pK_b higher than ca. 9. The present catalytic synthetic protocol has an extended substrate scope with high yields and represents, to the best of our knowledge, the first polyoxometalate-driven paradigm as an efficient method to produce cyclopentanone frameworks under mild reaction conditions.

Recent advances in Cu-catalyzed carbonylation with CO

Transition metal-catalyzed carbonylation has emerged as a powerful and versatile strategy for the efficient construction of complicated carbonyl-containing molecules from simple chemical feedstocks in the past decades.

Divergent Reaction of Isocyanides with o-Bromobenzaldehydes: Synthesis of Ketenimines and Lactams with Isoindolinone Cores

A divergent reaction of isocyanides with o-bromobenzaldehydes for the synthesis of isoindolinone-derived ketenimines and lactams was disclosed. The reaction features readily available reactants, relatively mild conditions, and high yields of products. Ketenimines could be applied in further transformations for access to other functional molecules. A mechanism study showed that the palladium-migration/imine-insertion process was the key step in this reaction.

TFBen (Benzene-1,3,5-triyl triformate): A Powerful and Versatile CO Surrogate

Carbonylative reactions by the using of CO surrogates constitute a facile avenue for the assembly of valuable carbonyl-containing compounds due to the colorless, toxic, flammable, and not easy-handing character of carbon monoxide gas. Recent advances in the carbonylative transformations with TFBen (benzene-1,3,5-triyl triformate) as a safe and convenient CO precursor are systematically summarized and discussed, which can be divided into three parts based on the patterns of the obtained products. This Review focuses on the discussion of the application of TFBen in carbonylative synthesis of various carbonyl-containing compounds.

Rhodium(III)-Catalyzed Oxidative Cyclization of Oxazolines with Cyclopropanols: Synthesis of Isoindolinones

The synthesis of C3-substituted isoindolin-1-ones from oxazolines and cyclopropanols has been achieved with oxazoline as a bifunctional nucleophilic directing group. The reaction proceeds by the cleavage of three chemical bonds and allows the formation of three new chemical bonds, a C-N bond, a C-C bond, and a C-O bond, in a single step.

Isoindolinone Synthesis via One-Pot Type Transition Metal Catalyzed C-C Bond Forming Reactions

Isoindolinone structure is an important privileged scaffold found in a large variety of naturally occurring as well as synthetic, biologically and pharmaceutically active compounds. Owing to its crucial role in a number of applications, the synthetic methodologies for accessing this heterocyclic skeleton have received significant attention during the past decade. In general, the synthetic strategies can be divided into two categories: First, direct utilization of phthalimides or phthalimidines as starting materials for the synthesis of isoindolinones; and second, construction of the lactam and/or aromatic rings by different catalytic methods, including C-H activation, cross-coupling, carbonylation, condensation, addition and formal cycloaddition reactions. Especially in the last mentioned, utilization of transition metal catalysts provides access to a broad range of substituted isoindolinones. Herein, the recent advances (2010-2020) in transition metal catalyzed synthetic methodologies via formation of new C-C bonds for isoindolinones are reviewed.

Carboxyboronate as a Versatile In Situ CO Surrogate in Palladium-Catalyzed Carbonylative Transformations

The application of carboxy-MIDA-boronate (MIDA=N-methyliminodiacetic acid) as an in situ CO surrogate for various palladium-catalyzed transformations is described. Carboxy-MIDA-boronate was previously shown to be a bench-stable boron-containing building block for the synthesis of borylated heterocycles. The present study demonstrates that, in addition to its utility as a precursor to heterocycle synthesis, carboxy-MIDA-boronate is an excellent in situ CO surrogate that is tolerant of reactive functionalities such as amines, alcohols, and carbon-based nucleophiles. Its wide functional-group compatibility is highlighted in the palladium-catalyzed aminocarbonylation, alkoxycarbonylation, carbonylative Sonogashira coupling, and carbonylative Suzuki-Miyaura coupling of aryl halides. A variety of amides, esters, (hetero)aromatic ynones, and bis(hetero)aryl ketones were synthesized in good-to-excellent yields in a one-pot fashion.

Palladium-catalyzed 1,2-amino carbonylation of 1,3-dienes with (N-SO2Py)-2-iodoanilines: 2,3-dihydroquinolin-4(1H)-ones synthesis

A palladium-catalyzed 1,2-amino carbonylation of 1,3-dienes with (N-SO₂Py)-2-iodoanilines has been developed for the construction of 2,3-dihydroquinolin-4(1H)-one scaffolds.

Synthesis of Polysubstituted Isoindolinones via Radical Cyclization of 1,3-Dicarbonyl Ugi-4CR Adducts Using Tetrabutylammonium Persulfate and TEMPO

The development of an efficient method for the synthesis of polysubstituted isoindolinones from 1,3-dicarbonyl Ugi-4CR adducts, employing an aromatic radical cyclization process promoted by tetrabutylammonium persulfate and 2,2,6,6-tetramethyl-1-piperidine 1-oxyl (TEMPO), is described. The protocol allowed the construction of a library of isoindolinones bearing a congested carbon in good to excellent yields under mild conditions and in short reaction times.

Palladium-catalyzed [2 + 2 + 1] annulation: access to chromone fused cyclopentanones with cyclopropenone as the CO source

A variety of chromone fused cyclopentanones are efficiently generated in good to high yields via palladium-catalyzed [2 + 2 + 1] annulation, in which cyclopropenone was utilized for the first time as the sole CO surrogate in the carbonylation process.

Palladium-catalyzed gaseous CO-free carbonylative C–C bond activation of cyclobutanones

A palladium-catalyzed carbonylative C–C bond activation reaction of cyclobutanones is reported, and it affords a variety of indanones bearing ester or amide groups using phenyl formate and benzene-1,3,5-triyl triformate as CO surrogates.

Cobalt-Catalyzed Direct C-H Carbonylative Synthesis of Free (NH)-Indolo[1,2-a]quinoxalin-6(5H)-ones

A cobalt-catalyzed direct C-H carbonylative reaction of N-(2-(1H-indol-1-yl)phenyl)picolinamides for the synthesis of (NH)-indolo[1,2-a]quinoxalin-6(5H)-one skeletons has been developed. Using benzene-1,3,5-triyl triformate (TFBen) as the CO source and picolinamide as the traceless directing group, various free (NH)-indolo[1,2-a]quinoxalin-6(5H)-ones were obtained in good yields (up to 88%). Additionally, a series of product derivatizations were demonstrated, and the core fragment of PARP-1 inhibitor C can be readily constructed by this protocol.

Synthesis of 3-Alkylideneisoindolin-1-ones via Sonogashira Cyclocarbonylative Reactions of 2-Ethynylbenzamides

Cyclocarbonylative Sonogashira reactions of ortho-ethynylbenzamides have been investigated. The process is carried out under CO pressure, in the presence of a very small amount of PdCl₂(PPh₃)₂ (0.4 mol %) as a catalytic precursor and without the need for a Cu salt as the co-catalyst. 2-Ethynylbenzamide reacted successfully with iodoarenes bearing electron-withdrawing and electron-donating groups, giving rise to different classes of compounds depending on the solvent used. On the contrary, N-(4-chlorophenyl)-2-ethynylbenzamide afforded exclusively polyfunctionalized isoindolinones with high stereoselectivity toward (E) isomers.

Synthesis of 3-Hydroxymethyl Isoindolinones via Cobalt-Catalyzed C(sp2)-H Carbonylation of Phenylglycinol Derivatives

An efficient method for the synthesis of 3-hydroxymethyl isoindolinones via cobalt-catalyzed C(sp²)-H carbonylation of phenylglycinol derivatives using picolinamide as a traceless directing group is demonstrated. The reaction proceeds in the presence of a commercially available cobalt(II) tetramethylheptanedionate catalyst and employs DIAD as a "CO" surrogate. This synthetic route offers a broad substrate scope, excellent regioselectivity, and full preservation of the original stereochemistry. Besides, the developed method provides a pathway for accessing valuable enantiopure 3-substituted isoindolinone derivatives.

Benzene-1,3,5-triyl Triformate (TFBen)-Promoted Palladium-Catalyzed Carbonylative Synthesis of 2-Oxo-2,5-dihydropyrroles from Propargyl Amines

In this letter, we developed a palladium-catalyzed procedure for the cyclocarbonylation of propargyl amines. Benzene-1,3,5-triyl triformate (TFBen) has been explored as the CO source and also as the key promotor. Various substituted 2-oxo-dihydropyrroles were produced in a facile manner in good yields (up to 90%).

Palladium-catalyzed double carbonylation of propargyl amines and aryl halides to access 1-aroyl-3-aryl-1,5-dihydro-2H-pyrrol-2-ones

A palladium-catalyzed carbonylative procedure for the synthesis of 1-aroyl-3-aryl-1,5-dihydro-2H-pyrrol-2-ones from propargyl amines and aryl halides with TFBen as the CO source has been developed.

Carbonylative synthesis of heterocycles involving diverse CO surrogates

Recent advances in the carbonylative synthesis of heterocycles by using diverse CO surrogates as sources of CO are summarized and discussed.

Palladium-catalyzed three-component carbonylative synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones from trifluoroacetimidoyl chlorides and amines

An efficient and practical approach for the synthesis of 2-(trifluoromethyl)quinazolin-4(3H)-ones through palladium-catalyzed three-component carbonylative reaction has been developed.

Access to 5H-benzo[a]carbazol-6-ols and benzo[6,7]cyclohepta[1,2-b]indol-6-ols via rhodium-catalyzed C–H activation/carbenoid insertion/aldol-type cyclization

The rhodium-catalyzed mono-ortho C–H activation/carbenoid insertion/aldol-type cyclization of 3-aldehyde-2-phenyl-1H-indoles with diazo compounds has been developed.

Cobalt-Catalyzed Direct Carbonylative Synthesis of Free (NH)-Benzo[cd]indol-2(1H)-ones from Naphthylamides

A cobalt-catalyzed C-H carbonylation of naphthylamides for the synthesis of benzo[cd]indol-2(1H)-one scaffolds has been developed. The reaction employs a traceless directing group and uses benzene-1,3,5-triyl triormate as the CO source, affording various free (NH)-benzo[cd]indol-2(1H)-ones in moderate to high yields (up to 88%). Using this protocol, the total synthesis of BET bromodomain inhibitors A and B was accomplished as well.

Chloroform as a CO surrogate: applications and recent developments

The carbonyl moiety is one of the indispensable sub-units in organic synthesis with significant applications in medicinal as well as materials chemistry. Hence the insertion of a carbonyl group via simple and highly efficient routes has been one of the most challenging tasks for organic chemists. Though the direct utilisation of CO gas in carbonylation is the fundamental procedure for the construction of carbonyl compounds, it has certain drawbacks due to its toxic and explosive nature. As a result, the need for cheap and efficient CO surrogates has gained much attention nowadays by which CO gas can be easily generated in situ or ex situ. In this review we discuss the advantages of chloroform as CO surrogate and have surveyed recent carbonylation reactions where chloroform has been used as CO source.

More than a CO source: palladium-catalyzed carbonylative synthesis of butenolides from propargyl alcohols and TFBen

Palladium-catalyzed direct carbonylation of propargyl alcohols for the synthesis of butenolides has been achieved.

Co(ii)/Cu(ii)-cocatalyzed oxidative C–H/N–H functionalization of benzamides with ketones: a facile route to isoindolin-1-ones

Co/Cu-cocatalyzed oxidative C–H/N–H annulation of amides with ketones is developed to synthesize isoindolin-1-ones.