Visible-Light-Induced C-H Cyanoalkylation of Azauracils with Cycloketone Oxime Esters via Catalytic EDA Complex.

Photoexcitation electron donor-acceptor (EDA) complexes provide an effective approach to produce radicals under mild conditions, while the catalytic version of EDA complex photoactivation remains scarce. Herein, we report a visible-light-induced organophotocatalytic pathway for the cyanoalkylation of azauracils using inexpensive and readily available 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalytic electron donor. This synthetic method exhibits exceptional compatibility with various functional groups and presents 34 examples in high yields. The efficient cyanoalkylation offers an environmentally friendly and sustainable route toward enhancing the structural and functional diversity of azauracils.

Lead-free Cs2AgBiBr6 double perovskite microcrystals for effective visible-light photocatalytic thio/selenocyanation.

Lead-free perovskite microcrystals (MCs) have been regarded as promising potential photocatalysts, owing to their high molar extinction coefficient, low economic cost, adjustable light absorption range, and ample surface-active sites. Herein, C-3 thio/selenocyanation of indoles is demonstrated in high selectivity and yield by using lead-free double perovskite Cs2AgBiBr6 MCs under visible light irradiation. Moreover, the photocatalyst can be recycled at least 5 times without a significant decrease in catalytic activity.

Neutral nickel-catalyzed dehydrosulfonylation of unactivated allylic alcohols under mild conditions.

Allyl sulfones are important sulfur-containing compounds that have widespread applications in organic synthesis, medicinal chemistry and materials science. Herein, nickel-catalysed dehydrosulfonylation of unactivated allyl alcohols with aryl sulfonyl hydrazides without additional active agents under mild conditions was developed. A variety of functional allyl sulfones could be efficiently synthesized in the presence of air-stable Ni(acac)2 as the catalyst and 1,1'-bis(diphenylphosphino)ferrocene (DPPF) as the ligand.

Visible-light-driven EDA complex-promoted cascade cyclization to construct 4-cyanoalkyl isoquinoline-1,3-diones.

Visible-light-induced EDA complex-promoted ring-opening of cycloketone oxime esters to synthesise various cyanoalkylated products with N-methacryloyl benzamides was developed. Various radical receptors were compatible with the current reaction system to furnish diverse heterocyclic compounds. Mechanistic analysis shows that the formation of an EDA complex was crucial to the photocatalytic strategy. Importantly, 4-cyanoalkyl isoquinoline-1,3-diones were obtained in high yields by using a catalytic amount of 1,4-diazabicyclo[2.2.2]octane (DABCO) through prolonging the reaction time, which provided a practical approach to give a variety of isoquinoline-1,3-dione derivatives.

Visible-light-induced decarboxylative cascade cyclization of acryloylbenzamides with N-hydroxyphthalimide esters via EDA complexes.

A visible-light-induced decarboxylative cascade reaction of acryloylbenzamides with alkyl N-hydroxyphthalimide (NHP) esters for the synthesis of various 4-alkyl isoquinolinediones mediated by triphenylphosphine (PPh3) and sodium iodide (NaI) was developed. This operationally simple protocol proceeded via the photoactivation of electron donor-acceptor (EDA) complexes between N-hydroxyphthalimide esters and NaI/PPh3, resulting in multiple carbon-carbon bond formations without the use of precious metal complexes or synthetically elaborate organic dyes, which provided an alternative practical approach to synthesize diverse isoquinoline-1,3(2H,4H)-dione derivatives.

Visible-light-enabled cascade cross-dehydrogenative-coupling/cyclization to construct α-chromone substituted α-amino acid derivatives.

Organophotocatalytic cascade cross-dehydrogenative-coupling/cyclization reaction of o-hydroxyarylenaminones with α-amino acid derivatives for the construction of α-chromone substituted α-amino acid derivatives was developed. Various N-arylglycine esters, amides and dipeptides underwent the cascade cyclization reaction well with o-hydroxyarylenaminones to afford the corresponding 3-aminoalkyl chromones in good to excellent yields. This approach consists of visible-light-promoted oxidation of α-amino acid derivatives, the Mannich reaction, and intramolecular nucleophilic cyclization under acidic conditions, and features a wide reaction scope, a simple operation and mild reaction conditions, which may have the potential to be used for the synthesis of bioactive molecules.

Nickel-catalyzed sulfonylative coupling of 2-chlorobenzothiazoles with sulfinates at room temperature.

An efficient nickel-catalyzed cross-coupling for the synthesis of 2-sulfonylthiazoles from readily available 2-chlorobenzothiazoles and sodium sulfinates has been developed. A variety of 2-chlorobenzothiazoles and sulfinates having a diverse range of substitution patterns can undergo the coupling process successfully at room temperature. Avoiding the use of precious catalysts and sensitive ligands, moderate to excellent yields of various 2-sulfonylthiazoles were observed.

Combining Enzyme and Photoredox Catalysis for the Construction of 3-Aminoalkyl Chromones.

Herein, we reported a practical and efficient strategy combining photoredox and enzyme catalysis for the construction of 3-aminoalkyl chromones from o-hydroxyaryl enaminones and N-arylglycine esters. A variety of 3-aminoalkyl chromones were synthesized with good yields under mild conditions in one pot. This synthetic protocol consists of sequential enzymatic hydrolysis and photoredox decarboxylation of N-arylglycine esters, oxidation of aminoalkyl radicals, Mannich reaction, and intramolecular nucleophilic cyclization, which affords a convenient pathway for the preparation of various 3-substituted chromones.

Copper-assisted preparation of pyridinyl sulfonate esters from hydroxypyridines and sodium sulfinates.

An efficient and powerful copper-assisted method for the effective conversion of a broad range of hydroxypyridines and sodium sulfinates into their corresponding pyridinyl tosylates was developed. Key features of this base- and ligand-free protocol include using the cheap and readily available CuBr2 as a medium and the use of sodium sulfinates as formal sulfonylation reagents. A variety of functional pyridinyl tosylates could be formed with good yields, which can easily be converted into C-C and C-N bond-containing compounds.

Visible-Light-Induced Dehydrogenative Imidoylation of Imidazo[1,2-a]pyridines with α-Amino Acid Derivatives and α-Amino Ketones.

A new and efficient visible-light-promoted dehydrogenative cross-coupling reaction of imidazo[1,2-a]pyridines with α-amino carbonyl compounds toward imidoyl imidazo[1,2-a]pyridines is developed. A diverse range of imidazo[1,2-a]pyridines undergoes the dehydrogenative imidoylation smoothly with α-amino carbonyl compounds to access the corresponding products in satisfactory yields. We have also proposed the possible reaction mechanism based on preliminary mechanistic studies. The synthetic method has the advantages of wide substrate scope, good functional tolerance, and mild reaction conditions, which make this transformation more practical and sustainable.

Efficient biocatalytic strategy for one-pot Biginelli reaction via enhanced specific effects of microwave in a circulating reactor.

A one-pot efficient biocatalytic strategy for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones was developed in a circulating microwave reactor selecting α-chymotrypsin as the promiscuous biocatalyst. In the circulating reaction system, the combination of microwave heating and external cooling could avoid the denaturation and inactivation of enzyme, and greatly improved the radiation power of microwave, thus improving the specific effects of microwave. During the reaction process, the microwave radiation power was automatically adjusted by adjusting the speed of the reaction mixture circulation. When the microwave power was maintained at 110 W, the best results could be obtained with the highest yield of 96% at 55 °C in 50 min, and the reaction had a wide range of substrates. But no obvious product was detected in a tank microwave reactor at 55 °C for 100 min, under this condition, the microwave power was maintained at about 3 W. As a contrast, the reaction only obtained 63% yield in 55 °C oil bath for 96 h.

Selective Synthesis of ortho-Substituted Diarylsulfones by Using NHC-Au Catalysts under Mild Conditions.

A single-step gold(I)-catalyzed chemoselective protocol to access ortho-substituted diarylsulfones has been established. Acenaphthoimidazolylidene gold complexes are effective catalysts for the arylsulfonylation of boronic acids by potassium metabisulfite (K2S2O5) and diaryliodonium salts to access (poly-) ortho-substituted diarylsulfones even in gram scale. Unlike the transition metal-catalyzed two-component coupling systems, the sterically hindered aryl groups in diaryliodonium salts are preferentially transferred over less bulky ones to form synthetically difficult targets, including those of pharmaceutical importance.

Cobalt-Catalyzed Oxidative Phosphonylation of α-Amino Acid Derivatives and α-Amino Ketones for α-Aminophosphonates.

A novel and efficient direct oxidative phosphonylation of α-amino ketones and α-amino acid derivatives with dialkyl phosphites by the catalysis of a cobalt salt under air is disclosed. A variety of α-amino ketones and α-amino acid derivatives underwent the reaction well with dialkyl phosphites to produce the desired α-aminophosphonates. This protocol not only provides an alternative synthetic route for the preparation of diverse α-aminophosphonates but also avoids the use of potentially explosive peroxide agents.

Synthesis, Characterization and Catalytic Application of Pyridine-Bridged N-Heterocyclic Carbene-Ruthenium Complexes in the Hydrogenation of Carbonates.

A series of bulky pyridine-bridged NHC-Ru complexes have been rationally designed and synthesized; these exhibited very high catalytic activity in the hydrogenation of cyclic and linear carbonates under mild reaction conditions. In the presence of catalytic amounts of a weak base, a broad range of substrates with different ring size and steric bulk were well tolerated, providing methanol and the corresponding diols in excellent yields with a catalyst loading as low as 0.5 mol %.

Ionic Liquid as an Efficient Medium for the Synthesis of Quinoline Derivatives via α-Chymotrypsin-Catalyzed Friedländer Condensation.

An efficient, convenient, and eco-friendly biocatalytic approach was developed for the synthesis of quinoline derivatives via the α-chymotrypsin-catalyzed Friedländer reaction. Interestingly, α-chymotrypsin exhibited higher catalytic activity in an ionic liquid (IL) aqueous solution as compared to that observed in our previous relevant study, which was conducted using an organic solvent, and a series of substrates gave similar excellent yields at lower reaction temperature and under reduced enzyme-loading conditions.

Copper-Catalyzed Aerobic Cascade Oxidative Coupling/Cyclization for the Construction of 1,4-Dihydropyridine Derivatives.

An efficient copper-catalyzed cascade cyclization reaction for the preparation of polysubstituted 1,4-dihydropyridines between N-arylglycine esters and 1,3-dicarbonyl compounds using molecular oxygen as the terminal oxidant has been described. Various N-arylglycine esters 1 and 1,3-dicarbonyl compounds 2 were able to undergo the cascade reaction smoothly to afford the desired products 3 in satisfactory yields. The cascade reaction has the advantages of good functional group tolerance and mild reaction conditions. A possible mechanism has also been proposed on the basis of control experiments.

Facile synthesis of bis(indolyl)methanes catalyzed by α-chymotrypsin.

A mild and efficient method catalyzed by α-chymotrypsin was developed for the synthesis of bis(indolyl)methanes through a cascade process between indole and aromatic aldehydes. In the ethanol aqueous solution, a green medium, a wide range of aromatic aldehydes could react with indole to afford the desired products with moderate to good yields (from 68% to 95%) using a little α-chymotrypsin as catalyst.

Trypsin-catalyzed tandem reaction: one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones by in situ formed acetaldehyde.

A simple, mild, one-pot tandem method catalyzed by trypsin was developed for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones by the Biginelli reaction of urea, ß-dicarbonyl compounds, and in situ-formed acetaldehyde. Trypsin was found to display dual promiscuous functions to catalyze transesterification and the Biginelli reaction in sequence.

The Henry reaction in [Bmim][PF6]-based microemulsions promoted by acylase.

An environmentally-friendly, enzyme-promoted procedure for the Henry reaction was first studied using water-in-[Bmim][PF6] microemulsions as reaction medium. The Amano acylase from Aspergillus oryzae showed better catalytic activity for the addition reactions of nitromethane with a series of aromatic aldehydes, and a highest yield of 90% was obtained.

One-pot synthesis of 2-phenylimidazo[1,2-α]pyridines from acetophenone, [Bmim]Br(3) and 2-aminopyridine under solvent-free conditions.

One-pot synthesis of 2-phenylimidazo[1,2-α]pyridines from acetophenone, [Bmim]Br(3) and 2-aminopyridine under solvent-free conditions in the presence of Na(2)CO(3), gave the corresponding 2-phenylimidazo[1,2-α]pyridines in excellent yields ranging from 72% to 89%.