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.

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.

A Green Route to Benzyl Phenyl Sulfide from Thioanisole and Benzyl Alcohol over Dual Functional Ionic Liquids.

Benzyl phenyl sulfide is a kind of important chemicals with wide usage, which is mainly prepared through a nucleophilic reaction of thiophenol with benzyl chlorides or benzyl alcohols, suffering from inherent drawbacks, such as low efficiency, requirements for equivalent acid or base catalysts and formation of harmful byproducts and waste. Herein, we report a green route to access various benzyl phenyl sulfide derivatives in good to excellent yields under mild conditions via the reaction of thioanisoles with benzyl alcohols over ionic liquid 1-propylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([SO3 HPrMIm][OTf]). Mechanism investigation indicates that the synergic effect of cation and anion of [SO3 HPrMIm][OTf] activates thioanisoles and benzyl alcohols via hydrogen bonding, thus catalyzes the dehydration of benzyl alcohol to dibenzyl ether and the subsequent metathesis reaction between dibenzyl ether and benzyl phenyl sulfide, finally generating benzyl phenyl sulfide derivatives. This is a simple, highly efficient, and green approach to produce benzyl phenyl sulfide derivatives, which has promising application potentials.

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.

Magnetic COFs as satisfied support for lipase immobilization and recovery to effectively achieve the production of biodiesel by great maintenance of enzyme activity.

BACKGROUND: Production of biodiesel from renewable sources such as inedible vegetable oils by enzymatic catalysis has been a hotspot but remains a challenge on the efficient use of an enzyme. COFs (Covalent Organic Frameworks) with large surface area and porosity can be applied as ideal support to avoid aggregation of lipase and methanol. However, the naturally low density limits its application. In this work, we reported a facile synthesis of core-shell magnetic COF composite (Fe3O4@COF-OMe) to immobilize RML (Rhizomucor miehei lipase), to achieve its utilization in biodiesel production. RESULT: This strategy gives extrinsic magnetic property, and the magnetic COFs is much heavier and could disperse in water medium well, facilitating the attachment with the enzyme. The resultant biocomposite exhibited an excellent capacity of RML due to its high surface area and fast response to the external magnetic field, as well as good chemical stability. The core-shell magnetic COF-OMe structure not only achieved highly efficient immobilization and recovery processes but also maintained the activity of lipase to a great extent. RML@Fe3O4@COF-OMe performed well in practical applications, while free lipase did not. The biocomposite successfully achieved the production of biodiesel from Jatropha curcas Oil with a yield of about 70% in the optimized conditions. CONCLUSION: Magnetic COFs (Fe3O4@COF-OMe) for RML immobilization greatly improved catalytic performance in template reaction and biodiesel preparation. The magneticity makes it easily recovered and separated from the system. This first successful attempt of COFs-based immobilized enzyme broadened the prospect of biodiesel production by COFs with some inspiration.

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.

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.

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 lipase-catalyzed aldol reaction combination of in situ formed acetaldehyde.

A facile tandem route to α,ß-unsaturated aldehydes was developed by combining the two catalytic activities of the same enzyme in a one-pot strategy for the aldol reaction and in situ generation of acetaldehyde. Lipase from Mucor miehei was found to have conventional and promiscuous catalytic activities for the hydrolysis of vinyl acetate and aldol condensation with in situ formed acetaldehyde. The first reaction continuously provided material for the second reaction, which effectively reduced the volatilization loss, oxidation, and polymerization of acetaldehyde, as well as avoided a negative effect on the enzyme of excessive amounts of acetaldehyde. After optimizing the process, several substrates participated in the reaction and provided the target products in moderate to high yields using this single lipase-catalyzed one-pot biotransformation.

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%.

Catalyst-free and solvent-free Michael addition of 1,3-dicarbonyl compounds to nitroalkenes by a grinding method.

An environmentally benign, fast and convenient protocol has been developed for the Michael addition of 1,3-dicarbonyl compounds to ß-nitroalkenes in good to excellent yields by a grinding method under catalyst- and solvent-free conditions.

Ionic liquid-promoted ring-closure reactions between 1,4-dihydroxyanthraquinone and diamines.

The reaction of 1,4-Dihydroxyanthraquinone with diamines was carried out in the presence of CuCl(2), CuCl in the ionic liquid [Bmim]PF(6), [Bmim]BF(4) or [Bmim]Cl x CuCl.