Synthesis of Acrylonitriles via Mild Base Promoted Tandem Nucleophilic Substitution-Isomerization of α-Cyanohydrin Methanesulfonates

We have developed an efficient synthesis of acrylonitriles via mild base promoted tandem nucleophilic substitution-isomerization of α-cyanohydrin methanesulfona...     

Cyclopropanation of Diazoacetate with Olefins

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Tandem Cyclization of β-Dicarbonyl Enolphosphates by Electrochemical Reduction

A series of β-dicarbonyl enol phosphates bearing unsaturated moieties has been electrochemically reduced to give synthetically useful yields of polycyclic esters.     

Photoinduced α-Alkylation of Tetrahydroisoquinolines with Organoboron Reagent Enabled by Organic Photocatalyst

We describe an efficient method for α-functionalization of N-aryl-tetrahydroisoquinolines under visible-light-irradiation catalyzed by organic photocatalyst. This protocol provides a concise and environmental approach for the rapid allylation and benzylation of N-aryl-tetrahydroisoquinolines, and shows broad substrate scope. Stable organoboron reagents have shown their ability in the construction of challenging Csp³−Csp³ bond. The load of the photocatalyst is low and the oxidant is inexpensive and less toxic.     

Simple and Mild One-Pot Synthesis of Dipeptidyl Ureas via Carbamoyl Azides of α-N-Protected Amino Acids

A simple and mild one-pot synthesis of potentially bioactive α-N-protected dipeptidyl ureas is reported. The procedure involves the reaction between the carbamoyl azide of an α-N-protected amino acid and an α-amino acid methyl ester. The reaction is fast (3 h at 45 °C), regardless of the nature of both the reagents, and racemization free. The reported protocol represents a valid alternative to existing methods.

An Efficient Method for α-Alkylation of γ-Butyrolactone

Alkylated lactone is a common structure and segment in many natural products and medicines. The examples of alkylating lactone system at -position, obtained by reaction with alkyl halide such as MeI, in the presence of strong base LDA or it抯 derivatives, are very few1a, 1b. When this method was applied to the aromatic compound, the self-condensation of g-butyrolactone could not be avoided. In our previous work we have reported the hydrogenation of ? -unsaturated carbonyl compounds by cat…     

Nickel-Catalyzed α-Allylation of Aldehydes and Tandem Aldol Condensation/Allylation Reaction with Allylic Alcohols

An additive-free nickel-catalyzed α-allylation of aldehydes with allyl alcohol is reported. The reaction is promoted by 1 mol % of in situ formed nickel complex in methanol, and water is the sole by-product of the reaction. The experimental conditions allow the conversion of various α-branched aldehydes and α,β-unsaturated aldehydes as nucleophiles. The same catalyst and reaction conditions enabled a tandem aldol condensation of aldehyde/α-allylation reaction.     

Direct Aroylation of Olefins through a Cobalt/Photoredox-Catalyzed Decarboxylative and Dehydrogenative Coupling with α-Oxo Acids

A photoredox/cobalt dual catalytic procedure has been developed that allows benzoylation of olefins. Here the photoredox catalyst effects the decarboxylation of α-ketoacids to form benzoyl radicals. After addition of this radical to styrenes, the cobalt catalyst abstracts a H-atom. Hydrogen evolution from the putative cobalt hydride intermediate allows a Heck-like aroylation without the need for a stoichiometric oxidant. Mechanistic studies reveal that electronically different styrenes lead to a curved Hammett plot, thus suggesting a change in product-determining step in the catalytic mechanism.     

Cyclometalated Ruthenium Pincer Complexes as Catalysts for the α-Alkylation of Ketones with Alcohols

Ruthenium PNP pincer complexes bearing supplementary cyclometalated C,N-bound ligands have been prepared and fully characterized for the first time. By replacing CO and H⁻ as ancillary ligands in such complexes, additional electronic and steric modifications of this topical class of catalysts are possible. The advantages of the new catalysts are demonstrated in the general α-alkylation of ketones with alcohols following a hydrogen autotransfer protocol. Herein, various aliphatic and benzylic alcohols were applied as green alkylating agents for ketones bearing aromatic, heteroaromatic or aliphatic substituents as well as cyclic ones. Mechanistic investigations revealed that during catalysis, Ru carboxylate complexes are predominantly formed whereas neither the PNP nor the CN ligand are released from the catalyst in significant amounts.     

Mild Deprotection of tert‐Butyl Carbamates of NH‐Heteroarenes under Basic Conditions

Aqueous methanolic potassium carbonate under reflux has been demonstrated to be a highly effective deprotective agent for the tert‐butyl carbamates of indoles, indazoles, carbazole, thiazoloindole, and pyrrole. The method is a mild one and is particularly expeditious for NH‐heteroarenes bearing electron‐withdrawing groups.     

Cyclization of the methyl ester of α-propionyllevulinic acid

Summary Cyclization of methyl -propionyllevulinate to 2,3-dimethylcyclopenten-2-one and methyl 3,4-dimethylcyclopenten-3-one-2-carboxylate was accomplished.     

Mild hydrolytic cleavage of α-ferrocenylalkyl-O-methyl ethers

The conversion of α-ferrocenylalkyl-O-methyl ethers into the corresponding alcohols was successfully achieved by solvolysis in water/acetone mixtures. The content of water in the solvent markedly influenced the reaction rates. The reactivity of structurally different classes of ferrocenyl ethers was evaluated and in most cases high yields of ferrocenyl alcohols or diols were obtained in a few hours without any additive. Deprotection of less reactive substrates was accelerated in the presence of montmorillonite. The method is simple, environmentally benign and valuable in providing easy access to a variety of ferrocenyl derivatives through the use of the –O-methyl ether protective group.     

Cyclization Reaction of α-Triazolyl-α, β-unsaturated Ketones with Phenyl hydrazine

InourpreviousworkwehavereportedthestudiesonthereactionofvinyItriazolcderivativeswithhydroxylamine,andfOundthatcycloadditiontookp1aceandthenewheterocycliccompoundsl,2-oxazocyclopentaneshavingplant-growthregulatingactivitywereobtainedl,2.InordertosynthesizenewheterocycliccompoundsandtosearchfOrnewcompoundshavingbioactivity,thereactionofa-triazolyl-a,ll-unsaturatedketones(Z)-or(E)-4,4-dimethyl-1-aryl-2-(l,2,4-triazol-l-yl)-l-penten-3-onesI.-bwithphenylhydrazinewasstudied.Theresultshowedthatcycl…     

Enantioselective Synthesis of (+)-Mitomycin K by a Palladium-Catalyzed Oxidative Tandem Cyclization

The mitomycins, a family of bioactive natural products, feature a compact 6/5/5-fused polycyclic ring structure densely decorated with highly reactive and/or fragile quinone, amino ketal, and aziridine as well as carbamate moieties. It is this striking feature that has defeated numerous synthetic attempts towards these apparently small molecules, rendering them one of the most formidable targets for total synthesis. We herein report the first enantioselective synthesis of (+)-mitomycin K, a representative of G series mitomycins. The key step of this synthesis is an enantioselective oxidative cyclization catalyzed by a palladium/(+)-sparteine system that had previously been developed by our group. The robustness of this method bodes well for further applications in the asymmetric total synthesis of natural products, particularly those with characteristic 6/5/5-fused pyrroloindole skeletons.     

Reaction of α-Halo-Enones with Heterocyclic Bases. A Mild and Efficient Synthesis of Amino-Steroids

A number of steroids containing cyclic amino functions have been prepared and studied for biological activities, and some of them have proved to be clinically useful as a neuromuscular blocking agent, an antitumour agent, and so on.¹ As the conventional methods, the reactions of cyclic amines with halides² or epoxides,³ the reductive amination of ketones,⁴ and the reduction of enamines⁵ have been widely used for introducing these amino functions into steroid nucleus.     

α-Alkylation of β-aminobutanoates with lk-1.2-induction

Dilithiated methyl- or ethyl-N-benzoyl-3-aminobutanoates are alkylated or added to benzaldehyde to give products of l- and u,u-configuration respectivly. Several methods are presented by which enantiomerically pure 3-aminobutanoic acid derivatives can be prepared.     

Photoactive Chiral Metal-Organic Frameworks for Light-Driven Asymmetric α-Alkylation of Aldehydes

Chiral metal-organic frameworks (MOFs) with porous and tunable nature show promise as heterogeneous asymmetric catalysts. Through incorporating the stereoselective organocatalyst l- or d-pyrrolidin-2-ylimidazole (PYI) and a triphenylamine photoredox group into a single framework, we have developed two enantiomeric MOFs, Zn-PYI1 and Zn-PYI2, to prompt the asymmetric α-alkylation of aliphatic aldehydes in a heterogeneous manner. The strong reductive excited state of the triphenylamaine moiety within these MOFs initiated a photoinduced electron transfer, rendering an active intermediate for the α-alkylation. The chiral PYI moieties acted as cooperative organocatalytic active sites to drive the asymmetric catalysis with significant stereoselectivity. Control experiments using the lanthanide-based metal-organic frameworks Ho-TCA and MOF-150, assembled from 4,4',4″-nitrilotribenzoic acid, as catalysts suggested that both the photosensitizer triphenylamine moiety and the chiral organocatalyst d-/l-PYI moiety were necessary for the light-driven α-alkylation reactions. Further investigations demonstrated that the integration of both photocatalyst and asymmetric organocatalyst into a single MOF makes the enantioselection superior to that of simply mixing the corresponding MOFs with the chiral adduct. The easy availability, excellent stereoselectivity, great separability, and individual components fixed with their well-defined porous and repeating structures make the MOF a versatile platform for a new type of tandem catalyst and cooperative catalyst.     

Tandem Reduction-Desulfonylation of α-Alkylidene-β-Keto Sulfones

α-Alkylidene-β-keto sulfones take place both reduction of carbon-carbon double bond and desulfonylation with the use of sodium hydrogen telluride in ethanol-N, N-dimethylformamide.     

Decarboxylative Cyclization of Allylic Cyclic Carbamates: Mechanism Studies and Applications to the Synthesis of Natural Products

The mechanism of decarboxylative cyclization of allylic cyclic carbamates 1 leading to 2-substituted △~3-piperidines and-pyrrolidines, as well as its applications to the total synthesis of (--)codonopsine, are described.     

Mild Regioselective Catalytic Hydrogenation of α,β-Unsaturated Carbonyl Compounds with Lindlar Catalyst

The hydrogen-Lindlar catalyst system is effective for the highly regioselective reduction of α,β-unsaturated carbonyl compounds to the corresponding α,β-saturated compounds.