Copper-Promoted Aerobic Oxidative [3+2] Cycloaddition Reactions of N,N-Disubstituted Hydrazines with Alkynoates: Access to Substituted Pyrazoles

A copper-promoted aerobic oxidative [3+2] cycloaddition reaction for the synthesis of various substituted pyrazoles from N,N-disubstituted hydrazines with alkynoates in the presence of bases is developed. This work involves a direct C(sp³)-H functionalization and the formation of new C-C/C-N bonds. In this strategy, inexpensive and easily available Cu₂O serves as the promoter and air acts as the green oxidant. The reaction exhibits the advantages of high atom and step economy, high regioselectivity, and easy operation.

Oxidative [3+2]-annulation of nitroalkenes and azolium ylides in the presence of Cu(II): efficient synthesis of [5,5]-annulated N-fused heterocycles

A facile synthesis of [5,5]-annulated N-fused heterocycles – pyrrolo[2,1-b]thiazoles and pyrrolo[1,2-b]indazoles via oxidative [3+2]-annulation between nitroalkenes and azolium ylides in the presence of copper (II) was developed. The reaction proceeds...

Copper-mediated oxidative [3 + 2]-annulation of nitroalkenes and pyridinium ylides: general access to functionalized indolizines and efficient synthesis of 1-fluoroindolizines

A general method for the synthesis of substituted indolizines by copper(ii) acetate-promoted oxidative [3 + 2]-annulation of α-fluoronitroalkenes with in situ generated pyridinium ylides was developed. Application of the copper(ii) acetate-2,6-lutidine system provides efficient access to various 1-fluoroindolizines in up to 81% yield. Both electron-rich and electron-deficient nitroalkenes as well as different pyridinium and isoquinolinium salts can be involved in the reaction. Moreover, it was found that copper-mediated annulation is applicable for other α-substituted (alkyl, chloro, and ester) nitroalkenes giving rise to the corresponding indolizines. First synthesis of monofluorinated [3,2,2]cyclazines was demonstrated via oxidative annulation of 3-unsubstituted fluoroindolizines with diethyl acetylene dicarboxylate.

External oxidant-free cross-coupling of arylcopper and alkynylcopper reagents leading to arylalkyne

External oxidant-free cross-coupling of arylcopper and alkynylcopper reagents for the formation of arylalkynes was performed.

Palladium-catalyzed oxidative carbonylative coupling of arylboronic acids with terminal alkynes to alkynones

The first example of palladium-catalyzed oxidative carbonylation of arylboronic acids with terminal alkynes has been developed. By an appropriate combination of a palladium salt, a ligand, and an oxidant, the desired alkynones were isolated in moderate to good yields.

Comparative Studies on Conventional and Ultrasound-Assisted Synthesis of Novel Homoallylic Alcohol Derivatives Linked to Sulfonyl Dibenzene Moiety in Aqueous Media

Novel homoallylic alcohols incorporating sulfone moieties were synthesized by the treatment of different carbonyl compounds with allylic bromides in aqueous mediaviasonochemical Barbier-type reaction conditions. Sulfonation ofα-bromoketones with sodium benzenesulfinate in presence of CuI/2,6-lutidine rapidly gaveβ-keto-sulfones in good yields. In general, ultrasound irradiation offered the advantages of high yields, short reaction times, and simplicity compared to the conventional methods. The structures of all the compounds were confirmed by analytical and spectral data.