Asymmetric Synthesis of Alkylzincs by Rhodium‐Catalyzed Enantioselective Arylative Cyclization of 1,6‐Enynes with Arylzincs

Abstract

A chiral diene-rhodium complex was found to catalyze the reaction of 1,6-enynes with ArZnCl to give high yields of 2-(alkylidene)cyclopentylmethylzincs with high enantioselectivity (95-99 % ee). The enantioenriched alkylzincs were readily converted in a one-pot approach into a wide variety of functionalized products by taking advantage of their unique reactivity. The catalytic cylcle involves arylrhodation of alkyne, intramolecular alkenylrhodation of alkene, and transmetalation of the alkyl-rhodium intermediate into alkylzinc.

Recent Advances in Cyclization Reactions of 1,6‐Enynes

“…In the same year, the Hayashi group described a protocol for the assembly of 2‐(alkylidene)cyclopentylmethylzincs employing 1,6‐enynes and arylzincs as the substrates, [RhCl( L 10 )] 2 as catalyst (Scheme 87). [68] The reaction proceeded smoothly through a two steps, the mixture was added firstly with CuCN•2LiCl and then with benzoyl chloride to furnish phenyl ketone with high enantioselectivity. In addition, the functionalization of alkylzincs were proceeded readily to give the corresponding products due to the unique reactivity of the enantioenriched alkylzincs.…”