Rh(I)-catalyzed nucleophilic addition of alkenylzirconocene chloride

Abstract

Alkenylzirconocene chlorides are readily available complexes through the hydrozirconation of alkynes with Schwartz reagent (Cp₂ZrHCl). We found that Rh(I)-catalyzed various addition reactions of the alkenylzirconocene chlorides proceeded efficiently to give alkenyl adducts. Thus, the 1,2-addition of alkenylzirconocene chlorides to aldehydes and imines and conjugate 1,4-addition to α,β-unsaturated ketones, esters and amides were brought about by the use of [RhCl(cod)]₂. A high diastereoselectivity (95% yield, 90% de) was obtained through the reaction of α,β-unsaturated amide derived from Oppolzer's sultam and 2-butenoyl chloride. Furthermore, alkenylzirconocene chlorides reacted with ω-alkynyl aldehyde in the presence of the Rh(I) catalyst to give a cyclization product, cyclopentanol.