Indium(III) Chloride-Promoted Intramolecular Addition of Allylstannanes to Alkynes

Abstract
In the presence of an equimolar amount of InCl3, 8-tributylstannyl-6-octen-1-ynes (allylstannanes bearing an alkynyl group) were efficiently cyclized to 2-allyl-1-methylenecyclopentanes. In contrast, catalytic use of InCl3 gave 2-allyl-1-(tributylstannylmethylene)cyclopentanes mainly by intramolecular allylstannylation. These cyclizations could proceed via intramolecular addition of an allylindium intermediate.