Unusual products from an alkoxide ion and a 1-bromoalk-1-yne: evidence for a vinylidene carbene intermediate

Abstract

Sodium 2,2-dimethyl-1,3-dioxolan-4-methanolate (II) reacts with 1-bromohept-1-yne by hydrogen abstraction at C-3 giving n-butylvinylidenecarbene (VIII) which reacts with the alcohol corresponding to (II) to give unusual products (IV–VII) that can be explained by nucleophilic attack on the ambident zwitterion-carbene, by prototropic shifts, and by insertion into the C–H bond on the carbon atom bearing the hydroxy-group.