Reactions of (CO)₅Cr=C(Me)N(CH₂CH₂)₂with enynes: Mechanistic insight and synthetic value of changing a carbene donor group from alkoxy to dialkylamino

Reactions of the title carbene complex (10) with 1,6-and 1,7-enynes are described and contrasted with the results of the 1-methoxyethylidene analogues. The more strongly electron-donating pyrrolidino substituent simultaneously provides considerable mechanistic insight and leads to a more generally useful synthetic tool for the preparation of bicyclic cyclopropanes.