1-(Alk-1-ynyl)cyclopropenes: synthesis by interaction of 1-(alk-1-ynyl)-1-halocyclopropanes with lithium N,N-dialkylamides and subsequent additions of the latter

A new synthetic approach to 1-(alk-1-ynyl)cyclopropenes 2 by the reaction of 1-(alk-1-ynyl)-1-chlorocyclopropanes 1 with lithium N,N-dialkylamides has been developed. Alkynylcyclopropenes 2, obtained by this method in situ or isolated in individual state can add dialkylamide anions across the double bond of the cyclopropene fragment to give hitherto unknown alkynyl-(dialkylamino)cyclopropanes 3, 4.