The chemistry of ketenes has been receiving increasing attention,'" but the way in which substituents affect the stability and reactivity of ketenes is not well understood. Conjugating substituents are of particular interest, 3a and reports3 of the first preparations of alkynylketene~~~ have recently appeared, although these species were not directly observed. There has been continued study of alkenyl-, 1cg2b* 4 cyano-, s and ...
