CYCLOHEPTATRIENYLIDENE

Attempts have been made to generate cycloheptatrienylidene by thermal and photolytic decomposition of the sodium salt of tropone tosylhydrazone, by the reaction of ethyl N-nitroso-N-cycloheptatrienylcarbamate with base, by α-elimination from the dimethyl carbamate, and by decarboxylation of carboxycycloheptatrienyl fluoroborate. Of these four methods, only the first two gave results consistent with formation of the carbene and the first, thermal and photolytic decomposition of the tosylhydrazone salt was by far the superior. In the absence of acceptor and in the presence of nucleophilic alkenes, the primary reaction product was the formal dimer cycloheptatrienylidene. In the presence of dimethyl fumarate, fumaronitrile, and maleonitrile, the primary product was found to be the spirononatriene that would result from addition of cycloheptatrienylidene to the double bond. Reaction in the presence of a variety of other potential acceptors failed to give adducts. All three of the isolated spirononatrienes undergo rapid acid-induced ring opening to give heptafulvenes. They are also thermally unstable, rearranging at about 150° to give substituted indanes. © 1969, American Chemical Society. All rights reserved.