Studies in the cycloproparene series:1 chemistry of the 1-trimethylsilyl-1H-cyclopropa[b]naphthalenyl anion

Desilylation of 1,1-bis(trimethylsilyl)-1H-cyclopropa[b]naphthalene 10 with tert-butoxide or hydroxide ion gives anion 9 as a highly reactive species. Formed with tert-butoxide 9 can be intercepted by iodomethane to give the 1-methyl-1-trimethylsilyl derivative 13. With hydroxide ion and water catalytic didesilylation regenerates cyclopropanaphthalene 6 quantitatively. Formation of 9 with hydroxide ion in the presence of benzophenone, fluoren-9-one or 4-(dimethylamino)benzaldehyde provides a simple and economic route to the methylidenecyclopropanaphthalenes 11, 17 and 18. With benzaldehyde and 4-fluorobenzophenone this revised protocol (to give 19 and 12, respectively) is effective only in the presence of 18-crown-6.