Cycloheptatrienyl Oxyallyl. An Observable Oxyallyl?

Density functional calculations have been carried out for cycloproylidene-, cyclopentylidene-, and tropyllideneallene oxides (7−9) and the reaction pathway for their conversion to the corresponding oxyallyls (10−12) and cyclopropanones (13−15) in order to probe the electronic structure of the intermediate oxyallyls. All three oxyallyls were found to be stabilized with respect to their allene oxides in comparison to the unsubstituted allene oxide and oxyallyl. For 7 and 9 the stabilization can be attributed to the zwitterionic character of the oxyallyls, while for 8 the stabilization can be attributed to its diradical character. This suggests that oxyallyl is capable of "adapting" to its local environment. Calculations predict that oxyallyl 12 should be an observable intermediate in the absence of nucleophiles, since it is calculated to be of lower energy than either the allene oxide 9 or the cyclopropanone 15.