Cyclopropenones Benzocyclopropenones

CO, then the alleged aryne adduct (390) could be formed via an adduct such as 401 and hence without the intervention of the aryne (4). Although such dienophilic reactivity has not been detected for benzocyclopropenones (33), even in the presence of several traditional dienes (146), it has been observed for cyclopropenone itself (but not for diphenylcyclopropenone) and for benzocyclopropene (402). The second step of the proposed sequence 400 to... 

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