Formation of an Isoquinoline in the Reaction of a Diazoketone with Boron Trifluoride

It has been reported through work in the field of diazo chemistry that normal reactions of diazo ketones with certain acids can result in some unusual products. In the normal type reaction substituted methyl ketones are the resulting products which occur as a result of the elimination of nitrogen. However, the presence of a nucleophilic center at the ortho position of an aromatic diazo ketone can override the normal replacement and result in a cyclization product with the elimination of nitrogen. In these reactions it was found that addition of excess neoleophile still did not form open-chain products. Both four-and five-membered rings have been formed by this method. The latter has been observed most often in work with o-substittued diazoacetophenones which lead directly to the formation of coumaranones. Catalytic amounts of acid converted o-methoxy-w-diazoacetophenone to coumaranone with the splitting off of methanol by solvolysis and the restoration of the proton to the system. This mechanism involved an oxonium ion intermediate