Conjugated nitrile ylides, cyclisation

The work of Sharp and his many co-workers at Edinburgh cannot be underestimated. In a more recent communication they have extended the scope of his cyclisation of diene-conjugated nitrile ylides to triene homologues <96CC2739>. Thus cyclisation of the triene 21 afforded the cyclopropa[c]isoquinoline 22, which on heating gave a mixture of 23 and 24. The isomeric triene 25 also gave 24 as the sole product (Scheme 4). In this instance the intermediate cyclopropane could not be isolated. 

It is rare that a year passes without a report on the cyclisation of triene-conjugated nitrile ylides from Sharp and co-workers, and this year is no exception. In this example. 

In earlier reports Sharp and co-workers have described the cyclisation of diene-conjugated nitrile ylides of the general type (3) (Scheme 1), where both A and B are benzene rings, to form benz[c,e]azepines <93JCS(p1)2961>. This work has now been extended to systems where A or B is a heteroaromatic ring, in particular furan, thiophene and pyridine <94JCS(pi)1193>. 

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