Cycloaddition with bisketene

Oxidation of 215 with CAN produces naphthoquinone 216 which, in a single cycloaddition step with bisketenes generated photochemically from 1,2- benzocyclobutanediones 217, gives daunomycinone derivatives 218 [76]. 

The bis(acyl chloride) from adipic acid reacts with imines generated in situ from 2-aminobenzothiazole and aryl aldehydes in the presence of zeohtes as acid catalysts resulting in formation of bis(p-lactams) (Scheme 4.31). The reactions were found to be enhanced by the use of ultrasound, and while the reactions were presumably largely stepwise bisketenes can be formed under these conditions. The preparation of bis- and poly(p-lactams) by ketene cycloadditions has been reviewed. 

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