REGIOCHEMISTRY OF THE CYCLOADDITION OF NITRILIUM N-PHENYLIMIDES TO DIBENZALACETONE - A REINVESTIGATION

Reaction of benzonitrilium N-phenylimide 3a with dibenzalacetone 1 yie lded a mixture of the mono- and biscycloadducts 8a and 11a in a 1:1 ra tio. A similar reaction of 1 with ethoxycarbonylnitrilium N-phenylimid e 3b afforded a mixture of the cycloadducts 7b, 8b, and 12b in a 1:3:6 ratio, respectively. The structures of these products were establishe d by spectral analyses and chemical transformations. The results inval idate the previously reported structure 4a assigned for the biscycload duct isolated from the reaction of 3a with 1. (C) 1996 John Wiley & So ns, Inc.