A study of the electronic effects of various substituents on the course of an aromatic cyclodehydration reaction vs. a Elbs-type reaction

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Virginia Tech


The acld-oata17zed oyclodehydrat1on reaction of 2-benzylphenyl l-naphthyl ketone gives two products! 9-(1-naphthyl)anthracene, the expected product and in addition lO-phenyl-l,2-benzanthracene. This second product is the one expected it the ketone were subjected to the conditions of an .Elba reaction.

The effect of substituents on the course of this reaction was investigated by synthesizing six 2-benzylphenyl 1- and 2-naphthyl ketones and subjecting each of them to the acid catalyzed reaction and to Elba reaction conditions. Of the six ketones, two had unsubstituted benzyl groups, two had 3'-methyl groups in the benzyl group and the remaining two had ,'-tr1fluoromethyl groups. The original finding was confirmed and the other ketones that cyoilzed by either treatment gave the expected products. When 2-(3'-methylbenzyl) 2-naphthl1 ketone was subjected to Elbs reaction conditions, 9-(2-naphthyl)anthraoene, the product of aromatic oyclodehydrat1on, was obtained.

An explanation oft the unusual experimental results is suggested. The results of treat1ng the ketones w1th alumina and w1th l1qu1d hydrogen fluoride are reported.