Dehydration of some 9-methyl-9-hydroxybicyclo[3.3.1]nona-3,7-dien-2-ones

Abstract

Dehydration of 9-hydroxy-4,8,9-trimethylbicyclo[3.3.1]nona-3,7-dien-2-one (3) by toluene-p-sulphonic acid in benzene gives a trimethylbicyclo[4.3.0]nonatrienone (7) by rearrangement. Dehydration of 9-hydroxy-4,8,9-trimethyl-6-phenylbicyclo[3.3.1]nona-3,7-dien-2-one (4) similarly gives a bicyclo[4.3.0]nonatrienone (6) and also the nonrearranged 9-methylenebicyclo[3.3.1]nonadienone (5). The mechanism of rearrangement is discussed and contrasted with the behaviour in acid of other hydroxybicyclo[3.3.1]nonadienones.