Mechanism of photorearrangement of 6-hydroxybicyclo[3.3.1]nona-3,7-dien-2-ones

Abstract

The 6-hydroxybicyclo[3.3.1]nona-3,7-dien-2-ones (1) and (2) have been synthesised and irradiated. The alcohol (2) gave only isomeric 9-hydroxy-4,8,9-trimethyl-6-phenylbicyclo[3·3.1]nona-3,7-dien-2-one (6) by 1,3-rearrangement, but (1) gave, in addition to compound (7) formed by similar 1,3-rearrangement, products of dehydration and of further rearrangement. The origin of each product is established and the observed rearrangements are contrasted with the different rearrangements found with bicyclo[3·3.1]nona-3,7-diene-2,6-diones. The differences are rationalised.