Preparation of indenes

Claim 1

A process for the synthesis of indene and substituted indenes by the catalytic cyclodehydration of a substrate substituted and unsubstituted 3-phenylpropionaldehydes and 3-phenylpropylketones, according to the equation: ##STR3## wherein no R group contains ethylenic or acetylenic unsaturation; wherein the R group attached to the carbonyl group is selected from H and hydrocarbyl and each of the remaining R groups is selected independently from hydrogen. halo, nitro. trihalomethyl, acyl, acyloxy, acylthio, lower alkyl secondary amino where each alkyl has 1-4 C atoms. and hydrocarbyl. hydrocarbyloxy and hydrocarbylthio having 1-10 C atoms; wherein hydrocarbyl ring(s) can be formed from one or more adjacent pairs of R groups on the benzene ring; and wherein one of the R groups attached to the benzylic carbon can form a hydrocarbyl ring with the R group attached to the ortho position, said cyclodehydration being effected by passing the starting material aldehyde or ketone in the vapor phase over a solid Lewis acid as catalyst.