Abstract
The acid catalysed dienol-benzene rearrangement of methyl substituted o- and p-propargylcyclohexadienols (18-22, 34 and35) was investigated. In the first step water is eliminated to yield the corresponding methyl propargyl benzonium ions (cf. scheme 6, a), which undergo [1s,2s] sigmatropic rearrangements to give propargylbenzenes (28, 29, 30, 38) and [3s,4s] sigmatropic rearrangements to give allenylbenzenes (24-27, 40) (cf. schemes 2, 3, 5, 6). [3s, 3s] sigmatropic rearrangements occur only to a small extend. In the rearrangement of 2-propargyl-2,4,6- trimethylcyclohexa-3,5-dien-1-ol (18) a [1s,2s] sigmatropic methyl shift is observed (4%).
Heimgartner, Heinz