Preparation of some heterocyclic enones and ynones by isomerisation of the propargylic alcohols

The propargylic alcohols were synthesised by treatment of aldehydes with substituted acetylenes. The conversion of propargylic alcohols to propynones and propenones takes place with pyridine hydrochloride in methanol at room temperature. In presence of pyridinium triflate and p-toluenesulfonate the propynone was the only product isolated in the isomerisation of alcohol. The silylated propenone undergoes with cyclopentadiene a Diels-Alder cycloaddition to give ketone whose skeleton is related to that of quinine.