Some aryl substituted spiro-bishexahydropyrimidones

Abstract

The methylphenylhexadienone (5), like phorone, condenses with urea to form a spiran. According to its structure (1) this spiran should exist in two stereoisomeric forms, and these have been isolated. The same two stereoisomers have been obtained from the condensation of the dimethyloxostyryltetrahydropyrimidine (2b) with urea. Compound (2b) and related compounds of its kind are readily formed by the thermal condensation of the trimethyloxotetrahydropyrimidine (3) with an aromatic aldehyde and so provide a general synthetic route to spirans (1). Compounds of type (2) dimerize in ethanolic hydrochloric acid by a Diels-Alder condensation. Four isomeric dimers of (2b) are described.