Tetrahydropyrimidin-2(1H)-ones with three neighbouring phenyl groups. Synthesis and allylic strain effects

Abstract

Favouredconformations of differently N-substituted cis,trans-4,5,6-triphenyltetrahydropyrimidin-2(1H)-ones and the allylic strain caused by different groups were studied. It was found that the diequatorial conformer is strongly preferred in equally N,N'-disubstituted products, where the effects of the two substituents negate each other. It was shown that a benzyl group gives rise to much stronger allylic strain than a methyl group. Additionally, unusual azetidine formation was observed upon acid hydrolysis of benzylideneamino azide via S N 2 mechanism. It was suggested that N-substitution does not significantly influence the ring geometry angle, while quaternisation affords serious increase of puckering.

Novel Syntheses of Azetidines and Azetidinones

“…Very recently, the method has been applied to the synthesis of a variety of enantiomerically pure azetidines with yields ranging from 44 to 80% . Only one example of a cyclic sulfate is recorded, as well as diphenylsulfonium and azide as leaving groups.…”

Methods for the Synthesis of Substituted Azetines

“…Subsequent amine deprotection ultimately led to free azetidines 12a , b in quantitative yields. It is worth noting that this represents a powerful approach to syn -azetidines, as most reports relate the formation of anti -azetidines …”