The N-N bond as a chiral axis: 3-Diacylaminoquinazolinones as chiral acylating agents

3-Diacylaminoquinazolinones 10 and 15 have high enough barriers to rotation around their N-N bonds to allow separation of each into diastereoisomers. Interconversion of diastereoisomers 10a and 10b occurs on heating in boiling toluene and thermodynamic parameters for this process have been measured, The barriers to rotation around the N-N bonds in analogous monoacylaminoquinazolinones are not sufficient to permit isolation of stereoisomers at room temperature unless the exocyclic nitrogen is additionally substituted e.g. by an alkyl group as in 28, X-Ray crystal structure determinations carried out on 10a, 10b, 15a and 28b confirm the presence of chiral axes, Reaction of both diastereoisomers 15a and 15b with 1-phenylethylamine takes place with exclusive reaction at the 1-acetoxypropionyl carbonyl group and with partial kinetic resolution: the preferred sense of enantioselectivity obtained is dominated by the N-N axis.