Conformational analysis of saturated heterocycles. Part 78. Passing pyramidal nitrogen inversions in some perhydro-1,3-oxazines and -1,3-diazines

Abstract

Variable temperature proton n.m.r. studies allowed the direct observation of pyramidal nitrogen inversion hindered by an adjacent equatorial alkyl group in some 2-alkyl-3-methylperhydro-1,3-oxazines and 2-alkyl-1,3-dimethylperhydro-1,3-diazines. The axial–equatorial free energy differences for the N-methyl groups and the conformer populations have been measured.