Stereoelectronic Effects in the Conformational Behavior and Ring Formation of some N,N'-Dimethyl- and N,N'-Diacetyl-1,5-Dioxa-4,8-diazadecalins.

Article abstract of DOI:10.1016/S0040-4020(01)88531-8

A series of 4,8-dimethyl- and 4,8-diacetyl-cis-octahydro-<1,4>oxazino<3,2-b>-1,4-oxazines (title compounds) 4 and 7 respectively, were synthesized and studied using 1H- and 13C-NMR techniques.Conformational analysis of 4 showed a strong preference for conformers possessing an anti-N/gauche-O array vs an anti-O/gauche-N relationship (ΔG⁰ = 0.88 Kcal/mol).However 7b exists exclusively as an anti-O/gauche-N conformer with a free energy of activation for the amide rotation barrier of 11.6 Kcal/mol (248 K).The stereoelectronic features of the C-N-C-O-C moieties of 4 and 7 are emphasized.A general reaction pathway is also discussed.