Stereoelectronic effects in the conformational behavior and ring formation of some N,N′-dimethyl- and N,N′-diacetyl- 1,5-dioxa-4,8-diazadecalins.
摘要:
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 H-1- and C-13-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 (DELTA-G(O) = 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.
Stereoelectronic effects in the conformational behavior and ring formation of some N,N′-dimethyl- and N,N′-diacetyl- 1,5-dioxa-4,8-diazadecalins.
作者:Benito Alcaide、Jesús Jimenez-Barbero、Joaquin Plumet、Ignacio M. Rodriguez-Campos
DOI:10.1016/s0040-4020(01)88531-8
日期:1992.3
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 H-1- and C-13-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 (DELTA-G(O) = 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.