RESUMO
The atropisomeric enantiomers of 7-, 8-, and 9-membered-ring dibenzolactams were separated by using chiral HPLC, and their stereochemistries were clarified by using X-ray crystallographic analysis. The atropisomers showed high stereochemical stability with the 8-membered ring being the most stable. In 7- and 8-membered dibenzolactams, highly stereoselective C7-methylation proceeded from the lower side of the ring to provide the products with a C7-methyl group in the pseudoaxial orientation, which converted to thermodynamically more stable isomers with the pseudoequatorial C7-methyl group. In 9-membered dibenzolactam, C7-methylation occurred from the opposite (upper) side of the ring to provide a thermodynamically stable product with the pseudoequatorial C7-methyl group.
Assuntos
Lactamas/química , Temperatura , Cromatografia Líquida de Alta Pressão , Cristalografia por Raios X , Lactamas/síntese química , Lactamas/isolamento & purificação , Modelos Moleculares , Conformação Molecular , Estereoisomerismo , TermodinâmicaRESUMO
Dibenzo[b,d]azepin-6-ones (2a,b) were separated by chiral HPLC into the aR- and aS-atropisomers with high stereochemical stability, and methylation at C7 of 2a stereoselectively gave the (aR*,7R*) isomer (4a), which converted to the thermodynamically stable (aS*,7R*) atropisomer (5a) after heating.