Effect of the position of the asymmetric center on the chiral-optical properties of seven-membered benzolactams

Abstract

The synthesis and chiral-optical properties of (+) -3-methyl- and (+) -4-methyl-2,3,4,5-tetrahydro-1H-benz [c] azepin-1-ones are described. A weak Cotton effect (CE) at 270 nm and a more intense positive CE are observed for both compounds in the 250 nm region. The considerably lower CE at 250 nm in the case of the 4-methyl isomer as compared with the 3-methyl isomer is explained by the remoteness of the asymmetric center in the 4-methyl isomer from the conjugated benzamide chromophore and the absence of the preferred conformation, which determines the sign of the CE.