Synthesis and chiroptical properties of bridged 2,2′-diaminobiphenyl derivatives

Abstract

The relationship between c.d. spectra and the conformation of chiral 2,2′-diaminobiphenyls was investigated as a function of the torsion angle between the benzene ring planes. The molecular structures of (S)-(+)-4,5,6,7,11,12,13,14-octahydro[1]benzazocino[7,6,5-efg][1]benzazocine (22), (S)-(–)-2,2′-diamino-6,6′-dimethylbiphenyl (25), and (S)-(–)-(6R,7R)-5,6,7,8-tetrahydro-1,6,7,12-tetramethyldibenzo[e,g][1,4]diazocine (27) were determined by X-ray analysis. The shape of the c.d. spectrum of (22)(trans-conformation) is similar to those of (25) and (27)(cis-conformation). The experimental results and theoretical consideration by the exciton approximation and the π-SCF-MO approximation indicated that the shape of the c.d. spectrum is the same at least for torsion angles of 0–120°. On the other hand, the shape of the c.d. spectrum of the protonated species was inverted with a critical torsion angle of ca. 90°.