One-pot Synthesis of Fused Aromatics possessing Helical Chirality and Assignment of Absolute Configuration Assisted by Theoretical Circular Dichroism

Abstract

Helical aromatics possessing a diazapentaphene skeleton were synthesized via one step in good quantity by solvent-free condensation reaction of N, N'-diphenyl-p-phenylenediamine and various carboxylic acids in the presence of a Lewis acid. Microwave irradiation greatly facilitated the condensation to furnish a helical aromatic with a 100% diastereo- and a 50% enantioselectivity, when a chiral carboxylic acid was utilized. The aromatic derived from 2-methylglutaric acid was quite stable, with no racemization taking place even at 200 °C. The assignment of the absolute configurations to the helical aromatics has been achieved by theoretical CD spectra calculated by time-dependent density functional theory.