New Synthesis of Octahelicene Involving Non-Interconvertible<i>Dl</i>- Intermediates

Abstract

Abstract The photocyclodehydrogenation of dl 2-styrylhexahelicane (VI), prepared from 2-oethoxycarbonylhexahelicene, leads to dl octahelicane in 40% yield. This reaction scheme should open the way to the synthesis of optically active helicanes. The 60 MHz 1H-NMR spectra of 2-hydroxymethyl-and 2-bromomethylhexahelicene (Va and Vb) show diastereotopic protons : δAB=0.14 ppn (J=12 Hz) and 0.11 ppm (J=10 Hz) respectively (CDC13; 60 MHz).