Synthetic and stereochemical studies of the octahydro-1-benzopyran system

Abstract

The cis and trans isomers of the octahydro-1-benzopyran system have been synthesised and their conformations studied by low-temperature ¹³C and highfield ¹H n.m.r. spectroscopy. The position of the conformational equilibrium in the cis isomer at –70 °C in CDCl₃–CFCl₃(50 : 50) has been determined as approximately 99.5 : 0.5 (ΔG⁰–8.9 kJ mol^–1) in favour of the conformation having the oxygen axially disposed towards the cyclohexane ring.