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.