Effect of boron trifluoride–diethyl ether (BF3·OEt2) in the Diels–Alder reaction of quinoline- and isoquinoline-5,8-dione with unsymmetrical aliphatic dienes: theoretical study on the orientation of cycloadditions
Abstract
The Diels–Alder reaction of quinoline- and isoquinoline-5,8-dione with piperylene or isoprene gave regioisomers of the substituted azaanthraquinones, while the Lewis acid catalyst boron trifluoride–diethyl ether showed a drastic effect on regioselectivity in the reactions with piperylene. The Frontier Molecular Orbital (FMO) theory (calculated by CNDO/2 method) was applied to explain the orientation of the catalysed regioselective cycloadditions, by considering secondary orbital interactions.