Unexpected stereoselective 6-exo versus 7-endo aryl radical cyclisation controlled by positional isomers in a chiral octahydro-1,3-benzoxazine moiety

Article abstract of DOI:10.1055/s-1997-1045

Chiral perhydro-1,3-benzoxazines which carry both olefinic and bromo-aromatic substituents undergo stereo- and regio- radical cyclisations mediated by Bu₃SnH. Diastereomeric six-membered and seven-membered rings are formed in positional isomers through selective 6-exo and 7-endo attack respectively.