Influence of quaternization or coordination of nitrogen with a Lewis acid upon the diastereoselectivity of 5-exo ring closure of β-aminoalkyl radicals

Article abstract of DOI:10.1016/S0040-4020(98)00772-8

Two methodologies, likely to enhance the diastereoselectivity of sulfonyl radical mediated cyclization of dienes 8 and 11, were investigated. Quatemization provided the expected result whatever the nature of the radical accepting double bond, so did complexation of 11 with BF₃ or AlMe₃. A more strongly coordinating reagent like BH₃ was necessary to improve selectivity in the case of 8.