QUANTITATIVE-DETERMINATION OF CONFORMATIONAL EQUILIBRIA IN 3,7-DIAZABICYCLO[3.3.1]NONANE DERIVATIVES

A method of quantitative determination of a conformational equilibrium in 3,7-diazabicyclo[3.3.1]nonane (bispidine) derivatives is described . It is based on a comparison of coupling constants J(1-2 beta) and ot hers with the corresponding ones from the models of pure conformers. 3 -Benzyl-7-methyl-3,7-diazabicyclo[3.3.1] (4) proved to exist mainly in a double-chair (CC) conformer, although there is also a significant c ontribution of chair-boat (CB) and boat-chair (BC) conformers. In benz yl-7-methyl-3,7-diazabicyclo[3.3.1]nonan-9-one (5), a CB conformer pre dominates over significant amounts of BC and CC. (C) 1998 Elsevier Sci ence B.V.