Conformational composition of stereoisomers of 2,4,5-trisubstituted 1,3,2-dioxaborinanes

摘要

~1H NMR spectroscopy and MM+ and AM1 calculations were used for configurational assessment of steroisomers of 4-methyl-2,5-disubstituted 1,3,2-dioxaborinanes (differing in the configuration of the ring C~4 atom).The molecules are conformationally inhomogeneous; this is due to the internal rotation of the substituent at the C~5 atom, while in the cis isomers, in addition, by the equilibrium between the S-4e5a and S-4a5e sofa conformations, shifted to the latter form.