A solution and solid state conformation of 2-diphenylphosphinoyl-1,3-dioxanes. The nature of O-C-P anomeric interactions.

Abstract

Diastereoisomeric 2-diphenylphosphinoyl-1,3-dioxanes 1–4 were synthesized either via the Arbuzov reaction of isopropyl diphenylphosphinite with (1,3-dioxan-2-yl) trimethylammonium iodides or via the transacetalization reaction between 1,3-diols and diphenyl (diethoxymethyl) phosphine oxide. The latter reaction afforded less thermodynamically stable isomers of 3 and 4 in a good yield (44 and 56%, respectively). The magnitude of the anomeric effect in this system determined according to the Franck's equation was found to be 19.7 kJ/mol. Both the NMR and X-ray structural data concerning cis-4,6-dimethyl-1,3-dioxane derivatives 4 suggest that the anomeric effect could stem from several interaction, including the n o-δ * C-P negative hyper-conjugation and intramolecular hydrogen bond formation.