Conformation of sterically hindered 4-methyl-2-oxo-2-trityl-1,3,2- dioxaphosphorinane in the solid state and the solution

Abstract

The cis- and trans-2-methyl-2-oxo-2-trityl-1,3,2-dioxaphosphorinanes were obtained in the Arbuzov reaction of 2-methoxy-4-methyl-1,3,2-dioxaphosphorinane with trityl chloride. The NMR spectra (1H, 13C and 31P) in solution indicated that trans isomer exists in the form of two noncongruent molecules and it adopts two different conformations: a halfchair and a sofa, while the cis isomer exists as the mixed half/chair-sofa conformer. The compounds crystallise as a pure chiral forms and as a racemates. The solid state structural studies show that NMR data are consistent with the single crystal X-ray analysis, but the conformation existing in the crystal structure is more complex than it can be supposed on sole NMR determination. Crystal data: cis-isomer chiral form: space group P32, a = 8.782, b = 8.782, c = 21.680, α = 90.00, β = 90.00, γ = 120.00, V = 1448.0; cis-isomer racemate: space group Pca21, a = 16.773, b = 8.491, c = 27.006, α = 90.00, β = 90.00, γ = 90.00, V = 3846.2; trans-isomer racemate: space group Cc, a = 16.133, b = 8.388, c = 16.158, α = 90.00, β = 117.20, γ = 90.00, V = 1944.8; trans-isomer chiral form: space group P 1, a = 8.397, b = 9.003, c = 14.944, α = 80.76, β = 74.38, γ = 63.31, V = 971.1). © 2011 The Author(s).