Dialkyl magnesium compounds from (-)-menthyl chloride and reactions with 1,4-dioxane, TMEDA, and diphenylchlorophosphane

Abstract

1,4-Dioxane (dx) reacts with the well-known Grignard reagent, prepared via reduction of (-)-menthyl chloride with magnesium in diethyl ether, to a mixture of the three diastereomeric magnesium compounds R2Mg(dx)x, R'2Mg(dx)x and RR'Mg(dx)x (R = (1R)-menthyl and R' = (1S)-neomenthyl). Addition of N,N,N’,N’-tetramethylethylenediamine (TMEDA) to this solution yields (tmeda)Mg(R/R’)2 (R : R’ ≈ 3 : 1) (1) via substitution of ligated dx ligands. The reaction of (R/R’)2Mg(dx)x with diphenylchlorophosphane (molar ratio 1 : 1) in diethyl ether at a temperature regime of 0 °C to reflux and subsequent oxidation with elemental sulfur leads to formation of pure (-)-menthyldiphenylphosphane sulfide RPh2P(S) (2). Compounds 1 and 2 have been authenticated by X-ray crystal structures determinations.