85186-00-1Relevant academic research and scientific papers
Optically Active Phosphines. Facile Preparation of the Optically Active n-Propylmethylbenzyl- and Methylphenylbenzylphosphine Oxides as Precursors to the Corresponding Tertiary Phosphines
Moriyama, Masaru,Bentrude, Wesley G.
, p. 4727 - 4733 (2007/10/02)
The optically active phosphine oxides MePhP(O)CH2Ph (6) and n-PrMeP(O)CH2Ph (9) are readily prepared by a new route from the easily available, essentially optically pure, O-isopropyl S-alkyl methylphosphonothioates 4 and 7.Two successive Grignard reactions give 6 in 52-55percent and 9 in 18-24percent overall chemical yields.Reductions of 6 and 9 with PhSiH3 afford the corresponding optically active phosphines MePhCH2Ph (1) and n-PrMePCH2Ph (2) of optical purities (45-70percent and 53-57percent, respectively) which are quite suitable for studies of the stereochemistries of reactions occurring at phosphorus.The relative ease of the procedure and the fact that both enantiomers are equally readily available especially recommend this route for the preperation of 1.Moreover, no other experimentally detailed, published method for the preparation of an optically active trialkylphosphine such as 2 in reasonably high optical purity is available.The route to phosphine 1 depends on the use of potentially tridentate ligand (SCH2CH2OCH2CH2OCH2CH3) on phosphorus which activates 4 toward reaction with PhMgBr and also allows CH3CH2OCH2CH2OCH2CH2 to be selectively displaced.Quite surprisingly, this displacement occurs with inversion of configuration at phosphorus by contrast to the retentive stereochemistry normally observed on reaction of O-alkyl S-alkyl methylphosphonothioates with Grignards.Evidence is also presented for the potential generality of this method for the preparation of optically active dialkylphenyl- and trialkylphosphines.
REACTIONS OF ETHOXY RADICALS WITH OPTICALLY ACTIVE TERTIARY PHOSPHINES. STEREOCHEMISTRY OF THE SUBSTITUTION PROCESS AND THE QUESTION OF PERMUTATION MODES FOR THE POSSIBLE PHOSPHORANYL RADICAL INTERMEDIATES.
Bentrude,Moriyama,Mueller,Sopchik
, p. 6053 - 6061 (2007/10/02)
The reactions were shown to yield substitution products MePhPOEt and n-PrMePOEt, respectively. Both reactions occur with net inversion of configuration at phosphorus. Optical yields are very sensitive to reaction times and conversions, because the product phosphonites are readily racemized by EtOH formed during reaction. If indeed these substitutions take place via phosphoranyl radicals, then the stereochemistry for reaction of (-)(S)-2 is consistent with the pi * electronic configuration and presumed tetrahedral geometry normally assigned to phenyl-substituted phosphoranyl radicals. Potential trigonal-bipyramidal intermediates are considered with the assumption that the EtO multiplied by (times) in initial adducts is apical and that the PhCH//2 departs exclusively from the apical position.
A CONVENIENT PREPARATION OF AN OPTICALLY ACTIVE TRIALKYLPHOSPHINE, (+)-(S)-n-PROPYLMETHYLBENZYLPHOSPHINE, FROM (-)-(S)-S METHYL O-ISOPROPYL METHYLPHOSPHONOTHIOATE
Moriyama, Masaru,Bentrude, Wesley G.
, p. 4547 - 4550 (2007/10/02)
Details are presented for the first convenient, reasonable-yield preparation of a chiral trialkylphosphine.The material is of optical purity suitable for stereochemical studies involving the phosphorus atom.
