1354049-89-0Relevant articles and documents
Lithium Borohydride for Achiral and Stereospecific Reductive Boronation at Phosphorus: Lack of Electronic Effects on Stereoselective Formation of Alkoxyphosphonium Salts
Al Sulaimi, Sulaiman S.,Rajendran, Kamalraj V.,Gilheany, Declan G.
, p. 5959 - 5965 (2015)
We report LiBH4 as a preferred, simple and effective reagent for reductive boronation of achiral and racemic chlorophosphonium salts (CPS) and for diastereomeric alkoxyphosphonium salts (DAPS), both of which are, in turn, easily generated from either the corresponding phosphane or, more conveniently, the phosphane oxide. Further, we have shown that the DAPS reduction/boronation could be achieved with complete stereocontrol to give scalemic phosphane-borane directly in excellent yield and enantiomeric excess (ee). This new methodology was employed to investigate the effects of aryl substitution on the outcome of dynamic kinetic resolution of arylmethylphenylphosphanes and phosphane oxides via DAPS. It was found that substitution at the ortho position strongly affects the degree of stereoselection. However, surprisingly, we confirmed that there was no variation of stereoselectivity seen with the electronic effect of substituents on the para position.
Dynamic Cross-Exchange in Halophosphonium Species: Direct Observation of Stereochemical Inversion in the Course of an SN2 Process
Nikitin, Kirill,Jennings, Elizabeth V.,Al Sulaimi, Sulaiman,Ortin, Yannick,Gilheany, Declan G.
supporting information, p. 1480 - 1484 (2018/02/06)
The complex fluxional interconversions between otherwise very similar phosphonium bromides and chlorides R3PX+X? (R=Alk, Ar, X=Cl or Br) were studied by NMR techniques. Their energy barriers are typically ca. 11 kcal mol?1, but rise rapidly as bulky groups are attached to phosphorus, revealing the importance of steric factors. In contrast, electronic effects, as measured by Hammett analysis, are modest (ρ 1.46) but still clearly indicate negative charge flow towards phosphorus in the transition state. Most significantly, detailed analysis of the exchange pathways unequivocally, and for the first time in any such process, shows that nucleophilic attack of the nucleophilic anion on the tetrahedral centre results in inversion of configuration.
Simple unprecedented conversion of phosphine oxides and sulfides to phosphine boranes using sodium borohydride
Rajendran, Kamalraj V.,Gilheany, Declan G.
supporting information; experimental part, p. 817 - 819 (2012/02/03)
A variety of phosphine oxides and sulfides can be efficiently converted directly to the corresponding phosphine boranes using oxalyl chloride followed by sodium borohydride. Optically active P-stereogenic phosphine oxides can be converted stereospecifically to phosphine boranes with inversion of configuration by treatment with Meerwein's salt followed by sodium borohydride.
Identification of a key intermediate in the asymmetric Appel process: One pot stereoselective synthesis of P-stereogenic phosphines and phosphine boranes from racemic phosphine oxides
Rajendran, Kamalraj V.,Gilheany, Declan G.
supporting information, p. 10040 - 10042 (2012/11/07)
Sequential treatment of racemic phosphine oxides with oxalyl chloride and chiral non-racemic alcohol generates the same ratios of diastereomeric alkoxyphosphonium salts obtained in the corresponding asymmetric Appel process, strongly implicating the intermediate chlorophosphonium salt in the stereoselecting step. Subsequent reduction allows a novel synthesis of enantioenriched P-stereogenic phosphines-phosphine boranes. The Royal Society of Chemistry 2012.
