Dynamic Cross-Exchange in Halophosphonium Species: Direct Observation of Stereochemical Inversion in the Course of an S<sub>N</sub>2 Process
作者:Kirill Nikitin、Elizabeth V. Jennings、Sulaiman Al Sulaimi、Yannick Ortin、Declan G. Gilheany
DOI:10.1002/anie.201708649
日期:2018.2.5
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
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
作者:Kamalraj V. Rajendran、Declan G. Gilheany
DOI:10.1039/c2cc34136k
日期:——
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.
Lithium Borohydride for Achiral and Stereospecific Reductive Boronation at Phosphorus: Lack of Electronic Effects on Stereoselective Formation of Alkoxyphosphonium Salts
作者:Sulaiman S. Al Sulaimi、Kamalraj V. Rajendran、Declan G. Gilheany
DOI:10.1002/ejoc.201500521
日期:2015.9
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