Rajendran, Kamalraj V.
Rajendran, Kamalraj V.
Rajendran, Kamalraj V.
Now showing 1 - 6 of 6
- PublicationCleavage of P=O in the Presence of P-N: Aminophosphine Oxide Reduction with In Situ Boronation of the PIII Product(Wiley-VCH, 2013-10-11)
; ; ;In contrast to tertiary phosphine oxides, the deoxygenation of aminophosphine oxides is effectively impossible due to the need to break the immensely strong and inert PO bond in the presence of a relatively weak and more reactive PN bond. This long-standing problem in organophosphorus synthesis is solved by use of oxalyl chloride, which chemoselectively cleaves the PO bond forming a chlorophosphonium salt, leaving the PN bond(s) intact. Subsequent reduction of the chlorophosphonium salt with sodium borohydride forms the PIII aminophosphine borane adduct. This simple one-pot procedure was applied with good yields for a wide range of PN-containing phosphoryl compounds. The borane product can be easily deprotected to produce the free PIII aminophosphine. Along with no observed PN bond cleavage, the use of sodium borohydride also permits the presence of ester functional groups in the substrate. The availability of this methodology opens up previously unavailable synthetic options in organophosphorus chemistry, two of which are exemplified. 542Scopus© Citations 25
- PublicationA U-Turn in the Asymmetric Appel Reaction: Stereospecific Reduction of Diastereomerically Enriched Alkoxyphosphonium Salts Allows the Asymmetric Synthesis of P-Stereogenic Phosphanes and Phosphane Boranes(Wiley, 2012-04-05)
; ; ;An efficient one-pot synthesis has been developed of enantioenriched P-stereogenic phosphanes and phosphane boranes from the corresponding racemic phosphanes in excellent yield under asymmetric Appel conditions. The chiral auxiliary (menthol) can also be recovered unchanged. The simple and efficient protocol significantly expands the scope of our asymmetric Appel process. The crucial step in the preparation involves stereospecific reduction of intermediate diastereomeric alkoxyphosphonium salts, which are obtained in the reaction of phosphane, hexachloroacetone, and menthol. Thereby, reaction with LiAlH4 or NaBH4 gives the corresponding phosphanes or phosphane boranes, respectively. 421Scopus© Citations 29
- PublicationIdentification of a key intermediate in the asymmetric Appel process: one pot stereoselective synthesis of P-stereogenic phosphines and phosphine boranes from racemic phosphine oxides(Royal Society of Chemistry, 2012-08)
;Sequential treatment of racemic phosphine oxides with oxalylchloride and chiral non-racemic alcohol generates the sameratios of diastereomeric alkoxyphosphonium salts obtained inthe corresponding asymmetric Appel process, strongly implicatingthe intermediate chlorophosphonium salt in the stereoselectingstep. Subsequent reduction allows a novel synthesis of enantioenriched P-stereogenic phosphines-phosphine boranes. 399Scopus© Citations 43
- PublicationAn easy and short preparation of pentachloroacetone by selective dechlorination of hexachloroacetone under Appel conditions(Elsevier, 2011-12)
; ;We report a very convenient laboratory preparation of pentachloroacetone (PCA) by selective dechlorination of hexachloroacetone (HCA) via reaction with triphenylphosphine in the presence of methanol or aromatic alcohols. 452Scopus© Citations 5
- PublicationSimple unprecedented conversion of phosphine oxides and sulfides to phosphine boranes using sodium borohydride(RSC Publishing, 2012-02)
;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. 943Scopus© Citations 118
- PublicationA convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions(RSC Publishing, 2012-03)
; ; ;A mild method for the facile removal of phosphine oxide from the crude products of Wittig and Appel reactions is described. Work-up with oxalyl chloride to generate insol. chlorophosphonium salt (CPS) yields phosphorus-free products for a wide variety of these reactions. The CPS product can be further converted into phosphine. 1113Scopus© Citations 69