A practical and efficient
method has been developed for the preparation
of optically active α-hydroxyphosphonates through resolution
of the racemates. Treatment of racemic diethyl 1-hydroxy-1-phenylmethylphosphonate
(1) with (+)-dibenzoyl-L-tartaric anhydride gave two
diastereomeric esters 2 and 3 in the presence
of bismuth triflate (15 mol %) in an 86:14 ratio. The two diastereomeric
esters were separated by simple column chromatography, and the structure
for the major diastereomer was determined by X-ray crystallographic
analysis. Simple hydrolysis of the isolated major diastereomer in
the usual manner afforded (R)-O,O-diethyl-1-[hydroxyl(phenyl)methyl] phosphonate 1. The advantages of the present method are that the operation is
simple and easy to handle, along with rapid and good yield preparations
of both enantiomers of the racemic α-phosphonates 1. Diastereoselective reactions of various racemic α-hydroxyphosphonates
with d-Bz-L-TA in the presence of Bi(OTf)3 are also described.
1-Aminophosphonates are valuable compounds with wide range applications in biological and industry. Various reaction conditions and catalysts have been reported for the synthesis of 1-aminophosphonates via three components (dialkylphos-phite+aldehyde+amine) or two component reaction (dialkylphos-phite+imine). We report here a solvent-free synthesis of 1-aminophosphonates under very mild reaction condition. Three component condensation reactions of dialkyl phosphite, carbonyl compound, and an amine gave 1-aminophosphonate in good to excellent yield under solvent- and catalyst-free condition at ambient temperature. Hydrophosphorylation of imines in the presence of dialkylphosphite under same condition gave also 1-aminophosphonates in good to excellent yield. These results showed that the reaction needs no to any catalyst or solvent for activation. It seems a tautomeric form of dialkylphosphite (as one of the components) catalysed the reaction. The reaction yield decreased using any solvent. In addition, a novel method will be reported for the synthesis of N-deprotected 1-aminophosphonates (analogues of 1-amino acids) from N-PMP 1-aminophosphonate in the presence of TCCA. To understand the activity of the dialkylphosphite under solvent free condition, the DFT calculations have provided insight into the basis of this activity.
In this report, two routes for the synthesis of phosphorothioates via a P−S cross coupling reaction of thiols with dialkyl phosphites or a three component reaction of alkyl halides, thiourea and dialkyl phosphite in the presence of CaO has been studied. By presented methods, various phosphorothioates are obtained under transition metal‐free condition. The reactions are proceeded with formation of a known intermediate of disulfide via the oxidation of thiols and followed by nucleophilic substitution of dialkyl phosphite with the disulfide intermediate gave phosphorothioate.
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