[3426-89-9] · C6H5Cl2OP · Phenyl Dichlorophosphite · (MW 194.98)
Physical Data: bp 90 °C/11 mmHg.
Solubility: sol most organic solvents.
Form Supplied in: liquid; not commercially available.
Preparative Methods: phenyl dichlorophosphite was first identified in the reaction between Phosphorus(III) Chloride and phenol (eq 1).1 However, the yield is low due to formation of side-products, bis- and tris-phosphite esters. Later, phenyl dichlorophosphite was formed in the reaction of phosphorus trichloride and triphenyl phosphite (eq 2), but, again, yields were not particularly high,8 even when the reaction was later optimized.9 By introducing MgCl2 into the former reaction and carefully monitoring the reaction by IR spectroscopy, phenyl dichlorophosphite is formed in high yield (eq 3).10
Purification: redistil under reduced pressure.6
Handling, Storage, and Precautions: irritant and moisture sensitive; incompatible with strong oxidizing agents and bases.7
The main use of phenyl dichlorophosphite is in the formation of phosphorus-containing compounds, particularly phosphite triesters (eq 4). These compounds are synthesized by adding alcohols to phenyl dichlorophosphite in the presence of a tertiary amine.11 However, use of one equivalent of each reagent produces phosphate esters instead (eq 5).11 Two equivalents of alcohol and base are needed to produce phosphite triesters (eq 4).
Phosphite triesters carrying three different alkoxy groups are chiral and can be synthesized from phenyl dichlorophosphite under carefully controlled conditions involving the use of a PtCl2 complex (eq 6).12 The racemic triesters have been resolved via a platinum complex carrying a chiral scalemic ligand.12
Cyclic phosphorus compounds (phospholes) can be synthesized from phenyl dichlorophosphite with a-hydroxy acids (eq 7),13 a-amino acids (eq 7),13 and dilithiated benzyl alcohol (eq 8).3
Phenyl dichlorophosphite can also be used to synthesize organophosphates by preparing the phosphite triester derivative and either oxidizing it to the phosphate triester14 (when ozone is used, the isolable intermediate, a trioxaphosphetane, decomposes to give singlet oxygen and the phosphate triester11a) or alkylating it with an alkyl halide (eq 9).15
Phenyl dichlorophosphite has been used in several reactions as an activating agent. Carboxylic acids form symmetrical anhydrides on reaction with phenyl dichlorophosphite;16 with amines or b-diamines; these form amides17 or imidazoles,18 respectively (eq 10). This methodology has been extended to the formation of polyamides/hydrazides from the reaction of diacids with diamines or hydrazines in the presence of phenyl dichlorophosphite.4
Phenyl dichlorophosphite has also been used with DMF to dehydrate amides to nitriles in high yields (eq 11).5
Richard A. Ewin
King's College London, UK