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Phosphite esters are typically prepared by treating phosphorus trichloride with an alcohol. For alkyl alcohols the displaced chloride ion can attack the phosphite, causing dealkylation to give a dialkylphosphite and an organochlorine compound. [1] [2] The overall reaction is as follows: PCl 3 + 3 C 2 H 5 OH → (C 2 H 5 O) 2 P(O)H + 2 HCl + C 2 ...
Phosphites, sometimes called phosphite esters, have the general structure P(OR) 3 with oxidation state +3. Such species arise from the alcoholysis of phosphorus trichloride: PCl 3 + 3 ROH → P(OR) 3 + 3 HCl. The reaction is general, thus a vast number of such species are known.
Phosphite esters with tertiary alkyl halide groups can undergo the reaction, which would be unexpected if only an S N 2 mechanism was operating. Further support for this S N 1 type mechanism comes from the use of the Arbuzov reaction in the synthesis of neopentyl halides, a class of compounds that are notoriously unreactive towards S N 2 reactions.
When aliphatic alcohols are used the HCl by-product can react with the phosphate esters to give organochlorides and a lower ester. O=P(OR) 3 + HCl → O=P(OR) 2 OH + RCl. This reaction is usually undesirable and is exacerbated by high reaction temperatures. It can be inhibited by the use of a base or the removal of HCl through sparging.
Since orthophosphoric acid has three −OH groups, it can esterify with one, two, or three alcohol molecules to form a mono-, di-, or triester. See the general structure image of an ortho- (or mono-) phosphate ester below on the left, where any of the R groups can be a hydrogen or an organic radical. Di- and tripoly- (or tri-) phosphate esters ...
The Abramov reaction is the related conversions of trialkyl to α-hydroxy phosphonates by the addition to carbonyl compounds. In terms of mechanism, the reaction involves attack of the nucleophilic phosphorus atom on the carbonyl carbon. [1] It was named after the Russian chemist Vasilii Semenovich Abramov (1904–1968) in 1957. [2]
The reaction mechanism of the Mitsunobu reaction is fairly complex. The identity of intermediates and the roles they play has been the subject of debate. Initially, the triphenyl phosphine (2) makes a nucleophilic attack upon diethyl azodicarboxylate (1) producing a betaine intermediate 3, which deprotonates the carboxylic acid (4) to form the ion pair 5.
It reacts with phenol to give triphenyl phosphite: 3 PhOH + PCl 3 → P(OPh) 3 + 3 HCl (Ph = C 6 H 5) Alcohols such as ethanol react similarly in the presence of a base such as a tertiary amine: [9] PCl 3 + 3 EtOH + 3 R 3 N → P(OEt) 3 + 3 R 3 NH + Cl −. With one equivalent of alcohol and in the absence of base, the first product is ...