Trialkyl phosphites displacement reactions

Trialkyl phosphites undergo reaction with molecular halogen via a mechanism reminiscent of the Michaelis-Arbuzov reaction to form the dialkyl phosphorochloridate in good yield (Equation 4.4).7 With cyclic esters, the halogen performing the displacement reaction at carbon remains attached within the molecule. 

Trialkyl phosphites displace 3,6-dithiaoctane from complex (7) by the usual chelate ring opening mechanism with k2 k3[L], equations (18) and (19). " An earlier study of the same reaction with complex 8 gave the... 

An interesting variation of this reaction that made use of a three-component, one-pot solventless procedure with the corresponding trialkyl phosphites gave dramatically improved yields of many heterosubstituted glyphosate phosphonate diesters (37). When exactly one equivalent of water, 25, and tris-p-chloroethyl phosphite were mixed and heated under neat conditions for a few hours, nearly quantitative yields of displaced p-chloroethanol and the desired triester product 27 were obtained. If desired, the displaced alcohol was first removed by vacuum distillation, or the mixture could be hydrolyzed directly to GLYH3. Various oxygen, sulfur, nitrogen, cyano, and carboxylate functionalities were similarly accommodated in the trialkyl phosphite. 

The kinetics of the reaction of trialkyl phosphites, dialkyl aryl-phosphonites, alkyl diarylphosphinites, and triarylphosphines with Sg has been studied the effects of structural changes on the rate (Ph2POR > PhP(OR>2 > P(OR)g > Ph P) and on the Hammett p values are interpreted with respect to the mechanism. A general method to displace mercapto groups from carbon with clean inversion includes... 

The mechanism for the reactions with phosphorus halides can be illustrated using phosphorus tribromide. Initial reaction between the alcohol and phosphorus tribromide leads to a trialkyl phosphite ester by successive displacements of bromide. The reaction stops at this stage if it is run in the presence of an amine which neutralizes the hydrogen bromide that is formed.9 If the hydrogen bromide is not neutralized the phosphite ester is protonated and each alkyl group is successively converted to the halide by nucleophilic substitution by bromide ion. The driving force for cleavage of the C—O bond is the... 

In 1952 Perkow discovered a new type of rearrangement in which trialkyl phosphites react with a-aldehyde.6,7 This anomalous Arbuzov reaction, which resulted in the formation of dialkylvinylphosphates, subsequently became known as the Perkow reaction. 1 The reaction of trialkyl phosphites with alkyl halides (Arbuzov reaction) proceeded to yield dialkoxy alkyl phosphonates.8 The alkyl halide undergoes a nucleophilic displacement to yield the nonisolable alkyl trialkoxy phophonium halide.8 The halide can then attack an alkoxy group to give phosphonate ester and RX. An increase in temperature favors the Arbuzov reaction leading to phosphonates (Sn2 displacement). 

A novel procedure has been developed for the synthesis of phosphate esters of hindered alcohols, and was designed to avoid nucleophilic displacement reactions. It involves photolysis of the alkyl nitrite in the presence of a trialkyl phosphite and proceeds by addition of the alkoxyl radical to phosphorus followed by elimination of an alkyl group (Scheme 3). ... 

Although other mechanisms are conceivable, the most likely scheme involves direct nucleophilic displacement by phosphite on carbon to furnish a trialkoxy phosphonium halide intermediate as in the Michaehs-Arbuzov reaction. Recently, we have developed an improved method for the preparation of Mannich bases of steroids and carried ouf reactions with their methiodides and trialkyl phosphite to obtain the first steroidal phosphonates to be reported (132). 

Polyhydroxy(cyclo)alkyl phosphonic esters in the /nyo-inositol series have been prepared through a simple application of the Michaelis-Arbuzov reaction, and the displacement of methanesulphonyl groups from (137) occurs in reactions with simple trialkyl phosphites to give, for example, (138). Interest continues in carbohydrate-like... 

F-Methylation. Phosphonium salts are prepared by the quat-ernization of phosphines with methyl iodide. The displacement reaction is usually conducted in polar solvents such as acetonitrile or DMF. Dialkyl phosphonates are prepared from the reaction of trialkyl phosphites with alkyl halides, commonly known as the Arbuzov reaction. For example, diisopropyl methylphosphonate is prepared by heating a mixture of methyl iodide and Triisopropyl Phosphite (eq 34). ... 

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