Acyl halides, reactions with phosphites

With acyl halides, the corresponding acyl phosphonates are obtained. Furthermore allylic and acetylenic halides, as well as a-halogenated carboxylic esters and dihalides, can be used as starting materials. If substituents R and R are different, a mixture of products may be obtained, because the reaction product RX 5 can further react with phosphite 1 that is still present ... 

In the alkyl chain hydroxy groups or side chains may be present. The reaction is somewhat different when acyl halides are used. Hydroxymethanediphosphonic acid is prepared by reacting phosgene with an alkali metal, dialkyl phosphite. The reaction is rapid and exothermic. The temperature is controlled between 10 and 20°C. After hydrolysis with HC1, hydroxymethanediphosphonic acid is recovered [91,92]. 

Sulfonic esters are most frequently prepared by treatment of the corresponding halides with alcohols in the presence of a base. The method is much used for the conversion of alcohols to tosylates, brosylates, and similar sulfonic esters. Both R and R may be alkyl or aryl. The base is often pyridine, which functions as a nucleophilic catalyst, as in the similar alcoholysis of carboxylic acyl halides (10-21). Primary alcohols react the most rapidly, and it is often possible to sulfonate selectively a primary OH group in a molecule that also contains secondary or tertiary OH groups. The reaction with sulfonamides has been much less frequently used and is limited to N,N-disubstituted sulfonamides that is, R" may not be hydrogen. However, within these limits it is a useful reaction. The nucleophile in this case is actually R 0 . However, R" may be hydrogen (as well as alkyl) if the nucleophile is a phenol, so that the product is RS020Ar. Acidic catalysts are used in this case. Sulfonic acids have been converted directly to sulfonates by treatment with triethyl or trimethyl orthoformate HC(OR)3, without catalyst or solvent and with a trialkyl phosphite P(OR)3. ... 

Reaction of an acyl halide with a trialkyl phosphite catalyzed by Ni(II)... 

The Michaelis-Arbuzov reaction has been applied to t/7.v(trialkylsilyl) phosphites, which, on reaction with aliphatic or aromatic acyl halides in Et2O or CgHg at room temperature, undergo the rearrangement in mild conditions to produce the valuable fczXtrialkylsilyl) 1-oxoalkyl- or 1-oxoarylphosphonates in good yields (50-77%, Scheme 7.6). - Free acylphosphonic acids are obtained by treatment of the trimethylsilyl) esters with EtOH or by exposure to air for several hours. 

Gazizov, T.K., Sudarev, Y.I., and Pudovik, A.N., Reactions of dialkyl trimethylsilyl phosphite and ethyl trimethylsilyl ethylphosphonite with alkyl and acyl halides, Zh. Obshch. Khim., 47, 1660, 1977 J. Gerr Chem. USSR (Engl. Transl.), 47, 1977. 

Although those Michaelis-Arbuzov reactions which involve acyl halides and phospho-rus(III) esters are yet a further route to phosphorus-carbon bond formation and will be discussed later in Section VI, the use of halogenated acyl halides has led to some unusual results which, conveniently, can be summarized here. The products obtained from reactions between trialkyl phosphites and perfluoroacyl chlorides contain both phosphonate and phosphate moieties and are structurally dependent on reaction temperature. The initial product (Scheme 4) is thought to be the ylide 66. In an ethereal solvent at low temperature, decomposition of the ylide yields [l-(dialkoxyphosphinoyl)oxy-l/f-perfluo-roalkyl]phosphonates (67) exclusively, but at -20 °C and above, and in the absence of a solvent, the products consist of (Z)-[l-(dialkoxyphosphinoyl)oxyperfluoroalkene]phos-phonates (68) . The treatment of the compounds 67 with Ida yields 68, and the action of BuLi-CuI on 68 results in loss of the phosphate moiety to give the esters 69 The structural isomers 70 of the compounds 68 have been obtained as illustrated in equation... 

The reaction between tris(trimethylsilyl) phosphite and a perfluoroacyl chloride proceeds without any apparent difficulty to give the predicted phosphonate diester 489 [R = Me3Si, R = CF3 or (CF3)2CH] but the use of longer chain polyfluorinated acyl halides or other heavily halogenated acyl chlorides leads to complications with such substrates, the initially formed acylphosphonate reacts with more phosphorus(III) ester to give the (Z)-enol phosphate 490 (Scheme 47). The halides, XCH2COX (X = Cl or Br) afford only the esters 491 (X = H). ... 

The oxidation of tetra alkoxydiphosphines can yield pyrophosphites, isohypo-phosphites or pyrophosphates. With dimethyl sulphoxide, the proportions used determine the product (6.733). With acyl halides, P-C bonds are formed in a reaction which can be represented approximately as (6.734). 

Phosphoramidites (89), derived from enamines, react with carboxylic acids in an irreversible manner because of the low basicity of the eliminated enamine. The anhydrides (90) may also conveniently be obtained from enol phosphites. Reactions of (89) with phenol were also studied and the kinetics found to be characteristic for bimolecular processes . In contrast to other carboxylic acid halides, acyl fluorides give tervalent phosphorus fluorides with tervalent esters (Scheme 7). ... 

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