Cleavage of carbon-phosphorus

Reductive Cleavage of Carbon-Phosphorus, Carbon-Sulfur, and Carbon-Selenium Bonds... 

Reductive Cleavage of Carbon-Phosphorus and Carbon-Sulfur Bonds 257... 

The cleavage of carbon phosphorus bonds in phosphoryl compounds is another matter for consideration. Once a carbon-phosphorus bond is generated, usually it is extremely difficult to cleave it without major damage to the remainder of the molecule. However, phosphonate and phosphinate esters, as well as phosphine oxides, in which a hydroxyl or carbonyl group is present at the carbon directly attached to phosphorus are subject to facile cleavage of the carbon-phosphorus bond. 

Denmark, S. E., Dorow, R. L. Stereospecific cleavage of carbon-phosphorus bonds stereochemical course of the phosphinoyl curtius (Harger) reaction. Chirality 2002,14, 241-257. 

A few reports do exist on the cleavage of carbon-phosphorus bonds in an aqueous medium under alkaline and acidic conditions (11,34). Oxidation is also an obvious side reaction, especially with the trialkyl-phosphines (22,27). However, separation of phosphines from phosphine oxides is possible by distillation or gas chromatography (10, 50,71). 

Pentaarylphosphoranes also undergo cleavage of carbon-phosphorus bonds in aqueous acid or base, as well as halogenolysis. In the latter instance, a quaternary phospho-nium salt is generated along with the haloaromatic product (equation 46). ... 

Preparation of Phosphines from Metallated Phosphines.- The generation of arylphosphide reagents by the reductive cleavage of carbon-phosphorus bonds using alkali metals has received detailed study for a wide range of functionalised triarylphosphines and related... 

Figure 4 Microbially catalyzed reactions involved in the cleavage of carbon-phosphorus linkages. Modified and redrawn after Ref. [34].

Species 5 (Scheme 8), commonly known as dialkylaminodifluorophosphines, are readily synthesized via the selective cleavage of the phosphorus-carbon bond of difluoro(trichloromethylphosphane) by the action of secondary amines [65,66]. Compounds 5 show selective F/H exchange with LiAlH4/HN(Tr)2 to give the respective PH2 (P-unsubstituted) phosphinous amides [13]. 

Chen C-M, Q-Z Zhuang, Z Zhu, BL Wanner, CT Walsh (1990) Molecuar biology of carbon-phosphorus bond cleavage Cloning and sequencing of the phn (psiD) genes involved in alkylphosphonate uptake and C-P lyase activity in Escherichia coli. J Biol Chem 265 4461-4471. 

Wanner BL (1994) Molecular genetics of carbon-phosphorus bond cleavage in bacteria. Biodegradation 5 175-184. 

Reactions and Properties of Phosphonic and Phosphinic Acids and their Derivatives.-A free radical mechanism has been proposed to account for the cleavage of the phosphorus-carbon bond in the alkylphosphonic acids (155) by E coli to give a mixture of alkane (methane only, from methylphosphonic acid) and terminal alkene. 

The mass spectra of certain metal carbonyl complexes of triphenyl-phosphine and l,2-bis(diphenylphosphino)ethane (Pf-Pf) have been investigated 48>. Besides the usual stepwise loss of carbonyl groups, cleavage of the phosphorus-carbon bond occurs. Thus triphenylphosphine complexes exhibit cleavage of the phenyl-phosphorus bond after all carbonyl groups are lost. The 1,2- bis(diphenylphosphino)ethane complexes (e.g. (Pf-Pf)[W(CO)5]2 and (Pf-Pf)M(CO)4) exhibit elimination of the ethylene bridge between two phosphorus atoms. 

Other chiral monophosphonito-systems, e.g. (63) have also been prepared, and their role in catalysis explored. The vinylphosphonite (64) has been shown to suffer cleavage of the phosphorus-carbon bond in protic solvent systems containing potassium carbonate. 

The photochemical cleavage of the phosphorus-carbon bond in many benzylic phosphonic acids occurs through intramolecular electron transfer and gives monomeric metaphosphate together with substituted toluenes and, in many cases, 1,2-diarylethanes. The ultraviolet irradiation of (4-nitrobenzyl)phosphonic acid dianion in solution in aqueous ethanol yields l,2-bis(4-nitrophenyl)ethane, 4-nitrotoluene, H3PO4 and monoethyl phosphate (Scheme Irradiation of the same acid in the presence of dbu (other tertiary... 

The dialkyl (triarylmethyl)phosphonates 35 seemed to be likely contenders for P—C bond cleavage on photolysis however, the first step in such treatment is evidently the formation of a phosphorylated carbene together with that of a biaryl in the presence of an alcohol, the ethers 36 are produced in moderate yields with no cleavage of the phosphorus-carbon bond ° . ... 

Probably the best known of all the many reactions which result in the cleavage of a phosphorus-carbon bond is one which is based on the Wittig reaction. The Wittig reaction consists in the interaction of a triphenylphosphonium ylide and an aldehyde or ketone, the outcome of the reaction being the formation of a tertiary phosphine oxide together with an... 

The facility with which the phosphorus-carbon bond in acylphosphonic derivatives is cleaved by the action of the more basic nucleophiles has already been commented upon. Those nucleophiles include alkoxides and amines, but it may be noted that thiols undergo normal addition to the carbonyl group. With regard to the latter, diethyl acetylphosphonate yields the monothioacetals 256 the derivatives may not be stable thermally but their decomposition occurs with cleavage of the phosphorus-carbon bond Reactions between the same substrate and simple carboxamides in the presence of an acid catalyst under dry conditions furnish the acylated enamides 257 ". ... 

Hydration in the presence of mercury(II) sulphate yields an (oxoalkyl) compound (equation The treatment of the phosphonic ester 364 (R = Et, Z= P03Et2) with a thiolate leads, via diethyl ethynylphosphonate, to the ethenylphosphonic diester 365 with the concomitant formation of thiophosphate ester in this particular case, the product 365 as initially formed, is of Z geometry, but isomerizes when distilled . In other cases of the reactions with thiols, for instance with 364 (R = Et, Z = Cl), the direct replacement of Z is accompanied by overall displacement plus addition at each carbon to give products of types 366 (as a mixture of E and Z stereoisomers) and 367. The same substrate 364 (R = Et, Z = Cl) with the monosodium salt of ethane-1,2-diol represents an alternative route (substitution followed by addition) to 361, but with more basic nucleophiles such as Bu O, and even MeO , cleavage of the phosphorus-carbon bond occurs, although the extent of this decreases, and the extent of addition (with EtO and PhO ) increases, when R = Me is replaced by R = Et. The additions of arylsulphenyl chlorides to 364 (R = Et, Z = Me) occur stereoselectively to give only the E products . 

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