Reduction carbon-phosphorus bonds

Nickel and palladium complexes also catalyze the formation of the carbon-phosphorus bonds in phosphorus(V) and phosphorus(III) compounds. Indeed, this chemistry has become a common way to prepare phosphine ligands by the catalytic formation of phosphine oxides and subsequent reduction, by the formation of phosphine boranes and subsequent decomplexation, or by the formation of phosphines directly. The catalytic formation of both aryl and vinyl carbon phosphorus bonds has been accomplished. 

Carbon-nitrogen bond formation, by reductive amination, 59, 1 Carbon-phosphorus bond formation, 36, 2 Carbonyl compounds, addition of... 

The o-acylaminobenzylphosphonium salts are available from two ways (1) reduction of o-nitrobenzylphosphonium saltZ with zinc in hydrobromic acid-ethanol (yield 95%). The reductive cleavage of the carbon-phosphorus bond can be avoided by using only two equivalents of reagent (2) condensation of o-aminobenzyl alcohols with triphenylphosphine and hydrobromic acid. 

Phosphonium compounds are reduced more easily than the corresponding ammonium compounds the reduction results in a breakage of a carbon-phosphorus bond. The ease with which a group is cleaved from a phosphonium compound depends on several variables, primarily the electrode material, the potential, and the temperature [196-199]. 

The presence of electron-withdrawing groups positioned on an aromatic nucleus bonded directly to phosphorus can be a source of instability in the phosphorus-carbon bond. This situation is found particularly in (4-nitrophenyl)phosphonic acids. (2-Methoxy-4-nitrophenyl)phosphonic acid can be demethylated in 40% HBr, but cleavage of the carbon-phosphorus bond becomes more pronounced in a reaction with 48% HBr moreover, hydrogenation of the same acid over Raney nickel yields the expected (4-amino-2-methoxyphenyl)phosphonic acid, but a similar reduction of (2-hydroxy-4-nitrophenyl)-phosphonic ac id results in the separation of 3-aminophenol. These and other, similar, reactions have been surveyed by Freedman and Doak ". ... 

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... 

Phosphorus-containing compounds provide useful substrates for ozonolysis reactions as well and can provide several products depending on the reaction workup. Several biological uses exist for -amino-a-hydroxy phosphonic acid derivatives and they can be readily prepared by ozonolysis of Al-(ethoxycarbonyl)-/3-amino-Q -methylene phosphonic esters after reductive workup with sodium borohydride (eq 54). When the reaction mixture is treated with sodium hydroxide in MeOH, an anomalous ozonolysis reaction occurs and cleavage of the methylene as well as the carbon-phosphorus bond occurs to yield (V-(ethoxycarbonyl)-a-amino methyl carboxylic esters. 

This compilation embraces a wide variety of subjects, such as solid-phase and microwave stereoselective synthesis asymmetric phase-transfer asymmetric catalysis and application of chiral auxiliaries and microreactor technology stereoselective reduction and oxidation methods stereoselective additions cyclizations metatheses and different types of rearrangements asymmetric transition-metal-catalyzed, organocatalyzed, and biocatalytic reactions methods for the formation of carbon-heteroatom and heteroatom-heteroatom bonds like asymmetric hydroamina-tion and reductive amination, carboamination and alkylative cyclization, cycloadditions with carbon-heteroatom bond formation, and stereoselective halogenations and methods for the formation of carbon-sulfur and carbon-phosphorus bonds, asymmetric sulfoxidation, and so on. 

Sulfonic acids are prone to reduction with iodine [7553-56-2] in the presence of triphenylphosphine [603-35-0] to produce the corresponding iodides. This type of reduction is also facile with alkyl sulfonates (16). Aromatic sulfonic acids may also be reduced electrochemicaUy to give the parent arene. However, sulfonic acids, when reduced with iodine and phosphorus [7723-14-0]y produce thiols (qv). Amination of sulfonates has also been reported, in which the carbon—sulfur bond is cleaved (17). Ortho-lithiation of sulfonic acid lithium salts has proven to be a useful technique for organic syntheses, but has litde commercial importance. Optically active sulfonates have been used in asymmetric syntheses to selectively O-alkylate alcohols and phenols, typically on a laboratory scale. Aromatic sulfonates are cleaved, ie, desulfonated, by uv radiation to give the parent aromatic compound and a coupling product of the aromatic compound, as shown, where Ar represents an aryl group (18). 

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

Diphosphaallene derivatives ArP=C=PAr are peculiar compounds because of the presence of the two orthogonal carbon-phosphorus double bonds. Those compounds were transformed into cation radicals upon electrochemical or chemical one-electron oxidation. As found, the unpaired electron is located on a molecular orbital constituted mainly of a p-orbital of each phosphorus atom and a p-orbital of the carbon atom (Chentit et al. 1997 Alberti, Benaglia et al. 1999). Upon electrochemical or chemical reduction, aromatic phos-phaallene derivatives yield anion radicals. These species have two equivalent phosphorus... 

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

The synthesis of polyphosphines containing combinations of primary, secondary, and tertiary phosphorus atoms by the base-catalysed addition of P—H across the carbon-carbon double bond of vinyl phosphonates, followed by reduetion with lithium aluminium hydride, has again been described. The preparation of I,2-bis(phosphino)ethane from the bis-phosphonate (17) by reduction with lithium aluminium hydride has been reported in detail. ... 

Utility of Enol and Aryl Triflates. Enol and aryl triflates are extensively used for cross-coupling reactions, the formation of carbon-carbon, carbon-tin, carbon-nitrogen, carbon-sulfur, carbon-phosphorus, and carbon-halogen bonds, and reduction/ deoxygenation. In recent examples, they were used to form enamines or enamides or were eliminated to cyclooctynes for copper-free cycloadditions in biological systems. 

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