Lithium-phosphorus coupling

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). 

Aminoalkyl and Related Acids. - Further development of the classical three component approach to aminoalkylphosphonates (the Kabachnik-Fields reaction) has been reported. The reaction of aldehydes, hydroxylamines and dimethyltrimethylsilyl phosphite using lithium perchlorate/diethyl ether as a catalyst gives N-trimethylsilyloxy-a-aminophosphonate derivatives. The catalytic activities of various lanthanide triflates as well as indium trichloride have been examined for the Kabachnik-Fields type reactions of aldehydes, amines and the phosphorus nucleophiles HP(0)(0Et)2 and P(OEt)3 in ionic liquids. TaCb-Si02 has been utilized as an efficient Lewis acid catalyst for the coupling of carbonyl compounds, aromatic amines and diethyl phosphite to produce a-... 

When the W-trimethylsilyltris(2-pyridyl)phosphinimine (22) was treated with one equivalent of methyllithium at - 78°C, a lithium complex (23) binding a dipyridyl moiety with a trivalent amino-methyl (2-pyridyl)phosphane was isolated. This compound results from a ligand coupling process taking place on the pentacoordinate phosphorus intermediate formed by addition of methyllithium on the imine bond. 

CH2PM62 substituents allowing Li-P contacts without disruption of the bond angles of the core. Multinuclear NMR studies indicate that the dimeric structure is preserved in solution. At 193 K the structure is static the Li and P spectra consist of a triplet and a quartet (c PLi = 44 Hz), respectively, indicating coordination of each lithium by two phosphorus atoms. However, at room temperature the Li and P spectra consist of a quintet and a septet, respectively (J u = 21 Hz), indicating that the dimer is fluxional, with each Li coupling to all four phosphorus nuclei and vice versa. A of 50 kJ moL was estimated for this process from the coalescence temperature. 

The chemistry of pyridylphosphines has been reviewed. Further studies have appeared of the reactions of phosphines bearing 2-pyridyl or 2-benzothiazolyl substituents with butyl-lithium, which result in the formation of biaryl coupling products via an initial nucleophilic attack at phosphorus. A study of the de-diazoniation of arenediazonium salts using triphenylphosphine (and trialkylphosphites) indicates that the reactions proceed via a radical-chain mechanism, initiated by single electron transfer from the phosphine to the diazonium salt, to give... 

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