Reductions phosphorus/iodine

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). 

Cymene is found in thyme oil, eucalyptus oil, and Roman cummin oil. It is also obtained by heating camphor with phosphorus pentoxide and from turpentine by reduction with iodine. 

Diphenylacetlc acid. The reduction of benzilic acid with red phosphorus and a little iodine in 98 per cent, acetic acid solution yields diphenylacetlc acid ... 

Complete reduction of sulfonyl chlorides to thiols can be achieved by lithium aluminum hydride [680,693], with zinc [696] and with hydriodic acid generated in situ from iodine and red phosphorus [230]. m-Nitrobenzenesulfonyl chloride, however, was reduced not to the thiol but to bis(m-nitrophenyl)disulfide by hydriodic acid in 86-91% yield [697]. 

Acyloins were converted to mixtures of stereoisomeric vicinal diols by catalytic hydrogenation over copper chromite [972]. More frequently they were reduced to ketones by zinc (yield 77%) [913, 914], by zinc amalgam (yields 50-60%) [975], by tin (yields 86-92%) [173], or by hydriodic acid by refluxing with 47% hydriodic acid in glacial acetic acid (yields 70-90%) [916], or by treatment with red phosphorus and iodine in carbon disulfide at room temperature (yields 80-90%) [917] Procedure 41, p. 215). Since acyloins are readily accessible by reductive condensation of esters (p. 152) the above reductions provide a very good route to ketones and the best route to macro-cyclic ketones [973]. 

Complete deoxygenation of quinones to hydrocarbons is accomplished in yields of 80-85% by heating with a mixture of zinc, zinc chloride and sodium chloride at 210-280° [932]. Refluxing with stannous chloride in acetic and hydrochloric acid followed by refluxing with zinc dust and 2 N sodium hydroxide reduced 4 -bromobenzo[5. 6 1.2]anthraquinone to 4 -bromo-benzo[5. 6 1.2]anthracene in 95% yield [181], and heating with iodine, phosphorus and 47% hydriodic acid at 140° converted 2-chloroanthraquinone to 2-chloroanthracene in 75% yield [222]. Also aluminum in dilute sulfuric add can be used for reductions of the same kind [151]. 

Previous preparations of 2-naphthalenethiol have included reduction of 2-naphthylsulfonyl chloride with zinc and acid4,5 or phosphorus and iodine.6-7 Alternatively, 2-naphthyldia-zonium chloride has been converted to the thiol using potassium ethyl xanthate and sodium carbonate.8 1 2 3 4... 

Chamaetine was isolated from a species of Chamaecytisus (156,157). Cham-aetine (127) was reduced by LAH to hydroxysparteine (111), and further reduction with red phosphorus in the presence of iodine gave sparteine (6) (Scheme... 

With more water, it passes into solution dilute solutions, which are brownish-yellow or red, according to the concentration, evolve chlorine and become blue on standing, undergoing reduction to the tetravalent state. On evaporation to dryness, aU the chlorine is evolved and the residue consists of the. pentoxide. Vanadium oxytrichloride is also soluble in ether and alcohol. It dissolves chlorine, bromine, iodine, yellow phosphorus, and sulphur, and is miscible with various liquid hydrocarbons and chlorinated hydrocarbons its use as an industrial solvent has therefore been suggested. ... 

Fumaric acid has been prepared from bromosuccinic acid by heating with water,1 or dilute hydrobromic add,2 and by heating the acid above its melting point.3 It has also been prepared by heating malic acid,4 by transmutation of maleic acid 5 and by the reduction of tartaric acid with phosphorus and iodine.6 The procedure described is the most satisfactory for laboratory use, and is a slight modification of one recently described in the literature.7... 

Adipic acid has been prepared by the following methods the action of silver1 or copper 2 on /3-iodopropionic acid the reduction of mucic add with phosphorus and iodine 3 the electrolysis of the potassium or sodium salts of monoethyl succinate 4 the condensation of ethylene chloride or bromide with malonic ester or cyanoacetic ester and subsequent hydrolysis 5 the oxidation of certain fractions of Baku petroleum 6 the oxidation of cyclohexanol or cyclohexanone with nitric acid 7 or potassium permanganate.8... 

Historically, hydrogen derived from dissociation of hydrogen iodide has been utilized widely for reduction. Acceleration of the hydrogenolysis rate is achieved by addition of phosphorus to remove the iodine formed.In general reduction with HI is efficient for acid-tolerant substrates and is a useful alternative to catalytic methods, especially to achieve chemoselectivity (equations 95 and 96).Application of HI to cleavage of allylic centers has not been useful as allylic and other unsaturated centers are more susceptible to HI addition and elimination effects. 

This acid is obtained when a-naphthylarsinic acid is nitrated it crystallises in pale yellow needles. The arsinic grouping is. so firmly attached that it is not replaced by iodine, and only slightly by bromine. Concentrated hydrochloric acid at 120° C. converts the acid into a-nitronaph-thalene, fusion with potassium hydroxide into a-naphthol, phosphorus pentachloride into 4-chloro-a-nitronaphthalene. Reduction to the corresponding amine is rendered difficult by the case with winch the arsinie grouping undergoes reduction. 

Many hydroxypyrazine A oxides have been A(-deoxygenated to pyrazines with a variety of reducing agents which include heating with hydrazine hydrate in alcohols hydriodic acid and red phosphorus in acetic or phosphoric acid iodine and red phosphorus in refluxing acetic acid phosphorus tribromide in ethyl acetate sodium dithionite catalytic reduction with hydrogen over Raney nickel dry distillation with copper-chromite catalyst and titanium trichloride in tetrahydrofuran at room temperature. 

Deoxyaspergillic acid was also produced from aspergillic acid by refluxing in acetic acid with red phosphorus and hydriodic acid, and by dry distillation with copper-chromite catalyst (86). Reduction of 2,5-dihydroxy-3,6-diisobutylpyrazine 1,4-dioxide (pulcherriminic acid) with red phosphorus and iodine in refluxing acetic... 

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