Alcohols diaryl methanols

Enantioface selection of prochiral diaryl ketones is generally difficult because electronically and sterically similar two aryl groups are attached to the carbonyl group. Overreduction of diaryl methanols to diaryl methanes is also another problem, but these problems are overcome by use of the Ru ternary catalyst system (Scheme 2.4b). Thus, by using (S,S)-20/KOC(CH3)3, 2-substituted benzophenones are quantitatively reduced to the diaryl methanols without any detectable diaryl methanes [102], With 3- or 4-substituted benzophenones, enantioselectivities are moderate. Benzoylferrocene is hydrogenated in the presence of trans-RuCl2 (S)-tol-binap (S)-daipen and a base to afford the S alcohol in 95% e.e. 

Chemical deoxygenation of sulfoxides to sulfides was carried out by refluxing in aqueous-alcoholic solutions with stannous chloride (yields 62-93%) [186 Procedure 36, p. 214), with titanium trichloride (yields 68-91%) [203], by treatment at room temperature with molybdenum trichloride (prepared by reduction of molybdenyl chloride M0OCI3 with zinc dust in tetrahydrofuran) (yields 78-91%) [216], by heating with vanadium dichloride in aqueous tetrahydrofuran at 100° (yields 74-88%) [216], and by refluxing in aqueous methanol with chromium dichloride (yield 24%) [190], A very impressive method is the conversion of dialkyl and diaryl sulfoxides to sulfides by treatment in acetone solutions for a few minutes with 2.4 equivalents of sodium iodide and 1.2-2.6 equivalents of trifluoroacetic anhydride (isolated yields 90-98%) [655]. 

Electrolysis of a tosylate in methanol as electrolyte recovers the alcohol with retention of configuration by cleavage of the 0-S02 bond 514 In aprotic solvents (CH3CN) this cleavage is not so clean, alcohol, ether and toluene being formed simultaneously 515 Electrolysis of diaryl and arylalkylsulfones forms... 

Dialkyl and diaryl ditellurium compounds are easily reduced to tellurols and tellurolates. Alkali metals in liquid ammonia or in an inert organic solvent, sodium borohydride in methanol, ethanol, alcohol/benzene, THF, DMF, or in a basic aqueous medium, lithium aluminum hydride in dioxane or THF/hexamethylphosphoric triamide, and thiourea dioxide in THF/50% aqueous sodium hydroxide have been used as reducing agents (p. 164). The tellurolates are easily oxidized in air. For this reason they are almost always used in situ. 

Diaryl methyl- and benzyl-phosphonates are conveniently prepared in high yields by heating mixtures of triaryl phosphites, methanol or benzyl alcohol, and a trace of methyl or benzyl halide. In a reaction that is usefully complementary to the previously reported formation of pyridine-2-phosphonic acid derivatives from sodium dialkyl phosphonates and //-methoxypyridinium compounds ( Organophosphorus Chemistry , Vol. 7, p. 111), N-triphenylmethylpyridinium tetrafluoroborate affords the pyridine-4-phosphonic dialkyl ester when heated with sodium dialkyl phosphonates. ... 

The liquid-phase hydroxyalkylation of 2-methoxyphenol with aqueous solutions of fonnaldehyde (formalin), catalyzed by solid acid materials, was investigated. Zeolitic catalysts, especially H-mordenites, yield the best results in terms of reactant conversion and selectivity to 3-methoxy-4-hydroxybenzyl alcohol (p-vanillol). Important reaction parameters are the formaldehyde-to-guaiacol ratio, the stirring rate and the reaction tenqjerature. The reaction scheme consists of parallel reactions for the formation of vanillic alcohol isomers and of monoarylic by-products, obtained by reaction between vanillols and methanol or hemiformal contained in formalin. The consecutive reactions mainly involve the transformation of p-vanillol to monoaryl and to diaryl compounds, the latter obtained by condensation of two vanillol molecules. 

The photoinduced anti-Markovnikov addition of methanol to 1,1-diphenylethene reported by Arnold and co-workers in 1973 provides the first example of the addition of a nucleophile to an arylalkene radical cation. There are now a number of studies that demonstrate the generality of nucleophilic addition of alcohols, amines, and anions such as cyanide to aryl- and diaryl-alkene radical cations. Product studies and mechanistic work have established that addition occurs at the 3-position of I-aryl or 1,1 -diarylalkene radical cations to give arylmethyl or diaryl-methyl radical-derived products as shown in Scheme I for the addition of methanol to 1,1-diphenylethene. For neutral nucleophiles, such as alcohols and amines, radical formation requires prior deprotonation of the 1,3-distonic radical cation formed in the initial addition reaction. The final product usually results from reduction of the radical by the sensitizer radical anion to give an anion that is then protonated, although other radical... 

Nishii et al. reported metal-mediated benzannulation reaction of diaryl(gm-dichlorocyclopropyl)methanols to synthesize unsymmetrically substituted a-arylnaphthalenes [61]. In particular. The reaction of optically active alcohol 145 in the presence of 1 equiv of HCU at —78 °C afforded chiral biaryl 146 with an excellent level of stereo induction (Scheme 27.48) [62]. It should be noted that chi-raUty exchange from sp central chiraUty to axial chirality takes place in this process. This methodology has been employed successfully for total synthesis of natural lignin lactones, justicidin B, and dehydrodesoxypodophyllotoxin (Scheme 27.49) [63]. 

Suitable mechanisms have been proposed following determination of the kinetic and activation parameters for oxidation of 2-naphthol and cyclic ketones by nicotinium dichromate some a-amino acids by tripropylammonium fluorochromate " distyryl ketone by quinaldinium fluorochromate methanol by benzyltriethylammonium chlorochromate catalysed by 1,10-phenanthroline substituted benzyl alcohols by tetraethylammonium bromochromate L-cysteine by pyridinium bromochromate lactic acid and 3,5-dimethyl-2,6-diaryl piperidin-4-one oximes by pyridinium chlorochromate allyl alcohol by IDC benzophenoxime by bispyridine silver(I) dichromate and alkyl phenyl sulfides by cetyltrimethylammonium dichromate. A non-linear Hammett plot obtained for the oxidation of substituted benzyl alcohols by IDC has been attributed to the operation of substituent effect on two steps of the proposed mechanism. " Kinetic and activation parameters for oxidation of o-toluidine and of A-methyl-2,6-diphenyl piperidin-4-one oxime and its 3-alkyl derivatives by sodium dichromate have been determined and suitable mechanisms have been suggested. Micellar catalysis in the 1,10-phenanthroline-promoted chromic acid oxidation of propanol... 

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