Benzils, reduction

Baeyer-Villiger reaction, 9, 3 43, 3 Bamford-Stevens reaction, 23, 3 Barbier Reaction, 58, 2 Bart reaction, 2, 10 Barton fragmentation reaction, 48, 2 Bechamp reaction, 2, 10 Beckmann rearrangement, 11, 1 35, 1 Benzils, reduction of, 4, 5 Benzoin condensation, 4, 5 Benzoquinones ... 

Fragmentation processes of photoinitiators form a number of volatile products, which may contribute to indoor air pollution. Benzaldehyde and alkyl-substituted benzalde-hydes are usual components, because Norrish-I is the most important reaction for cleavage. Awell known example is l-phenyl-2-hydroxy-2-methyl-propane-l-one (PHMP). a-Cleavage generates two radicals in the first step. The benzoyl radical may recombine to form benzil, reduction of PHMP leads to l-phenyl-2-methy 1-1,2-propane and acetone, and recombination of the 2-hydroxypropyl radical gives 2,3-dimethyl-2,3-butanediol... 

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

Benzilic acid melts at 149-150°, i.e., very close to that of diphenylacetic acid. The completeness of the reduction can easily be tested by treating a little of the product with concentrated sulphuric acid if even a trace of benzilic acid remains, the sulphuric acid will have a rod colour. 

Benzilic acid rearrangement Benzoin reaction (condensation) Blanc chloromethylation reaction Bouveault-Blanc reduction Bucherer hydantoin synthesis Bucherer reaction Cannizzaro reaction Claisen aldoi condensation Claisen condensation Claisen-Schmidt reaction. Clemmensen reduction Darzens glycidic ester condensation Diazoamino-aminoazo rearrangement Dieckmann reaction Diels-Alder reaction Doebner reaction Erlenmeyer azlactone synthesis Fischer indole synthesis Fischer-Speior esterification Friedel-Crafts reaction... 

An 80% yield of tetraphenylfuran is obtained by treatment of benzoyl chloride with active titanium generated by lithium aluminum hydride reduction of titanium trichloride (Scheme 84e) (8UOC2407). The reaction nroceeds via benzil and tetraphenylbut-2-ene-l,4-dione, both of which are minor products of the reaction. 

Electrochemical reduction of 2,3-diphenylthiirene 1-oxide yields acetylene (80%) and benzil (10%). Electrolysis of 2,3-diphenylthiirene 1,1-dioxide in DMF gives trans-stilbene (30%) but in the presence of acetic acid, 1,2-diphenylvinylmethyl sulfone (27%) is obtained in addition to the stilbene (40%) (81CC120). 

Benzopinacol has been prepared by the action of phenylmag-nesium bromide on benzil 1 or methyl benzilate. Usually it has been obtained by reduction of benzophenone, the reducing agents being zinc and sulfuric acid or acetic acid, aluminum amalgam, and magnesium and magnesium iodide. The present... 

Amino-5-hydrazinopyrazole dihydrochloride 300 is a good source for the synthesis of this type of heterocyclic compound [78JCS(P1)885] and it was prepared by reaction of malononitrile with two equivalents of hydrazine. Reaction of 300 with ethyl pyruvate afforded 301. Unstable hydra-zone 302 formed when 300 was boiled with diacetyl rapidly cyclized to 303. Reaction of 300 with benzil gave 304 directly, which gave an acetyl derivative and resisted reductive deamination. On the other hand, a polymer was isolated from the reaction of 300 with glyoxal (Scheme 65). 

Support for the initial ring expansion (18a ->158) can be inferred from the fact that benzil was also isolated (although in low yield) in the electrochemical reduction of the thiirene oxide 18a171. 

Benzil, 4,4 -bis(di-n-propylamino)-, 41,3 Benzoic acid, conversion to peroxy-benzoic acid, 43, 93 reduction to 1,4-dihydrobenzoic acid, 43, 22... 

Cathodic reduction of mixtures of benzil imines 58 and N-arylcarbonimidoyl dichlorides 59 produces 3,4,5-triaryl-2-(arylimino)-4-oxazolines 60 <95T10375>. Carbodiimides 61... 

Only a few other cobalt complexes of the type covered in this review (and therefore excluding, for example, the cobalt carbonyls) have been reported to act as catalysts for homogeneous hydrogenation. The complex Co(DMG)2 will catalyze the hydrogenation of benzil (PhCOCOPh) to benzoin (PhCHOHCOPh). When this reaction is carried out in the presence of quinine, the product shows optical activity. The degree of optical purity varies with the nature of the solvent and reaches a maximum of 61.5% in benzene. It was concluded that asymmetric synthesis occurred via the formation of an organocobalt complex in which quinine was coordinated in the trans position (133). Both Co(DMG)2 and cobalamin-cobalt(II) in methanol will catalyze the following reductive methylations ... 

Preparation of the quaternary anticholinergic agent benzilonium bromide (47) is begun by conjugate addition of ethylamine to methylacrylate, giving aminoester 42. Alkylation of 42 with methyl bromo-acetate leads to diester 43, which is transformed into pyrrolidone 44 by Dieckmann cyclization, followed by decarboxylation. Reduction of 44 by lithium aluminum hydride leads to the corresponding amino-alcohol (45). Transesterification of alcohol 45 with methyl benzilate leads to 46. Benzilonium bromide (47) is obtained by alkylation of ester 46 with ethyl bromide. 2... 

Literature reports on diazaquinones derived from o-benzoquinone are very rare. Compound 74 was suggested to be a common intermediate formed during heating of 2,5-bis(diazo)-3,4-diketoadipate 73 with isopropanol and with various bases (76T269). Direct reduction of the intermediate with isopropanol provided pyridazine 75. A base-catalyzed benzilic acid rearrangement of 74 followed by decarboxylation of 76 afforded pyrazole 77 (Scheme 18). 

Benzil is reductively triethylsilylated to the bis(silyl) ether in 83% yield.411 The combination of Et3SiH/ZnCl2 reductively triethylsilylates ketones in good yield.382 Excellent yields of triethylsilyl ethers from ketones are accomplished with the use of triethylsilane and catalyst 73 or 74.412 tert-liutyIditnelliyIsily 1 ethers can be synthesized by the reaction of TBSH/TBSOTf with a ketone (Eq. 240).392... 

The procedure described is essentially that of Ballard and Dehn.1 Stilbene has also been prepared by reduction of desoxy-benzoin,20 benzaldehyde,23 and benzil 2o-2c by dehydrogenation of ethyl benzene,30 toluene,30- 33- 3, and bibenzyl 33-3alkaline reduction of phenylnitromethane,40 phenylnitroacetonitrile,40 and desoxybenzoin 43 by distillation of benzyl sulfone,50 benzyl sulfide,60-63 calcium cinnamate,5 cinnamic acid,5d phenyl cinna-mate,6e-6/ and diphenyl fumarate ie by dehydrohalogenation of a,a -dichlorobibenzyl60 and benzyl chloride 63 by dehalogenation of a,a,c/,a -tetrachlorobibenzyl70 and benzal chloride 73 by the coupling of cinnamic acid and phenyldiazonium chloride 8 by de-... 

Reduction of benzoyl chloride at mercury yields an acyl radical that dimerizes to form benzil. As quickly as it forms, benzd accepts an electron to form an anion radical that is acylated by a molecule of benzoyl... 

Reduction of 2-amino-3-nitrodibenzothiophene in the presence of acetic acid yields the imidazole (109) and by conducting this reaction in the absence of acetic acid 2,3-diaminodibenzothiophene should be readily accessible. A similar reduction of 3-amino-4-nitrodibenzothio-phene yields 3,4-diaminodibenzothiophene (60%). In addition to the typical reactions described above for the 1,2-diamino compound, 3,4-diaminodibenzothiophene condenses with benzil to give the quinoxaline... 

ReCl3(PPh3)(benzil)] reacts with bipy and related ligands or terpy to form a number of rhe-nium(III) and rhenium(II) compounds which are useful precursors for the synthesis of lower-valent rhenium complexes. " Thus, reduction of [Re(bipy)3][PF6]2 with zinc amalgam results in the rhenium(I) compound [Re(bipy)3][PF6] in excellent yields. The corresponding terpyridyl bis-chelate [Re(terpy)2][PF6] has been prepared in a similar manner. " The electrochemistry of the products provides a convenient measure of the chemical reactivity associated with the redox processes. Thus, the one-electron oxidation of [Re(bipy)3]" is reversible at -0.33 V, whereas the Re"/Re" redox couple is irreversible and occurs at relatively low potentials (-1-0.61 V) which is consistent with the instability of [Re(bipy)3] + in solution. However, in the presence of a small coordinating molecule such as CNBu, oxidation to the rhenium(III) state is readily available by the formation of seven-coordinate complexes of the composition [Re(bipy)3(L)]. " ... 

Nickel prepared by reduction of nickel chloride with sodium borohydride was used for desulfurization of diethyl mercaptole of benzil. Partial desulfurization using 2 mol of nickel per mol of the mercaptole gave 71% yield of ethylthiodesoxybenzoin while treatment with a 10-fold molar excess of nickel over the mercaptole gave 61% yield of desoxybenzoin (benzyl phenyl ketone) 937. ... 

Scheme 6.34 Electrochemical reduction of aromatic carboxylates to benzils in the presence of thiourea catalyst 33, 34, or 35.

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