Ketones desoxybenzoins

Ketones are cleaved oxidatively by Cr(VI) or Mn(VIII) reagents. The reaction is sometimes of utility in the synthesis of difunctional molecules by ring cleavages. The mechanism for both reagents is believed to involve reaction of an enolic intermediate, although in neither case have all the details been established. A study involving both kinetic data and accurate product-yield determination has permitted a fairly complete description of the Cr(VI) oxidation of benzyl phenyl ketone (desoxybenzoin). The products include both oxidative-cleavage products and... 

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. ... 

Lutz, R. E., J. A. Freek, and R. S. Miirphey Secondary and tertiary amino ketones and alcohols derived from desoxybenzoin and 1,2-di-phenylethanol. Ring-chain tautomerism of the a-(p-hydroxyethyl-amino)-ketones. J. Amer. chem. Soc. 70, 2015 (1948). 

Cavallo et al. from (+)-dihydrocarvone and evaluated in the asymmetric epoxida-tion of several silyl enol ethers [32]. Enantiomeric excess up to 74% was achieved in the epoxidation of the TBDMS trans-enol ether of desoxybenzoin with the fluoro ketone 19d (30 mol% of the ketone catalysts). In earlier work Solladie-Cavallo et al. had shown that the fluoro ketones 19a and 19e can be used to epoxidize trans-stilbene with up to 90% ee (30 mol% ketone catalyst) [33], Asymmetric epoxidation of trans-methyl 4-para-methoxycinnamate using ketone 19e as catalyst is discussed in Section 10.2. 

The alkylthio group in an aromatic ketone may be removed with Raney Ni without affecting the carbonyl group. Thus, treatment of desyl thioethers (a-alkylthiodesoxy-benzoins) with Raney Ni, which had been deactivated by refluxing in acetone,149 gave desoxybenzoins in yields of 55-90% (eq. 13.73).150... 

Similar results were obtained with enamines of acyclic ketones such as desoxybenzoin. Nitrostyrene gave only the less substituted mono-alkylated enamine and hence the / -nitro-a-phenylethyl ketone on hydrolysis117. Surprisingly 2-nitropropene gives mainly the tetrasubstituted cyclohexanone enamine106. A hexahydrobenzo-l,2-oxazine-7V-oxide (55) was isolated at low temperatures (in 80% yield) which rearranged at room temperature to a mixture of alkylated enamine isomers107 (Scheme 39). 

SYNS BENZYL PHENYL KETONE DEOXYBENZO-IN DESOXYBENZOIN 1,2-DIPHENYLETHANONE 2-PHENYL, CETOPHENONE PHENYL BENZYL KETONE... 

The reaction has been extended to other pinacols however, their preparation may involve lengthy procedures. Certain benzoins on reduction with metals and acids yield diols which are then converted to desoxybenzoins. These conversions involve the migration of a hydrogen atom rather than an alkyl group. Similarly, aromatic keto ethers and amino ketones have been prepared. 

Desoxybenzoins. Benzoins are reduced to desoxybenzoins by treatment with red phosphorus and iodine in carbon disulfide containing pyridine (3.5 hr., 25°). Presumably an a-iodo ketone is formed as an intermediate. This deoxygenation has been carried out also with hydriodic acid (1,449). 

Benzil crystallizes from alcohol in yellow needles which melt at 95°. It takes part in many reactions which are characteristic of ketones. It may be reduced to desoxybenzoin,... 

Dimethyl-desoxybenzoin-oxiin 7, 455. Athyi-benzhydryl-keton-oxiin 7 II 393. Hochsohmelzendes Benzhydrylacetoti.oxim... 

The acid-catalysed Fischer indole synthesis is an electrophilic substitution, and the evidence suggests that it occurs less readily with pyridylhydrazones than with benzene derivatives. Some failures with derivatives of 2-pyridyl-hydrazine have been recorded but cyclohexanone and desoxybenzoin 2-pyridylhydrazones were cyclized in about 50 per cent yields with poly-phosphoric acid. Zinc chloride has been used successfully with methyl isopropyl ketone 2-pyridylhydrazone 82, The Brunner oxindole synthesis worked... 

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