O-nitrophenyl ketones

In acidic or slightly basic aqueous media, Ai-hydroxyindoles can be prepared after electrolysis of a-(o-nitrophenyl) ketones vide supra Scheme 9) [13], at a working potential corresponding to the first cathodic wave. In an acidic medium, indoles are directly obtained at a working potential corresponding to the second cathodic wave. 

Anthranils from o-nitrophenyl ketones and triethyl phosphite, 48, 115 Apocamphane-l-carboxylic acid, 45, 56... 

The sheer number of o-nitrophenyl ketone reductive cychzations to form indoles necessitates an abbreviated section of this material. It is obvious that the challenge in this methodology is the preparation of the precursor nitro ketone because its cyclization is fait accompli. Scheme 7 [48-75] illustrates a range of indoles synthesized by... 

One route to o-nitrobenzyl ketones is by acylation of carbon nucleophiles by o-nitrophenylacetyl chloride. This reaction has been applied to such nucleophiles as diethyl malonatc[l], methyl acetoacetate[2], Meldrum s acid[3] and enamines[4]. The procedure given below for ethyl indole-2-acetate is a good example of this methodology. Acylation of u-nitrobenzyl anions, as illustrated by the reaction with diethyl oxalate in the classic Reissert procedure for preparing indolc-2-carboxylate esters[5], is another route to o-nitrobenzyl ketones. The o-nitrophenyl enamines generated in the first step of the Leimgruber-Batcho synthesis (see Section 2.1) are also potential substrates for C-acylation[6,7], Deformylation and reduction leads to 2-sub-stituted indoles. 

The reduction of a dinitro ketone to an azo ketone is best achieved with glucose. 2,2 -Dinitrobenzophenone treated with glucose in methanolic sodium hydroxide at 60° afforded 82% of dibenzo[c,f [i 2]diazepin-l 1-one whereas lithium aluminum hydride yielded 24% of bis(o-nitrophenyl)methanol [575], Conversion of aromatic nitro ketones with a nitro group in the ring into amino ketones has been achieved by means of stannous chloride, which reduced 4-chloro-3-nitroacetophenone to 3-amino-4-chloroacetophenone in 91% yield [178]. A more dependable reagent for this purpose proved to be iron which, in acidic medium, reduced m-nitroacetophenone to m-aminoacetophenone in 80% yield and o-nitrobenzophenone to o-aminobenzophenone in 89% yield (stannous chloride was unsuccessful in the latter case) [903]. Iron has also been used for the reduction of o-nitrochalcone, 3-(o-nitrophenyl)-l-phenyl-2-propen-l-one, to 3-(o-aminophenyl)-l-phenyl-2-propen-l-one in 80% yield [555]. 

Ketone synthesisThe preparation of ketones via /1-hydroxy o-nitrophenyl... 

KETONES Bis(phcnylthio)mcthanc. Chlomihexylborane. (irignard reagents. Nickel chloride-Zinc. o-Nitrophenyl sclcnocyanate. Organomagnesium(ll) iodides. PhcnylthiophenyKtrimethyl-silyllnielliane. 

Catalyst or with acetyl chloride and aluminum chloride catalyst have been reported. o-Nitrophenyl 2-thienyl ketone has been prepared. ... 

Ketone synthesis. The preparation of ketones via /i-hydroxy o-nitrophenyl selenoxides has been extended to deoxy keto sugars. 

Bis(o-nitrophenyl)ethanediol (50) has been proposed as a practical photolabile protecting group for ketones and aldehydes which is superior to the monosub-stituted o-nitrophenylethanediol. The presence of a single stereocentre in the latter leads to the formation of two diastereomers when it is used with another chiral molecule, thus complicating NMR signal patterns, and often making purification difficult. In addition, the obvious alternative of ketal formation from two molecules of o-nitrobenzyl alcohol instead of a diol is usually impractical. On the other hand (50) is easily accessible as a pure enantiomer, and the ketals which it forms with aldehydes and ketones are smoothly deprotected in neutral conditions by irradiation at 350 nm. 

The ridge-like polyarylesteiketones have been synthesized by means of one-stage polycondensation in solution of bis(4-nitrophenyl)ketone with phenolphthalein, o-cresolphthaleine, 2,5,2 -5 -tetramethylphenol-phthaleine and timolphthaleine [352]. Authors have shown that the free volume within the macromolecule depends on position, type and number of alkyl substitutes. 

Halogenation of steroid 3-ketones can lead to complicated mixtures by virtue of the fact that the kinetic enol leads to 3 halo products, whereas the thermodynamic product is that halogenated at the 4 position. Carefully controlled reaction of the 5a-androstanolone with chlorine thus leads to the 2a-chloro derivative (29). Reaction of that intermediate with O(p-nitrophenyl)-hydroxylamine affords the androgenic agent ni stremine acetate (30). ... 

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