Potassium salts, enolate derivatives

Phenylmercury derivatives of 3-aminomethylene-l-methyloxindols have also been investigated (79KGS65). For studies of the effect of substituents on the electronic structure of silver and potassium salts of 3-(aryl)imi-nooxindole see 76MI2. The keto-enol and imino-enamine tautomerism of compounds of type 127 (with 128 and 129) has been investigated (85KGS921). 

Examples in which heterocyclic haloarenes have been used include the photostimulated reactions of 2-chlorothiazole, 2-chloro-4-methylthiazole and 2-chloro-5-methylthiazole with pinacolone potassium enolate which lead to the formation of mono- and bis-2-thia-zolyl ketones672 and a study of the reactions of 3-halo-2-amino derivatives of benzo[ ]thio-phene with the potassium salts of acetophenone, pinacolone and cyclohexanone which indicated that, under S l conditions, mainly reduction products were formed673. 

In general, examples of substitution of sodium and potassium in organometallic derivatives by fluorine are limited to the salts of active methylene compounds. Their fluorination is achieved with perchloryl fluoride.fluorine, N-F reagents. " and xenon difluoride " (Table 10). The fluorination of metal enolates is discussed under metal-assisted substitution ot... 

Mukaiyama and coworkers have pioneered many routes to the total syntheses of rare carbohydrates such as the 2-amino-2-deoxypentoses [75]. In 1982, they reported that the potassium enolate derived from the magnesium salt of the (/ )-atrolactic acid derivative 85 adds to 2,3-0-isopropylidene-D-glyceraldehyde in a highly stereoselective manner giving, after alcohol protection, imine hydrolysis and amine protection, the D-arabinopentoate derivative 86 (Scheme 13.35). Further elaboration leads to 2-acetamido-2-deoxy-D-arabinose 87. In a similar fashion, starting from (5 )-atrolactic acid, 2-acetamido-2-deoxy-D-ribose 88 was prepared [76]. 

Mukaiyama and co-workers have pioneered many routes to the total s)uitheses of rare carbohydrates such as the 2-amino-2-deoxypentoses. In 1982 they reported that the potassium enolate derived from the magnesium salt of a (R)-atrolactic acid derivative adds to... 

Potassium fluoride in a two-phase system was also efficient when 18-crown-6 was present as a phase-transfer catalyst. The desilylation by fluoride produced a 7-0x0 enolate which could be reacted with various electrophiles. Appropriately substituted bicyclo[3.1.0]hexane derivatives 42 and 44 have been used to study this reaction.a,/l-Unsaturated carbonyl compounds gave rise to the formation of Michael adducts, while treatment with triphenylvinylphos-phonium salts gave bicyclo[3.3.0]octenes 46 as the result of a subsequent intramolecular Wittig reaction. 

A similar beneficial effect of 1,1-diphenylethylene on the yields of arylation products was later observed in the synthesis of benzonitrile derivatives by reaction of diaryliodonium salts with potassium cyanide and in the reaction of diaryliodonium salts with the sodium salt of nitroalkanes. 7 In the latter case, the reaction was therefore considered to result from intermediate inner-sphere radicals. Some years later. Barton et al. showed that 1,1-diphenylethylene acts as an efficient inhibitor of the radical chain process in the reaction of enolates with diaryliodonium salts. They concluded that the arylation products arose from a non-radical process. 

Diaryliodonium salts react more or less easily with carbonyl compounds to afford the C-arylated derivatives. Depending upon the nature of the substrate, different experimental conditions have been used. These reactions are generally performed in alcoholic solvents (r-BuOH, r-AmOH.) or in DMF, at temperatures ranging from low (- 78°C) to reflux of the solvent. Arylation of simple ketones has been obtained either by reaction of the ketone enolates with an appropriate diaryliodonium salt, i or by reaction of the ketone enol silyl ether with diaryliodonium fluoride. Phenylation of the potassium enolate of acetone (13) with diphenyliodonium bromide (14) afforded a modest yield of the monophenylation product, but the stimulation with solvated electrons led to overreaction due to the subsequent reaction of the iodobenzene, a good SrnI arylating agent under these conditions. 9... 

The enolate salts of simple ketones react with aryllead reagents, but the reaction is of little practical value. Indeed, only trisubstituted a-carbon atoms are reactive. The case of the potassium enolate of cyclohexanone derivatives is significant no reaction with cyclohexanone enolate (78), 36% with the mixture of enolates of 2-methylcyclohexanone (79), and 75% in the case of 2,6-dimethyl cyclohexanone enolate (80). ... 

Indoles and Carbazoles. - Formation. 2-Arylindoles (132) are formed by intramolecular Wittig reaction of the phosphonium salts (131). The hydroxamic acids PhN(OH)COCH2COR (R = alkyl or aryl) cyclize in boiling toluene to mixtures of indoles (133) and 3-isoxazolones (134). Irradiation of a solution of o-iodoaniline and the potassium enolate of acetone affords 2-methylindole. The enamino-ketone (135) cyclizes photochemically to 1,2-dimethylindole (136) with elimination of acetaldehyde/ The styrene derivative (137), obtained by the action of Meerwein s acetal, Me2NCH(OMe)2, on o-nitrotoluene, yields 1-hydroxyindole on treatment with zinc/ Azidobenzocyclobutanes (138 R = Me, Ph, or CH2Ph) are converted into indoles (133) by the action of concentrated sulphuric acid/ ... 

The 1,2-adducts (32) of 2-litho-l,3-dithians and cyclohex-2-enone can be isomerized to the more stable 1,4-adducts (33) by conversion into the potassium alkoxides (but not the less dissociated sodium or lithium salts).Direct formation of enone 1,4-adducts occurs when HMPA-THF is used as the solvent, and enolate trapping can be effected when the initial enone 1,4-adduct is treated with methyl iodide.The allylic anion derived from (34) undergoes cr-1,4-addition to cyclohexenone in the presence of Cul (Scheme 2). In the absence of the copper salt, both y-1,4- and cr-1,4-addition occur, with the former predominating. In contrast, allylation of (34) in the presence of Cul occurs primarily at the y-position, while cr-allylation is observed otherwise.The lithio-anion of 2-(yff-styryl)-... 

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