Benzyl methyl ketone formation

The versatility of 5-nitrosopyrimidines in pteridine syntheses was noticed by Pachter (64MI21603) during modification of the Timmis condensation between (262) and benzyl methyl ketone simple condensation leads to 4-amino-7-methyl-2,6-diphenylpteridine (264) but in the presence of cyanide ion 4,7-diamino-2,6-diphenylpteridine (265) is formed (equation 90). The mechanism of this reaction is still uncertain (63JOC1187) it may involve an oxidation of an intermediate hydroxylamine derivative, nitrone formation similar to the Krohnke reaction, or nucleophilic addition of the cyanide ion to the Schiff s base function (266) followed by cyclization to a 7-amino-5,6-dihydropteridine derivative (267), oxidation to a quinonoid-type product (268) and loss of the acyl group (equation 91). Extension of these principles to a-aryl- and a-alkyl-acetoacetonitriles omits the oxidation step and gives higher yields, and forms 6-alkyl-7-aminopteridines, which cannot be obtained directly from simple aliphatic ketones. 

Two distinct mechanisms have been proposed. In the first, the formation of free enolates by nucleophilic attack of F at silicon was supported by a study180 of the interaction of tris(diethylamino)sulphonium (TAS) difluorotrimethylsilicate and the enol trimethylsilyl ether of benzyl methyl ketone. An equilibrium mixture appears to be produced (equation 17), which may be displaced in the direction of the TAS enolate by removal of the volatile fluorotrimethylsilane. 

Benzoic acid Benzoic anhydride Benzonitnle Benzophenone 3,4 Benzopvrene Benzopyrene Benzoyl acetone Benzovi chloride Benzyl acetate Benzyl alcohol Benzylamine Benzvl chloride Benzyl formate Benzyhdeneaniline Benzylidene chloride Benzylidenemethylamme Benzyl methyl ketone Bibenzyl... 

NPf) protected amine. The final ring formation was carried out by deprotonation of the benzylic methyl with potassium hexamethyldisilazide (KHMDS) which then added to the methyl ester to provide ketone 316. This compound was then carried on through a series of transformations to provide a common intermediate for every member of the FR900482 family. 

Aromatic and aliphatic amino ethers have been synthesized by this method. An example of the formation of a cyano ether is the preparation of p-cyano benzyl methyl ether from the substituted benzyl bromide and sodium methoxide (84%). Also, certain aryloxyacetonitriles, AtOCHjCN, are made by the condensation of chloroacetonitrile with sodium phenoxides in a solution of methyl ethyl ketone containing a small amount of sodium iodide (70-80%). Aromatic nitro ethers, like o- and p-nitrodiphenyl ether, have been prepared by the Ullmann procedure (84%). The synthesis of alkyl p-nitrophenyl ethers has also been accomplished with good yields (55-92%). ... 

Benzyl salicylate Geranyl anthranilate Amyl heptyl acetaldehyde Amyl methyl ketone M ethylacetophenone Benzylacetone Anisyl formate... 

Thus, the aldol shown, which is susceptible to Sharpless-type epoxidation, has been obtained from phytal and the protected hydroquinone (ref. 120). Formation of the epoxide presumably with a chiral peracid (or perhaps with a conventional peracid relying on the asymmetry of the substrate) and then cleavage reductively in t-butyl methyl ketone containing lithium aluminium hydride led to a diol. The benzylic hydroxyl group of this was hydrogenolysed to afford the hydroquinone dimethyl ether in 85% yield. Ceric ammonium nitrate (CAN) oxidation afforded the intermediate benzoquinone hydrogenation of which was reported to result in 2R,4 R,8 R-a-tocopherol by, presumably, avoidance of a racemisation step. 

After discovering the catalytic activity of aldehydes, Xu and co-workers later extended the method to TM-free aldehyde-catalyzed C-alkylation of secondary alcohols with primary alcohols [199] and catalyst-free C-alkylation reactions of methyl ketones with alcohols [200]. In 2013, Wu and co-workers also reported a closely related TM-free ketone-initiated C-alkylation of indole and pyrrole with secondary alcohols [201]. Similarly, Shi and co-workers employed conjugated ketones to catalyze the TM-free A/-alkylation reaction of amines with alcohols in 2015 (Scheme 42) [202], which is mainly suitable for benzylic and heterobenzylic alcohols, and anilines and heteroarylamines. Different ketones showed variant activities in the reaction (the catalysts were added in the same amount of 50 mg regardless of their molecular weights). In mechanistic studies such as the control reactions of the ketone catalyst and the substrate alcohol, up to 92 % ratio of the corresponding alcohol derived from reduction of the ketone catalyst can be detected in addition to formation of aldehdye intermediates derived from substrate alcohol. 

A number of 2,6-dideoxy-6,6,6-trifluorohexoses were prepared from a six-carbon acetylenic precursor via selective hydroxylation of the derived alkene diastereomers, and differences in stereoselectivity of reduction of a trifluoro-methyl ketone compared with the corresponding methyl ketone are outlined in Chapter 18. Oxidation of methyl 5-0-benzyl-3(2)-deoxy-3(2)-fluoro-a-D-pento-furanosides (DMSO/TFAA) was accompanied by epimerization at the fluori-nated carbon atom a- to the ketone resulting in formation of the corresponding 2-(or 3-) keto derivatives as mixtures of two epimers. Reduction then afforded various mixtures of 2- and 3- fluoro compounds. ... 

Alkylation of enamines requires relatively reactive alkylating agents for good results. Methyl iodide, allyl and benzyl halides, a-halo esters, a-halo ethers, and a-halo ketones are the most successful alkylating agents. The use of enamines for selective alkylation has largely been supplanted by the methods for kinetic enolate formation described in Section 1.2. 

FORMATION AND ALKYLATION OF SPECIFIC ENOLATE ANIONS FROM AN UNSYMMETRICAL KETONE 2-BENZYL-2-METHYL-CYCLOHEXANONE AND 2-BEN-ZYL-6-METHYLCYCLOHEXA-NONE 52 39... 

Because carbohydrates are so frequently used as substrates in kinetic studies of enzymes and metabolic pathways, we refer the reader to the following topics in Ro-byt s excellent account of chemical reactions used to modify carbohydrates formation of carbohydrate esters, pp. 77-81 sulfonic acid esters, pp. 81-83 ethers [methyl, p. 83 trityl, pp. 83-84 benzyl, pp. 84-85 trialkyl silyl, p. 85] acetals and ketals, pp. 85-92 modifications at C-1 [reduction of aldehydes and ketones, pp. 92-93 reduction of thioacetals, p. 93 oxidation, pp. 93-94 chain elongation, pp. 94-98 chain length reduction, pp. 98-99 substitution at the reducing carbon atom, pp. 99-103 formation of gycosides, pp. 103-105 formation of glycosidic linkages between monosaccharide residues, 105-108] modifications at C-2, pp. 108-113 modifications at C-3, pp. 113-120 modifications at C-4, pp. 121-124 modifications at C-5, pp. 125-128 modifications at C-6 in hexopy-ranoses, pp. 128-134. 

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