Ketones, aryl methyl synthesis

Aryl methyl ketones have been obtained [4, 5] by a modification of the cobalt-catalysed procedure for the synthesis of aryl carboxylic acids (8.3.1). The cobalt tetracarbonyl anion is converted initially by iodomethane into the methyltetra-carbonyl cobalt complex, which reacts with the haloarene (Scheme 8.13). Carboxylic acids are generally obtained as by-products of the reaction and, in several cases, it is the carboxylic acid which predominates. Unlike the carbonylation of haloarenes to produce exclusively the carboxylic acids [6, 7], the reaction does not need photoinitiation. Replacement of the iodomethane with benzyl bromide leads to aryl benzyl ketones in low yield, e.g. 1-bromonaphthalene produces the benzyl ketone (15%), together with the 1-naphthoic acid (5%), phenylacetic acid (15%), 1,2-diphenylethane (15%), dibenzyl ketone (1%), and 56% unchanged starting material [4,5]. a-Bromomethyl ketones dimerize in the presence of cobalt octacarbonyl and... 

Selected examples of the synthesis of aryl methyl ketones ... 

Mechanistically, the reaction proceeds through Michael addition of the aryl methyl ketone to the enone. Hydride abstraction and cyclization then yield the pyrylium salt. The route is capable of considerable diversification and therefore has much potential. The detailed method for the synthesis of 2,4,6-triphenylpyrylium perchlorate is worthy of mention... 

Singular examples to form aromatic ethers are a base-catalyzed, multistep, one-pot reaction of aryl methyl ketones with the appropriate fluorinated arylidenemalonitriles, the mercury acetate assisted synthesis of pentahalophenylvinyl ethers from vinyl acetate and the corresponding phenol, and the radical displacements in aryloxycyclohexadienones (e.g., 27) by halophenols. 2,3-Dichloro-5,6-dicyanohydroquinone (28) and products such as 29 are readily formed when cyclohexadienone 27 is treated with different phenols. 

The application of microwave heating to a silica-assisted solution-phase synthesis has been utilized by Humphries and Finefield [24] for an efficient two-step protocol for the preparation of pyrazoles (xxiii) from aryl methyl ketone and aryl hydrazine monomers. 

Pent-2-ene-l,5-diones 23 are intermediates in this reaction. Variation of this synthesis is achieved using related bis-electrophiles. For instance, 2,6-disubstituted pyrylium salts 25 are formed from two molecules of aryl methyl ketone and orthoformic ester in the presence of strong acids (HCIO4, HBF4) ... 

When reacted with aryl methyl ketones in acetic anhydride in the presence of a hydride acceptor, e.g. FeCl3, chalcones 32 yield trisubstituted pyrylium salts 34 Dilthey synthesis) ... 

The first iodine-catalyzed synthesis of 2-alkyl substituted oxazoles 130 by a decarboxylative domino reaction was reported. Aryl methyl ketones 128 were transformed in situ into a-iodo ketones and then, by the Kornblum oxidation, into 1,2-diketones. After the addition of the a-amino acid 129, an l2-mediated cyclization/decarboxylation gave oxazoles 130. The reaction proceeds better if the Ar has electron-donating substituents and if the R group is a branched alkyl chain or phenyl residue. The reaction used oxone to regenerate iodine (13JOC6065). 

One of great synthetic applications of electrochemical fixation of carbon dioxide is synthesis of 2-arylpropanoic acids, nonsteroidal anti-inflammatory drugs (NSAlDs), and their derivatives. Electrochemical carboxylations of benzyl halides [1, 3, 8-13], aryl methyl ketones [14, 15], and a-bromostyrenes [16] are reported to be successfully applied to the synthesis of several NSAIDs, such as ibuprofen and naproxen, and their precursors and derivatives (Scheme 4). 

Ladani et al. have synthesized one-pot synthesis of 3-(2,6-diaiylpyrid-n-4-yl)quinolin-2(l//)-ones (12) in high yield by cyclocondensation reaction under Kibhnke s reaction conditions using aldehyde (1), aryl methyl ketone and various A -phenacylpyridiniiim bromides (11) in a mixture of ammonimn acetate and aeetic acid imder MWI (Scheme 6.5). The synthesized compounds were screened for their antimicrobial activity [41,42],... 

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