Methyl arylacetates, selective

Selective monoalkylation of methyl aryl-acetates by alkylhalides is difficult with conventional bases. It may be achieved by application of the three-step procedure outlined above adding (33) to the methyl arylacetates at a low temperature... 

A new perspective for safe and highly selective mono-N-and mono-C-alkylations Selective Mono-Methylation of Arylacetoni-triles and Methyl Arylacetates by Dimethylcarbonate... 

The unusually high selectivity observed in the monomethylation of methyl aryloxyacetates and aryloxyacetonitriles may be explained by the mechanism previously described for the reaction of DMC with methyl arylacetates and arylacetonitriles (6) in which ArCH(COOCH3)X and ArC(CH3)(COOCH3)X are the key intermediates. It is likely that this reaction proceeds through the formation of methyl-carboxymethyl intermediates, ArOC(CH3)(COOCH3)X, as these derivatives were actually detected by GC/MS during the course of the reaction. In this case, the attack on the acyl carbon, which produce the possible intermediate PhC(COOCH3)2X, does not affect selectivity, because it is an equilibrium reaction. 

Selective Mono-Methylation of Arylacetonitriles and Methyl Arylacetates by Dimethylcarbonate... 

The methylation of arylacetic acid derivatives is chosen as a model reaction for the mechanistic discussion. Experimental evidence of DMC-mediated alkylation of A1CH2X (X = CN, C02Me) with DMC supports the hypothesis that the reaction does not proceed through a 8 2 displacement of the ArCH X nucleophile on DMC (Bai2 mechanism).Rather, the selectivity arises from consecutive... 

Among the different synthetic procedures available for the preparation of hydratropic acids (e.g., indirect methylation of arylacetic acids,4 asymmetric hydroformylation of styrenes,5 rearrangements of a-bromoalkyl aryl ketals,6 etc.), direct methylation of arylacetic acid derivatives seems the most attractive from both economical and synthetic aspects the reagents are easily accessible and a one-pot reaction is involved. Nevertheless, this procedure is seldom used since the yields of the monomethyl derivatives are severely limited by the low selectivity of the reaction. Sizeable amounts of dimethylated by-products form.2 Even under phase-transfer catalysis conditions, high selectivity in monomethylation is elusive.7-8... 

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