Toluene → Ethyl benzoate

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Reaction Steps

As is shown in the reaction scheme, the (2,2-dialkyl-4-alkyl, aryl or heteroaryl-2H-chromen-6-yl) boronic acid compounds of Formula 24 (or their corresponding thiochrom-3-ene analogs) are reacted with ethyl 2-bromobenzoate in the presence of Pd(0) catalyst in an inert solvent or solvent mixture, such as toluene and methanol, to provide 2-(2,2-dialkyl-4-alkyl, aryl or heteroaryl-2H-chromen-6-yl)benzoic acid ethyl ester compounds of Formula 60. The reagent ethyl 2-bromobenzoate is available in accordance with the chemical literature, see for example J. Org. Chem. 14 (1949) 509, 512 and Helv. Chim. Acta 39 (1956) 505-511. Other examples of reagents which can be used in this reaction instead of ethyl 2-bromobenzoate are: ethyl 2-bromopyridine-3-carboxylate, ethyl 4-bromopyridine-3-carboxylate, ethyl 3-bromothiophene-2-carboxylate, ethyl 2-bromothiophene-3-carboxylate, ethyl 3-bromofuran-2-carboxylate, ethyl 2-bromofuran-3-carboxylate, ethyl cis 2-bromo-cyclopentanecarboxylate and ethyl cis 2-bromo-cyclohexanecarboxylate. However, in the ensuing desription the primary emphasis remains on the 1,2 substituted phenylene derivative actually shown in the reaction scheme.

Provenance & Evidence