Trimethyl orthoformate → 2,3-Dihydro-5-(4-nitrobenzoyl)oxy-2,2,4,6,7-pentamethyl-1-benzofuran-3-carboxylic acid, methyl ester

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Reaction Steps

A heterogeneous mixture of 30.20 g (0.079 mol) of 3,4-dihydro-6-(4-nitrobenzoyl)oxy-2,2,5,7,8-pentamethyl-2H-1-benzopyran-4-one, 36.86 g (0.083 m) of thallium (III) nitrate trihydrate, 200 ml of trimethylorthoformate, and 200 ml of methanol is stirred at room temperature for 4 days. The resulting solid is collected and washed with methanol. The residue is slurried in 100 ml of chloroform and filtered; this process is repeated three times. The combined filtrates are heated to boiling and the chloroform is gradually replaced by an equal volume of methanol until crystallization occurs to give 27.44 g (84%) of 2,3-dihydro-5-(4-nitrobenzoyl)oxy-2,2,4,6,7-pentamethyl-1-benzofuran-3-carboxylic acid, methyl ester, m.p. 215°-216° C. Elemental analysis, IR, UV, and 1H-NMR spectra confirm the structure. This procedure was scaled up to 402 g, and 380.9 g (87.8%) of product was obtained.

Provenance & Evidence