Trimethyl orthoformate → 3-Oxo-cyclopentanecarboxylic acid methyl ester

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Reaction Steps

A solution of 193.8 g (1.51 moles) of 3-oxocyclopentane carboxylic acid in 580 ml of methanol, analytical grade, is treated with 1.8 g (9.5 mmoles) of toluene sulphonic acid hydrate with stirring, then 192.4 g (1.81 moles) of trimethyl orthoformate are added in the course of 10 minutes and the mixture is heated to boiling under reflux. This temperature is maintained for 1 hour. The solution is evaporated in vacuo (i.v.), the residue is treated with 200 ml of H2O, 220 ml of toluene and 1.9 ml of concentrated H2SO4 and stirred at room temperature for 1 hour. The phases are separated, the aqueous phase is extracted 3× using 50 ml of toluene each time, the combined organic phases are washed 1× using 90 ml of 2.5% strength LiOH solution and 2× using 50 ml of H2O each time. The organic phase is dried using magnesium sulphate and evaporated in vacuo. The oily residue is fractionally distilled using a water-jet vacuum.

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