3-(2-Methylpropyl)cyclohexan-1-one → 1-Methyl-3-(2-methylpropyl)cyclohexanol

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Reaction Steps

A solution of 62.7 g (0.407 mol) of the distilled ketone in 200 ml ether was added dropwise to a stirred solution of 0.6 mol methyl magnesium iodide in 200 ml ether at such a rate that the reaction mixture was allowed gradually to reach and then maintain a steady reflux. When the addition was complete heat was applied to maintain reflux for a further 30 minutes. Thereafter the reaction mixture was quenched with 1.01 of water and the resulting precipitate in the aqueous phase dissolved by the addition of saturated aqueous ammonium chloride (1.01). The organic phase was separated, washed, dried and the solvent was removed in vacuo. The crude consisted of a mixture of trans and cis 1-methyl-3-(2-methylpropyl)cyclohexan-1-ol in a ratio of 2:1. It could be purified by distillation under reduced pressure to obtain a mixture of about the same isomer distribution. Alternatively it could be separated into the cis and trans isomers by column chromatography over silica (200 g for 4 g of crude) using a mixture of diethyl ether and pentane (1.5 v/v ratio) as the eluent. It could also be separated into the isomers by fractional distillation under reduced pressure over a 1 m Sulzer column using a reflux: take off ratio of 10:1. Thus, 217 g of crude yields 102 g (>94% pure on gc) of the trans isomer (head temperature 69° C. at 0.04 kPa) and 50 g (>97% pure on gc) of the cis isomer (62° C. at 0.01 kPa) and 43 g of an intermediate fraction consisting of a mixture of the two isomers.

Provenance & Evidence