Methanol → 3-Penten-2-one, 3-methyl-5-(2,2,3-trimethyl-3-cyclopenten-1-yl)-

Participants

Reaction Steps

To a stirred solution of 400 g (6.1 moles) of methyl ethyl ketone, 1025 g (32 moles) of methanol, 30.5 g (0.54 mole) of potassium hydroxide and 380 g of water cooled to -5° to -10° C was added 152 g (1.0 mole) of campholenic aldehyde over 15-30 minutes. The mixture was maintained at 0° to -10° C for 24-36 hours and then at 25°-35° C for 18-24 hours. The mixture was neutralized by addition of 36.8 g of 62.5% sulfuric acid and the unreacted methyl ethyl ketone and excess methanol were removed by atmospheric distillation. The residual liquid was added to 200 ml of hexane and 200 ml of water. The aqueous layer was drawn off and the hexane layer was washed with 200 ml of brine. The hexane was removed by atmospheric distillation and the oil fractionally distilled under vacuum to give 3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl) pent-3-en-2-one and two other isomers in a ratio of ca. 86:6:8 by glc. Yield 140.3 g (85% theory); bp 102°-105° C (1.3 mm); nD20 1.4888; mol wt. 206 (ms); nmr, 0.8δ (3H, s), 1.0 (3H, s), 1.6 (3H, broad s), 1.8 (3H, broad s), 2.3 (3H, s, acetyl CH3), 5.3 (1H, broad multiplet, olefinic H), 6.7 (1H, complex, β-olefinic H of an α,β-unsaturated carbonyl system); ir, 3030, 1670, 1635, 790 cm-1.

Provenance & Evidence