New Synthetic Method of (6E, 9E)-2, 3-Epoxy-3, 7, 11, 11- tetramethylcycloundeca - 6, 9 - diene

Abstract

Synthesis of (6E, 9E)-2, 3-epoxy-3, 7, 11, 11-tetramethylcycloundeca-6, 9-diene (2) from humulene (1) by the known method has been carried out through 4 reaction steps, in very low total yield, and the final step needs troublesome purification of 2 by chromatography over silica gel impregnated with silver nitrate (10 per cent). In order to overcome the above problems and research for reactions leading for epoxide 2, we developed a new synthesis of 2 from 1 in good total yield.
Diepoxidation of 1 with 2 molar amounts of m-chloroperbenzoic acid p roduced compound 8, of which purification was done by recrystallization from hexane. Selective reduction of 6, 7-epoxy ring in 8 with Ti (II) into a double bond was successful and gave 2 contaminated with a small amount of (2E, 9E)6, 7-epoxy-3, 7, 11, 11-tetramethylcycloundeca-2, 9-diene (3) in 42.7% yield together with 1(27.3%)and unchanged 8(25%). By the formation of crystalline silver nitrate complex of 2 in a similar manner used for 1, pure epoxide 2 was obtainable without use of the troublesome chromatography over silica gel impregnated with silver nitrate.
Merits of our new synth etic method of 2 are: (i) it requires only 2 reaction steps to give a good total yield (32%) of 2, and (ii) very simple purification procedure is necessary to obtain 2, and the byproducts 1 and 3 are recyclable.