ALKYLATION-REDUCTION OF CARBONYL SYSTEMS .10. REGIOSPECIFIC SYNTHESIS OF 1,4-DIENES BY ALKYLATION-REDUCTION OF ALPHA,BETA,GAMMA,DELTA-UNSATURATED KETONES

1, 4-Dienes are conveniently prepared from α, β, γ, δ-unsaturated ketones by tandem alkylation-reduction. By this procedure substituted 1, 3-diene 5-alkoxides, generated in situ by alkylation of a, α, β, γ, δ-unsaturated ketones, are reduced by lithium-ammonia-ethanol to the corresponding substituted 1, 4-dienes. Examples include the synthesis of 2, 6-dimethyl-2, 5-heptadiene (4), 2, 6-dimethyl-2, 5-decadiene (5), and 2, 6, 7, 7-tetramethyl-2, 5-octadiene (6) by the methylation-, n-butylation-, and tert-butylation-reduction of 6-methyl-3, 5-heptadien-2-one (1), respectively. By this procedure 2, 6, 10-trimethyl-2, 5, 9-undecatriene (7), 2, 6, 10-trimethyl-2, 6, 9-tetradecatriene (8), and 2, 6, 10, 11, 11-pentamethyl-2, 6, 9-dodecatriene (9) were also prepared from 6, 10-dimethyl-3, 5, 9-undecatrien-2-one (pseudoionone, 2), as well as l-(2, 6, 6-trimethyl-l-cyclohexen-l-yl)-3-methyl-2-butene (10), l-(2, 6, 6-trimethyl-lcyclohexen-l-yl)-3-methyl-2-heptene (11), and l-(2, 2, 6-trimethyl-l-cyclohexen-l-yl)-3, 4, 4-trimethyl-2-pentene (12) from β-ionone (3). © 1979, American Chemical Society. All rights reserved.