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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 12, Number 1
BKCSDE 12(1)
January 20, 1991 

Novel Syntheses of Isomers of Damascenone from Ethyl 2,6,6-Trimethyl-4-oxo-2-cyclohexene-1-carboxylate
Woo Young Lee*, Se Young Jang, Jun-Gu Lee, Woo Ki Chae
Three isomers of damascenone, odorous terpenic ketones, have been synthesized conveniently from a same starting material, ethyl 2,6,6-trimethyl-4-oxo-2-cyclohexene-1-carboxylate( 1), which was easily available by the acid-catalyzed condensation of mesityl oxide or acetone with ethyl acetoacetate. α -Damascenone(7) was prepared by converting the enone ester 1 into the corresponding tosylhydrazone(4), followed by treating with 4 molar equiv of allyllithium. β-Damascenone(12) was synthesized by chemoselective reduction of 1 with sodium borohydride/cerium chloride to give corresponding allylic alcohol 8, conversion of 8 into acetate 9, and thermal decomposition of 9 with DBU to afford ethyl β-safranate(10), followed by reaction with an excess amount of allyllithium. γ-Damascenone(15) was obtained by dehydration of 8 with boric acid to furnish γ -safranate(13), followed by treatment with 2 molar equiv of allyllithium.
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