title: A Novel Method for a Stereoselective Synthesis of Trisubstituted Olefin Using Tricarbonyliron Complex: A Highly Stereoselective Synthesis of (all-E)- and (9Z)-Retinoic Acids.
abstract: In order to establish the stereoselective synthesis of retinoic acids, which are ligand molecules of the retinoic acid receptors (RARs, all-E-isomer) and the retinoid X receptors (RXRs, 9Z-isomer), the reaction of beta-ionone-tricarbonyliron complex 7 with carbanions was investigated. Treatment of 7 with the lithium salt of acetonitrile afforded (7E,9E)-beta-ionylideneacetonitrile-tricarbonyliron complex 8 exclusively, via addition, dehydration, and migration of tricarbonyliron complex. On the contrary, the reaction of 7 with the lithium enolate of ethyl acetate and subsequent dehydration by thionyl chloride afforded the ethyl (7E,9Z)-beta-ionylideneacetate-tricarbonyliron complex 16b predominantly. These compounds (8 and 16b) were converted to the corresponding beta-ionylideneacetaldehyde-tricarbonyliron complexes (10 and 22) in excellent yields, respectively. The Emmons-Horner reaction of these compounds with C5-phosphonate followed by the sequence of decomplexation and alkaline hydrolysis gave the corresponding retinoic acids (26 and 29).
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakita-machi, Higashinada-ku, Kobe 658, Japan, and Tanabe Seiyaku Co., Ltd., 3-16-89, Kashima, Yodogawa-ku, Osaka 532, Japan.
authors.forename: Akimori
authors.initials: A
authors.lastname: Wada
authors.forename: Saeko
authors.initials: S
authors.lastname: Hiraishi
authors.forename: Norio
authors.initials: N
authors.lastname: Takamura
authors.forename: Tadamasa
authors.initials: T
authors.lastname: Date
authors.forename: Keiichi
authors.initials: K
authors.lastname: Aoe
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ito