title: Stereospecific 1,3-migration of an Fe(CO)3 group on acyclic conjugated polyenes: application to remote and iterative asymmetric induction.
abstract: The stereochemical outcome of the 1,3- and 1,5-migration of an Fe(CO)3 group on (acyclic polyene)Fe(CO)3 complexes and their application to stereoselective construction of remote and contiguous stereogenic centers are described. Treatment of the [(eta(4)-4-7)triene]Fe(CO)3 complexes 1a-d bearing an electron-withdrawing group on the terminal position of an uncomplexed olefin with a base such as KN(SiMe3)2 (KHMDS) and LiCH2CN induced the 1,3-migration reaction of the Fe(CO)3 group, giving the [(eta4-2-5)triene]Fe(CO)3 complexes 2a-d in moderate to good yields, depending on the electron-withdrawing groups. From an experiment using the chiral (trienenitril)Fe(CO)3 complex 5, it is revealed that the 1,3-migration proceeds with inversion of configuration. Similarly, the 1,5-migration reaction of the[(eta4-6-9)tetraenone]Fe(CO)3 complexes 9 occurred with a catalytic amount of KHMDS, giving the [(eta4-2-5)tetraenone]Fe(CO)3 complexes 10 with retention of configuration. Furthermore, we have succeeded in the first regio- and stereoselective nucleophilic substitution of the (3,5-diene-1,2-diol) Fe(CO)3 complexes (15 --> 24a-h) with various nucleophiles via the ortho esters 21. By using iterative manipulation of the above two reactions, remote stereocontrol of the terminal substituents on acyclic polyene (9 --> 12) and construction of contiguous stereogenic centers (19, 28) have been achieved.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. takemoto@pharm.kyoto-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Takemoto
authors.forename: K
authors.initials: K
authors.lastname: Ishii
authors.forename: T
authors.initials: T
authors.lastname: Ibuka
authors.forename: Y
authors.initials: Y
authors.lastname: Miwa
authors.forename: T
authors.initials: T
authors.lastname: Taga
authors.forename: S
authors.initials: S
authors.lastname: Nakao
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Ohishi
authors.forename: Y
authors.initials: Y
authors.lastname: Kai
authors.forename: N
authors.initials: N
authors.lastname: Kanehisa