Construction of a chiral quaternary carbon center by indium-catalyzed asymmetric alpha-alkenylation of beta-ketoesters.
Construction of a nonracemic all-carbon quaternary stereocenter at the alpha-position of beta-ketoesters was achieved by way of an indium(III)-catalyzed diastereoselective alpha-alkenylation reaction of chiral enamines with 1-alkynes. The enamine bearing a chiral auxiliary derived from l-isoleucine was added to the alkyne to give an alpha-alkenylated product in excellent yield and with a stereoselectivity better than 90% ee. One can ascribe the high selectivity to a chelate intermediate involving the auxiliary and the metal atom and the high yield to efficient interactions between the indium(III) atom and the alkyne. The selectivity increased as the reaction temperature was raised to 120 degrees C and decreased at higher temperatures.
Fujimoto
Taisuke
T
Department of Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Endo
Kohei
K
Tsuji
Hayato
H
Nakamura
Masaharu
M
Nakamura
Eiichi
E
D000478:Alkylation; D000480:Alkynes / Q000737:chemistry; D000588:Amines / Q000737:chemistry; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D004952:Esters / Q000138:chemical synthesis* / Q000737:chemistry; D007204:Indium / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry
D000480:Alkynes; D000588:Amines; D004952:Esters; D007659:Ketones; D009942:Organometallic Compounds; D007204:Indium; D002244:Carbon; D015032:Zinc