title: Diphenylprolinol silyl ether catalyzed asymmetric Michael reaction of nitroalkanes and β,β-disubstituted α,β-unsaturated aldehydes for the construction of all-carbon quaternary stereogenic centers.
abstract: The asymmetric Michael reaction of nitroalkanes and β,β-disubstituted α,β-unsaturated aldehydes was catalyzed by diphenylprolinol silyl ether to afford 1,4-addition products with an all-carbon quaternary stereogenic center with excellent enantioselectivity. The reaction is general for β-substituents such as β-aryl and β-alkyl groups, and both nitromethane and nitroethane can be employed. The addition of nitroethane is considered a synthetic equivalent of the asymmetric Michael reaction of ethyl and acetyl substituents by means of radical denitration and Nef reaction, respectively. The short asymmetric synthesis of (S)-ethosuximide with a quaternary carbon center was accomplished by using the present asymmetric Michael reaction as the key step. The reaction mechanism that involves the E/Z isomerization of α,β-unsaturated aldehydes, the retro-Michael reaction, and the different reactivity between nitromethane and nitroethane is discussed.
authors.affiliation: Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza Aoba, Aoba-ku, Sendai 980-8578 (Japan). yhayashi@m.tohoku.ac.jp.
authors.forename: Yujiro
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Yuya
authors.initials: Y
authors.lastname: Kawamoto
authors.forename: Masaki
authors.initials: M
authors.lastname: Honda
authors.forename: Daichi
authors.initials: D
authors.lastname: Okamura
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Umemiya
authors.forename: Yuka
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Takasuke
authors.initials: T
authors.lastname: Mukaiyama
authors.forename: Itaru
authors.initials: I
authors.lastname: Sato
mesh_terms: D000447:Aldehydes; D000473:Alkanes / Q000737:chemistry*; D002244:Carbon; D002384:Catalysis; D004987:Ethers / Q000737:chemistry*; D015394:Molecular Structure; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D000473:Alkanes; D004987:Ethers; C529940:diphenylprolinol silyl ether; D002244:Carbon; D011392:Proline
keywords: Michael addition; asymmetric synthesis; enantioselectivity; isomerization; organocatalysis