title: Organocatalytic aza-Michael/retro-aza-Michael reaction: pronounced chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction.
abstract: A detailed experimental investigation of an aza-Michael reaction of aniline and chalcone is presented. A series of Cinchona alkaloid-derived organocatalysts with different functional groups were prepared and used in the aza-Michael and retro-aza-Michael reaction. There was an interesting finding that a complete reversal of stereoselectivity when a benzoyl group was introduced to the cinchonine and cinchonidine. The chirality amplification vs. time proceeds in the quinine-derived organocatalyst containing silicon-based bulky group, QN-TBS, -catalyzed aza-Michael reaction under solvent-free conditions. In addition, we have demonstrated for the first time that racemization was occurred in suitable solvents under mild conditions due to retro-aza-Michael reaction of the Michael adduct of aniline with chalcone. These indicate the equilibrium of retro-aza-Michael reaction and aza-Michael reaction produce the happening of chirality amplification in aza-Michael reaction and racemization via retro-aza-Michael reaction under different conditions, which would be beneficial to the development of novel chiral catalysts for the aza-Michael reactions.
authors.affiliation: Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou, People's Republic of China.
authors.forename: Yong-Feng
authors.initials: YF
authors.lastname: Cai
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Meng-Xian
authors.initials: MX
authors.lastname: Luo
authors.forename: Ke-Fang
authors.initials: KF
authors.lastname: Yang
authors.forename: Guo-Qiao
authors.initials: GQ
authors.lastname: Lai
authors.forename: Jian-Xiong
authors.initials: JX
authors.lastname: Jiang
authors.forename: Li-Wen
authors.initials: LW
authors.lastname: Xu
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D002384:Catalysis; D002930:Cinchona Alkaloids / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001372:Aza Compounds; D002930:Cinchona Alkaloids