title: Theoretical studies of the asymmetric binary-acid-catalyzed tert-aminocyclization reaction: origins of the C(sp 3)-H activation and stereoselectivity.
abstract: A mechanistic study of the tert-aminocyclization reaction was performed by using DFT calculations and labeling experiments. The results showed that the reaction proceeded through a rate-limiting-, stereospecific-, and suprafacial 1,5-H-transfer pathway, followed by a barrier-less C-C bond formation. The mode of stereocontrol for facial selection could be ruled out owing to the high activation energy of C-N bond rotation. The intrinsic feature of this Lewis acid activation was found to be the activation of the LUMO, as well as an intermediate-stabilization effect. The catalytically active species was believed to be a 1:1 complex of phosphoric acid and MgCl(2), which was stabilized by a H⋅⋅⋅Cl hydrogen bond. The chiral catalytic complex selectively recognizes and activates one of the two helical conformations of substrate A, required for 1,5-suprafacial H-transfer, which dictates the stereoselectivity of the forming products.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key of Molecular Recognition and Function Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.forename: Liujuan
authors.initials: L
authors.lastname: Chen
authors.forename: Jian
authors.initials: J
authors.lastname: Lv
authors.forename: Jin-Pei
authors.initials: JP
authors.lastname: Cheng
authors.forename: Sanzhong
authors.initials: S
authors.lastname: Luo