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Theoretical Studies of the Asymmetric Binary‐Acid‐Catalyzed tert ‐Aminocyclization Reaction: Origins of the C sp 3 H Activation and Stereoselectivity
Author(s) -
Zhang Long,
Chen Liujuan,
Lv Jian,
Cheng JinPei,
Luo Sanzhong
Publication year - 2012
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201200674
Subject(s) - chemistry , stereoselectivity , stereospecificity , catalysis , phosphoric acid , substrate (aquarium) , stereochemistry , hydrogen bond , activation energy , molecule , organic chemistry , oceanography , geology
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 CC bond formation. The mode of stereocontrol for facial selection could be ruled out owing to the high activation energy of CN 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.