Li, Yan; Li, Zhilin; Zhang, Zhiqiang published an article in 2021, the title of the article was Mechanism and regio- and stereoselectivity in an NHC-catalyzed Mannich/lactamization domino reaction.Formula: C21H24BF4N3 And the article contains the following content:
D. functional theory (DFT) calculations (M06-2X) have been employed to disclose the mechanisms and regio- and stereo-selectivities of the N-heterocyclic carbene (NHC)-catalyzed reaction of 2-benzothiazolimines and α-chloroaldehydes. The preferred mechanism is initiated by the nucleophilic attack of NHC on α-chloroaldehyde (first step), followed by 1,2-proton transfer which was assisted by the Bronsted acid DABCO·H+ to generate the Breslow intermediate (second step). The cleavage of the C-Cl bond (third step) and deprotonation (fourth step) form the enolate intermediate. This further reacts with 2-benzothiazolimine which leads to the formation of a new C-C bond (fifth step). Subsequent cyclization takes place via the formation of a new C-N bond (sixth step). Catalyst regeneration completes the whole catalytic cycle and affords the final product (seventh step). The DFT results indicate that the fifth step determines the stereochem. of the reaction and leads to benzothiazolopyrimidinone with the SS configuration, which agrees well with exptl. observations. Intramol. cyclization is found to be the regioselectivity-determining step, for which the [4+2] annulation pathway is more preferred than that via [2+2] annulation, which again agrees well with exptl. observations. Based on the mechanism proposed, the origins of regio- and stereoselectivities have also been investigated by performing distortion/interaction, natural bond orbital (NBO) and non-covalent interaction (NCI) analyses. The mechanistic insights gained in this work should be helpful in the rational design of potential catalysts for analogous reactions. The experimental process involved the reaction of (R)-5-Benzyl-2-mesityl-6,7-dihydro-5H-pyrrolo[2,1-c][1,2,4]triazol-2-ium tetrafluoroborate(cas: 1469801-67-9).Formula: C21H24BF4N3
The Article related to heterocyclic carbene catalyst mannich lactamization mechanism, Physical Organic Chemistry: Ring Formation, Cleavage, Enlargement, and Contraction and other aspects.Formula: C21H24BF4N3
Referemce:
1,2,3-Triazole – Wikipedia,
Triazoles – an overview | ScienceDirect Topics