The DFT Quest for Possible Reaction Pathways, Catalytic Species, and Regioselectivity in the InCl3-Catalyzed Cycloaddition of N-Tosyl Formaldimine with Olefins or Allenes

The present work focuses on a theoretical investigation of the plausible mechanism, determination of catalytically active species, and understanding of the regioselectivity in the InCl3-catalyzed cycloaddition of N-Tosyl formaldimine with alkenes or allenes. InCl3 and InCl2+ coordinated by dichloroethane (InCl2+-DCE) were investigated as model catalytic systems. DFT data supported that InCl2+-DCE represent the plausible in situ generated catalytic species. The catalytic cycle starts from the coordination of N-Tosyl formaldimine to InCl2+-DCE, generating an In-complexed iminium intermediate. This then undergoes intermolecular reaction (aza-Prins) with alkene substrate to form a carbocation intermediate, which is chemoselectively attacked by the second N-Tosyl formaldimine molecule to form a formaldiminium intermediate. In a final step, this intermediate undergoes the ring closure, leading to hexahydropyrimidine along with the regeneration of catalyst. In addition, our DFT results indicate that N-Tosyl formaldimine not only acts as a reactant but also accelerates the 1,3-H-shift as a proton acceptor, giving an experimentally observed allylamide product. Also, the "iminium/alkene/imine" path was supported by calculation results for diastereoselective [2 + 2 + 2] reaction using an internal alkene. Finally, the regioselectivity of the InCl3-catalyzed cycloaddition using allenes along with N-Tosyl formaldimine was also analyzed. Copyright © 2020 American Chemical Society.

Fang R.1, 2 , Zhang Y. 2 , Kirillov A.M. 3, 4 , Yang L. 1, 2
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  • 1 College of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
  • 2 State Key Lab. of Appl. Organ. Chem. and Key Lab. of Nonfer. Met. Chem. and Rsrc. Utiliz. of Gansu Prov., College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
  • 3 Centro de Quimica Estrutural, Complexo I, Instituto Superior Tecnico, Universidade de Lisboa, Av. Rovisco Pais, Lisbon, 1049-001, Portugal
  • 4 Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya st., Moscow, 117198, Russian Federation
Catalysis; Olefins; Reaction intermediates; Regioselectivity; Calculation results; Catalytic species; Catalytically active species; Diastereoselective; Intermolecular reactions; Plausible mechanisms; Regeneration of catalyst; Theoretical investigations; Chlorine compounds; alkene; allene derivative; allylamide; amide; formaldehyde; hexahydropyrimidine; indium chloride; n tosyl formaldimine; pyrimidine derivative; unclassified drug; Article; catalysis; chemical structure; cycloaddition; density functional theory; regioselectivity
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