• Uncatalyzed gas phase aziridination of alkenes by organic azides. Part 2. Whole azide reaction with alkene

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      https://www.ias.ac.in/article/fulltext/jcsc/131/01/0006

    • Keywords

       

      Alkene aziridination by azides; 1,3-dipolar cycloaddition; triazoline decomposition; density functional theory.

    • Abstract

       

      The B3LYP/6-31G(d,p) DFT method was used to study alkene aziridination by azides through uncatalyzed thermal gas phase routes which involve the whole azide reactant molecule without dissociation.Two mechanisms were studied – Route I involving concerted azide addition to alkene with the elimination of N2, and the multi-step Route II involving 1,3-dipolar cycloaddition between azide and alkene. Three azides RN3 (R = H, Me, Ac) are reacted with alkene substrates forming aziridine products. The concerted addition–elimination step of Route I is exothermic with an appreciable barrier, where the facility order Ac > Me > Hpoints to electrophilicity of the azide reactant. The initial 1,3-dipolar cycloaddition step of Route II involves smaller barriers than Route I, while thermal decomposition of the triazoline intermediate to aziridine and N2 involves two more steps with an N-alkylimine intermediate. The very high barrier for N-alkylimine cyclization to aziridine could be offset by the high exothermicity of the previous step. Geometries of the transition states for various reaction steps studied here are described as ‘early’ or ‘late’ in good accordance with the Hammondpostulate. Two other mechanisms (Routes A and B) studied earlier (involving discrete nitrene intermediates) are compared with Routes I and II, where Route II involving 1,3-dipolar cycloaddition is predicted to be energeticallythe most favored of all the four mechanisms for thermal gas-phase aziridination of alkenes by azides.

    • Author Affiliations

       

      S PREMILA DEVI R H DUNCAN LYNGDOH1

      1. Department of Chemistry, North-Eastern Hill University, Shillong, Meghalaya 793 022, India
    • Dates

       
  • Journal of Chemical Sciences | News

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