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Abnormal Addition of NHC to a Conjugate Acid of CAAC: Formation of N-Alkyl-Substituted CAAC

Authors
  • MANDAL, D
  • DOLAI, R
  • KALITA, P
  • NARAYANAN, RS
  • KUMAR, R
  • SOBOTTKA, S
  • SARKAR, B
  • RAJARAMAN, G
  • CHANDRASEKHAR, V
  • JANA, A
Publication Date
Dec 03, 2018
Source
DSpace at IIT Bombay
Keywords
License
Unknown
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Abstract

The addition reactions of N-heterocyclic carbenes (NHCs) are mostly known to occur through the carbenic centre (C2), which leads to a "normal" adduct. Herein, we report the abnormal addition of NHCDip 1 (1,3-(2,6-iPr(2)C(6)H(3))-imidazole-2-ylidene) to a conjugate acid of cyclic (alkyl)(amino)carbene 2 (CAAC(iPr)=1-iPr-3,3,5,5-Me-4-pyrrolinium triflate). Mechanistic study revealed that this reaction proceeded through the in situ formation of 1,3-(2,6-iPr(2)C(6)H(3))-imidazolium cation 4 and N-iPr-substituted CAAC 5 followed by the oxidative addition of compound 5 across the C4-H bond (alias backbone C-H) of compound 4. The in situ formation of compound 5 was also proven by the oxidative addition of it to the N-H group of iPrNH(2). DFT calculations also supported the mechanistic findings. A different methodology for the in situ generation of compound 5 by using TMPLi is also described.

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