Copper-catalyzed N-alkylation of sulfonamides with benzylic alcohols: Catalysis and mechanistic studies

Xinjiang Cui, Feng Shi, Man Kin Tse, Dirk Gördes, Kerstin Thurow, Matthias Beller, Youquan Deng

Research output: Contribution to journalArticlepeer-review

85 Scopus citations

Abstract

The N-alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfonamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing Iigands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol-d 7 with p-toluenesulfonamide, Nbenzyl-p-toluenesulfonamide or N-benzylidenetoluenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alconol-d7 with ptoluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N-benzylidene-p-toluenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step.

Original languageEnglish
Pages (from-to)2949-2958
Number of pages10
JournalAdvanced Synthesis and Catalysis
Volume351
Issue number17
DOIs
StatePublished - Nov 2009
Externally publishedYes

Keywords

  • Alcohols
  • Alkylation
  • C-n bond formation
  • Copper catalysts
  • Sulfonamides

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