N-tert-Butyl Triazolylidenes: Catalysts for the Enantioselective (3+2) Annulation of α,β-Unsaturated Acyl Azoliums


  • The authors thank the Australian Research Council (Discovery and Future Fellowship programs) for financial support. We acknowledge suggestions and donation of catalyst from Professors Tomislav Rovis (A4), Michel Gravel (cat. not shown), and Jonathan Morris (cat. not shown). We acknowledge help with DFT calculations from Dr. Christopher Thompson.


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But(yl) not futile: A range of N-tert-butyl-substituted triazolylidene N-heterocyclic carbenes have been prepared. Of these, the morpholinone-derived catalyst (1) proved best suited to the enantioselective synthesis of cyclopentanes from donor–acceptor cyclopropanes and α,β-unsaturated acyl fluorides. The performance of this catalyst has been correlated to the electronic nature of the catalyst by 13C NMR analysis. M.S.=molecular sieves, TMS=trimethylsilyl.