1,5-Cyanotrifluoromethylation of Vinylcyclopropanes

  • Author: ChemistryViews.org
  • Published: 02 October 2019
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Organic Letters/ACS Publications
  • Associated Societies: American Chemical Society (ACS), USA
thumbnail image: 1,5-Cyanotrifluoromethylation of Vinylcyclopropanes

Compounds with trifluoromethyl groups have useful properties, e.g., for pharmaceutical and agrochemical products. These groups can be introduced into molecules, e.g., by trapping ·CF3 radicals with alkenes, combined with a second functionalization to give 1,2-difunctionalized products. There are enantioselective variants of this type of reaction, as well as analogous enantioselective 1,6-difunctionalization reactions. However, enantioselective 1,5-difunctionalization reactions are more challenging.


Xi-Sheng Wang, University of Science and Technology of China, Hefei, and colleagues have developed a copper-catalyzed enantioselective method for the 1,5-cyanotrifluoromethylation of vinylcyclopropanes (pictured). The team used Togni’s reagent as a source of ·CF3 radicals, Cu(acac)2 (acac = acetylacetone) as a catalyst together with a chiral bisoxazoline ligand, and trimethylsilyl cyanide (TMSCN) as a cyano source to convert vinylcyclopropanes bearing different (hetero)arenes into the desired products.


The reaction proceeds at room temperature and provides good to excellent yields and enantioselectivities. The team proposes a Cu(I)/Cu(III)-catalyzed reaction mechanism that involves the reaction of the ·CF3 radical with the alkene, followed by ring-opening of the cyclopropane, and the remote functionalization with the cyano reagent mediated by the chiral copper complex.


 

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