One Step to Difluoromethyl Cyclopropanes

  • Author: ChemistryViews.org
  • Published: 03 November 2016
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Source / Publisher: Chemical Communications/Royal Society of Chemistry (RSC)
  • Associated Societies: Royal Society of Chemistry (RSC), UK
thumbnail image: One Step to Difluoromethyl Cyclopropanes

Difluoromethyl-substituted cyclopropanes can be useful functional groups, e.g., for biologically active molecules. However, there had only been elaborate multi-step syntheses for compounds with such groups so far, some using hazardous fluorinating reagents.


Rene M. Koenigs and colleagues, RWTH Aachen University, Germany, have developed the first catalytic one-step synthesis of difluoromethyl cyclopropanes from readily available reactants. The team first prepared difluoromethyl diazomethane in a continuous-flow process starting from difluoroethylamine, tBuONO, and acetic acid.


Then the researchers reacted this precursor with styrene derivatives in the presence of a rhodium(II) catalyst (Rh2esp2, esp = α,α,α',α'-tetramethyl-1,3-benzenedipropionic acid) to give the desired product in one step. The reaction gives good isolated yields and tolerates substituted styrenes. Heterocyclic and non-aromatic substrates, in contrast, did not give the desired difluoromethyl cyclopropanes.


 

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