HFIP-Assisted C-H Functionalization by Cp*CoIII : Access to Key Reactive Cobaltacycles and Implication in Catalysis.

Described here is a synthetic approach to access two of the most widely invoked cationic cobaltacycles in Cp*CoIII -catalyzed C-H functionalization reactions by C-H activation. The unique stabilizing capability of MeCN was used to surmount the previously proposed reversible nature of the C-H metalation step. Moreover, it is revealed the boosting effect of 1,1,1,3,3,3-hexafluoroisopropanol in the metalation step and in the reaction between N-pyrimidinylindole and diphenylacetylene under catalytic conditions.

Nickel-Catalyzed Cyclopropanation with NMe4OTf and nBuLi.

Nickel was identified as a catalyst for the cyclopropanation of unactivated olefins by using in situ generated lithiomethyl trimethylammonium triflate as a methylene donor. A mechanistic hypothesis is proposed in which the generation of a reactive nickel carbene explains several interesting observations. Additionally, our findings shed light on a report by Franzen and Wittig published in 1960 that had been retracted later owing to irreproducibility, and provide a rational basis for the systematic development of the reaction for preparative purposes as an alternative to diazomethane or Simmons-Smith conditions.