Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates : synthetic and computational studies
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The regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates is described, with DMAP giving preferential N-carboxylation and triazolinylidenes promoting selective C-carboxylation (both with up to >99 : 1 regioselectivity). An enantioselective O- to C-carboxyl variant using NHC catalysis is demonstrated (up to 92% ee), while mechanistic and DFT studies outline the pathways operative in this system and provide insight into the reasons for the observed selectivity.
Gould , E , Walden , D M , Kasten , K , Johnston , R C , Wu , J , Slawin , A M Z , Mustard , T J L , Johnston , B , Davies , T , Ha-Yeon Cheong , P & Smith , A D 2014 , ' Catalyst selective and regiodivergent O- to C- or N- carboxyl transfer of pyrazolyl carbonates : synthetic and computational studies ' Chemical Science , vol 5 , no. 9 , pp. 3651-3658 . DOI: 10.1039/C4SC00879K
© Royal Society of Chemistry 2014. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/).
The authors acknowledge the Royal Society for a University Research Fellowship (ADS) and the EPSRC and Merck Sharp & Dohme Ltd (CASE award to EG) for funding, and the EPSRC National Mass Spectrometry Service Centre (Swansea). The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° 279850.
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