Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates: synthetic and computational studies

Eoin Gould; Daniel M. Walden; Kevin Kasten; Ryne C. Johnston; Jiufeng Wu; Alexandra M. Z. Slawin; Thomas J. L. Mustard; Brittany Johnston; Tony Davies; Paul Ha-Yeon Cheong; Andrew D. Smith

doi:10.1039/C4SC00879K

Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates: synthetic and computational studies†

Eoin Gould,^a Daniel M. Walden,^b Kevin Kasten,^a Ryne C. Johnston,^b Jiufeng Wu,^a Alexandra M. Z. Slawin,^a Thomas J. L. Mustard,^b Brittany Johnston,^b Tony Davies,^c Paul Ha-Yeon Cheong*^b and Andrew D. Smith*^a

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* Corresponding authors

^a EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, UK
E-mail: ads10@st.andrews.ac.uk

^b Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, Oregon, USA

^c Merck Sharp & Dohme Limited, Hertford Road, Hoddesdon, Hertfordshire, UK

Abstract

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.

Chemical Science

Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates: synthetic and computational studies†

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Catalyst selective and regiodivergent O- to C- or N-carboxyl transfer of pyrazolyl carbonates: synthetic and computational studies

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