Isothiourea-Mediated Asymmetric O- to C-Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies (pages 2398–2408)
Caroline Joannesse, Craig P. Johnston, Louis C. Morrill, Philip A. Woods, Madeleine Kieffer, Dipl.-Chem. Tobias A. Nigst, Prof. Herbert Mayr, Dr. Tomas Lebl, Prof. Douglas Philp, Dr. Ryan A. Bragg and Dr. Andrew D. Smith
Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102847
As easy as O to C: The ability of a series of tetrahydropyrimidine-based isothioureas to promote the asymmetric Steglich reaction has been evaluated (see scheme). Good to excellent levels of enantioselectivity were generally observed for the rearrangement of oxazolyl carbonates, with markedly different catalytic efficiencies observed with variation of the stereodirecting group(s). Crossover and dynamic 19F NMR experiments were also used to develop a mechanistic understanding of this transformation.