Amidine catalysed O- to C-carboxyl transfer of heterocyclic carbonate derivatives
作者:Caroline Joannesse、Carmen Simal、Carmen Concellón、Jennifer E. Thomson、Craig D. Campbell、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1039/b805850d
日期:——
The structural requirements of amidines necessary to act as efficient O- to C-carboxyl transfer agents are delineated and the scope of this process outlined through its application to a range of oxazolyl, benzofuranyl and indolyl carbonates.
Isothiourea-Mediated Asymmetric O- to C-Carboxyl Transfer of Oxazolyl Carbonates: Structure-Selectivity Profiles and Mechanistic Studies
作者:Caroline Joannesse、Craig P. Johnston、Louis C. Morrill、Philip A. Woods、Madeleine Kieffer、Tobias A. Nigst、Herbert Mayr、Tomas Lebl、Douglas Philp、Ryan A. Bragg、Andrew D. Smith
DOI:10.1002/chem.201102847
日期:2012.2.20
The structural motif within a series of tetrahydropyrimidine‐based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolylcarbonates is fully explored, with crossover and dynamic 19F NMR experiments used to develop a mechanistic understanding of this transformation.
充分探索了一系列四氢嘧啶基异硫脲中的结构基序,这些结构对于恶唑碳酸酯的不对称Steglich重排产生高不对称诱导是必要的,并使用交叉和动态19 F NMR实验来发展对该转变的机理理解。
Probing the Efficiency of N-Heterocyclic Carbene Promoted <i>O</i>- to C-Carboxyl Transfer of Oxazolyl Carbonates
作者:Jennifer E. Thomson、Craig D. Campbell、Carmen Concellón、Nicolas Duguet、Kathryn Rix、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/jo702720a
日期:2008.4.1
Screening of a range of azolium salts, bases and solvents for reactivity indicates that triazolinylidenes, generated in situ with KHMDS in THF, promote the Steglich rearrangement of oxazolyl carbonates with high catalytic efficiency (typical reaction time 5 min at < 1.5 mol % NHC). This protocol shows wide substrate applicability, even allowing the efficient generation of vicinal quaternary centers. An improved experimental procedure is also described that allows a simplified one-pot reaction protocol to be employed with similarly high catalytic efficiency.
Development of Chiral Nucleophilic Pyridine Catalysts: Applications in Asymmetric Quaternary Carbon Synthesis
作者:Scott A. Shaw、Pedro Aleman、Edwin Vedejs
DOI:10.1021/ja037223k
日期:2003.11.1
TADMAP (1a), a new chiral DMAP catalyst, has been designed to place a C(3)-benzylic trityl group over one face of the pyridine ring, while a C(3)-benzylic acetoxy group creates a chirotopic environment on the other face. TADMAP was prepared in four steps (37% overall) from triphenylacetic acid and (dimethylamino)pyridine and was resolved using camphorsulfonic acid. TADMAP catalyzes the enantioselective rearrangement from oxazolyl phenyl carbonates 4 to azlactones 5, from furanyl phenyl carbonate 8 to the furanone 9, from the benzofuranyl carbonates 11a and 11b to benzofuranones 12a and 12b, and from the indolyl carbonates 11c and 11d to oxindoles 12c and 12d. The products are formed in good yield and, in most cases, with practical levels of enantiomer excess at the newly formed quaternary carbon.