Asymmetricsynthesis: A class of cinchona alkaloid-derived zwitterions has been successfully applied to highly enantioselective Steglich rearrangement of oxindoles. The same catalytic system is also applicable in the asymmetric aldol reaction of oxindoles. This finding paves the way to the development of new reaction protocols exploiting cinchona alkaloid-derived zwitterions as asymmetric nucleophilic
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.
[EN] PYRIDINE DERIVATIVE HAVING AXIAL CHIRALITY OR SALT THEREOF, AND ASYMMETRIC CATALYST COMPRISING SAME<br/>[FR] DÉRIVÉ DE PYRIDINE AYANT UNE CHIRALITÉ AXIALE OU SEL DE CELUI-CI, ET CATALYSEUR ASYMÉTRIQUE LE COMPRENANT<br/>[JA] 軸不斉を有するピリジン誘導体又はその塩、及びそれからなる不斉触媒