Asymmetric Synthesis of Palladacycles by Regioselective Oxidative Cyclization of C2-Symmetrical, Chiral Alkenes and Determination of the Configuration of All Stereocenters
摘要:
The reaction of Pd-2(dba)(3) . CHCl3 with 2 equiv of chiral, C-2-symmetrical cyclopropenes bearing lactate esters at the 1- and 2-positions provided trans-5-palladatricyclo[4.1.0.0(2,4)]heptanes (PTHs) in high diastereomeric excess. The configuration of all stereocenters in the major diastereomer was determined by X-ray structure analyses of the complexes of the PTH-with norbornadiene; the C-2 symmetry of the (+)-DIOP complex of the minor diastereomer proves that this was also a trans isomer.
types of cyclopropene-1,2-dicarboxylates 1 have been obtained by photochemical methods from the corresponding pyrazoles 11, 12, or 13. These pyrazoles were synthesized by 1,3-dipolarcycloadditions of alkynes 8 or 9 with either preformed diazoalkanes or diazoalkanes generated photochemically in situ, by use of oxadiazolines as diazoalkane precursors. The numerous substrates have clearly established the
Asymmetric Synthesis of Palladacycles by Regioselective Oxidative Cyclization of <i>C</i><sub>2</sub>-Symmetrical, Chiral Alkenes and Determination of the Configuration of All Stereocenters
作者:A. Stephen K. Hashmi、Frank Naumann、Michael Bolte
DOI:10.1021/om9802663
日期:1998.6.1
The reaction of Pd-2(dba)(3) . CHCl3 with 2 equiv of chiral, C-2-symmetrical cyclopropenes bearing lactate esters at the 1- and 2-positions provided trans-5-palladatricyclo[4.1.0.0(2,4)]heptanes (PTHs) in high diastereomeric excess. The configuration of all stereocenters in the major diastereomer was determined by X-ray structure analyses of the complexes of the PTH-with norbornadiene; the C-2 symmetry of the (+)-DIOP complex of the minor diastereomer proves that this was also a trans isomer.