Cyclopropanation with Diazomethane and Bis(oxazoline)palladium(II) Complexes.
Studies toward the development of an enantioselective diazomethane-based cyclopropanation reagent derived from bis(oxazoline)palladium(II) complexes are reported. Several simple palladium chelates, 2 and 7, in addition to the novel carbon-bound complexes 15 were synthesized and evaluated in the cyclopropanation of various electron-deficient olefins. The X-ray crystal structure of aryl-bis(oxazoline)palladium complex 15c is described. Although all catalysts efficiently affected cyclopropanation, all products were racemic. An intriguing relationship between substitution on the oxazoline ring, particularly the commonly-derivatized 4-position, and catalyst efficiency was discovered. The results are rationalized by either partial or complete bis(oxazoline) decomplexation during the course of the reaction.
Denmark
Scott E.
SE
Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801.
Stavenger
Robert A.
RA
Faucher
Anne-Marie
AM
Edwards
James P.
JP