CP-ASTERISK-RU(II) AND CP-ASTERISK-RU(IV)-CATALYZED REACTIONS OF CHX WITH VINYL C-H BONDS - COMPETITION BETWEEN DOUBLE-BOND HOMOLOGATION AND OLEFIN CYCLOPROPANATION BY ALKYL DIAZOACETATE

When diazoesters are used as carbene precursors, new Ru(II) and Ru(IV) complexes bearing various substitutents tethered ligands mediate the formal carbene insertion into C-H vinyl bonds of(substituted) styrenes to yield mostly E- and Z-styrylacetic esters (e.g. 4-phenylbut-3-enoa tes with styrene). This rarely observed reaction competes with the cyc lopropanation of the double bond. The influence of steric and electron ic factors on the two competitive reactions is reported. The observati on that the most efficient C-H insertion catalysts also promote the RO MP of norbornene lend support to the formation of ruthenacyclobutanes as reaction intermediates. (C) 1998 Elsevier Science S.A. All rights r eserved.