Driving Catalyst Reoxidation in Wacker Cyclizations with Acetal-Based Metal-Hydride Abstractors
作者:Nikki A. Cochrane、Maurice S. Brookhart、Michel R. Gagné
DOI:10.1021/om2001958
日期:2011.5.9
reduced to Pd(0) after C-O bond formation and beta-H elimination and must be reoxidized to the electrophilic Pd(II) state via a stoichiometric oxidant like benzoquinone, CuCl(2), or O(2). We report herein a Pt-catalyzed Wacker-type process that regenerates the electrophilic Pt(2+) state by H(-) abstraction from a [Pt]-H using an oxocarbenium ion generated from an acetal or ketal under acidic conditions.
Protonolysis of Cationic Pt−C Bonds with Mild Acids: Can Ligand Torsional Effects Speed Associative Processes?
作者:Jeremy A. Feducia、Alison N. Campbell、Jeffrey W. Anthis、Michel R. Gagné
DOI:10.1021/om051066b
日期:2006.6.1
Tridentate phosphine pincer ligands facilitate the protonolysis of cationic Pt-CH3 compounds ( to Pt dications and CH4) with the ammonium acid Ph2NH2 center dot BF4. Large rate enhancements over nonpincer analogues (> 50 000) are observed. A mechanism is proposed wherein ring strain present in the planar ground-state arrangement of three phosphine ligands is released in putative five-coordinate intermediates and transition states.