title: An alternative approach to PEPPSI catalysts: from palladium isonitriles to highly active unsymmetrically substituted PEPPSI catalysts.
abstract: A series of new pyridine-enhanced precatalyst preparation, stabilization, and initiation (PEPPSI)-type complexes bearing different types of carbene ligands was prepared by the modular and convergent template synthesis strategy. Nitrogen acyclic carbenes, saturated and unsaturated five-membered NHC, saturated six-membered NHCs, and five-membered N-heterocyclic oxo-carbene (NHOC) ligands on palladium were prepared this way. These new organometallic compounds then were tested in Suzuki and Negishi cross-coupling reactions by using substrates with one or two substituents in ortho-position of the new CC bond being formed. Both aryl chlorides and bromides were tested as coupling partners. In some cases, the new ligands gave results similar to Organ's successful IPr-based and IPent-based PEPPSI derivatives, with aryl bromides 0.05 mol % catalyst load still gave satisfactory results, with aryl chlorides 0.5 mol % were needed.
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-4205 http://www.hashmi.de.
authors.forename: Anna
authors.initials: A
authors.lastname: Zeiler
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-4205 http://www.hashmi.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Rudolph
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-4205 http://www.hashmi.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Rominger
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany), Fax: (+49) 6221-54-4205 http://www.hashmi.de. hashmi@hashmi.de.|Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia). hashmi@hashmi.de.
authors.forename: A Stephen K
authors.initials: AS
authors.lastname: Hashmi
keywords: amines; carbenes; cross-coupling; isonitriles; palladium