Intramolecular Hydroarylation of Alkynes Catalyzed by Platinum or Gold: Mechanism and endo Selectivity

✍ Scribed by Cristina Nevado; Antonio M. Echavarren

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 397 KB
• Volume: 11
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200401069

✦ Synopsis

Abstract

The cyclization of differently substituted aryl alkynes with Pt^II^ or Au^I^ catalysts proceeds by endo‐dig pathways. When Ag^I^ was used to generate reactive cationic Au^I^ catalysts, 2__H__‐chromenes dimerize to form cyclobutane derivatives by a Ag^I^‐catalyzed process. A DFT study on the cyclization mechanism shows a kinetic and thermodynamic preference for 6__‐endo‐dig__ versus 5__‐exo‐dig__ cyclizations in Pt^II^‐catalyzed processes. Calculations indicate that although Friedel–Crafts and the cyclopropanation processes via metal cyclopropyl carbenes show very similar activation energies, platinum cyclopropyl carbenes are the stationary points with the lowest energy.