Angewandte Chemie. International edition in English 2009-01-01

Pd-PEPPSI-IPent: an active, sterically demanding cross-coupling catalyst and its application in the synthesis of tetra-ortho-substituted biaryls.

Michael G Organ, Selçuk Calimsiz, Mahmoud Sayah, Ka Hou Hoi, Alan J Lough

Index: Angew. Chem. Int. Ed. Engl. 48 , 2383, (2009)

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Abstract

Incredible Bulk: A series of N-heterocyclic carbene catalysts (see picture) were prepared and evaluated in the Suzuki-Miyaura reaction. A variety of sterically encumbered tetra-ortho-substituted biaryl products were formed from unreactive aryl chlorides using the isopentyl-substituted catalyst at temperatures ranging from 65 degrees C to room temperature. The cyclopentyl-substituted catalyst was virtually inactive, demonstrating that "flexible bulk" is essential to promote these transformations.