Green Chemistry Blog

French scientists report a new method to generate the oxidative homocoupling of N-phenylpyrazole using  Ru(OAc)₂(p-cymene) catalyst.

Traditionally, the transition metal-catalysed Heck reaction has proven to be a useful method to synthesize unsaturated molecules and conjugated materials viacross-coupling and C-C bond formation.  However, a potentially more efficient, greener route to the same family of compounds is through the catalytic oxidative alkenylation of aromatic C-H bonds.  This process would avoid the prehalogenation of the substrate as in the Heck reaction and therefore would be more atom economical.

The team of scientists here, led by Christian Bruneau and Pierre Dixneuf, report the direct dehydrogenative alkenylation of N-aryl pyrazoles with styrene and alkyl acrylates, catalysed by Ru(OAc)₂(p-cymene) in the presence of Cu(OAc)₂·H₂O and acetic acid in air.  The authors show that the acetic acid plays an important role, and believe its action lies in C-H bond cleavage as an autocatalytic process.

This article is free to access until the 20th October 2011!  To read more, just click below:

Ruthenium diacetate-catalysed oxidative alkenylation of C–H bonds in air: synthesis of alkenyl N-arylpyrazoles, Percia B. Arockiam, Cedric Fischmeister, Christian Bruneau and Pierre H. Dixneuf, Green Chem., 2011, DOI: 10.1039/C1GC15875A