11.8.6 Nigishi Coupling

The coupling of organozinc compounds with alkenyl, akynyl, aryl, allylic and benzyl halides using Pd(0) provides another powerful method for carbon-carbon bond formation (Scheme 15). Section 3.3.3 presents the mechanism.

Scheme 15

 

Examples:

 

11.8.7 C-H Activation

Palladium-based catalysts have been explored for carbon-heteroatom bond formation via cross-coupling as well as C-H activation. For example, the synthesis of 1-aryl-1H-benzotrizole can be accomplished from triazene via C-H activation using Pd(OAc) 2 under aerobic conditions (Scheme 16).

Scheme 16

Mechanism

Molecular oxygen reoxidizes the reduced palladium (0) to palladium (II) to complete the catalytic cycle (Scheme 15).

Scheme 15

Examples:

J. P. Wolfe, S. Wagaw, S. L. Buchwald, Acc. Chem. Res. 1998 , 31 , 805.

R. K. Kumar, M. A. Ali, T. Punniyamurthy, Org. Lett. 2011 , 13 , 2102; Synfacts 2011 , 596.