Copper-catalyzed arylation of nitrogen heterocycles from anilines under ligand-free conditions.

The arylation of pyrazole and derivatives can be achieved by coupling arenediazonium species (formed in situ from anilines) by using a catalytic system that employs low-toxicity and inexpensive copper metal under very mild and ligand-free conditions (T=20 °C). From other nitrogen heterocycles, the presence of an additive (NBu4 I) significantly improves the efficiency of the catalytic system. These results represent the first examples of CN bond formation from arenediazonium species.

Iron-catalyzed homocoupling of aryl halides and derivatives in the presence of alkyllithiums.

Direct synthesis of biaryl derivatives from aryl halides takes place under very mild temperature conditions by using a ligand-free iron catalytic system. The procedure, which proceeds via an in situ quantitative aryl halide exchange with alkyllithiums, allows for excellent control of the reactivity and is in line with the sustainable development. The method is also applicable to styryl and benzyl halides and to phenylacetylene.