Iron-Catalyzed Homo-Coupling of Arylmagnesium Reagents

arylmagnesium reagents - iron - catalysis

Significance

A very simple and convenient method for preparation of symmetrical biaryls and bis-heteroaryls from corresponding aryl- and hetaryl halides. Various functionalized Grignard reagents can be used in the reaction. The intra­molecular variant allows synthesizing interesting polycyclic systems.

Comment

The preparation of functionalized arylmagnesium compounds can be readily performed by using a halogen-magnesium exchange reaction (see, for example: A. Krasovskiy, P. Knochel Angew. Chem. Int. Ed. 2004, 43, 3333-3336) and references cited therein). There was still a need for a simple, cheap and reliable method for the homo-coupling of the highly functionalized aryl Grignard reagents. Use of FeCl₃ as a catalyst makes it also environmentally friendly and convenient for large scale synthesis.