3.6.3 Chromium-Carbene Complex

Chromium forms Fischer carbene complexes that serve as reagents for various cyclization reactions like benzannulation and cyclopropanation reactions. These reactions are believed to take place via insertion of an alkene or alkyne to the carbene to form a new carbene complex which undergoes further reaction (Scheme 13-14).

Scheme 13

Scheme 14

3.6.4 Nozaki-Hiyama-Kishi Reaction

Much of the carbon-carbon bond forming reactions using chromium(II)-based protocols can be summarized as involving the coupling of an organic halide (or equivalent) with a carbonyl compound (Scheme 15).

Scheme 15