The metal-catalyzed reactions of diazo compounds have broad utility in organic synthesis. The resulting high-energy metal carbenoid intermediates are capable of a range of useful transformations, including cyclopropanation, ylide formation, and C-H insertion.
The intermolecular C-H insertion by metal carbenoids is the most versatile reaction to date for stereoselective C-H functionalization. This chapter covers the historical background of C-H insertions and describes how the utilization of new catalysts and more stabilized carbenoids has resulted in major advances in the field. Now that highly diastereoselective and enantioselective C-H functionalization can be achieved, the method can be effectively applied to the synthesis of pharmaceutical agents and natural products. This chapter focuses exclusively on intermolecular C-H insertions of metal carbenoids in sp3-hybridized C-H bonds. The carbenoids can be classified into three major classes: 1, acceptor-substituted carbenoids; 2, acceptor/acceptor-substituted carbenoids; and 3, donor/acceptor-substituted carbenoids