The metal catalyzed reactions of diazo compounds have been broadly used in organic synthesis. The resulting metal-carbenoid intermediates are capable of undergoing a range of unconventional reactions, and due to their high energy, they are ideal for initiating a cascade sequence leading to rapid the rapid generation of structural complexity. This tutorial review will be give an overview of the most versatile reactions of donor/acceptor carbenoids, an exciting class of intermediates capable of highly selective reactions. This will include cyclopropanation, [4 + 3] cycloaddition, and C–H functionalization methodologies. The application of this chemistry to the synthesis of a range of natural products will be described.

The total synthesis of (−)-5-epi-vibsanin E (2) has been achieved in 18 steps. The synthesis combines the rhodium-catalyzed [4 + 3] cycloaddition between a vinylcarbenoid and a diene to rapidly generate the tricyclic core with an effective end game strategy to introduce the remaining side-chains. The [4 + 3] cycloaddition occurs by a cyclopropanation to form a divinylcyclopropane followed by a Cope rearrangement to form a cycloheptadiene. The quaternary stereogenic center generated in the process can be obtained with high asymmetric induction when the reaction is catalyzed by the chiral dirhodium complex, Rh2(S-PTAD)4.

The reaction of a variety of alpha-aryl-alpha-diazo ketones with activated olefins, catalyzed by the adamantyl glycine-derived dirhodium complex Rh(2)(S-PTAD)(4), generates cyclopropyl ketones with high diastereoselectivity (up to >95:5 dr) and enantioselectivity (up to 98% ee). Intermolecular C-H functionalization of 1,4-cyclohexadiene by means of carbenoid-induced C-H insertion was also possible with this type of carbenoid.