Cycloadditions of Carbonyl Ylides Derived from Diazocarbonyl Compounds

[3 + 2] cycloadditions of carbonyl ylides with dipolarophiles provides a synthetically powerful way to make a variety of 5-membered oxacycles. One of the best ways to generate carbonyl ylide intermediates is by transition metal-catalyzed loss of nitrogen from diazocarbonyl compounds and trapping of the resultant metallocarbenes by a carbonyl group. This chapter covers the metal-catalyzed intra- and intermolecular cycloadditions of carbonyl ylides derived from diazocarbonyl compounds with various dipolarophiles. The literature up to the end of 2011 is covered. A comprehensive discussion is provided of mechanism and stereochemistry, regioselectivity, stereoselectivity, and asymmetric cycloadditions. The structural scope at the diazo group, of the carbonyl group forming the ylide, and of the dipolarophile is delineated. A systematic analysis is presented of the scope and limitations of intra- and intermolecular cycloadditions of cyclic diazocarbonyl-derived carbonyl ylides from ketones, esters, amides or imides, including cycloadditions of aromatic pyrylium and isomunchnone ylides. The generation of acyclic carbonyl ylides from aldehydes, ketones, or imides and their cycloadditions is also reviewed. Finally, important applications to the total synthesis of natural products and a critical comparison with other methods for carbonyl ylide generation-cycloaddition are presented. Keywords: cycloaddition reaction(s); [3 + 2] reaction(S); intermolecular cycloaddition(s); intramolecular cycloaddition(s); metal catalyzed; diazo compound(s); carbonyl ylide(s); pyrylium(s); isomunchnone(s); natural product(s); asymmetric catalysis; stereochemistry; method comparisons; experimental procedures