This review highlights the recent advances in donor and donor–donor carbenes.

Three kinds of transformations based on benzo-fused donor- and acceptor-enynals/enynones, including reactions with alkenes, alkynes, and H ₂ O, were discussed.

An efficient method for the synthesis of poly-substituted naphthalene derivatives via Fe(III)-catalyzed [4 + 2] cycloaddition of 2-(2-oxo-alkyl)benzketones with alkynes or enols (generated in situ from alkyl aldehydes or alkyl ketones) is described. A variety of poly-substituted naphthalene derivatives could be synthesized in up to 90% yield under mild reaction conditions. Poly-substituted 1,2-dihydronaphthalene derivatives could be obtained instead through Zn(II)-catalyzed cyclization of 2-(2-oxo-alkyl)benzketones with alkenes. Furthermore, the Fe(III)-catalyzed intramolecular version could lead to isoquinoline derivatives in high yields.

A new method for the synthesis of furan-/benzo-fused fluorenes through copper(I)-catalyzed coupling of conjugated enynones or α-diazocarbonyl compounds with dialkynylbenzenes has been developed. This process includes 5-exo-dig cyclization, carbene migratory insertion, Schmittel cyclization and 1,5-H transfer. The obvious advantages of wide substrate scopes, mild reaction conditions, and high atom efficiency make this system highly appealing for the construction of six-substituted benzofuran-embedded fluorenes in a one-pot manner.