A family of four-membered enones, polysubstituted alkylidenecyclobutenones, were easily prepared by a Lewis acid catalyzed [2+2] cycloaddition of ynamides and propargyl silyl ethers. This challenging regioselective [2+2] cycloaddition enables the efficient construction and conversion of four-membered enones, which provides high-value and structurally diverse products through the unexpected ring-opening and ring expansion of alkylidenecyclobutenone with Grignard reagents, organolithium, primary amines, and water.

A regio- and stereoselective synthesis of highly substituted α-haloenamides was described via the zinc halide mediated direct addition of benzhydryl halides to ynamides under mild conditions. The products α-haloenamides were further transformed into multisubstituted enamides via Suzuki and Sonogashira cross-coupling reactions.

A novel synthesis of imidazoles from electron-withdrawing group-substituted allenyl sulfonamides with amines was developed. The 4- and 5-functionalized imidazoles were constructed regioselectively, which depended on the substituents on the nitrogen atoms.

A novel synthesis of α,β-unsaturated amides from N,N-disulfonyl ynamides with aldehydes was developed. By utilization of salicylaldehydes, a variety of substituted iminocoumarins were prepared.

•A comprehensive timeline of catalytic carbonylation of formic acid and formaldehyde is presented.•The catalytic synthesis of various carbonyl compounds by transition-metal complexes is discussed.•The catalytic application of formic acid and formaldehyde as non-gaseous C1 source are highlighted.•The mechanistic rationale of transfer carbonylation with HCOOH and HCHO is outlined.While carbon monoxide (CO) gas has been extensively applied in the bulk chemical industry, its intrinsic properties such as high toxicity, flammability, and special equipment requirement for handling, limit its utilization in organic synthesis, fine chemical industry and academia. Recently, considerable effort has been devoted to the development of CO surrogates to avoid the direct use of carbon monoxide gas. Among the various CO surrogates, formic acid and formaldehyde, have a broad range of applications in organic synthesis. The direct carbonylation with formic acid (HCOOH) and formaldehyde (HCHO) represents one of the most atom-economical substitutes owing to their high weight percentage of CO. In this review, the potential roles of both formic acid and formaldehyde in transition-metal catalyzed carbonylation reactions are discussed. In order to understand these transfer carbonylation reactions, the mechanistic rationale for representative examples is also provided.

A family of four-membered enones, polysubstituted alkylidenecyclobutenones, were easily prepared by a Lewis acid catalyzed [2+2] cycloaddition of ynamides and propargyl silyl ethers. This challenging regioselective [2+2] cycloaddition enables the efficient construction and conversion of four-membered enones, which provides high-value and structurally diverse products through the unexpected ring-opening and ring expansion of alkylidenecyclobutenone with Grignard reagents, organolithium, primary amines, and water.

A regio- and stereoselective synthesis of highly substituted α-haloenamides was described via the zinc halide mediated direct addition of benzhydryl halides to ynamides under mild conditions. The products α-haloenamides were further transformed into multisubstituted enamides via Suzuki and Sonogashira cross-coupling reactions.

A novel synthesis of α,β-unsaturated amides from N,N-disulfonyl ynamides with aldehydes was developed. By utilization of salicylaldehydes, a variety of substituted iminocoumarins were prepared.