Mechanism and selectivity of nickel-catalyzed [3 + 2] cycloaddition of cyclopropenones and α,β-unsaturated ketones: A computational study

Unanticipated Three-Component Cascade and Sequential Cyclization: Highly Diastereoselective Synthesis of Polyfunctionalized Cyclohexanes

Herein, we reported a DBU-catalyzed cascade and sequential [1 + 2 + 3] annulation of malononitrile with α,β-unsaturated ketones to access polyfunctionalized cyclohexanes with high yield and excellent diastereoselectivity (>93% yield, >19:1 dr). Intriguingly, this appears to be the new strategy for using α,β-unsaturated ketones either as 2C or 3C synthon to react with dinucleophile 1C synthon to construct six-membered carbocycles in one-pot manner. In addition, these synthesized compounds suppressed the growth of phytopathogenic fungi in vitro. Among them, compound 3l exhibited excellent and broad antifungal activity, which possesses potential as an agricultural antifungal agent.

Palladium-Catalyzed Regioselective [3 + 2] Annulation with N-Allenamides at the Proximal C═C Bond: Synthesis of γ-Amino-α'-methylenecyclopentenones

A palladium-catalyzed [3 + 2] cycloaddition of cyclopropenones with N-allenamides has been developed. This methodology facilitates the synthesis of γ-amino-α'-methylenecyclopentenones in moderate to excellent yields with good regioselectivity and compatibility with various functional groups. The employment of N-allenamides as versatile 2C synthons enables simultaneous incorporation of both a nitrogen atom and a methylene group into cyclopentenones. Furthermore, this approach exhibits reverse regioselectivity when compared to general allenes. Density functional theory calculations successfully elucidated the origin of the observed regioselectivity.

Amine-Induced Selective C-C Bond Cleavage of 2,2,2-Trifluoroethyl Carbonyls for the Synthesis of Ureas and Amides

An efficient and selective transformation of 2,2,2-trifluoroethyl carbonyls into ureas/amides with amines is reported. This protocol allows the selective cleavage of the C-C bond of 2,2,2-trifluoroethyl carbonyls under transition metal-free and oxidant-free conditions, which is in contrast to the analogous C-F or C-CF₃ bond functionalization. This reaction reveals the unexplored reactivity of 2,2,2-trifluoroethyl carbonyls and exhibits a broad substrate range and good functional group tolerance.