Pd-Catalyzed Three-Component Coupling of Cyclopropenones via Sequential C–C Bond Activation and Allylation

Abstract

A novel Pd-catalyzed three-component domino reaction for the stereoselective synthesis of highly functionalized allyl cinnamates has been developed. In this protocol, a sequential process of C–C bond activation and intermolecular allylic substitution was well-organized. The key for this transformation is the in situ generated hydrolysis product of cyclopropenone, which triggered a new reaction with vinylethylene carbonates. The reaction mechanism was investigated, demonstrating the high stereoselectivity and excellent atomic economy in this process.

Ag-Catalyzed Selective C–C Bond Activation of Cyclopropenones to Access α-Alkylidene Lactones

“…Previously, we observed that 2-methyl-3-phenylcyclopropenone exhibited excellent regioselectivity in coupling reactions . We hypothesized that the C­(phenyl)–C­(O) bond may be easier to cleave than the C­(methyl)–C­(O) bond.…”

“…Cyclopropenones, the smallest “Hückel aromatic” compounds, have demonstrated their exceptional suitability as candidates for ring-strain-driven C–C bond cleavage, serving as a versatile C 3 synthon for the construction of diverse important molecules . In this context, a number of valuable transformations have been successfully developed, including metal-catalyzed oxidative addition of cyclopropenones and β-carbon elimination reactions (Scheme a). , However, the regioselectivity of unsymmetric cyclopropenones has been challenging in most of the transformations, limiting their synthetic utility. Recently, Prescher’s group developed a PPh 3 -catalyzed method for synthesizing butenolides from hydroxymethylcyclopropenones (Scheme b) .…”