Silylcarboxylic Acids as Bifunctional Reagents: Application in Palladium‐Catalyzed External‐CO‐Free Carbonylative Cross‐Coupling Reactions

Palladium-catalyzed Heck-carbonylation of alkene-tethered carbamoyl chlorides with aryl formates

We report a palladium-catalyzed Heck-carbonylation of alkene-tethered carbamoyl chlorides by utilizing aryl formates as convenient CO surrogates. One C-O and two C-C bonds are constructed to give diversiform esterified oxindoles/γ-lactams bearing an all-carbon quaternary stereocenter under gas-free conditions. This transformation features a wide substrate scope and good functional group tolerance and can be easily applied to late-stage functionalization.

Palladium-Catalyzed Carbonylative Hiyama-Denmark Reaction toward the Synthesis of Aryl Carbonyl-Containing Oxindoles

A palladium-catalyzed domino Heck cyclization/carbonylative Hiyama-Denmark cross-coupling reaction between alkene-tethered aryl iodides and silylcarboxylic acids is presented. This reaction proceeds well without toxic carbon monoxide (CO) gas and has good functional group tolerance, providing an alternative access to carbonyl-containing oxindoles. In this transformation, silylcarboxylic acids play a dual role as a CO source and a nucleophile.

Highly Selective Synthesis of 6-Glyoxylamidoquinoline Derivatives via Palladium-Catalyzed Aminocarbonylation

The aminocarbonylation of 6-iodoquinoline has been investigated in the presence of large series of amine nucleophiles, providing an efficient synthetic route for producing various quinoline-6-carboxamide and quinoline-6-glyoxylamide derivatives. It was shown, after detailed optimization study, that the formation of amides and ketoamides is strongly influenced by the reaction conditions. Performing the reactions at 40 bar of carbon monoxide pressure in the presence of Pd(OAc)₂/2 PPh₃, the corresponding 2-ketocarboxamides were formed as major products (up to 63%). When the monodentate triphenylphosphine was replaced by the bidentate XantPhos, the quinoline-6-carboxamide derivatives were synthesized almost exclusively under atmospheric conditions (up to 98%). The isolation and characterization of the new carbonylated products of various structures were also accomplished. Furthermore, the structure of three new mono- and double-carbonylated compounds were unambiguously established by using a single-crystal XRD study.

Feeding Carbonylation with CO2 via the Synergy of Single-Site/Nanocluster Catalysts in a Photosensitizing MOF

Solar-driven carbonylation with CO₂ replacing toxic CO as a C1 source is of considerable interest; however it remains a great challenge due to the inert CO₂ molecule. Herein, we integrate cobalt single-site and ultrafine CuPd nanocluster catalysts into a porphyrin-based metal-organic framework to construct composite photocatalysts (Cu₁Pd₂)_z@PCN-222(Co) (z = 1.3, 2.0, and 3.0 nm). Upon visible light irradiation, excited porphyrin can concurrently transfer electrons to Co single sites and CuPd nanoclusters, providing the possibility for coupling CO₂ photoreduction and Suzuki/Sonogashira reactions. This multicomponent synergy in (Cu₁Pd₂)_1.3@PCN-222(Co) can not only replace dangerous CO gas but also dramatically promote the photosynthesis of benzophenone in CO₂ with over 90% yield and 97% selectivity under mild condition. Systematic investigations clearly decipher the function and collaboration among different components in these composite catalysts, highlighting a new insight into developing a sustainable protocol for carbonylation reactions by employing greenhouse gas CO₂ as a C1 source.

Palladium-catalyzed [2 + 2 + 1] annulation: access to chromone fused cyclopentanones with cyclopropenone as the CO source

A variety of chromone fused cyclopentanones are efficiently generated in good to high yields via palladium-catalyzed [2 + 2 + 1] annulation, in which cyclopropenone was utilized for the first time as the sole CO surrogate in the carbonylation process.