We describe a highly step and atom economical cobalt-catalyzed cyclization of 1,6-enynes with aldehydes to synthesize functionalized pyrrolidines and dihydrofurans with high chemo- and stereoselectivity. The catalytic reaction plausibly proceeds via the cobaltacycle intermediate generated from the reaction of enyne substrate with cobalt catalyst, followed by switchable C-H functionalization of weakly coordinating aldehydes depending on the electronic nature of the ligand.
Transition‐metal‐catalyzed C−H functionalizations with allenes lead to unique selectivity challenges due to the presence of two adjacent carbon–carbon double bonds, which enables a series of atom‐ and step‐economical alkenylation, allenylation, allylation, dienylation, and annulation reactions of different substrates. This Focus Review highlights the recent remarkable advancements made in transition‐metal‐catalyzed C−H functionalization with allenes.
A highly chemo- and stereoselective cobalt-catalyzed hydroarylative cyclization of 1,6-enynes with aromatic ketones and esters to synthesize functionalized pyrrolidines and dihydrofurans is described. A mechanism involving cobaltacycle triggered C-H activation of aromatic ketones and esters was proposed.
A Co(III)-catalyzed [4 + 1] annulation of amides with allenes to synthesize isoindolone and 1,5-dihydro-pyrrol-2-one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide-directed CÀH activation, followed by carbocobaltation of allene, b-hydride elimination, and an intramolecular 1,2hydroamination.
Catalytic CÀHf unctionalization has emerged as an efficient alternative to traditional coupling reactions. However,s omeo ft hese reactions depend on environmentally harmful solvents, weakening the overall green nature of these methods. As organic processes consume large amount of solvents, the use of less harmful solvents enhance the sustainability of these reactions. Herein, we present an overview of transition metal-catalyzed CÀHf unctionalization reactions for the synthesis of heterocycles in sustainable solvents based on CHEM21 solvent selection guide.[a] Dr.
A cobalt-catalyzed C−H/N−H annulation of anilides with allenes to synthesize 1,2-dihydroquinolines is described. The reaction proceeds via a C−H activation, allene insertion, followed by β-hydride elimination and an intramolecular 1,4-addition to a butadiene-group-containing intermediate. Allenes act as a threecarbon source in the present C−H activation strategy.
An iron‐catalyzed synthesis of α,β‐unsaturated carboxylic acids from alkynes and carbon dioxide was developed. This reaction proceeds through hydromagnesiation of alkynes followed by carbon dioxide insertion under atmospheric pressure and ambient temperature in the presence of iron and a Grignard reagent as a catalyst and hydride source, respectively. Several symmetrical and unsymmetrical alkynes were transformed into the corresponding acids in good to excellent yields. The methodology provides an efficient route to the synthesis of vinyl carboxylic acids.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.