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

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.

Brønsted Acid-Catalyzed Intramolecular Tandem Double Cyclization of γ-Hydroxy Acetylenic Ketones with Alkynes into Naphtho[1,2-b]furan-3-ones.

A metal-free and atom-economic route for the synthesis of naphtho[1,2-b]furan-3-ones has been realized via p-TsOH·H2O-catalyzed intramolecular tandem double cyclization of γ-hydroxy acetylenic ketones with alkynes in formic acid. The benzene-linked furanonyl-ynes are the key intermediates obtained by the scission/recombination of C-O double bonds. Further, the structural modifications of the representative product were implemented by reduction, demethylation, substitution, and [5 + 2]-cycloaddition.

Dual Proton/Silver-Catalyzed Serial (5 + 2)-Cycloaddition and Nazarov Cyclization of (E)-2-Arylidene-3-hydroxyindanones with Conjugated Eneynes: Synthesis of Indanone-Fused Benzo[cd]azulenes.

A one-pot step-economic tandem process involving (5 + 2)-cycloaddition and Nazarov cyclization reactions has been reported for the facile synthesis of indanone-fused benzo[cd]azulenes from (E)-2-arylidene-3-hydroxyindanones and conjugated eneynes. This highly regio- and stereoselective bisannulation reaction is enabled by dual silver and Brønsted acid catalysis and opens up a new avenue for the construction of important bicyclo[5.3.0]decane skeletons.

Visible-Light-Mediated Tandem Difluoromethylation/Cyclization of Alkenyl Aldehydes toward CF2H-Substituted Chroman-4-one Derivatives.

An efficient and facile visible-light-mediated tandem difluoromethylation/cyclization of alkenyl aldehydes, with easily accessible and air-stable [Ph3PCF2H]+Br- as the difluoromethylation reagent, has been established. A range of CF2H-substituted chroman-4-one skeletons and their derivatives, such as 2,3-dihydroquinolin-4(1H)-ones, chroman, 3,4-dihydronaphthalen-1(2H)-one, 2,3-dihydrobenzofuran, and 2,3-dihydro-1H-inden-1-one, are efficiently produced in moderate to good yields with excellent chemoselectivity under mild reaction conditions.

Progress towards the Total Syntheses of Amaryllidaceae Alkaloids γ-Lycorane.

γ-Lycorane, a degradation product of the Aromaticaceae alkaloid lycorine, is one of the most attractive molecules in the Aromaticaceae family. It remains a popular target for synthesis due to its pentacyclic structure, which presents a vehicle for demonstrating the utility of new synthetic strategies. Various synthetic methods have been developed by synthetic chemists since the first synthesis of γ-lycorane by Nasuo in 1966. Thus, this review presents an overview of the literature on the ways utilized within the synthesis of γ-lycorane in racemic and enantiopure forms via electrophilic arylation, Pd-catalyzed C-C coupling, Bischler-Napieralski cyclization, Pictet-Spengler cyclization, photocyclization, radical cyclization, chiral pool synthesis, chiral auxiliary-mediated synthesis, and catalytic asymmetric synthesis, ranging from 1966 to 2022.

Transition-metal-free three-component coupling approach to QUINAP derivatives.

The aluminum(III) triflate catalyzed three-component coupling reaction of alkynes, amines and phosphorylated aryl aldehydes to access phosphoryl quinoline derivatives has been developed. The reaction proceeds in a simple system without the use of transition metals, ligands or additives, thus making it attractive for the fast preparation of a variety of new potential N-P bidentate ligands.

Visible-light-mediated tandem phosphorylation/cyclization for the synthesis of phosphorylated oxindoles.

The visible-light-mediated tandem phosphorylation/cyclization of N-arylacrylamides with H-phosphine oxides has been developed for the synthesis of phosphorylated oxindoles. This efficient and facile process was useful for the construction of a C-P bond and triggered the formation of a C-C bond with good compatibility with functional groups undermild reaction conditions.

A unique copper-catalyzed cross-coupling reaction by hydrogen (H2) removal for the stereoselective synthesis of 3-phosphoindoles.

The first Cu(i)-catalyzed cross-coupling reaction by hydrogen (H2) removal for the stereoselective synthesis of 3-phosphoindoles is reported. Going beyond the oxidative dehydrogenative coupling reactions reported recently, this reaction completely omits the oxidant and base, producing hydrogen (H2) as the only byproduct.

Regio- and stereoselective allylic C-H arylation with electron-deficient arenes by 1,1'-bi-2-naphthol-palladium cooperation.

A palladium-catalyzed allylic C-H arylation reaction with electron-deficient arenes with high regio- and stereoselectivity is reported. This work represents the first successful use of 1,1'-bi-2-naphthol as the ancillary ligand in allylic C-H activation, which is the key factor for chemoselectivity. Furthermore, high selectivity allylic C-H acetoxylation and amination were also successfully achieved under the same catalytic system.

Palladium-catalyzed sp2 and sp3 C-H bond activation and addition to isatin toward 3-hydroxy-2-oxindoles.

The first Pd(II)-catalyzed C-H addition to isatins by direct sp(2)/sp(3) C-H bond activation for the construction of 3-substituted-3-hydroxy-2-oxindoles is reported. The bidentate nitrogen ligands were found to promote this reaction. Specifically, the preliminary bioassay indicated that 3-(5-chlorobenzoxazole)-3-hydroxy-N-benzyl-2-oxindole (2w) is a new inhibitor of human kidney cancer and hepatocellular carcinoma cells. Moreover, this reaction system exhibits great functional group tolerance and requires no directing group, extra base, or additives.

Pd(II)-catalyzed Ph2(O)P-directed C-H olefination toward phosphine-alkene ligands.

The Pd(II)-catalyzed Ph2(O)P-directed C-H olefination to synthesize alkene-phosphine compounds is reported. In contrast to previous examples of various directing groups that guide selective C-H activation, the Ph2(O)P group not only acts as the directing group but also serves to construct the alkene-phosphine ligands. The monoprotected amino acid (MPAA) ligand Ac-Leu-OH is found to promote this reaction in a significant manner.

Silver-catalyzed carboazidation of arylacrylamides.

A novel and inexpensive method of nontoxic, silver-salt-catalyzed carboazidation of arylacrylamides to afford corresponding azide oxindoles is reported. This reaction system exhibits great functional group tolerance. All products form a crucial skeleton for the synthesis of various indole alkaloids.

Palladium-catalyzed divergent reactions of 1,6-enyne carbonates: synthesis of vinylidenepyridines and vinylidenepyrrolidines.

A method for preparing five- or six-membered heterocyclic compounds from enyne carbonates via palladium catalysis was developed. Enyne carbonates were transformed into 3-vinylidene-1-tosylpyridines 2 in the presence of PdI(2) as the catalyst. Using Pd(dba)(2) as the catalyst, 3-vinylidene-1-tosylpyrrolidines 3 were obtained. Further functionalizations of compounds 3 were carried out in a one-pot manner.

Copper-catalyzed direct thiolation of azoles with aliphatic thiols.

Cu(II)-catalyzed direct thiolation of azoles with thiols is described via intermolecular C-S bond formation/C-H functionalization under oxidative conditions. Both aryl thiols and aliphatic thiols are used as coupling partners, and furnished the thiolation products in moderate to good yields. The reaction is compatible with a wide range of heterocycles including oxazole, thiazole, imidazole and oxadiazole.

Pd(0)-catalyzed [1,5]-sigmatropic hydrogen shift of propargylic esters toward substituent naphthylamines.

A novel and convenient carboannulation method for the synthesis of highly substituted naphthylamine derivatives has been developed though a Pd(0)-catalyzed [1,5]-sigmatropic hydrogen shift and cyclization reaction of propargyl esters.