Palladium-Catalyzed Direct Arylation of Cyclic Enamides with Aryl Silanes by sp2 CH Activation

Rhodium(iii)-catalyzed olefinic C–H alkynylation of enamides at room temperature

Rh(iii)-catalyzed C–H olefinic alkynylation of enamides for the stereospecific construction of synthetically useful Z-type enynamides is reported. This protocol displays good functionality tolerance and operational simplicity thus providing an alternative synthetic opportunity for the ease of access to specific 1,3-enyne derivatives.

Preparation of highly substituted (β-acylamino)acrylates via iron-catalyzed alkoxycarbonylation of N-vinylacetamides with carbazates

A simple and efficient iron-catalyst system was applied for the synthesis of various (β-acylamino)acrylate derivatives under mild reaction conditions.

Silver-mediated oxidative vinylic C–H bond sulfenylation of enamides with disulfides

A silver-mediated oxidative vinylic C–H bond sulfenylation of enamides was developed. This method is compatible with diaryl and dialkyl disulfides to deliver the biologically precious chalcogenated olefins efficiently. A plausible non-chain radical mechanism was proposed for understanding this novel sulfenylation based on the mechanistic studies.

Synthesis of multi-substituted pyrroles using enamides and alkynes catalyzed by Pd(OAc)2 with molecular oxygen as an oxidant

A cyclization reaction between enamides and alkynes catalyzed by palladium(ii) acetate is described. In this method, the molecular oxygen serves as an efficient oxidant for the Pd(ii)/Pd(0) catalytic cycle. The simple reaction conditions permit this methodology to be used as a general tool for the preparation of multi-substituted pyrroles.

Direct alkenyl C–H functionalization of cyclic enamines with carboxylic acids via Rh catalysis assisted by hydrogen bonding

Enamines and enamides are important synthetic intermediates.

Directing-group-assisted copper-catalyzed olefinic trifluoromethylation of electron-deficient alkenes

Assistance provided: The directing group in the title reaction not only activates the substrates but also allows the stereospecific formation of cis-trifluoromethylated products. The reaction is operationally simple and tolerates a wide variety of functional groups, thus providing an efficient method for the stereoselective synthesis of β-CF3 -functionalized acrylamide derivatives.

Synthesis of Phenanthridinones from N-methoxybenzamides and aryltriethoxysilanes through Rh(III)-catalyzed C-H and N-H bond activation

An efficient method for the one-pot synthesis of substituted phenanthridinone derivatives from N-methoxybenzamides and aryltriethoxysilanes through rhodium-catalyzed dual C-H bond activation and annulation reactions is described. A double-cycle mechanism is proposed to account for this catalytic reaction. In addition, isotope-labeling studies were performed to understand the intimate mechanism of the reaction.

Copper-assisted palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids

Described herein is a palladium(II)-catalyzed direct arylation of cyclic enaminones with arylboronic acids. The versatility of this method is that both electron-rich and electron-poor boronic acids can be coupled in high yields. A mixture of two Cu(II) additives was crucial for efficient cross-coupling. The role of each Cu(II) reagent appears to be distinct and complementary serving to assist catalyst reoxidation and transmetalation through a putative arylcopper intermediate.

Ligand-accelerated cross-coupling of C(sp2)-H bonds with arylboron reagents

A ligand-accelerated Pd(II)-catalyzed C(sp(2))-H/arylboron cross-coupling reaction of phenylacetic acid substrates is reported. Using Ac-Ile-OH as the ligand and Ag(2)CO(3) as the oxidant, a fast, high-yielding, operationally simple, and functional group-tolerant protocol has been developed for the cross-coupling of phenylacetic acid substrates with aryltrifluoroborates. This ligand scaffold has also been shown to improve catalysis using 1 atm O(2) as the sole reoxidant, which sheds light on the path forward in developing optimized ligands for aerobic C-H/arylboron cross-coupling.

Direct Hiyama cross-coupling of enaminones with triethoxy(aryl)silanes and dimethylphenylsilanol

2,3-Dihydropyridin-4(1H)-ones undergo direct C-H functionalization at C5 in the palladium(II)-catalyzed Hiyama reaction, using triethoxy(aryl)silanes and dimethylphenylsilanol. The reagent CuF(2) has a dual role in the reactions with triethoxy(aryl)silanes. It is a source of fluoride to activate the silane in the Hiyama reaction and also serves as the reoxidant to convert Pd(0) to Pd(II) in the catalytic cycle.

Regioselective orthopalladation of (Z)-2-aryl-4-arylidene-5(4H)-oxazolones: scope, kinetico-mechanistic, and density functional theory studies of the C-H bond activation

Orthopalladated complexes derived from (Z)-2-aryl-4-arylidene-5(4H)-oxazolones have been prepared by reaction of the oxazolone with palladium acetate in acidic medium. The reaction is regioselective, only the ortho C-H bond of the arylidene ring being activated, producing a six-membered ring. The scope and reaction conditions of the orthopalladation are dependent on the acidity of the solvent. In CF(3)CO(2)H a large number of oxazolones can be metalated under mild conditions. As acidity decreases a lesser number of oxazolones can be efficiently palladated and harsher conditions must be used to achieve similar yields. The C-H bond activation in acidic medium agrees with an ambiphilic mechanism, as determined from kinetic measurements at variable temperature and pressure for different oxazolones substituted at the arylidene ring. The mechanism has been confirmed by density functional theory (DFT) calculations, where the formation of the six-membered ring is shown to be favored from both a kinetic and a thermodynamic perspective. In addition, the dependence of the reaction rate on the acidity of the medium has also been accounted for via a fine-tuning between the C-H agostic precoordination and the proton abstraction reaction in the overall process occurring on coordinatively saturated [Pd(κ(N)-oxazolone)(RCO(2)H)(3)](2+).