Cobalt‐catalyzed C−H amination of arenes with alkylamines by the assistance of 8‐aminoquinoline as auxiliary through sp2 C−H bond functionalization has been achieved. Attractive features of this protocol include the low loading of the cobalt catalyst and the readily available reagents.
N‐Alkenylated triazolinone ylides were generated through copper‐catalyzed oxy‐N‐alkenylation of triazolopyridines. The mechanistic course of this aerobic tandem reaction has been experimentally elucidated and primary photophysical data of the ylide products are also given.
A palladium‐catalyzed cross‐coupling of activated amides with arylboronic acids has been developed via C–N bond cleavage. This approach demonstrated high tolerance to a variety of alkyl, aryl, heterocyclic and vinyl substituents. Unsymmetrical ketones could be achieved in excellent yield under mild conditions with 1% catalyst loadings.
The bis(N‐heterocyclic carbene)(diphenylacetylene)palladium complex [Pd(ITMe)2(PhC≡CPh)] (ITMe=1,3,4,5‐tetramethylimidazol‐2‐ylidene) acts as a highly active pre‐catalyst in the diboration and silaboration of azobenzenes to synthesize a series of novel functionalized hydrazines. The reactions proceed using commercially available diboranes and silaboranes under mild reaction conditions.
A copper‐catalyzed three‐component (arenes, iodohydrocarbon, and sulfur powder) synthesis of substituted aryl sulfides has been developed. Water is used as the green solvent in a simple and environmentally friendly procedure. Various functional groups attached to the substrates were well tolerated in this process to afford the corresponding products in moderate to good yields.
We have established a mild and direct platinum on carbon (Pt/C)‐catalyzed multi‐deuterium labeling of various saturated fatty acids including bioactive compounds with high deuterium efficiencies in a mixed solvent of isopropyl alcohol and deuterium oxide (i‐PrOH)/D2O under neutral conditions at 120 °C without the external addition of deuterium or hydrogen gas.
The sodium iodide/hydrogen peroxide‐mediated oxidation/lactonization of indolepropionic acids was achieved, affording the corresponding spirocyclic oxindole‐lactones in moderate to high yields. This metal‐free procedure features mild reaction conditions, non‐toxicity and easy handling, with hydrogen peroxide (H2O2) as a clean oxidant.
A novel one‐pot reaction which combines halogenation, decarboxylation/desulfonamidation with oxidation has been developed. Diverse valuable 3,3‐dihalo‐2‐oxindole compounds can be produced rapidly and safely with isolated yields of up to 98% under mild conditions.
An efficient metal‐free organocatalytic activation of hydrogen peroxide (H2O2) towards thioethers leading to the corresponding sulfoxides in high yields at room temperature within hours was promoted by the hexameric capsule formed by the self‐assembly of resorcin[4]arene units. The capsule plays a dual role of activating the oxidant through hydrogen bonding and favouring the oxidation reaction inside the cavity. Inactivation of the supramolecular organocatalyst was observed by using competitive ammonium guests, mimicking the inactivation of enzymes by competitive inhibitors.
A palladium‐catalyzed domino strategy has been developed for the synthesis of 2,3‐disubstituted benzofuran derivatives. This cascade reaction sequence involves intermolecular carbopalladation and C(sp3)−H functionalization followed by isomerization.
The base metal complex tetrabutylammonium nitrosyltricarbonylferrate {Bu4N[Fe(CO)3(NO)] (TBA[Fe])} – catalyzes the conjugate addition of ketones to polar olefins. The reaction is applicable to a wide range of substrates leading to interesting building blocks for organic synthesis. Clear indications for an acid‐base type rather than a C−H activation pathway exist.
The first highly enantioselective intramolecular N−H bond insertion was realized by using copper catalysts modified with chiral spirobisoxazoline ligands, which provides a novel strategy for the synthesis of chiral 2‐carboxytetrahydroquinolines. This reaction features fast reaction rate, high yield, high enantioselectivity, and mild reaction conditions.
A multifunctional chiral phosphine‐catalyzed enantioselective [3+2] annulation of Morita–Baylis–Hillman carbonates with barbiturate‐derived alkenes has been achieved under mild conditions, providing a variety of chiral spirobarbiturate‐cyclopentenes in moderate to excellent yields with moderate to excellent diastereo‐ and enantioselectivities.
1‐Alkynylcyclopropyl tosylates react with alkylmagnesium halides in the presence of catalytic ferric acetylacetonate [Fe(acac)3] under net propargylic substitution; allene formation, which is the prevalent reactivity mode of propargylic substrates otherwise, was noticed as a side reaction only when branched alkyl‐ or aryl‐Grignard reagents were used. These transformations represent the first successful iron‐catalyzed cross‐coupling reactions of tert‐alkyl electrophiles.
This review describes the recent developments in the field of Suzuki–Miyaura cross‐coupling reaction, in particular with regard to ligand‐free catalysis. The catalysts outlined here allow convenient and green synthetic pathways specifically for the construction of C–C bonds. They enable the synthesis of biaryls by the coupling arylboronic acids with aryl halides. The literature reporting ligand‐free synthesis of biaryls from 2010 to May 2015 has been reviewed.
A stereocontrolled [4+1] annulation of α‐hydroxycyclobutenones has been disclosed. For the first time, α‐hydroxycyclobutenones have been proven as facile diene precursors for [4+1] annulation. Meanwhile, the reported transformation presents a concise synthetic route to polysubstituted cyclopentenones with high stereoselectivity.
The introduction of a trifluoromethyl group into the 2′‐position of spiro‐pyrrolidine‐3,3′‐oxindoles is described. By using 1 mol% of a quinine‐derived squaramide as catalyst, the 2,2,2‐trfluoroethylamine (CF3CH2NH2)‐derived ketimine is transformed initially into a trifluoromethylimine through an umpolung reaction. The subsequent 1,3‐dipolar cycloaddition gives the pharmaceutical important target compounds in excellent yields, enantioselectivities and diastereoselectivies.
An iron(III)‐catalyzed C‐3 functionalization of flavones has been achieved using tert‐butyl peroxybenzoate (TBPB)/potassium persulphate (K2S2O8) oxidant combinations with a suitable solvent. In the presence of iron(III)/tert‐butyl peroxybenzoate/potassium persulphate, the reaction of flavones in cycloalkanes afforded exclusive C‐3 cycloalkylation via C –C coupling, whereas the solvent N,N‐dialkylformamide provided C‐3 amidation via C –C coupling. Under identical reaction conditions just by switching the solvent to chlorobenzene, C‐3 methylated flavones were obtained where tert‐butyl peroxybenzoate (TBPB) served as the source of the methyl group.
