A highly regioselective synthesis of β‐aryl enaminones and 1,4,5‐trisubstituted 1,2,3‐triazoles from chalcones and benzyl azides based on reaction solvent selection is reported. In the presence of a catalytic amount of Ce(OTf)3, reactions of chalcones with benzyl azides in DMF at 100 °C afforded densely substituted Z‐β‐aryl enaminones in good to excellent yields, whereas treatment of chalcones with benzyl azides in toluene at 100 °C selectively produced 1,4,5‐trisubstituted 1,2,3‐triazoles in excellent yields.
A concise synthesis of 1‐naphthols via cyclization of o‐iodoacetophenones and methyl ketones has been realized under very mild conditions. The cyclization process is initiated by a rare copper‐catalyzed arylation of simple methyl ketones with ortho‐iodoacetophenones.
Copper chloride‐catalyzed aerobic oxidative annulation of N‐furfuryl‐β‐enaminones provides access to polysubstituted pyrroles and indoles. This protocol involves an unprecedented copper chloride‐catalyzed oxidative chlorination of furan and pyrrole rings with oxygen as the terminal oxidant.
A rhodium(I)‐catalyzed direct C H bond olefination of pyridyl‐substituted arenes with readily available vinyl carboxylic acids has been realized. This reaction occurred efficiently without the need for any external oxidant, affording the ortho‐olefinated products in high yields and excellent regioselectivities. Diversely substituted vinyl carboxylic acids behaved as efficient olefination reagents under the reaction conditions, and a range of functional groups in both coupling partners was well tolerated. Mechanistic studies indicated that a decarbonylation step is involved in this catalytic process, and pivalic anhydride [(t‐BuCO)2O] acts as the activator of the carboxylic acids for the in situ generation of highly active anhydrides.
An efficient dehydrogenative Diels–Alder (DHDA) reaction of prenyl derivatives with 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) has been developed under mild conditions, leading to a series of cyclohexene derivatives with good to excellent yields and excellent diastereoselectivity.
A recyclable fluorous bifunctional Cinchona alkaloid/thiourea‐catalyzed and four‐component Michael/Mannich/cyclization sequence has been developed for the asymmetric synthesis of spirooxindoles containing 2‐piperidinone and tetrahydropyridine rings. This one‐pot reaction process affords the products in good to excellent yields and up to 99% ee and 9:1 dr.
A facile one‐pot, catalyst‐free reaction has been developed for the synthesis of 2,3,6,7‐tetrahydro‐1H‐pyrrolo[3,2‐c]pyridin‐4(5H)‐ones from readily available 1‐acryloyl‐1‐N‐arylcarbamylcyclopropanes and amines using a domino ring‐opening/cyclization/aza‐addition sequence.
A three‐component reaction involving isocyanides, o‐alkynyltrifluoroacetanilides, and amines for the efficient synthesis of 2‐substituted 1H‐indole‐3‐carboxamidines has been developed. The reaction proceeds through intramolecular aminopalladation of alkynes activated by isocyanide‐ligated palladium(II) species. Dioxygen acts as the sole oxidant to regenerate the active palladium(II) species.
An efficient regioselective synthesis of 2‐acylpyrroles via palladium‐catalyzed addition of pyrroles with benzonitriles and subsequent hydrolysis is developed. The direct acylation reaction of protected as well as (NH)‐free pyrroles proceeded smoothly to afford 2‐acylpyrrole scaffolds of high biological interest.
Herein an improved protocol for the synthesis of imidazo[4,5‐b]pyridines and imidazo[4,5‐b]pyrazines using a palladium‐catalyzed amidation that utilizes Xantphos as an ancillary phosphine ligand is reported. The use of a binary solvent system comprised of 1,4‐dioxane and tert‐amyl alcohol was crucial in eliminating unwanted by‐products.
A synthetic strategy has been developed for the synthesis of 2‐dialkylaminoquinolines from easily available quinoline N‐oxides, tertiary amines, diisopropyl H‐phosphonate and carbon tetrachloride (CCl4) in one pot under metal‐free conditions at room temperature.
The highly catalytic asymmetric α‐hydroxylation of β‐indanone esters and β‐indanone amides using peroxide as the oxidant was realized with a new C‐2′ substituted Cinchona alkaloid derivatives. The two enantiomers of α‐hydroxy‐β‐indanone esters could be obtained by simply changing the oxidant. This protocol allows a convenient access to the corresponding α‐hydroxy‐β‐indanone esters and α‐hydroxy‐β‐indanone amides with up to 99% yield and 98% ee.
The first active aza analogue of narciclasine was synthesized from a pentasubstituted derivative of nicotinic acid. The key features of the synthesis include a halogen dance of bromopyridine and an intramolecular Heck reaction with a conduramine derived chemoenzymatically from bromobenzene. 10‐Aza‐narciclasine was found to have reasonable activity against several cancer cell lines.
A one‐pot transformation of aldehydes into α,β‐unsaturated aldehydes was developed using both N‐benzyl‐N‐methylamine and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) as catalysts and MnO2 as a terminal oxidant. An oxidative and enantioselective reaction of aldehydes and nitromethane was established using both diphenylprolinol silyl ether and DDQ as a catalyst with MnO2 as a terminal oxidant, in which synthetically important β‐substituted γ‐nitro aldehydes were obtained with excellent enantioselectivity.
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.
Gold carbenes generated via 1,2‐migration of a propargylic ester group can be transferred over a tethered alkyne. The use of aromatic backbones leads after a 1,7‐carbene transfer to a benzyl‐stabilized carbene as intermediate. A 1,2‐shift of a methyl group delivers vinyl‐substituted β‐naphthol derivatives as the final products.
