An efficient copper‐catalyzed α‐aminoxylation of ketones with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) is presented for the synthesis of 2‐aryloxy‐1‐aryl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethanones in moderate to excellent yields. It is noteworthy that the copper/iron (Cu/Fe) catalyst can be recovered and reused several times with high catalytic reactivity.
The palladium‐catalyzed acylation of 2‐aryl‐1,2,3‐triazoles with aldehydes via C H bond activation is described. A wide variety of products was isolated in good to excellent yields. This finding provides a new and useful strategy for the synthesis of aromatic ketones.
The first example of enantioselective nitronate protonation following Michael addition of a carbon nucleophile to an α,β,β‐trisubstituted nitroalkene is reported. An N‐sulfinylurea catalyst was employed to catalyze the addition of a variety of 3‐substituted pyrazol‐5‐one nucleophiles to trisubstituted nitroalkenes incorporating an oxetane or azetidine ring at the β‐position. The nitroalkane‐pyrazolone adducts were obtained with good yield and enantioselectivity. Furthermore, the Michael addition products can be reduced to the corresponding enantioenriched amines with minimal loss of enantiomeric purity.
A novel methodology has been developed for the synthesis of chiral phosphoryl‐1,4‐dihydropyridazine derivatives based on an asymmetric allylic alkylation/intramolecular 1,3‐dipolar cycloaddition/rearrangement reaction sequence, various chiral 3‐phosphoryl‐4‐aryl‐1,4‐dihydropyridazine‐5‐carboxylates were achieved in high yields with high enantioselectivities. Moreover, chiral 4,5‐dihydropyridazinone derivatives were also facilely furnished by the reduction of the allylic alkylation products of Morita–Baylis–Hillman carbonates and α‐diazophosphonates.
A straightforward assisted tandem palladium(II)‐ and palladium(0)‐catalyzed direct C‐3 and N‐4 arylation of quinoxalin‐2(1 H)‐ones with boronic acids and aryl halides in water as safe and cheap solvent is reported. This environmentally friendly catalytic protocol is compatible with a wide range of functional groups and allows construction of various biologically important quinoxalin‐2(1 H)‐one backbones.
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.
A versatile strategy for the synthesis of fused cyclopentenones, key structural motifs in biologically relevant compounds such as indenones and indole alkaloids, has been established successfully through regioselective palladium‐catalyzed cyclization of 2‐iodoaryl allenols.
A highly efficient dearomatization reaction of α‐substituted β‐naphthols with excellent chemoselectivity and regioselectivity has been developed. Mechanistic studies demonstrated that the dearomatized alkylation product is the thermodynamically more stable compound. The etherification product could be further transformed to the dearomatization product.
The combination of benzyl bromide, sodium hydroxide and 15‐crown‐5 in tetrahydrofuran is shown to be an efficient method for installing benzyl groups at both the 4‐ and 6‐positions regioselectively directly from peracetylated N‐trichloroacetyl‐protected glucosamine and galactosamine. Application of this benzylation strategy proved to significantly shorten the synthetic route to hyaluronic acid tetra‐ and hexamers.
A novel and efficient oxidative annulation of 2‐aminobenzamides with nitromethane has been developed for the chemoselective synthesis of N‐substituted 1,2,3‐benzotriazine‐4(3H)‐ones in moderate to excellent yields under transition metal‐free conditions. Two N N bonds were constructed in one pot via C N cleavage of nitromethane, which was selectively employed as the nitrogen synthon. The preliminary mechanistic studies revealed that this protocol proceeded under hypoiodite catalysis generated in situ.
Porous organic polymers have prospects as functional substrates for catalysis, with quite different molecular properties from inorganic substrates. Here we disclose for the first time that porous palladium(II)‐polyimines are excellent catalysts for cooperatively catalyzed and enantioselective cascade reactions. In synergy with a chiral amine co‐catalyst, polysubstituted cyclopentenes and spirocyclic oxindoles, including the all‐carbon quaternary stereocenter, were synthesized in high yields. High diastereo‐ and enantioselectivities were achieved for these dynamic kinetic asymmetric transformations (DYKAT) of enals with propargylic nucleophiles.
Copper‐catalyzed C X activation‐phosphorylation of aryls bearing different groups has been achieved using P(O) H compounds as efficient phosphorylation reagents without the assistance of any ligand. Optically active H‐phosphinates can also act as good substrates in the reaction, giving the (Sp)‐phosphoryl substituted phenolic compounds stereospecifically with retention of configuration at the phosphorus center. Furthermore, it is shown that the migration of phosphorus on O‐aryl phosphonates from oxygen to carbon also proceeds stereospecifically to produce the corresponding optically active (Rp)‐phosphoryl‐substituted phenolic compounds with retention of configuration at phosphorus via treatment with lithium diisopropylamide (LDA). Plausible mechanisms have been proposed for these reactions.
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 transition metal‐free and efficient method for the synthesis of 3‐alkynylpyrrole‐2‐carboxylates from diynones and glycine esters or 2‐aminoacetophenone hydrochloride has been developed. This transformation provides a large range of substituted pyrroles in good to excellent yields with the elimination of water as the only by‐product. The detailed mechanistic studies elucidated that this transformation involves a Michael addition/intramolecular cyclodehydration process.
A transition metal‐free direct arylation of 2‐substituted cyanoacetates with diaryliodonium salts was developed. With this approach, a wide range of α‐tolunitrile derivatives has been synthesized in good to excellent yields of 45–92%. Furthermore, the practicability of this approach is further manifested in the synthesis of a related bioactive agent of glutarimide.
Visible light irradiation of N‐bromosuccinimide serves as an effective means to convert methyl 2‐(azidomethyl)‐3‐arylpropenoates and 2‐(azidomethyl)‐3‐arylacrylonitriles to the corresponding iminyl radicals via α‐hydrogen abstraction and subsequent extrusion of dinitrogen. Thus formed iminyl radicals then undergo intramolecular ortho attack on the aryl ring, affording methyl quinoline‐3‐carboxylates and quinoline‐3‐carbonitriles respectively.
