Search

2-Aminophenyl-1H-pyrazole was discovered as a removable bidentate directing group for copper-mediated aerobic oxidative C(sp2–H) bond amidation and sulfonamidation. When Cu(OAc)2 was employed as the copper source and 1,1,3,3-tetramethylguanidine as an organic base, the reaction, optimally carried out overnight in DMSO at 80 °C in open air, produced a variety of amides and sulfonamides in moderate to excellent yields. This directing group has proven to be particularly efficient in C–H sulfonamidation.

A palladium(II)-catalyzed oxidative Mizoroki–Heck reaction of arylsulfonyl hydrazides with alkenes was developed employing atmospheric air as the sole oxidant in an open-vessel manner. By using palladium(II) acetate associating with inexpensive, air-stable and moisture stable pyridine ligand L9 as the catalyst system, the efficiency of the reaction could be significantly enhanced. A wide range of arylsulfonyl hydrazides underwent the oxidative Mizoroki–Heck reaction with alkenes smoothly. Good-to-excellent product yields and excellent regio- and stereoselectivity were achieved. Functional groups such as halo, ester etc. were well-tolerated under these optimized reaction conditions.

A practical approach for the synthesis of phosphinic amides via the coupling of secondary phosphine oxides (SPOs) with O-benzoylhydroxylamines has been reported. Simply heating the mixture of SPOs and O-benzoylhydroxylamines in the presence of K(2)CO(3) gave the phosphinic amides in moderate to excellent yields under an open air system. This method provides a practical and catalyst-free method for the synthesis of various synthetically valuable phosphinic amides.

PhSe(O)OH was found to be a good pre-catalyst for aldoxime dehydrations in open air. Compared with the previously reported (PhSe)2-H2O2 system, it is more stable and milder, affording broader application scopes due to a higher functional group tolerance. The control experiments for mechanism study disclosed that air was the key factor for the reaction to maintain enough concentration of PhSeOH, which should be the real catalytic species.

An efficient and convenient method for the synthesis of diaryl sulfones was developed through the Cu-catalyzed cross-couplings of arylsulfonyl chlorides and arylboronic acids at room temperature in open air. This method is characterized by the use of inexpensive and readily available catalyst and substrates, mild reaction conditions, wide functionality tolerance, short reaction times for most substrates, and moderate to good yields.

The copper-catalyzed formation of C–O bonds by oxidative coupling of benzylic alcohols with ethers was realized in open air. A series of α-acyloxy ethers were obtained in good yields with aqueous tert-butyl hydroperoxide as the oxidant.

Solvent-free oxidative synthesis of benzimidazoles, benzoxazoles, and benzothiazoles from aromatic primary amines and o-phenylenediamine, o-aminophenol, and o-aminothiophenol has been achieved by using Fe(NO3)3 and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl). This reaction can use air as an economical and green oxidant, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a direct, practical, and efficient approach for the preparation of substituted benzimidazoles, benzoxazoles, and benzothiazoles.

A practical and efficient construction of C-O bonds via oxidative cross-coupling reaction of aldehydes and ethers has been realized under open air. When 2 mol% copper was used as the catalyst, various α-acyloxy ethers were obtained with up to 93% isolated yield.

A practical C–H functionalization method for the methylation of heteroarenes is presented. Inspiration from Nature’s methylating agent, S-adenosylmethionine (SAM), allowed for the design and development of zinc bis(phenylsulfonylmethanesulfinate), or PSMS. The action of PSMS on a heteroarene generates a (phenylsulfonyl)methylated intermediate that can be easily separated from unreacted starting material. This intermediate can then be desulfonylated to the methylated product or elaborated to a deuteriomethylated product, and can divergently access medicinally important motifs. This mild, operationally simple protocol that can be conducted in open air at room temperature is compatible with sensitive functional groups for the late-stage functionalization of pharmacologically relevant substrates.

Synthesis of imines from amines and aliphatic alcohols (C1–C6) in the presence of base on supported palladium nanoparticles has been achieved for the first time. The catalytic system shows high activity and selectivity in open air at room temperature.

A novel I2/TBHP-mediated direct oxidative diamination reaction of indoles with anilines was developed. The reaction proceeded smoothly under aqueous and open air reaction conditions. This protocol provides a practical synthetic method for the synthesis of Tryptanthrin and the construction of N-C3 linked pyrrolidinoindolines which is the core structure of Psychotrimine.

An unexpected formation of cis-1,2,2-trimethyl-3-(benzoxazol-2-yl)cyclopenta-necarboxylic acids was observed as the result of an oxidative C-C bond cleavage of the camphor ring in the intermediate imine during the condensation reactions between camphoroquinone and o-aminophenols conducted under open air conditions. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

A rapid, inexpensive and high yielding method has been developed for the synthesis of 1,8-dioxodecahydroacridines using Amberlite IR-120H as a reusable catalyst under open air. These compounds were designed as potential inhibitors of sirtuins and prepared via the MCR of 5,5-dimethyl-1,3-cyclohexanedione, (hetero)aryl aldehydes and (hetero)aromatic amines under mild conditions. Further structure elaboration of a representative compound was performed via Pd catalyzed C–C bond forming reactions. The crystal structure analysis and H-bonding patterns along with in vitro inhibitory activity against yeast Sir2 of the same compound is presented. Docking studies indicated that the compound interacts well with the yeast Sir2.

A general, green, and scalable synthesis of the useful imines and α,β-unsaturated imines is successfully achieved by a low-loading and powerful, mild and efficient copper-catalyzed aerobic oxidative reaction of alcohols and amines in the open air at room temperature under base- and dehydrating reagent-free conditions. This practical reaction can use air as the economic and green oxidant, tolerates a wide range of substrates, can afford high yields of the target imines on a large scale, and produces water as the only by-product, and thus being the best imination method as yet using alcohols and amines directly.

A highly thermal stable, hydrophobic, reusable (5 times), easily preparable, and complete heterogeneous catalyst, which can also be stored and handled under open air , is successfully applied to the title reaction.

A Pd-catalyzed method has been developed for the intramolecular oxidative coupling of 3-indolylarylketones under open air as terminal oxidant toward the synthesis of indeno[1,2-b]indol-10(5H)-ones. This reaction represents an intramolecular coupling with dual activation of C–H bonds for electron-deficient arenes, while such reactions are common for electron-rich arenes. Pd(II)-catalysis with pivalic acid as co-catalyst has been found to be crucial. The reaction undergoes without indole N–H-protection.

Reactions directly involving triplet oxygen are an important issue in organic and biological chemistry. We now report that exposure of tetramic acids in the open air (molecular oxygen) at room temperature can lead to the formation of succinimide derivatives in high to excellent yields via tandem oxidation/1,2-benzyl migration. In this reaction, the dithiolane moiety plays a crucial role and succinimides are produced either in the presence or absence of dibutyl sulfide as reductant.

A general method for the A3 coupling of unactivated alkyl and aryl aldehydes in open air, in technical grade MeOH, and without any purification of the coupling partners is described with in very short reaction times.

The PdCl2-catalyzed cross coupling of sodium tetraarylborates (I) proceeds in an atom-efficient manner with four equivalents of aryl bromides or iodides under mild reaction conditions (open air atmosphere, room temperature, ligand-free).

The ligandless palladium-catalyzed Suzuki cross-coupling reaction of potassium aryl- and heteroaryltrifluoroborates with aryl- or heteroaryl halides or triflates proceeds readily with very good yields. The cross coupling can be effected in methanol or water, in the open air, using Pd(OAc)2 as a catalyst in the presence of K2CO3. A variety of functional groups are tolerated.

The first examples of the direct arylation of benzo-fused 1,4-quinones by the dicationic Pd(II)-catalyzed addition of arylboronic acids are reported. The addition reaction is carried out under very mild conditions (dioxane−H2O, rt, open air atmosphere) and is tolerant of free OH groups. In addition, the reaction shows high regioselectivity when using nonsymmetrical quinones as starting materials.

A simple and efficient procedure for the synthesis of 2-substituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with aromatic aldehydes in the presence of an ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmim]BF4 at room temperature in open air without any organic solvent. The ionic liquid is recycled. A remarkable influence of the substituent on the imidazolium unit of the ionic liquid on the outcome of the reaction is observed.

Oxidative Heck reactions of arylboronic acids and alkenes are carried out in the presence of polyaniline-supported palladium catalysts using air as a co-oxidant to afford the Heck products with excellent yields and selectivities under base- and ligand-free conditions. The catalyst was recovered by simple filtration and used for several cycles with consistent activity.

Ester condensation is one among the most fundamental organic transformations, and more environmentally benign alternatives to current esterification processes are needed. Under solvent-free and drying agent-free conditions, catalytic amounts of sulfonic acids promote ester condensation between an equimolar mixture of carboxylic acids and alcohols. In particular, p-toluenesulfonic acid (TsOH) and 10-camphorsulfonic acid (CSA), which have appropriate acidities, efficiently catalyze the ester condensation of secondary alcohols without their decomposition. Since the present protocol does not require solvents under simple open-air conditions, a large amount of esters can be synthesized in a rather small apparatus.

Catalyzed by samarium triiodide (SmI3), substitution of acyl with N‐acylbenzotriazoles for acetyl in acetoacetic esters and acetylacetone proceeds smoothly under neutral conditions in open air, affording the corresponding β‐keto esters and β‐diketones in good yields.

A facile triphenylphosphine-catalyzed Michael addition of alcohols to acrylic compounds was described. The reaction was carried out in open air at refluxing temperature in the presence of 10 mol% PPh3. Michael addition of saturated and unsaturated alcohols to acrylonitrile or acrylates has been examined. The reaction gave β-alkoxy derivatives with isolated yields of 5%–79%. PPh3 is cheaper and more stable than those trialkylphosphines previously used for the similar reactions, and the products can be easily separated from the reaction mixture via distillation.

PMHS (polymethylhydrosiloxane) used in catalytic amounts has a remarkable ability to prevent catalyst poisoning by oxygen contamination during palladium catalyzed cyanation reactions. The procedure is applicable to a wide range of substrates and is so effective that it allows the reactions to be run fully open to the atmosphere.

The low-cost and commercially available (−)-ephedrine hydrochloride was firstly employed in the [RuCl 2 ( p -cymene)] 2 -catalyzed asymmetric transfer hydrogenation of prochiral ketones in water. The reaction could be performed in the open air at rt, affording excellent yields (up to 99%) and good enantioselectivities (up to 83% ee). It provided a further step toward the discovery of simplified catalyst systems for eventual availability.