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N-Heterocycles, such as pyrroles, pyrimidines, quinazolines, and quinoxalines, are important building blocks for organic chemistry and the fine-chemical industry. For their synthesis, catalytic borrowing hydrogen and acceptorless dehydrogenative coupling reactions of alcohols as sustainable reagents have received significant attention in recent years. To overcome the problems of product separation and catalyst reusability, several metal-based heterogeneous catalysts have been reported to achieve these transformations with good yields and selectivity. In this Minireview, we summarize recent developments using both noble and non-noble metal-based heterogeneous catalysts to synthesize N-heterocycles from alcohols and N-nucleophiles via acceptorless dehydrogenation or borrowing hydrogen methodologies. Furthermore, this Minireview introduces strategies for the preparation and functionalization of the corresponding heterogeneous catalysts, discusses the reaction mechanisms and the roles of metal electronic states, and the influence of support Lewis acid-base properties on these reactions. more...

A one-pot synthesis of β-amino α,α-difluoro ketones is developed without any additives. Through a series of control experiments we found that water plays a crucial and indispensable role. The hydrogen bond between water and fluorinated enol silyl ether has a significant impact on the addition reaction. more...

Regioselective arylthiolations of aromatic amines, arenols and ketones via C–H bond functionalization have been achieved with I2 and PPh3 in an aqueous system, whereby arylsulfenyl radicals are in situ generated from odorless sodium arylsulfinates. The arylsulfenyl radicals can react with free anilines containing electron-withdrawing groups and complex substrates (estrone and progesterone). Further experiments and quantum chemical calculations were also performed to deduce a mechanism for the formation of arylsulfenyl radicals. more...

A highly efficient dimethylformamide (DMF)-promoted decarboxylative trifluoromethylation of α,β-unsaturated carboxylic acids with Togni (II) reagent under metal-free conditions has been developed. The reactions showed good yields, high stereoselectivities and excellent functional group tolerance. Mechanistic studies confirmed that free-radical processes were involved in this system since the CF3 radical had been clearly trapped by scavengers. This method has been extended to the denitrative trifluoromethylation of β-nitrostyrenes in the presence of an iron(III) catalyst. more...

A new method for CF3SO2Na-based direct trifluoromethylthiolation of C(sp(2))-H bonds has been developed. CF3SSCF3 is generated in situ from cheap and easy-to-handle CF3SO2Na, and in the presence of CuCl can be used for electrophilic trifluoromethylthiolation of indoles, pyrroles, and enamines. The method has been extended to perfluoroalkylthiolation reactions using RfSO2Na. more...

A newly developed protocol for the reduction of nitroarenes using thiourea as the hydrogen source is described. The method is simple, inexpensive and easily applicable to the preparation of a variety of substituted anilines with high yields and selectivity. In contrast to traditional hydrogenation methods, this chemistry does not require a catalyst, elaborated work-up procedures, or the use of high-pressure equipment. more...

Several N-heterocyclic carbene precursors are synthesized and used in the α-alkylations of ketones with primary alcohols. With the assistance of a base, these N-heterocyclic carbenes can catalyze the reaction smoothly to furnish dialkylated ketones in good-to-excellent yields. more...

An efficient method for the preparation of isothiochromene derivatives through the palladium-catalyzed intramolecular hydrothiolation reaction of halides and thiourea is reported. Two carbon–sulfur bonds are formed in this one-pot palladium-catalyzed cascade reaction. This new protocol is free from foul-smelling thiols and operates under mild conditions to give isothiochromene derivatives in excellent yields and with excellent 6-endo-dig selectivity. more...

A one-pot, efficient protocol for the synthesis of polyfunctionalized pyrido[2,3-d]pyrimidines and uncyclized adducts by 6-aminouracils in poly(ethylene glycol) 200/H2O or AcOH was described. An interesting family of pyrido[2,3-d]pyrimidines and uncyclized adducts bearing fused pharmacological active units are prepared. The reaction is free of toxic solvents and catalysts, has simple workup procedure, and has high atom economy, making it more environmentally friendly and suitable for large-scale operations. more...

The preparation of vinyl sulfides via a three-component reaction of organohalides, thiourea, and alkynes was reported. Two carbon-sulfur bonds are formed in one pot in this palladium-catalyzed system. The protocol is free of foul-smelling thiols and is operated under mild conditions to obtain cis-configured anti-Markovnikov products with moderate to excellent yields and excellent selectivity. In addition, this method is noteworthy given its experimental simplicity, high generality, good functional group tolerance, and the low cost of the catalyst system. more...

Thioesterification can be realized via an odorless, one-pot reaction through the in situ generation of S-alkylisothiouronium salts from organic halides and thiourea in aqueous Triton X-100 (TX100) micelles. The protocol is free of foul-smell thiols and organic solvents, and operates under mild conditions, thereby offering considerable potential for applications in organic synthesis. more...

A mild, simple and metal-free radical [4 + 2] benzannulation for the generation of phenanthrenes has been developed. A substoichiometric reductant, ascorbic acid (vitamin C), is harnessed as the radical initiator. This method has a broad substrate scope, and various substituted phenanthrenes were obtained in moderate to good yields at room temperature without irradiation. more...

The photoreaction of arene diazonium salts (I) with silyl enol ethers (II) gives rise to desired α-aryl-β,β-difluoroketones (III), which are converted into difluoromethylarenes (IV) by cleavage of the benzoyl group with KOH. more...

α,α-Difluorodiaroylmethane can be used as a nucleophilic difluoromethylation reagent for generating α-thioaryl-α,α-difluoroacetophenones (Ar1COCF2SAr) and difluoromethylthiolated arenes (ArSCF2H) under transition-metal-free conditions. The reaction selectivity is mainly dependent on temperature. The method has also been extended to the synthesis of α-thioaryl-α-monofluoroacetophenones using α-monofluorodibenzoylmethane. Moreover, the benzoyl cation derived from α,α-difluorodibenzoylmethane can react with nucleophiles to afford the desired products in a one-pot process. more...

An efficient, one-pot method was described for the synthesis of various polysubstituted 4H-pyrans via piperidine catalyzed three-component condensation in aqueous medium. The reaction could be promoted effectively by adding sodium dodecyl sulfate to aqueous medium. J. Heterocyclic Chem., (2010). more...

Objectives Partial liquid ventilation (PLV) with perfluorocarbons (PFC) seems not superior to conventional ventilation clinically. We hypothesized that a combination of continuous tracheal gas insufflation (TGI) with protective strategy of PLV (low dose of PFC, low inflation pressure, moderate inhalation of oxygen and moderate anesthesia) would improve cardiopulmonary function in acute lung injury. Methods Twenty-four healthy juvenile piglets were anesthetized and mechanically ventilated at PEEP of 2 cmH2O with a peak inspiratory pressure of 10 cmH2O and FIO2 of 0.4. The piglets were challenged with lipopolysaccharide and randomly assigned to four groups (n = 6 each): (1) mechanical ventilation alone (MV); (2) PLV with perfluorodecalin (10 ml/kg); (3) TGI with continuous airway flow 2 L/min; and (4) combination of PLV and TGI. The outcome was assessed functionally and histologically. Results All treatments except MV improved pH, PaO2/FIO2, PaCO2, ventilation efficacy index (VEI) and tidal volume. Both PLV-associated treatments also improved heart rate, respiratory rate, pulse contour cardiac output, systemic vascular resistance, dynamic lung compliance, mean airway resistance and mean airway pressure. The combination group resulted in higher PaO2/FIO2, VEI and a better lung histology score than any other treatments. Conclusions The new protective strategy may provide a better treatment for sepsis-induced acute lung injury. Pediatr Pulmonol. 2010; 45:700–707. © 2010 Wiley-Liss, Inc. more...

Iridium-catalyzed methylation of indoles and pyrroles using methanol as the methylating agent was achieved. This transformation takes place via a borrowing hydrogen methodology under an air atmosphere, which constitutes a direct route to 3-methyl-indoles and methyl-pyrroles. more...

A mild, metal-free synthesis of aryl sulfides has been disclosed. Aryl diazonium ion was generated by the in situ nitrosation of aniline, and it was reduced by ascorbic acid (vitamin C) to form aryl radical, which underwent a thiolation with disulfide to yield aryl sulfide. The reaction proceeded smoothly without heating or irradiation. This strategy was also expanded to the synthesis of aryl selenides. more...

A highly regioselective protocol for the direct synthesis of γ,δ-unsaturated ketones from β-ketoacids and allylic alcohols was proposed and accomplished relying on the combination of [Ir(cod)Cl]2 and 10-camphorsulfonic acid via decarboxylative allylation. more...

A simple homogeneous catalyst system composed of commercially available [IrCl(cod)]2 and 1,10-phenanthroline is used for the selective transfer hydrogenation of nitroarenes to anilines.

A newly developed regio- and stereoselective radical addition of alkyne under metal-free conidtions has been disclosed. This chemistry, in which odorless sodium arenesulfinates in place of thiols are used as the sulfur reagent, provides an efficient, one-pot approach for the generation of β-iodoalkenyl sulfides, which can be easily further functionalized to derive various alkenes and alkynyl sulfides rendering this methodology attractive to both synthetic and medicinal chemistry. more...

The protocol is extended to coupling reactions of indoles with cyclic ethers and tetrahydroisoquinolines.

An atom-economic, environmentally benign method for the oxidative cross-coupling of isochroman derivatives with thiol derivatives is examined.

A new tandem catalytic process has been established for the synthesis of quinolines. This process utilizes the [IrCp*Cl2]2/KOH catalyzed isomerization/cyclization of allylic alcohols with 2-aminobenzyl alcohol. Both the secondary and primary allylic alcohols were investigated in this catalytic system to afford different substituted quinoline derivatives in moderate to good yields. A mechanism study showed the reaction following a tandem process integrating isomerization of allylic alcohols and oxidative cyclization of 2-aminobenzyl alcohol. more...

The synthesis of various β-sulfido carbonyl compounds via hydrolysis of Bunte salts is described.

An operationally simple and selective method for the direct conversion of benzylic C–H to C–F to obtain mono- and difluoromethylated arenes using Selectfluor™ as a fluorine source is developed. Persulfate can be used to selectively activate benzylic hydrogen atoms toward C–F bond formation without the aid of transition metal catalysts. more...

Depending on the base, a wide range of α,β-unsaturated ketones are reduced to saturated ketones or alcohols by using a simple homogeneous catalytic system based on the commercially available Iridium catalyst under optimized reaction conditions. more...

A new protocol for the reduction of nitroarenes using thiourea as the hydrogen source is described.

An unprecedented protocol for the synthesis of thioesters via direct oxidative cross-coupling of benzylic ethers with thiophenols or thiols under metal and base free conditions is developed.

N-Heterocyclic carbenes are used as efficient catalysts for the synthesis of dialkylated ketones.

The nonionic surfactant Triton X-100, which self-assembles in water to form micelles, proves to enhance the title reaction remarkably.

Ortho-brom benzyl alcohols are also applicable in these reactions with slightly lower yields.

An efficient method for the preparation of isothiochromene derivatives through the palladium-catalyzed intramolecular hydrothiolation reaction of halides and thiourea is reported. Two carbon–sulfur bonds are formed in this one-pot palladium-catalyzed cascade reaction. This new protocol is free from foul-smelling thiols and operates under mild conditions to give isothiochromene derivatives in excellent yields and with excellent 6-endo-dig selectivity. more...

An optimized methodology is given for the synthesis of nitriles from substituted oxadiazoles (I) by base-induced ring opening.

Attempts upon an asymmetric allylation using a chiral bisoxazoline ligand provide only racemic product.

The synthesis and catalytic evaluation of palladium complexes containing NCN Pincer ligand is reported. The pincer palladium complexes as (pre)catalyst showed efficient catalytic activity for the C–H arylation of N-substituted indoles, allowing the synthesis of 2-arylindoles with moderate to good yields and excellent regioselectivities. more...

The cyanation of aryl bromides with malononitrile proceeds by a copper-mediated cleavage of the carbon-nitrile bond via a C(sp3) to C(sp2) cyano group transfer process.

This method uses thiourea as an odorless sulfur source and proceeds generally with high Z-selectivity.

A palladium(II)-catalyzed oxidative ortho-arylation of 2-phenylpyridines via direct C–H activation with aryl boric acids is described. The reaction could be conducted under mild conditions in the presence of Pd(OAc)2/Cu(OTf)2/TBHP system, and a variety of the azacyclic compounds bearing a biaryl unit were obtained with moderate to good yields. more...

Thioester formation is achieved in a one-pot, three-component reaction via in situ generated S-alkylisothiouronium salts.

The nonionic amphiphile TPGS-750-M enables efficient Stille coupling reactions between a wide range of substrates in water as the only medium.

Various indole substrates can be efficiently arylated in a regio- and chemoselective manner in the absence of any toxic solvents.

A new set of conditions is developed for the highly stereoselective and mild reaction of (Z)-alkenyl halides along with improved yields.