Ligand‐free,copper‐catalyzed,one‐pot,three‐component synthesis of novel 1,2,3‐triazole‐linked indoles in magnetized water

Magnetized water (MW) is used as a green and new solvent‐promoting medium for the one‐pot, three‐component synthesis of novel 1,2,3‐triazole‐linked indoles catalyzed by copper iodide. A broad range of 2‐aryl‐1‐(prop‐2‐ynyl)‐1H‐indole‐3‐carbaldehydes were reacted with alkyl halides and sodium azide via copper‐catalyzed azide–alkyne cycloaddition reactions in MW in the absence of any ligand. This method offers the advantages of short reaction times, green procedure, low cost, simple work‐up, quantitative reaction yields, and no need for any organic solvent.     

Rhodium(III)‐Catalyzed Directed C−H Amidation of N‐Nitrosoanilines and Subsequent Formation of 1,2‐Disubstituted Benzimidazoles

An efficient rhodium‐catalyzed direct C−H amidation of N ‐nitrosoanilines with 1,4,2‐dioxazol‐5‐ones as amidating agents has been developed. This method featured mild reaction conditions, a wide substrate scope and satisfactory yields. Besides, the amidated products could be readily converted to pharmaceutically valuable 1,2‐disubstituted benzimidazoles via an HCl‐mediated deprotection/cyclization process in one pot.     

Regio‐ and Enantioselective Synthesis of N‐Allylindoles by Iridium‐Catalyzed Allylic Amination/Transition‐Metal‐Catalyzed Cyclization Reactions

Regio‐ and enantioselective synthesis of N‐allylindoles was realized through an iridium‐catalyzed asymmetric allylic amination reaction with 2‐alkynylanilines and subsequent transition‐metal‐catalyzed cyclization reactions. The highly enantioenriched allylic amines prepared from Ir‐catalysis were treated with catalytic amount of NaAuCl₄ ? 2 H₂O or PdCl₂ providing various substituted N‐allylindoles in excellent yields and enantioselectivities.     

One‐Pot,Three‐Component Synthesis of Novel Spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones in an Ionic Liquid as a Reusable Reaction Media

A facile one‐pot, three‐component protocol for the synthesis of novel spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones by condensing 1H‐indole‐2,3‐diones, 4H‐1,2,4‐triazol‐4‐amine and 2‐sulfanylpropanoic acid in [bmim]PF₆ (1‐butyl‐3‐methyl‐1H‐imidazolium hexafluorophosphate) as a recyclable ionic‐liquid solvent gave good to excellent yields in the absence of any catalyst (Scheme 1 and Table 2). The advantages of this protocol over conventional methods are the mild reaction conditions, the high product yields, a shorter reaction time, as well as the eco‐friendly conditions.     

Facile Access to Polycyclic Fused Azo[2,1‐b] [1,3]‐benzothiazinone via Iron‐Catalyzed Cascade Reaction

FeCl₃‐catalyzed cross‐coupling of o‐iodobenzoic acids with azole‐2‐thiols and amidation followed by in situ acidic condensation delivered azo[2,1‐b][1,3]‐benzothiazinones. A simple “one‐pot” operation is conducted for this reaction. This reaction avoids the use of expensive catalytic reagents and provides the desired products containing different azole rings and substituents in good yields.     

Cationic Iridium/S‐Me‐BIPAM‐Catalyzed Direct Asymmetric Intermolecular Hydroarylation of Bicycloalkenes

Highly enantioselective cationic iridium‐catalyzed hydroarylation of bicycloalkenes, by carbonyl‐directed C H bond cleavage, was accomplished using a newly synthesized sulfur‐linked bis(phosphoramidite) ligand (S‐Me‐BIPAM). The reaction provides alkylated acetophenone or benzamide derivatives in moderate to excellent yields and good to excellent enantioselectivities. Notably, the hydroarylation reaction of 2‐norbornene with N,N‐dialkylbenzamide proceeds with excellent enantioselectivity (up to 99 % ee) and high selectivity for the mono‐ortho‐alkylation product.     

An efficient and facile ultrasonic‐accelerated one‐pot synthesis of N‐acetyl‐2‐aryl‐1, 2‐dihydro‐(4H)‐3,1‐benzoxazin‐4‐ones

An application of ultrasonic irradiation in the one‐pot synthesis of N‐acetyl‐2‐aryl‐1,2‐dihydro‐(4H)‐3,1‐benzoxazin‐4‐ones from the condensation reaction between aromatic aldehydes and anthranilic acid in the presence of excess amount of acetic anhydride has been explored. The reactions proceed smoothly under mild and solvent‐free conditions at room temperature in the absence of any catalyst to afford the products in good to excellent yields. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:106–113, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20663     

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

A simple, efficient and green method for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes by a one‐pot condensation reaction of β‐naphthol and aryl aldehydes using silica gel‐supported polyphosphoric acid (PPA/SiO₂), an effective and reusable catalyst, under solvent‐free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy work‐up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.     

Organocatalytic Oxidative Amidation of Aldehydes with Tetrazoles to Construct 2,5‐Diaryl 1,3,4‐Oxadiazoles

A practical and metal‐free oxidative amidation of aldehydes with tetrazoles into 1,3,4‐oxadiazoles has been developed by employing tetrabutylammonium iodide (TBAI) as catalyst and tert‐butyl hydroperoxide (TBHP) as oxidant. A wide range of 2,5‐disubstituted 1,3,4‐oxadiazoles can be conveniently generated in moderate to good yields. Gram‐scale reaction was also realized in this catalytic system.     

Iridium‐Catalyzed Intramolecular Methoxy C−H Addition to Carbon–Carbon Triple Bonds: Direct Synthesis of 3‐Substituted Benzofurans from o‐Methoxyphenylalkynes

Catalytic hydroalkylation of an alkyne with methyl ether was accomplished. Intramolecular addition of the C?H bond of a methoxy group in 1‐methoxy‐2‐(arylethynyl)benzenes across a carbon–carbon triple bond took place efficiently either in toluene at 110 °C or in p‐xylene at 135 °C in the presence of an iridium catalyst. The initial 5‐exo cyclization products underwent double‐bond migration during the reaction to give 3‐(arylmethyl)benzofurans in high yields.     

Selective Synthesis of Z‐Cinnamyl Ethers and Cinnamyl Alcohols through Visible Light‐Promoted Photocatalytic E to Z Isomerization

A photocatalytic E to Z isomerization of alkenes using an iridium photosensitizer under mild reaction conditions is disclosed. This method provides scalable and efficient access to Z‐cinnamyl ether and allylic alcohol derivatives in high yields with excellent stereoselectivity. Importantly, this method also provides a powerful strategy for the selective synthesis of Z‐magnolol and honokiol derivatives possessing potential biological activity.     

Iridium‐Catalyzed Direct C−H Amidation Polymerization: Step‐Growth Polymerization by C−N Bond Formation via C−H Activation to Give Fluorescent Polysulfonamides

We report a powerful strategy for activation of C−H bonds to produce polysulfonamides by an atom‐economical and green method using iridium‐catalyzed direct C−H amidation polymerization (DCAP). After screening various directing groups, additives, silver salts, concentrations, and temperatures to optimize DCAP, high‐molecular‐weight (up to 149 kDa) and defect‐free polysulfonamides were synthesized from various bis‐sulfonyl azides. Although these polymers do not have conventional fluorescent conjugated cores, they emit blue light with large Stokes shifts and high quantum yields upon photoexcitation owing to an excited‐state intramolecular proton‐transfer process.     

Solid‐Phase Approach for the Synthesis of 2‐Amido‐1,3,4‐oxadiazoles

A new solid‐phase approach for the synthesis of 2‐amido‐1,3,4‐oxadiazoles has been developed. In this synthesis, hydroxypentyl JandaJel polymer support was treated with excess of oxalyl chloride to give resin‐bound 2‐chloro‐2‐oxoacetate, and this intermediate was then coupled with different hydrazides to give resin‐bound 2‐(N′‐acylhydrazinyl)‐2‐oxoacetate. Intramolecular dehydrative cyclization of resulting resin‐bound linear precursor followed by direct amidation using aluminum amide reagent provided 5‐substituted 1,3,4‐oxadiazoles as 2‐carboxamides. To explore the scope of this reaction sequence, we synthesized a small set of library using a combination of hydrazides and amines, and the desired products were obtained in good to high yields.     

Iridium‐Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

A new iridium ‐ catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)₂Cl]₂ (coe=cyclooctene) and racemic 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (rac‐BINAP) in a mesitylene solution saturated with water. A catalytic amount of lithium chloride was also added to improve the catalyst turnover. The reaction has been applied to a variety of primary alcohols and gives rise to products in good to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)–BINAP species. First, dehydrogenation of the primary alcohol to the corresponding aldehyde takes place, which is then followed by decarbonylation to the product with one less carbon atom.     

Iridium‐Catalyzed Reductive Nitro‐Mannich Cyclization

A new chemoselective reductive nitro‐Mannich cyclization reaction sequence of nitroalkyl‐tethered lactams has been developed. Relying on the rapid and chemoselective iridium(I)‐catalyzed reduction of lactams to the corresponding enamine, subsequent nitro‐Mannich cyclization of tethered nitroalkyl functionality provides direct access to important alkaloid natural‐product‐like structures in yields up to 81 % and in diastereoselectivities that are typically good to excellent. An in‐depth understanding of the reaction mechanism has been gained through NMR studies and characterization of reaction intermediates. The new methodology has been applied to the total synthesis of (±)‐epi‐epiquinamide in four steps.     

Anilines as C‐Nucleophiles in Ir‐Catalyzed Intramolecular Asymmetric Allylic Substitution Reactions

Anilines generally act as N‐nucleophiles in transition‐metal‐catalyzed allylic substitution reactions. In this paper, a highly enantioselective intramolecular Friedel–Crafts‐type allylic alkylation of aniline derivatives was realized by using an iridium catalyst derived from [Ir(cod)Cl]₂ and (R _a)‐BHPphos. Various tetrahydroisoquinilin‐5‐amines were obtained in moderate to good yields, excellent enantioselectivity and regioselectivity under mild reaction conditions. BHPphos=N ‐benzhydryl‐N ‐phenyldinaphthophosphoramidite.     

溴化镁催化的1,2,3,4-四氢吡啶酮无溶剂合成研究

An efficient and environmentally friendly procedure for the one-pot synthesis of tetrahydropyrimidinones from aldehydes, β-diketones and urea/thiourea by using magnesium bromide as an inexpensive and easily available catalyst under solvent-free conditions was described. Compared with the classical Biginelli reaction conditions, this new method has the advantage of good to excellent yields (74%-94%) and short reaction time (45-90 min). The structure of the Biginelli reaction product from β-diketone, salicylaldehyde and urea has been proposed to possess an oxygen-bridge by cyclization (intramolecular Michael-addition).     

One‐pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalysed by Cupric Acetate under Solvent‐free Conditions

A solvent‐free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones from aromatic aldehydes, β‐keto ester/acetyl acetone and urea catalysed by cupric acetate under thermal condition is reported as a simple and an efficient protocol. Compared with classical Biginelli reaction reported in 1893, this new method provides much improved modification in terms of yield and reaction time. The usage of milder catalyst, environmental friendly procedures and excellent yields within a very short time (5–15 min) are the advantages of the method in which the involvement of solvent‐free condition adds an edge to the method. Thus, the efficiency of the protocol enabled the rapid synthesis of 3,4‐dihydropyrimidin‐2(1H)‐one derivatives in a short duration.     

One‐Pot N‐Deprotection and Catalytic Intramolecular Asymmetric Reductive Amination for the Synthesis of Tetrahydroisoquinolines

A one‐pot N‐Boc deprotection and catalytic intramolecular reductive amination protocol for the preparation of enantiomerically pure tetrahydroisoquinoline alkaloids is described. The iodine‐bridged dimeric iridium complexes displayed superb stereoselectivity to give tetrahydroisoquinolines, including several key pharmaceutical drug intermediates, in excellent yields under mild reaction conditions. Three additives played important roles in this reaction: Titanium(IV) isopropoxide and molecular iodine accelerated the transformation of the intermediate imine to the tetrahydroisoquinoline product; p ‐toluenesulfonic acid contributed to the stereocontrol.     

Molecular Iodine Catalyzed One‐pot Aza‐Diels‐Alder Reaction under Solvent‐free Conditions

Catalyzed by molecular iodine at room temperature, under solvent‐free conditions, a two component aza‐Diels‐Alder cyclization of N‐vinyl‐2‐pyrrolidinone with N‐arylimine gave tetrahydroquinoline derivatives in good yields and high stereo‐selectivity. And three components aza‐Diels‐Alder reaction of N‐vinyl‐2‐pyrrolidinone, anilines and indole‐3‐carbaldehydes under the same condition afford only cis‐product in good yields.