Synthesis of Fused [5,5]‐1,2,4‐Triazoles via Tandem Thioimidate Cyclopropane Rearrangement–Cyclization

The synthesis of fused [5,5]‐1,2,4‐triazoles via a tandem cyclopropane rearrangement–cyclization sequence is described. Optimization of the cyclization reaction was achieved thermally using iPrOH as the solvent in the presence of TEA. This method was applied to the preparation of 3‐substituted‐7‐aryl‐pyrrolo‐1,2,4‐triazoles in good to excellent yields.     

Ytterbium Perfluorooctanesulfonate–Catalyzed Synthesis of 1,5‐Benzodiazepine Derivatives in Fluorous Solvents

Ytterbium perfluorooctanesulfonate [Yb(OPf)₃] catalyses the highly efficient synthesis of 2,3‐dihydro‐1H‐1,5‐benzodiazepines in fluorous solvents. By simple separation of the fluorous phase containing only the catalyst, the reaction can be repeated several times.     

Highly Efficient One-Pot Synthesis of α-Aminophosphonates Catalyzed by Ytterbium Triflate in Water

A facile one-pot, three-component synthesis of α -aminophosphonates catalyzed by ytterbium triflate [Yb(OTf)₃] in water using polyoxyethanyl α -tocopheryl sebacate (PTS) as amphiphile has been developed. The catalytic system could be readily recycled and reused several times without significant loss in its activity.     

Synthesis and Biological Evaluation of Novel Isonucleosides with 1,2,4‐Triazole‐3‐Carboxamide

Novel 1,2,4‐triazole isonucleosides (1 and 2) were efficiently synthesized starting from D‐ribose and D‐xylose, respectively. The key steps were condensation of cyclic sulfate 8 with methyl‐1,2,4‐triazole‐3‐carboxylate and nucleophilic displacement of the tosylate 15 with methyl‐1,2,4‐triazole‐3‐carboxylate, respectively.     

Synthesis of 3‐Aryl‐5‐methyl 4‐Substituted [1,2,4]Triazoles

Treatment of N‐substituted acetamides with oxalyl chloride generates imidoyl chlorides, which react readily with aryl hydrazides. Following cyclization, triazoles can easily be obtained in moderate to good yields. 5‐Methyl triazoles can be further functionalized through α‐lithiation and subsequent reaction with an electrophile.     

Solvent‐Free,Palladium‐Catalyzed Suzuki–Miyaura Cross‐Couplings of Aryl Chlorides with Arylboronic Acids

Pd(MeCN)₂Cl₂/PCy₃ was found to be an efficient catalytic system for the Suzuki–Miyaura cross‐couplings of aryl chlorides with arylboronic acids under solvent‐free conditions. Furthermore, the presence of the conventional solvents had deleterious effect on the reaction. In the presence of Pd(MeCN)₂Cl₂, PCy₃, and TBAF (tetra‐n‐butylammonium fluoride), a number of aryl chlorides including heteroaryl chlorides were coupled with arylboronic acids or heteroarylboronic acids smoothly to afford the corresponding products in moderate to excellent yields.     

Europium Triflate–Catalyzed One‐Pot Synthesis of 2,4,5‐Trisubstituted‐1H‐imidazoles via a Three‐component Condensation

A simple, efficient, and practical procedure for synthesis of 2,4,5‐trisubstituted‐1H‐imidazoles via the condensation of benzoin or acetoin, aromatic aldehydes, and ammonium acetate using europium triflate [Eu(OTf)₃] as a novel catalyst in high yields is described. The catalyst can be recovered conveniently and reused at least four times without any loss of activity.     

New Route to Synthesis and QSAR Study of 1,2,4‐Aryl Substituted Triazoles

Abstract

Several substituted 1,2,4‐triazoles have been synthesized by a new route and characterized by IR, NMR, mass spectral, and x‐ray diffraction studies. The computer programme PASS for the prediction of biological activities established that these compounds are potential candidates for the screening.     

Pd‐Catalyzed Synthesis of Biphenyls with Methylthio Group

The synthesis of unsymmetrical biaryls with a methylthio group is achieved using the air‐stable palladium–phosphinous acid complexes, [(t‐Bu)₂P(OH)]₂ PdCl₂ (POPd), as the catalyst. A great variety of substituted bromobenzenes having electron‐withdrawing and electron‐donating functional groups in para and meta positions have been successfully coupled with 3‐methylthiophenylboronic acid.     

Novel Synthesis of Dihydrothiazoles from the Selenium‐Induced Cyclization of Allyl Thioureas

The reaction of allylic thioureas with phenylselenenyl chloride affords 2‐amino dihydrothiazoles in excellent yields by selenium‐induced cyclization of allylic thioureas.     

Synthesis of Isagarin,a Tetracyclic Naphthoquinone via a Palladium‐Catalyzed Cyclization

Total synthesis of isagarin (2) has been accomplished in five steps with 24.1% overall yield from 2‐bromonaphthoquinone (6). The key step is a palladium‐catalyzed cyclization to form a bicyclic ketal ring.     

Ytterbium(III) Triflate–Catalyzed Stereoselective Synthesis of β‐Lactams via [2+2] Cyclocondensation in Ionic Liquid

Catalyzed by ytterbium(III) triflate [Yb(OTf)₃], β‐lactams were stereoselectively synthesized from imines and acetyl chlorides in ionic liquid under mild conditions. The ionic liquid and catalyst could be recycled and reused as opposed to traditional solvent–catalyst systems.     

Copper Triflate–Catalyzed Cross‐Aldol Condensation: A Facile Synthesis of α,α′‐Bis(Substituted Benzylidene) Cycloalkanones

A facile, efficient, and clean procedure is described for synthesis of α,α′‐bis(substituted benzylidene) cycloalkanones with good yields by the reaction of cycloalkanones with aromatic aldehydes using Cu(OTf)₂ as catalyst. The catalyst was easily recovered and reused without loss of activity.     

Novel Synthesis of 5‐Substituted‐3‐phenylindole‐2‐(1,2,4‐triazole) Derivatives

Various substituted 3‐phenylindole 2‐carboxylates (1a–c) were prepared according to the literature methods. These carboxylates (1a–c) on reaction with thiosemicarbazide yielded 5‐substituted‐3‐phenylindol‐2‐(1,2,4‐triazole‐3‐thione) (2a–c) on refluxing in pyridine for 8 h. The 5‐substituted‐3‐phenylindole‐2‐[1,2,4‐triazolo‐3‐thioacetic acid] (3a–c) were prepared from 5‐substituted‐3‐phenyl indole‐2‐[1,2,4‐triazole‐3‐thione] (2a–c) on reaction with an appropriate alkylating agent and sodium acetate in acetic acid. Further, (3a–c) were reacted with acetic anhydride to bring about a cyclocondensation reaction to yield 5‐substituted‐3‐phenylindol‐2‐thiazolo(2,3‐b)‐triazole (4a–c). The 5‐substituted‐3‐phenylindole‐2‐[1,2,4‐triazolo‐3‐acetic acid] (3a–c) were reacted with o‐phenylenediamino dihydrochloride in ethylene glycol to yield 5‐substituted‐3‐phenylindole‐1,2,4‐triazolo‐3′‐yl‐thiomethyl)benzimidazoles (5a–c).     

Practical and Phase Transfer–Catalyzed Synthesis of 6‐Methoxytryptamine

A convenient and cost‐effective synthesis of 6‐methoxytryptamine (1), starting from commercially available phthalimide and 1‐bromo‐3‐chloropropane via PTC N‐alkylation, PTC C‐alkylation, Japp–Klingemann reaction, hydrolysis, and decarboxylation, has been accomplished with a 44% overall yield.     

Triflic Salt–Catalyzed Coupling: Iron Triflate–Catalyzed Homocoupling of Aryl Bromides in the Presence of Metallic Magnesium

In the presence of metallic magnesium, the homocoupling reaction of aryl bromides catalyzed by iron triflate was carried out readily in one pot. The catalyst was used successfully in this coupling reaction without preparation of Grignard reagent in advance. Meanwhile, the catalyst was recovered easily and reused smoothly with only a little loss of its activity.     

Heterocyclization of Imidates with 3‐Alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles: Synthesis of New Triazolotriazines

Some novel triazolo[4,3‐a]triazines derivatives were synthesized by reaction of N‐cyanoimidates and N‐ethoxycarbonylimidates with 3‐alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles.     

Zinc Hydroxyapatite–Catalyzed Efficient Synthesis of 5‐Substituted 1H‐Tetrazoles

Zinc hydroxyapatite (ZnHAP) is an effective heterogeneous catalyst for the (2+3)‐cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles in good yields. The catalyst is recovered and reused for several cycles with consistent activity.     

Pd-Catalyzed Cross-Coupling of Acyl Chlorides with In Situ–Generated Alkynylzinc Derivatives for the Synthesis of Ynones

A mild and operationally simple procedure by Pd-catalyzed cross-coupling of acyl chlorides with in situ–generated alkynylzinc derivatives was developed, giving the corresponding ynones in good yields.

Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® full experimental and spectral details.     

Novel Method for the Synthesis of [1,2,4]Triazino[4,3‐c]quinazoline System

4‐Hydrazinoquinazoline was found to form new 2‐(3,4‐dihydro‐3oxo‐2H‐[1,2,4]triazino[4,3‐c]quinazolin‐4‐yl)acetic acid with maleic anhydride in on‐step sequence. Proposed heterocyclization includes, probably, acylation reaction followed by intramolecular uncleophilic addition.