A Facile One‐Pot Three‐Component Synthesis of 5‐(Trifluoromethyl)‐4,7‐dihydro‐[1,2,4]‐triazolo[1,5‐a]pyrimidine Derivatives in Ionic Liquid

An efficient one‐pot synthesis of 5‐(trifluoromethyl)‐4,7‐dihydro‐7‐aryl‐[1,2,4]triazolo[1,5‐a]pyrimidine derivatives was performed via the reaction of aryl aldehyde, 3‐amino‐1,2,4‐triazole and ethyl 4,4,4‐trifluoro‐3‐oxobutanoate or 4,4,4‐trifluoro‐1‐phenylbutane‐1,3‐dione in ionic liquid. This method has the advantages of short synthetic route, operational simplicities, mild reaction conditions, high yields and eco‐friendliness.     

An Efficient One‐pot Three‐component Method for the Synthesis of 5‐Amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles

A facile, convenient, and adequate method has been developed for the synthesis of novel 5‐amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles ( 6 ) by employing 2‐(4‐(2‐oxo‐2H‐chromen‐3‐yl)thiazol‐2‐yl)acetonitrile ( 3 ) as an important precursor. Initially, we have synthesized the target compounds in a stepwise manner and then approached a tandem method to examine the feasibility of one‐pot method. Subsequently, one‐pot three‐component protocol has been established for the synthesis of title compounds by the reaction of 3 with benzaldehyde and malononitrile in refluxing ethanol engender a new six‐membered thiazolo[3,2‐a] pyridine as a hybrid scaffold. Reaction conditions were optimized for this reaction and a broad substrate scope with various aryl and heteroaryl aldehydes make this protocol very practical, attractive, and worthy. Mechanistic aspects for the formation of these compounds were outlined comprehensively. Characterization of these newly synthesized compounds was achieved by means of IR, ¹H NMR, ¹³C NMR, and HRMS.     

One‐Pot Synthesis of 7‐chloro‐2‐arylthieno[3,2‐b]pyridin‐3‐ols and Their Derivatization to the Corresponding Arylamino,Arylthio, and Aryloxy Derivatives

A simple and efficient domino reaction for synthesis of 7‐chloro‐2‐arylthieno[3,2‐b ]pyridin‐3‐ols ( 3 ) followed by derivatization into their corresponding aminoaryl ( 7a–7j ), aryloxy ( 9a–9c ), and thioaryloxy derivatives ( 8a–8k )is presented. The synthesis includes thioalkylation on 3‐position of methyl 4‐chloropicolinate ( 1 ) followed by in situ cyclization to give 7‐chloro‐2‐arylthieno[3,2‐b ]pyridin‐3‐ols ( 3 ). The substitution of the chloro group with amines, phenols and thiophenols afforded the corresponding derivatives.     

Efficient One‐Pot Syntheses of 7‐Alkyl‐6H,7H‐naphtho[1,2:5,6]pyrano‐[3,2‐c]chromen‐6‐ones by 1‐Methyl‐3‐(2‐(sulfooxy)ethyl)‐1H‐imidazol‐3‐ium Chloride

An efficient synthesis of 7‐alkyl‐6H,7H‐naphtho‐[10,20:5,6]pyrano[3,2‐c]chromen‐6‐ones by three‐component condensation reaction of β‐naphthol, aromatic aldehydes, and 4‐hydroxycoumarin catalyzed by 1‐methyl‐3‐(2‐(sulfooxy)ethyl)‐1H‐imidazol‐3‐ium chloride is reported in good to excellent yields and short reaction times.     

Solvent‐free three‐component synthesis of 7‐aryl‐1,1‐dioxothieno[3,2‐b]pyran derivatives catalyzed by ammonium acetate

An efficient synthesis of 7‐aryl‐1,1‐dioxothieno[3,2‐b]pyran derivatives via the reaction of aryl aldehyde, tetrahydrothiophene‐3‐one‐1,1‐dioxide and malononitrile or ethyl 2‐cyanoacetate was performed at room temperature catalyzed by ammonium acetate under solvent‐free conditions. Compared with the conventional methods, this protocol features mild reaction conditions, high yields, and eco‐friendliness. J. Heterocyclic Chem., (2011).     

Synthesis and conversion of 6‐fluoro derivatives of 1,3,4‐thiadiazolo‐[3,2‐a]pyrimidine

2‐Alkyl‐, 2‐aryl‐, and 2‐halo‐substituted derivatives of 7‐methyl‐6‐fluoro‐1,3,4‐thiadiazolo[3,2‐a]pyrimidin‐6‐one ( 3 ) were prepared by reaction of 2‐substituted 5‐amino‐1,3,4‐thiadiazoles ( 1 ) and ethyl 2‐fluoroacetoacetate ( 2 ) in polyphosphoric acid. A convenient procedure was developed for the synthesis of new 2‐amino derivatives of 2‐R‐7‐methyl‐6‐fluoro‐1,3,4‐thiadiazolo[3,2‐a]pyrimidin‐6‐one ( 5 ). J. Heterocyclic Chem., (2011).     

Preparation of Furo[3,2‐c]coumarins from 3‐Cinnamoyl‐4‐hydroxy‐2H‐chromen‐2‐ones and Acyl Chlorides: A Bu3P‐Mediated C‐Acylation/Cyclization Sequence

A Bu₃P‐mediated cyclization reaction of 3‐cinnamoyl‐4‐hydroxy‐2H‐chromen‐2‐ones though electrophilic addition of acyl chlorides towards the synthesis of highly functionalized furo[3,2‐c]coumarins bearing a phosphorus ylide moiety is described. These unprecedented cyclization reaction proceeds under mild reaction conditions within short reaction times (1 min to 1 h), and can be further applied in the synthesis of alkenyl‐substituted furo[3,2‐c]coumarins by the treatment with carbonyl electrophiles under basic conditions.     

The Divergent Synthesis of Nitrogen Heterocycles by Rhodium(II)‐Catalyzed Cycloadditions of 1‐Sulfonyl 1,2,3‐Triazoles with 1,3‐Dienes

The first rhodium(II)‐catalyzed aza‐[4+3] cycloadditions of 1‐sulfonyl 1,2,3‐triazoles with 1,3‐dienes have been developed, and enable the efficient synthesis of highly functionalized 2,5‐dihydroazepines from readily available precursors. In some cases, the reaction pathway could divert to formal aza‐[3+2] cycloadditions, thus leading to 2,3‐dihydropyrroles. In this context, the titled reaction represents a capable tool for the divergent synthesis of two types of synthetically valuable aza‐heterocycles from common rhodium(II) iminocarbene intermediates.     

Synthesis of N‐aryl‐2‐amino‐4‐oxo‐3,4‐dihydrothieno[2,3‐d]pyrimidine‐6‐carboxamides

Synthetic routes for the preparation of methyl 2‐amino‐4‐methoxythieno[2,3‐d]pyrimidine‐6‐carboxylate (4) ‐ useful intermediate for lipophilic and classical antifolates from 2‐amino‐4,6‐dichloropyrimidine‐5‐car‐baldehyde (1) have been studied. It has been shown that more efficient synthesis of compound 4 includes the preparation of 4‐methoxy derivative 7 and subsequent tandem substitution/annulation reaction with methyl mercaptoethanoate in dimethylformamide in the presence of potassium carbonate and molecular sieves 4 Å. Compound 4 was used for the synthesis of N‐aryl 2‐amino‐4‐oxo‐3,4‐dihydrothieno[2,3‐d]‐pyrimidine‐6‐carboxamides 10a‐c, including an analog of folic acid with amide bridge ‐ N‐(4‐{[(2‐amino‐4‐oxo‐3,4‐dihydrothieno[2,3‐d]pyrirnidin‐6‐yl)carbonyl]amino}‐benzoyl)‐L‐glutamic acid (10c) .     

A Simple One‐Pot Synthesis of Fully Substituted 1H‐Pyridone[1,2‐a]‐Fused‐1,3‐Diazaheterocycles

An efficient procedure for the synthesis of 7‐(aryl)‐8‐nitro‐2,3,6,7‐tetrahydroimidazo[1,2‐a]pyridinones, 8‐(aryl)‐9‐nitro‐3,4,7,8‐tetrahydropyridone[1,2‐a]pyrimidines and 9‐(aryl)‐10‐nitro‐2,3,4,5,8,9‐hexahydropyridone[1,2‐a]diazepine via one‐pot three component reaction of diamine, nitroketene dithioacetal (1,1‐bis(methylsulfanyl)‐2‐nitroethene), and coumarine‐3‐ carboxylic acid derivatives in EtOH under reflux conditions is reported. The advantages of this procedure are simplicity, easy purification, good yields, and catalyst‐free conditions. All products were confirmed by ¹H‐ and ¹³C‐NMR, IR, MS, and X‐ray crystal structure analyses.     

Synthesis of nitrogen‐containing heterocycles 9. Preparation and carbon‐carbon bond cleavage of spiro[cycloalkane[1′,2′,4′]‐triazolo[1′,5′‐a][1′,3′,5′]triazine] derivatives and related compounds

Diaminomethylenehydrazones of cyclic ketones 1–5 reacted with ethyl N‐cyanoimidate (I) at room temperature or with bis(methylthio)methylenecyanamide (II) under brief heating to give directly the corresponding spiro[cycloalkane[1′,2′,4′]triazolo[1′,5′,‐a][1′,3′‐5′]triazine] derivatives 7–12 in moderate to high yields. Ring‐opening reaction of the spiro[cycloalkanetriazolotriazine] derivatives occurred at the cycloalkane moiety upon heating in solution to give 2‐alkyl‐5‐amino[1,2,4]triazolotriazines 13–16. Diaminomethylenehydrazones 17–19, of hindered acyclic ketones, gave 2‐methyl‐7‐methylthio[1,2,4]‐triazolo[1,5‐a][1,3,5]triazines 21–23 by the reaction with II as the main products with apparent loss of 2‐methylpropane from the potential precursor, 2‐tert‐butyl‐2‐methyl‐7‐methylthio[1,2,4]triazolo[1,5‐a]‐[1,3,5]triazines 20, in good yields. In general, bis(methylthio)methylenecyanamide II was found to be a favorable reagent to the one‐step synthesis of the spiro[cycloalkanetriazolotriazine] derivatives from the diaminomethylenehydrazones. The spectral data and structural assignments of the fused triazine products are discussed.     

Synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones using nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl2 nanoparticles

Nano‐Zn‐[2‐boromophenyl‐salicylaldimine‐methylpyranopyrazole]Cl₂ (nano‐[Zn‐2BSMP]Cl₂) as a nanoparticle Schiff base complex and a catalyst was introduced for the solvent‐free synthesis of 4‐((2‐hydroxynaphthalen‐1‐yl)(aryl)methyl)‐5‐methyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐ones by the multicomponent condensation reaction of various aromatic aldehydes, β‐naphthol, ethyl acetoacetate, and phenyl hydrazine at room temperature.     

An Efficient,Multicomponent Synthesis of Pyrazolyl Triazolo Thiadiazinyl Chromen ‐ 2 ‐ Ones

One‐pot synthesis of 3‐(3‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazin‐6‐yl)‐2H‐chromen‐2‐ones was achieved via the multicomponent reaction of purpald, acetyl acetone, and different derivatives of 3‐(2‐bromo‐acetyl)‐2H‐chromen‐2‐one in absolute ethanol. All the synthesized compounds were characterized by analytical and spectral data.     

Brominated Trihalomethylenones as Versatile Precursors to 3‐Ethoxy, ‐Formyl, ‐Azidomethyl, ‐Triazolyl,and 3‐Aminomethyl Pyrazoles

5‐Bromo[5,5‐dibromo]‐1,1,1‐trihalo‐4‐methoxy‐3‐penten[hexen]‐2‐ones are explored as precursors to the synthesis of 3‐ethoxymethyl‐5‐trifluoromethyl‐1H‐pyrazoles from a cyclocondensation reaction with hydrazine monohydrate in ethanol. 3‐Ethoxymethyl‐carboxyethyl ester pyrazoles were formed as a result of a substitution reaction of bromine and chlorine by ethanol. The dibrominated precursor furnished 3‐acetal‐pyrazole that was easily hydrolyzed to formyl group. In addition, brominated precursors were used in a nucleophilic substitution reaction with sodium azide to synthesize the 3‐azidomethyl‐5‐ethoxycarbonyl‐1H‐pyrazole from the reaction with hydrazine monohydrate. These products were submitted to a cycloaddition reaction with phenyl acetylene furnishing the 3‐[4(5)‐phenyl‐1,2,3‐triazolyl]5‐ ethoxycarbonyl‐1H‐pyrazoles and to reduction conditions resulting in 3‐aminomethyl‐1H‐pyrazole‐5‐carboxyethyl ester. The products were obtained by a simple methodology and in moderate to good yields.     

Synthesis of alcohol ester 12 in 1, 8‐diazabicyclo [5.4.0] undec‐7‐ene (DBU)‐based Self‐separation catalytic system

The synthesis of alcohol ester 12 is one of the valuable industrial processes, but it was impeded by poor separating property and recycling ability of the catalytic systems. Herein, four novel DBU‐based basic ionic liquids (DBILs) of [BDBU]IM, [BDBU]OH, [ODBU]IM, [[ODBU]OH were synthesized successfully by introducing the alkyl chains of 1‐bromobutane or 1‐bromooctane to 1,8‐diazabicyclo [5.4.0] undec‐7‐ene (DBU), and then, employing imidazole (IM^?) or hydroxide (OH^?) as counter ions. The above obtained four ionic liquids were applied in the synthesis of alcohol ester 12 in isobutyraldehyde (IBD)/aqueous media for the first time. Interestingly, after reaction, production of alcohol ester 12 can be self‐separated from ionic liquids/water (ILs/W) catalytic system automatically. Furthermore, the self‐separated ILs/W can be recycled and used in next catalytic reaction for at least 5 times without obvious loss of catalytic performance. In this work, the structure, purity, thermal stability and alkalinity of DBILs were characterized systematically. [BDBU]IM shows high alkalinity and thus enhances yield of 66.17%. From thermo gravimetric analyzer (TGA), [BDBU]IM also exhibits excellent thermal stability. So [BDBU]IM was chosen for the further studying. Furthermore, quantum chemistry is applied to calculate the interaction forces and electron energies of reactants by DFT, and the calculation results illustrate the feasibility of synthetic process of DBILs. The self‐separation strategy of DBILS in this work may open up a new avenue for the clean synthesis of other industrial products.     

Synthesis of New tert‐Butyl‐ and Bromo‐functionalized [1,2,4]Triazino [5,6‐b]indole‐3‐thiols and Indolo[2,3‐b]quinoxalines

In the present investigation, the synthesis of a series of structurally new and interesting tert‐butyl‐ and bromo‐functionalized [1,2,4]triazino[5,6‐b ]indoles ( 6a – f ) and indolo[2,3‐b ]quinoxalines ( 8a – f ) has been achieved, involving the condensation reaction of 7‐bromo‐5‐tert‐butylisatins ( 4a – f ) with thiosemicarbazide ( 5 ) and benzene‐1,2‐diamine ( 7 ). The substrates 4a – f were prepared through bromination reaction of 5‐tert‐butylisatin ( 3 ) with NBS in PEG‐400 followed by alkylation reaction. The molecular structures of these newly synthesized compounds were elucidated on the basis of their elemental analyses and spectral data.     

Synthesis of Triazolo[1,5‐a]triazin‐7‐one Derivatives and Highly Functionalized [1,2,4]Triazoles

The synthesis of novel triazolo[1,5‐a]triazin‐7‐ones is presented. Starting from 3‐amino‐5‐sulfanyl‐1,2,4‐triazole, the synthetic sequence involved alkylation with benzyl bromide, reaction with p‐nitrophenyl chloroformate followed by treatment with a primary amine, and condensation with diethoxymethyl acetate. Final oxidation of the thioether moiety with 3‐chloroperbenzoic acid provided 2‐(benzylsulfonyl)[1,2,4]triazolo[1,5‐a][1,3,5]triazin‐7‐ones 5a and 5b in good overall yields. Treatment of 5a and 5b with secondary amines provided highly functionalized [1,2,4]triazoles through an unexpected triazinone ring opening. A mechanism for this transformation is proposed.     

Reactions of 2‐amino‐4h‐1‐benzopyran‐4‐one with 4‐oxo‐4h‐1‐benzopyran‐3‐carbaldehydes

The title aldehyde 1 reacts smoothly with the enamine moiety of 2 ‐aminochromone 2 to produce hitherto unreported 3‐(2‐hydroxybenzoyl)‐5H‐1‐benzopyrano[2,3‐b]pyridin‐5‐one (azaxanthone) 5 . This reaction has been extended for the synthesis of bisazaxanthone 9.     

Synthesis of 1,3‐Dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates via Intramolecular Cyclization of 2‐[2‐(Dimethoxymethyl)phenyl]‐ 2‐hydroxyalkanoates Followed by Oxidation

A novel and efficient method for the preparation of 1,3‐dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates 4 under mild conditions has been developed. Thus, the reaction of [2‐(dimethoxymethyl)phenyl]lithiums, generated easily from 1‐bromo‐2‐(dimethoxymethyl)benzenes 1 , with α‐keto esters gives the corresponding 2‐[2‐(dimethoxymethyl)phenyl]‐2‐hydroxyalkanoates 2 . The TsOH‐catalyzed cyclization of these hydroxy acetals is followed by the oxidation of the resulting cyclic acetals 3 with PCC to give the desired products in satisfactory yields. The reaction of [2‐(dimethoxymethyl)‐4,5‐dimethoxyphenyl]lithium with (MeOC?O)₂, followed by treatment with NaBH₄ or organolithiums, affords 2‐[2‐(dimethoxymethyl)‐4,5‐dimethoxyphenyl]‐2‐hydroxyalkanoates 6 , which can similarly be transformed into the corresponding 1,3‐dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates 7 in reasonable yields.     

Synthesis of p‐tert‐Butyl‐calix[6] ‐biscrown‐3 via Intramolecular Ring‐closure of 1,4‐Bis (2‐(2‐chloroethoxy) ethoxy) ‐p‐tert‐butyl‐calix[6]arene

With a variation in reaction conditions, 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐calix[6]arene (3) and l,3,5‐tris(2‐(2‐chloroethoxy) ethoxy)‐calix [6] arene (4) or 4 and 4‐chloroethoxyethoxy‐calix[6]crown‐3 (5) were selectively synthesized from p‐tert‐butyl‐calix [6] arene and 2‐(2‐chloroethoxy)ethyltosylate. l,3–4,6‐p‐tert‐butylcalix[6]‐bis‐crown‐3 (6) with (u,u,u,d,d,d) conformation and 1,3–4,5‐p‐tert‐butylcalix[6]‐biscrown‐3 (7) with self‐anchored (u,u, u, u, u, d) conformation were synthesized through an intramolecularly ring‐closing condensation of 1, 4‐bis (2‐(2‐chloroethoxy)ethoxy)‐p‐tert‐butyl‐calix[6]arene (3) in 25% and 15% yield, respectively. Using 5 instead of 3, only 7 was obtained in 65% high yield. 6 and 7 show different complexation properties toward alkali metal and ammonium ions.