One‐pot synthesis of new 3‐substituted coumarins by tandem reactions

The synthesis of new 3‐substituted coumarins appended to imidazolium, pyridinium, 3‐dimethylamino pyridinium, 3‐chloro pyridinium and 3‐bromo pyridinium salts is reported. These salts were prepared by tandem reactions, followed by quantitative anionic metathesis. The structure of these new 3‐substituted coumarins was established by NMR (¹H, ¹³C) and high‐resolution mass spectrometry.     

A simple one‐pot synthesis of 1,2,3,4‐tetrahydro‐2‐thioxopyrimidine derivatives

5‐Benzoyl‐4‐(substituted phenyl)‐6‐phenyl‐1,2,3,4‐tetrahydro‐2‐thioxopyrimidines ( 4a‐d ) were synthesized using the Biginelli three component cyclocondensation reaction of an appropriate β‐diketone, arylaldehyde, and thiourea in acetic acid under reflux condition in approximately 52‐65% yields. The acetylation of compounds 4a‐d gave 3‐acetyl thioxopyrimidine derivatives 5a‐d . Also, pyrimidothiazine compounds 6a‐d were prepared by a simple one‐pot condensation reaction of starting pyrimidine derivatives 4a‐d and 3‐bromopropionic acid. The structures of compounds were characterized on the basis of elemental analyses, IR, ¹H and ¹³C‐NMR spectra.     

Transformations of phenylhydrazones of 5‐acyl‐1,2,4‐triazines to pyrazolo[4,3‐e][1,2,4]triazines or 4‐cyanopyrazole

A simple and high yielding preparation of pyrazolo[4,3‐e][1,2,4]triazines and 4‐cyano‐3‐methyl‐1‐phenylpyrazole derivatives from corresponding phenylhydrazones of 5‐acyl‐1,2,4‐triazines by melt under acidic medium and by thermal heating, respectively.     

New one step synthesis of 3,5‐disubstituted 1,2,4‐oxadiazoles

Disubstituted 1,2,4‐oxadiazoles have been synthesized in good yields and good purity in one pot procedure by reaction of aromatic nitriles, hydroxylamine hydrochloride and sodium carbonate in ethylene glycol under heating at 195°C. The structures of different 1,2,4‐oxadiazoles obtained were confirmed by ¹H, ¹³C NMR and mass spectroscopy.     

A simple one pot synthesis of novel tricyclic quinazolinones

Synthesis of a series of tricyclic quinazolinones have been accomplished starting from anthranilamide and 1,3-cyclic dione promoted by TsOH·H₂O The protocol presented herein based on retro-Dieckmann type reaction, leading to incorporation of dione as an acyclic unit into the product. Simple reaction conditions, broad scope, excellent yields are the advantages of this protocol. Further, this methodology is extended to the synthesis of pyridopyrimidinones and benzimidazopyridines.     

A three‐component,one‐pot synthesis of oxazinoquinolin‐3‐one derivatives

Oxazino[5,6‐f]quinolin‐3‐one derivatives have been synthesized in a one‐pot, and efficient process by condensation of 6‐quinolinol, aromatic aldehydes and urea under microwave‐assisted and thermal solvent‐free conditions.     

Microwave‐assisted synthesis of some 1,2,4‐triazol‐5‐one derivatives

A series of 3‐alkyl(aryl)‐4‐(p‐hydroxy‐phenyl)‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ones 2 were obtained from the reaction of alkyl (aryl) ester ethoxycarbonyl hydrazones 1 with p‐hydroxy aniline. The reaction of 1 with 1,4‐diamino benzene (1:1) to afford 3‐alkyl(aryl)‐4‐(p‐aminophenyl)‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ones 3 . The reaction of 3 with benzaldehyde gave 3‐alkyl(aryl)‐4‐(4′‐benzilidenamino)‐4,5‐dihydro‐1H‐1,2,4‐triazol‐5‐ones 4 . All of the above reactions occurred under microwave heating and conventional methods. Their structures were confirmed by ¹H NMR, ¹³C NMR, IR, and elemental analyses. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:38–42, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20381     

Fused pyridines by a tandem aza‐wittig / heterocyclization strategy: Synthesis of 1,2,4‐triazolo[1,5‐a]pyridines and pyrido[1,2‐b][1,2,4]triazines

The iminophosphorane 1‐amino‐6‐(triphenylphosphoranylideneamino)‐2‐oxo‐4‐phenyl‐1,2‐dihydro‐pyridine‐3,5‐dicarbonitrile 2 prepared from 1,6‐diaminopyridine 1 reacts with heterocumulenes such as carbon disulfide and phenylisocyanate, and with acid chlorides, acid anhydrides and haloketones to give directly the title compounds in an one‐pot aza‐Wittig / heterocyclic‐ring closure process with good yields.     

One‐pot synthesis of star‐block copolymers using double click reactions

3‐Arm star‐block copolymers, (polystyrene‐b‐poly(methyl methacrylate))₃, (PS‐b‐PMMA)₃, and (polystyrene‐b‐poly(ethylene glycol))₃, (PS‐b‐PEG)₃, are prepared using double‐click reactions: Huisgen and Diels–Alder, with a one‐pot technique. PS and PMMA blocks with α‐anthracene‐ω‐azide‐ and α‐maleimide‐end‐groups, respectively, are achieved using suitable initiators in ATRP of styrene and MMA, respectively. However, PEG obtained from a commercial source is reacted with 3‐acetyl‐N‐(2‐hydroxyethyl)‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2‐carboxamide (7) to give furan‐protected maleimide‐end‐functionalized PEG. Finally, PS/PMMA and PS/PEG blocks are linked efficiently with trialkyne functional linking agent 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane 2 in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at 120 °C for 48 h to give two samples of 3‐arm star‐block copolymers. The results of the peak splitting using a Gaussian deconvolution of the obtained GPC traces for (PS‐b‐PMMA)₃ and (PS‐b‐PEG)₃ displayed that the yields of target 3‐arm star‐block copolymers were found to be 88 and 82%, respectively. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7091–7100, 2008     

A facile one pot synthesis of 2, 4‐diamino‐6‐substituted s‐triazine derivatives

A novel and facile one‐pot procedure for the preparation of 2,4‐diamino‐6‐substituted‐s‐triazine derivatives (IIa‐n) was reported. The scope of its application was demonstrated with a number of examples. The new procedure involved treatment of proguanil or chloroproguanil with acyl chloride or alky chlorooxoacetate in pyridine at ice cold temperature followed by reflux overnight to give good yields of the desired products.     

A facile one‐pot regioselective synthesis of [1,2,4]triazolo[4,3‐a]5(1H)‐pyrimidinones via tandem Japp–Klingemann,Smiles rearrangement,and cyclization reactions

Coupling of active [(4‐oxo‐6‐phenyl‐3H‐pyrimidin‐2‐yl)thio]methine compounds ( 3 ) with diazotized anilines in the presence of base gave [1,2,4]triazolo[4,3‐a]pyrimidines ( 7 ). The latter products were also obtained by reactions of hydrazonoyl chlorides ( 10 ) with either 6‐phenyl‐2‐thiouracil ( 1 ) or the 2‐methylthio derivative 9 . The mechanisms and the regiochemistry of the reactions studied are discussed. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:136–140, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10008     

Computational study of the catalytic synthesis of 5‐nitro‐1,2,4‐triazol‐3‐one

In this study, 5‐nitro‐1,2,4‐triazol‐3‐one (NTO) was theoretically synthesized from urea via chlorination followed by amination, formylation, and nitration under aqueous and gaseous environments based on experience of experimental methods, and metal chlorides and metal oxides were used as catalysts to promote reaction. Reaction routes closely related to experimental processes were successfully constructed, and the corresponding energy barriers were estimated for each elementary reaction. Reaction conditions distinct from those reported in the literature (including the adoption of aluminum chloride, ferric chloride, aluminum oxide, ferrous oxide, and chromium oxide catalysts, the use of nitric acid and dinitrogen pentoxide as nitration agents, and adjustment of the reaction temperature) were used in corresponding reaction systems, and the modeling results suggested that ferric chloride is a good catalyst for the chlorination reaction, ferrous oxide is suitable for catalyzing amination, formylation, and nitration, and nitric acid is the better agent for nitration. Estimates of the comparable energy barriers for each reaction stage were considered to imply more feasible pathways for NTO synthesis. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Convenient one pot synthesis of 5‐unsubstituted pyrazolo [3,4‐c]isoquinolines

The convenient one pot synthesis of pyrazolo[3,4‐c]isoquinolines 1 from 5‐aminopyrazoles 2 and paraformaldehyde in formic or trifluoroacetic acids is described.     

Facile one‐pot synthesis of [1,2,4]triazolo[3,4‐b][1,3,4]thiadiazines and 3,7‐dimethyl‐4H‐[1,2,4]triazino[3,4‐b][1,3,4]thiadiazin‐6‐one using heteropolyacid catalysts

[1,2,4]Triazolo[3,4‐b][1,3,4]thiadiazines 2a , 2b , 2c , 2d , 2e , 2f and 3,7‐dimethyl‐4H‐[1,2,4]triazino[3,4‐b][1,3,4]thiadiazin‐6‐one 4 were synthesized by one‐pot cyclocondensation reaction with α‐chloroacetonitrile and α‐haloketones in the presence of catalytic amounts of heteropolyacids in very high yields and rates. J. Heterocyclic Chem., (2011).     

A Novel Iron‐catalyzed One‐pot Synthesis of 3‐Amino‐1,2,4‐triazoles

A novel one‐pot synthesis of 3‐amino‐1,2,4‐triazole developed via iron (III) catalyzed route is reported. The new method is more efficient, simple, and convenient and presents a concise new strategy for the synthesis of 3‐amino‐1,2,4‐triazole derivatives. The iron (III) complex intermediate assisted in the intramolecular bond cyclization owing to its Lewis acidity or oxidizing properties. A series of aromatic nitriles bearing different electron‐donating and electron‐withdrawing groups substituted at para and/or ortho positions were also investigated. The position of the substituents affected the yield of the final compound, with the para‐substituted substrates giving relatively higher yields.     

A new route to functionalized 3‐aminopyridazines by ANRORC type ring transformation of 1,2,4‐triazines with carbon nucleophiles

The reaction of 3‐chloro‐6‐phenyl‐1,2,4‐triazine 1a with carbon nucleophiles 2a? d bearing a cyano substituent at a carbanionic center has been studied. In all reactions the formation of the corresponding 3‐aminopyridazines 3a? d takes place via ANRORC mechanism involving addition of the nucleophile at position 5 in compound 1a , ring opening with breaking of the N₄? C₅ bond and intramolecular ring closure of the resulting open‐chain intermediate. A ¹⁵N study with labeled phenylacetonitrile 2a* has shown that the nitrogen atom of the exocyclic amino group of 3‐amino‐4,6‐diphenylpyridazine 3a was originally present in phenylacetonitrile.     

On triazoles XLV [1]. synthesis of 5,7‐diamino‐1,2,4‐triazolo[1,5‐a] [1,3,5]triazines

Dedicated to Professor András Messmer on the occasion of his 80^th birthday The reaction of differently substituted 5‐amino‐1,2,4‐triazoles ( 5 ) with isothiourea derivatives ( 3 ) to yield isomeric 5,7‐diamino‐1,2,4‐triazolo[1,5‐a][1,3,5]triazines ( 6 and 7 ), previously described as not proceeding in melt, was performed in different solvents as well as in the melt at 150‐160°. It was proved that the above reaction had rather general validity. The structure of isomers 6 and 7 were proved spectroscopically. The structure of 6/5 (Q = ethylamino) was corroborated with single crystal X‐ray diffraction determination, as well.