Conventional and microwave irradiation assisted synthesis of new 1,2,4‐triazepine‐3‐thiones

New 1,2,4‐triazepine‐3‐thiones have been obtained during the respective reactions of N‐substituted‐hydrazino carbothioamides with dimethyl acetylenedicarboxylate and dibenzoyl acetylene under prolonged reflux in acetic acid and/or DMF. However, the reaction of the starting materials in DMF under microwave irradiation afforded the same products in higher yields within a few minutes.     

Microwave‐assisted synthesis of novel 4‐N,N‐dimethylamino‐ and 4‐cycloamino‐ substituted 1,2,4‐triazole‐3‐thiones

4‐N,N‐Dimethylamino‐ and 4‐cycloamino‐5‐phenyl‐1,2,4‐triazole‐3‐thiones 1–13 have been synthesized from benzhydrazides and substituted methyl dithiocarbazates under various conditions including short microwave irradiations. The last method seemed faster than the classical refluxing one. The influence of base and solvent types on the reaction direction has been also examined. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:188–195, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20594     

Photodesulfurization of 2,4‐diaryl‐1,2, 4‐triazole‐3‐thiones

Irradiation of triazole thiones in thin‐film reactor furnished the corresponding desulfurized triazoles in good yield. The required triazole thiones were synthesized from the respective acid hydrazide and isothiocyanate. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:269–272, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10140     

Enaminones in heterocyclic synthesis: A new regioselective synthesis of 2,3,6‐trisubstituted pyridines, 6‐substituted‐3‐aroylpyridines and 1,3,5‐triaroylbenzenes

1‐Substituted‐3‐dimethylaminopropenones 1a‐d reacted with acetylacetone and with ethyl acetoacetate to yield regioselectively 2,3,6‐trisubstituted pyridines. Refluxing 1a‐d in acetic acid/ammonium acetate resulted in the formation of 6‐substituted‐3‐aroylpyridines, whereas refluxing in acetic acid alone afforded 1,3,5‐triaroylbenzene.     

Dicationic ionic liquids as recyclable catalysts for one‐pot solvent‐free synthesis of α‐aminophosphonates

Some task‐specific ionic liquids N,N,N′,N′‐tetramethyl‐N,N′‐dipropanesulfonic acid ethylene‐diammonium hydrogen sulfate, N,N,N′,N′‐tetramethyl‐N,N′‐dipropanesulfonic acid‐1,3‐propanediammonium hydrogen sulfate, N,N,N′,N′‐ tetramethyl‐N,N′‐ dipropanesulfonic acid‐1,6‐hexanediammonium hydrogen sulfate were prepared. These ionic liquids could be used as efficient and recyclable catalysts for the synthesis of α‐aminophosphonates at room temperature via an one‐pot three‐component reaction under organic solvent‐free conditions with good yields of 83–96%. The postprocessing was simple, and the catalysts could be reused at least six times without noticeably decreasing the catalytic activity. The novel clean procedure offers the advantages including short reaction time, good yields, operational simplicity, and environmentally benign. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:1–5, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20647     

Regioselective synthesis of 1,2,4‐triazol‐3(2H)‐ones and their 3(2H)‐thiones: Kinetic studies and selective pyrolytic deprotection

Selective pyrolytic deprotection of 2‐ethyl and 2‐cyanoethyl‐4‐arylidenimino‐1,2,4‐triazol‐3(2H)‐ones and their 3(2H)‐thiones was studied by flash vacuum pyrolysis. This study is useful in regioselective synthesis of 2‐ and 4‐substituted 1,2,4‐triazoles of potential biological applications. The kinetic results and product analysis lend support to a reaction pathway involving a six‐membered transition state. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:50–55, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10086     

Fe3O4@SiO2@sulfated boric acid as superparamagnetic and recyclable nanocatalyst‐assisted,one‐pot,pseudo four‐component synthesis of 5‐amino‐2‐aryl‐3H‐chromeno[4,3,2‐de][1,6]naphthyridine‐4‐carbonitrile derivatives

The catalytic performance of the superparamagnetic nanocatalyst Fe₃O₄@SiO₂@Sulfated boric acid as a green, recyclable, and acidic solid catalyst in the synthesis of chromeno[4,3,2‐de][1,6]naphthyridine derivatives has been studied. Chromeno[4,3,2‐de][1,6]naphthyridine derivatives via a pseudo four‐component reaction from aromatic aldehydes (1 mmol), malononitrile (2 mmol), and 2′‐hydroxyacetophenone in the presence of Fe₃O₄@SiO₂@Sulfated boric acid (0.004 g) as a nanocatalyst in 3 mL of water as a green solvent at 80°C has been synthesized. The advantages of this method are higher product yields in shorter reaction times, easy recyclability and reusability of the catalyst, and easy work‐up procedures. The nanocatalyst was reused at least six times. The nanocatalyst retained its stability in the reaction, and after reusability, it was separated easily from the reaction by an external magnet.     

Microwave‐assisted synthesis of α‐hydroxy‐benzylphosphonates and ‐benzylphosphine oxides

A series of α‐hydroxy‐benzylphosph‐ onates and ‐benzylphosphine oxides was synthesized by the Na₂CO₃‐catalyzed microwave‐assisted addition of dialkyl phosphites and dipenylphosphine oxide to P‐substituted benzaldehydes. The solventless reaction provided the products in short reaction times and in 71–88% yield. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:15–17, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20649     

One—Pot Synthese of 3,4—Dihydropyrimidine—2（1H）—thiones Catalyzed by La（OTf）3

A general and practical procedure for the syntheses of 3,4-di-hydropyrimidine-2(1H)-thiones by a one-pot condensation of aldehyde,β-ketoester or β-diketone and thiourea using La(OTf)3 as the catalyst is described.Mild reaction conditions,excellent yields as well as the environmentally friendly character of La(OTf)3 make it an important alternative to the classic acid-catalyzed Biginelli‘s reaction.     

A silicon‐assisted synthesis of (E)‐β‐haloenamides from N‐vinylamides

(E)‐β‐Iodoenamides and (E)‐β‐iodoenimides can be easily obtained from N‐vinyl derivatives (N‐vinylamides and N‐vinylimides) by stereoselective ruthenium‐catalysed silylative coupling with vinyltrimethylsilane (Marciniec coupling) and subsequent stereospecific silicon–iodine exchange. Bromodesilylation of (E)‐β‐silylenimides affords (E)‐β‐bromoenimides, while the analogous reactions involving (E)‐β‐silylenamides lead to decomposition of substrates. N‐Halosuccinimides have been found as the most effective halogenating agents in the desilylation step under mild conditions. The ruthenium‐catalysed silylation/halodesilylation sequence can be performed in a one‐pot procedure. Copyright © 2015 John Wiley & Sons, Ltd.     

One‐pot synthesis of 1‐ and 5‐substituted 1H‐tetrazoles using 1,4‐dihydroxyanthraquinone–copper(II) supported on superparamagnetic Fe3O4@SiO2 magnetic porous nanospheres as a recyclable catalyst

An effective one‐pot, convenient process for the synthesis of 1‐ and 5‐substituted 1H‐tetrazoles from nitriles and amines is described using1,4‐dihydroxyanthraquinone–copper(II) supported on Fe₃O₄@SiO₂ magnetic porous nanospheres as a novel recyclable catalyst. The application of this catalyst allows the synthesis of a variety of tetrazoles in good to excellent yields. The preparation of the magnetic nanocatalyst with core–shell structure is presented by using nano‐Fe₃O₄ as the core, tetraethoxysilane as the silica source and poly(vinyl alcohol) as the surfactant, and then Fe₃O₄@SiO₂ was coated with 1,4‐dihydroxyanthraquinone–copper(II) nanoparticles. The new catalyst was characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, thermogravimetric analysis, vibration sample magnetometry, X‐ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherm analysis and inductively coupled plasma analysis. This new procedure offers several advantages such as short reaction times, excellent yields, operational simplicity, practicability and applicability to various substrates and absence of any tedious workup or purification. In addition, the excellent catalytic performance, thermal stability and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst could be magnetically separated and reused six times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

A Simple and Efficient One‐pot Synthesis of 1,4‐dihydropyridines Using Nano‐WO3‐ supported Sulfonic Acid as an Heterogeneous Catalyst under Solvent‐free Conditions

Nano‐tungsten trioxide‐supported sulfonic acid (n‐WSA) was found to be an effective heterogeneous cat‐ alyst for the one‐pot reaction of aromatic aldehydes, β‐dicarbonyl compounds and ammonium acetate to afford 1,4‐dihydropyridine derivatives in good to excellent yields. The other main advantages of the pres‐ ent method are short reaction times, simple workup, ease in purification and environmentally benign methodology. The reaction conditions were optimized employing Response Surface Method technique (Central Composite Design (CCD)) which is economically considerable because of the minimum number of experiments required to evaluate the effects of multiple parameters on the response.