Synthesis and fungicidal activity of 1,3‐thiazoline derivatives bearing nitrophenyl group on the 2‐position

Ortho‐, meta‐, or para‐nitro benzoic acid were refluxed with excess SOCl₂ to give acyl chloride, which condensed with β‐amino alcohol in the presence of Et₃N in dichloromethane to afford β‐hydroxyamide; finally, sulphonation and cyclization were simultaneously conducted to afford 1,3‐thiazoline derivatives. Fungicidal activity of these new thiazolines against eight agrocultural fungi were evaluated, and two of this type of compounds displayed good fungicidal activity comparable or superior to commercial fungicide chlorothalonil against two fungi at a concentration of 50 mg/L. J. Heterocyclic Chem., (2011).     

Potassium tert‐Butoxide Catalyzed Synthesis and Characterization of Novel 3‐Aryl‐3‐(phenylthio)‐1‐(thiophen‐3‐yl)propan‐1‐one Derivatives

A series of thiophenyl‐containing 3‐thiophene derivatives ( 4a – 4i ) were prepared via the reaction of chalcone‐analogua compounds ( 3a – 3i ) and thiophenol in the presence of catalytic amount of KOBu‐t in CH₂Cl₂ with moderate to high yields. The mechanistic pathway of the reaction was explained by the Michael‐type addition of thiophenol to chalcone derivatives ( 3a – 3i ).     

Highly selective hydroarylation of propiolic acid derivatives using a PtCl2/AgOTf catalytic system

Hydroarylation of propiolic acid derivatives with arenes in trifluoroacetic acid efficiently proceeded in the presence of PtCl₂/AgOTf catalyst to give cis-cinnamic acid derivatives in good to high yields. This PtCl₂/AgOTf-catalyzed reaction did not afford any 4-arylbuta-1,3-diene-1,3-dicarboxylic acid derivatives formed by Pd(OAc)₂-catalyzed hydroarylation. The specific optimization of the catalytic hydroarylation and application to electron-rich arenes are reported.     

Mannich‐Type Reaction Catalyzed by Silica‐Supported Fluoroboric Acid under Solvent‐Free Conditions

Three‐component Mannich‐type reaction of aldehydes, aromatic amines, and silyl enolate proceeded smoothly to afford β‐amino carbonyl compounds with good yields in the presence of a catalytic amount of HBF₄‐SiO₂.     

Synthesis and Reactions of Some Heterocyclic Candidates Based on 2‐Amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene Moiety as Anti‐Arrhythmic Agents

In continuation of our previous work, a series of novel thiophene derivatives 4 , 5 , 6 , 8 , 9 , 9a , 9b , 9c , 9d , 9e , 10 , 10a , 10b , 10c , 10d , 10e , 11 , 12 , 13 , 14 , 15 , 16 were synthesized by the reaction of ethyl 2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxylate ( 1 ) or 2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carbonitrile ( 2 ) with different organic reagents. Fusion of 1 with ethylcyanoacetate or maleic anhydride afforded the corresponding thienooxazinone derivative 4 and N‐thienylmalimide derivative 5 , respectively. Acylation of 1 with chloroacetylchloride afforded the amide 6 , which was cyclized with ammonium thiocyanate to give the corresponding N‐theinylthiazole derivative 8 . On the other hand, reaction of 1 with substituted aroylisothiocyanate derivatives gave the corresponding thiourea derivatives 9a , 9b , 9c , 9d , 9e , which were cyclized by the action of sodium ethoxide to afford the corresponding N‐substituted thiopyrimidine derivatives 10a , 10b , 10c , 10d , 10e . Condensation of 2 with acid anhydrides in refluxing acetic acid afforded the corresponding imide carbonitrile derivatives 11 , 12 , 13 . Similarly, condensation of 1 with the previous acid anhydride yielded the corresponding imide ethyl ester derivatives 14 , 15 , 16 , respectively. The structures of newly synthesized compounds were confirmed by IR, ¹H NMR, ¹³C NMR, MS spectral data, and elemental analysis. The detailed synthesis, spectroscopic data, LD₅₀, and pharmacological activities of the synthesized compounds are reported.     

Liquid‐Phase Synthesis of 2‐Methyl‐2‐Aryloxypropanoic Acid Derivatives from Polyethylene Glycol) Supported 2‐Bromo‐2‐Methylpropanoate

An efficient liquid‐phase synthesis of 2‐methyl‐2‐aryloxypropanoic acid derivatives with good yields and high purity on soluble polyethylene glycol (PEG) has been developed by treatment of PEG‐bound 2‐bromo‐2‐methylpropanoate with phenoxides in the presence of a catalytic amount of NBu₄I and KI, and subsequent cleavage from the PEG.     

Fluoroboric acid adsorbed on silica gel catalyzed regioselective ring opening of epoxides with nitrogen heterocycles

Aryl epoxides can be opened in a regioselective and efficient manner with nitrogen heterocycles such as indoles, pyrroles and imidazoles in the presence of a catalytic amount of HBF₄-SiO₂ under mild conditions to afford the corresponding C-alkylated derivatives in good yields and with a high regioselectivity.     

First example of the activation of polymethylhydrosiloxane with molecular iodine: a facile synthesis of 3,6-dihydropyran derivatives

Glycals react rapidly with polymethylhydrosiloxane (PMHS) in the presence of a catalytic amount of molecular iodine under mild conditions to afford the corresponding 3,6-dihydropyran derivatives in excellent yields. Et₃SiH/I₂ was also found to be effective for this conversion.     

Generation of metalated thiophenes with Grignard reagent and catalytic secondary amine for the cross coupling reaction with aryl halides

The reaction of thiophene derivatives with Grignard reagent (EtMgCl) and a catalytic amount of amine (Cy₂NH) induced the metalation at the α-position. Following addition of several aryl halides in the presence of a nickel or palladium catalyst afforded C-H arylated products in good to excellent yields. The method was successfully applied to facile synthesis of differently-substituted 2,5-diarylthiophenes.     

Synthesis of new thieno[2,3‐d]pyrimidines,thieno[3,2‐e]pyridines,and thieno[2,3‐d][1,3]oxazines

o‐Aminothiophene dicarbonitrile 1 on neat reaction with cyclic ketones in anhydrous ZnCl₂ yielded mixture of fused aminopyridine 3 and iminospirooxazine 4 derivatives. Similarly, pyrimidine derivatives 5 and 8 were obtained by the reaction of this intermediate 1 with formic acid and DMF‐DMA followed by hydrazine hydrate, respectively. The reaction of o‐amino‐thiophene dicarboxamide 2 at ambient temperature with cyclic ketones yielded spiropyrimidine 10 as a sole product in quantitative yield. The regioselective anellated pyrimidine 9 , 11 , and dihydropyrimidine 12 derivatives were also obtained by the reaction with aromatic aldehydes in presence of piperidine and iodine respectively. J. Heterocyclic Chem., (2012).     

Reaction of (2-amino-5,10,15,20-tetraphenylporphyrinato)nickel(II) with quinones

(2-Amino-5,10,15,20-tetraphenylporphyrinato)nickel(II) reacts with 1,4-benzoquinone, 1,4-naphthoquinone and 2-hydroxy-1,4-naphthoquinone, in the presence of a catalytic amount of sulfuric acid, to afford new porphyrin-quinone dyads and π-extended heterocyclic-fused porphyrin derivatives.     

Ru(II) complexes bearing tertiary phosphine ligands: a novel and efficient homogeneous catalyst for one‐pot synthesis of dihydropyrano[3,2‐c]chromene and tetrahydrobenzo[b]pyran derivatives

A number of ruthenium complexes were prepared and their catalytic activities in three‐component one‐pot condensation of aldehydes, malononitrile and 4‐hydroxycoumarin or dimedone was considered to afford dihydropyrano[3,2‐c]chromenes and tetrahydrobenzo[b]pyran derivatives under optimum reaction conditions. We found that a catalytic amount of RuBr₂(PPh₃)₄ efficiently promotes the reaction in a short time (3–15 min) and with high yield (75–88%). Copyright © 2012 John Wiley & Sons, Ltd.     

A rhodium‐catalyzed route for oxidative coupling and cyclization of 2‐aminobenzyl alcohol with ketones leading to quinolines

2‐Aminobenzyl alcohol undergoes oxidative cyclization with aryl(alkyl), alkyl(alkyl) and cyclic ketones in dioxane at 80° in the presence of a catalytic amount of RhCl(PPh₃)₃ along with KOH to afford the corresponding quinolines in good yields. The catalytic pathway seems to be proceeded via a sequence involving initial oxidation of 2‐aminobenzyl alcohol to 2‐aminobenzaldehyde by a rhodium catalyst, cross aldol reaction between 2‐aminobenzaldehyde and ketones, and cyclodehydration.     

An Efficient and Practical Synthesis of Dibenzo[d,f][1,3]‐dioxepines from 2,2′‐Dihydroxybiphenyl with Terminal Alkynes Catalyzed by Lewis Acid TiCl4

A synthetic strategy toward the cyclic addition of 2,2′‐dihydroxybiphenyl to terminal alkynes has been developed using Lewis acid TiCl₄ as catalyst. The reactions generated dibenzo[d,f][1,3]dioxepines derivatives in good yields with excellent regio‐selectivity in the presence of catalytic amount of TiCl₄ under mild reaction conditions.     

Synthesis of hantzsch 1,4‐dihydropyridines under solvent‐free condition using zn[(L)proline]2 as lewis acid catalyst

The present short communication describes a Lewis acid (Zn[(L)proline]₂) catalysed one pot synthesis of Hantzsch 1,4‐dihydropyridine (DHP) derivatives under solvent‐free condition by conventional heating and microwave irradiation. The Lewis acid catalyst Zn[(L)proline]₂ used in this reaction afford moderate to good yield. The catalyst is reusable upto five cycles without appreciable loss of its catalytic activity.     

Cross-aldol Condensation of Cycloalkanones and Aromatic Aldehydes in the Presence of Nanoporous Silica-based Sulfonic Acid (SiO2-Pr-SO3H) under Solvent Free Conditions

The aromatic aldehydes underwent cross aldol condensation with cycloalkanones in the presence of a catalytic amount of nanoporous silica-based sulfonic acid (SiO2-Pr-SO3H) under solvent-free conditions to afford the corresponding α,α’-bis(substituted benzylidene)cycloalkanones in excellent yields with short reaction time without any side reactions. This method is very general, simple and environmentally friendly in contrast with other existing methods. SiO2-Pr-SO3H was proved to be an efficient heterogeneous solid acid catalyst, which could be easily handled and removed from the reaction mixture by simple filtration, and also recovered and reused without loss of reactivity.     

Efficient Synthesis of Highly Substituted Furan,Thiophene, Pyrrole and 2‐Aminothiazole Derivatives

Ethyl cyanoacetate dimer (1) undergoes bromination with N‐bromosuccinimide (NBS) to afford 3‐amino‐4‐bromo‐2‐cyano‐pent‐2‐enedioic acid diethyl ester (2). This bromo derivative reacts with potassium carbonate, sodium hydrogen sulfide, aromatic amines, ammonium thiocyanate, thiourea, N‐phenylthiourea, and thiosemicarbazide to afford highly substituted furan, thiophene, pyrrole, and 2‐aminothiazole derivatives. Mechanistic explanations as well as structure elucidations are discussed.     

Highly Regioselective Palladium‐Catalyzed Carboxylation of Allylic Alcohols with CO2

Various allylic alcohols were carboxylated in the presence of a catalytic amount of PdCl₂ and PPh₃ using ZnEt₂ as a stoichiometric transmetalation agent under a CO₂ atmosphere (1 atm). This carboxylation proceeded in a highly regioselective manner to afford branched carboxylic acids predominantly. The β,γ‐unsaturated carboxylic acid thus obtained was successfully converted into an optically active γ‐butyrolactone, a known intermediate of (R)‐baclofen.     

Synthesis of the Coumarins via Pechmann Method in the Presence of Environmentally Friendly Y(NO3)3×6H2O

Several substituted coumarins can be prepared in high yield and purity by direct reaction of β‐keto esters and phenol derivatives in the presence of a catalytic amount Y(NO₃)₃×6H₂O as Lewis acid and at ambient temperature under solvent‐free conditions.     

Copper-catalyzed oxidative C‒H,N‒H coupling of azoles and thiophenes

C?H, N?H coupling of azole and thiophene derivatives takes place in the presence of a catalytic amount of Cu(OAc)₂ and an additive. The reaction of azoles smoothly occurs with several amines and amides catalyzed by 20 mol % of Cu(OAc)₂–2PPh₃ and 4 equiv of NaOAc under O₂ or in the presence of Ag₂CO₃ under N₂. The coupling reaction leads to a facile synthesis of a N-substituted analogue of 2,5-diarylthiazole, which shows photoluminescent properties with extended π-conjugation. Spectroscopic characteristics of the obtained thiazole derivatives are discussed by measurements of UV–vis absorption and photoluminescent spectra. Under the reaction conditions using Ag₂CO₃ as an additive and Cu(OAc)₂–2PPh₃ as a catalyst, thiophene derivatives also react with 2-pyrrolidone to undergo C?H, N?H amidation.