Synthesis of 4,4′-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol) derivatives in water

An environmentally friendly and simple method for the synthesis of some 4,4′-(arylmethylene)bis(3-methyl-1H-pyrazol-5-ol) derivatives via a one-pot pseudo five-component reaction of hydrazine hydrate, ethyl acetoacetate and aldehydes in water using pyridine trifluoroacetate or acetic acid at 70 °C is reported.     

Synthesis,Characterization and Crystal Structures of new 1,2,4‐Triazole based Schiff‐bases and their Copper(I) Complexes

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, 1 ) with 4‐methoxy benzaldehyde and 3‐methoxybenzaldehyde in methanol led to the iminic derivatives 4‐(4‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)thione ( 2 , L1) and 4‐(3‐methoxybenzylideneamino)‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione ( 3 , L2). The reaction of the latter with [(PPh₃)₂CuCl] in methanol solution gave the first Cu^I complex of 3 , [(PPh₃)₂CuCl(L2)] ( 4 ) and in chloroform solution the complex [(PPh₃)₂CuCl(L2)]·2CHCl₃ ( 5 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for 2 at ?80 °C: space group P2₁/c with a = 1351.3(3), b = 399.4(1), c = 2225.2(5) pm, β = 96.50(2)°, Z = 4, R₁ = 0.0667, for 3 at ?80 °C: space group R3c with a = b = 3020.4(2), c = 708.2(1) pm, Z = 18, R₁ = 0.0435, for 4 at ?80 °C: space group P2₁/c with a = 1427.8(1), b = 1129.0(1), c = 2622.8(2) pm, β = 97.19(1)°, Z = 4, R₁ = 0.0517 and for 5 at ?80 °C: space group with a = 1280.5(1), b = 1316.1(1), c = 1731.4(1) pm, α = 78.14(1)°, β = 86.06(1)°, γ = 64.69(1)°, Z = 2, R₁ = 0.0525.     

Silica Sulfuric Acid as an Inexpensive and Recyclable Solid Acid Catalyzed Efficient Synthesis of Quinolines

Summary. Silica sulfuric acid as an inexpensive and recyclable solid acid efficiently catalyzes the Fridedl?nder synthesis of quinolines through a condensation reaction of a 2-aminoaryl ketone with an activated α-CH acid compound under solvent-free conditions in high yields at 100°C.     

An isocyanide-based three-component reaction: synthesis of fully substituted N-alkyl-2-triphenylphosphoranylidene glutarimides

A three-component condensation reaction between an isocyanide, an electron-deficient acetylenic ester and (ethoxycarbonylmethyl)triphenylphosphonium bromide efficiently provides fully substituted N-alkyl-2-triphenylphosphoranylidene glutarimides in a one-pot reaction without any activation or modification.     

Novel isocyanide-based four-component reaction: a facile synthesis of fully substituted 3,4-dihydrocoumarin derivatives

A novel isocyanide-based four-component reaction between a 2-hydroxybenzaldehyde, Meldrum's acid, an isocyanide, and an aromatic or an aliphatic alcohol efficiently provide 3,4-dihydrocoumarin derivatives in good to excellent yields without using any catalyst or activation. The reaction can be carried out as a simple one-pot protocol at room temperature.     

Steric effects on the dialkyl substituted X2C2Si silylenes: A theoretical study

With the aim of recognizing the steric effects on the silylenic H₂C₂Si structures, ab initio and DFT calculations are carried out on 24 structures of X₂C₂Si (where X is hydrogen (H), methyl (Me), isopropyl (i‐pro), and tert‐butyl (tert‐Bu)). These species are at either triplet (t) or singlet (s) states. They are confined to the following three sets of structures ( 1 _X, 2 _X and 3 _X). Structures 1 _X include silacyclopropenylidenes ( 1 _s‐H and 1 _t‐H) and their 2,3‐disubstituted derivatives ( 1 _t‐Me, 1 _s‐Me; 1 _t‐i‐pro, 1 _s‐i‐pro; 1 _{t‐tert‐Bu}, 1 _{s‐tert‐Bu}). Structures 2 _X include vinylidenesilylenes ( 2 _s‐H and 2 _t‐H) and their 3,3‐disubstituted derivatives ( 2 _t‐Me, 2 _s‐Me; 2 _t‐i‐pro, 2 _s‐i‐pro; 2 _{t‐tert‐Bu}, 2 _{s‐tert‐Bu}). Structures 3 _X include ethynylsilylenes ( 3 _s‐H and 3 _t‐H) and their 1,3‐disubstituted derivatives ( 3 _t‐Me, 3 _s‐Me; 3 _t‐i‐pro, 3 _s‐i‐pro; 3 _{t‐tert‐Bu}, 3 _{s‐tert‐Bu}). Singlet–triplet energy separations (Δ E_{s‐t, X}) and relative energies for the above structures are acquired at HF/6‐31G*, B₁LYP/6‐31G*, B3LYP/6‐31G*, MP2/6‐31G*, HF/6‐31G**, B1LYP/6‐31G**, B3LYP/6‐31G**, and MP2/6‐31G** levels of theory. The highest Δ E_{s‐t, X} is encountered for 1 _X. All singlet states of X₂C₂Si, are more stable than their corresponding triplet states. Linear correlations are found between the LUMO–HOMO energy gaps of the singlet 1 _s‐X and 2 _s‐X with their corresponding singlet–triplet energy separations calculated at B3LYP/6‐31G**. The seven structures 2 _s‐Me, 2 _t‐Me, 3 _s‐Me, 1 _t‐Me, 1 _s‐Me, 1 _{s‐tert‐Bu}, and 3 _{t‐tert‐Bu} do not appear to be real isomers. Different stability orders are obtained as a function of the substituents (X). The order of stability for six isomers of H₂C₂Si is 1 _s‐H > 2 _s‐H > 3 _s‐H > 2 _t‐H > 3 _t‐H > 1 _t‐H. Replacing hydrogen atoms by methyl group (X = Me) presents a new stability order: 1 _s‐Me > 3 _s‐Me > 2 _s‐Me > 3 _t‐Me > 2 _t‐Me > 1 _t‐Me; and for (i‐pro)₂C₂Si is 1 _s‐i‐pro > 2 _s‐i‐pro ≈ 3 _s‐i‐pro > 3 _t‐i‐pro ≈ 2 _t‐i‐pro > 1 _t‐i‐pro. Using the larger tert‐butyl group as a substituent (X), yet it offers a more different stability order for six structures of (tert‐Bu)₂C₂Si: 1 _{s‐tert‐Bu} > 3 _{s‐tert‐Bu} > 2 _{s‐tert‐Bu} > 3 _{t‐tert‐Bu} > 1 _{t‐tert‐Bu} > 2 _{t‐tert‐Bu}. Among eight levels employed, B3LYP/6‐31G** appears as the method of choice. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:619–633, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20204     

A Novel Synthesis and Antioxidant Evaluation of Functionalized [1,3]‐Oxazoles Using Fe3O4‐Magnetic Nanoparticles

In this research, green procedure was employed for biosynthesis of magnetic nanoparticles of iron oxide (Fe₃O₄‐MNPs) by reduction of ferric chloride solution with Orange peel water extract. Also, dihydro‐2H‐cyclopenta[d][1,3]oxazole was generated through multicomponent reaction of 1,3‐oxazole‐2(3H)‐thione, dialkyl acetylenedicarboxylates, α‐haloketones, and Fe₃O₄‐MNPs as catalyst at ambient temperature in good yield. Initially, 1,3‐oxazole‐2(3H)‐thione derivatives as one of the precursors are produced through the reaction of alkyl bromides, isothiocyanate, sodium hydride, and Fe₃O₄‐MNPs as catalyst water at ambient temperature in 83–95% yields. Also, diphenyl‐picrylhydrazine radical trapping and ferric reduction activity potential assays are used for evaluation of antioxidant activity of some synthesized compounds. Among investigated compounds, 4b has good power for radical trapping activity and 4d has good reduction power to butylated hydroxytoluene and 2‐tert‐butylhydroquinone.     

A novel method for the synthesis of substituted 3,4-dihydrocoumarin derivatives via isocyanide-based three-component reaction

A new one-pot procedure for the efficient synthesis of novel 3,4-dihydrocoumarin derivatives using commercially available substituted 2-hydroxybenzaldehydes, Meldrum's acid, and isocyanides by a three-component condensation reaction in dichloromethane at room temperature without using any catalysts and activation was developed.