Ethyl 3,5‐dimethyl‐4‐phenyl‐1H‐pyrrole‐2‐carboxylate

In the title compound, C₁₅H₁₇NO₂, the ethoxy­carbonyl group is anti with respect to the pyrrole N atom. The angle between the planes of the phenyl and pyrrole rings is 48.26 (9)°. The mol­ecules are joined into dimeric units by a strong hydrogen bonds between pyrrole N—H groups and carbonyl O atoms. The geometry of the isolated mol­ecule was studied by ab initio quantum mechanical calculations, employing both molecular orbital Hartree–Fock (MO–HF) and density functional theory (DFT) methods. The minimum energy was achieved for a conformation where the angle between the planes of the phenyl and pyrrole rings is larger, and that between the ethoxy­carbonyl and pyrrole planes is smaller than in the solid‐state mol­ecule.     

Combined experimental and computational modeling studies on 3,5‐dimethyl‐pyrazole‐1‐carbodithioic acid benzyl ester

The title compound, 3,5‐Dimethyl‐pyrazole‐1‐carbodithioic acid benzyl ester, has been synthesized and structurally characterized by X‐ray single crystal diffraction, elemental analysis, IR spectra, and UV‐Vis spectrum. The crystal belongs to orthorhombic, space group P212121, with a = 5.3829(15), b = 11.193(3), c = 21.824(6) Å, V = 1315.0(6) ų, and Z = 4. The molecules are connected via intermolecular C–H···N hydrogen bonds into 1D infinite chains. The crystal structure is consolidated by the intramolecular C–H···S hydrogen bonds. Furthermore, Density functional theory (DFT) calculations of the structure, stabilities, orbital energies, composition characteristics of some frontier molecular orbitals and Mulliken charge distributions of the title compound were performed by means of Gaussian 03W package and taking B3LYP/6‐31G(d) basis set. The time‐dependent DFT (TD‐DFT) calculations have been employed to calculate the electronic spectrum of the title compound, and the UV‐Vis spectra has been discussed on this basis. The results show that DFT method at B3LYP/6‐31G(d) level can well reproduce the structure of the title compound. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Microwave‐assisted from synthesis of 2‐arylamino‐2‐imidazolines on a solid support

An efficient synthesis of 2‐arylamino‐2‐imidazolines from dimethyl N‐aryldithioimidocarbonates and ethylenediamine on solid support under microwave irradiation has been developed. The reaction time has been reduced from hours to minutes with improved yields as compared to conventional heating. Their piperidin‐4‐ylmethyl and morpholin‐4‐ylmethyl derivatives were synthesized by treatment with formaldehyde and piperidine or morpholine. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:142–222, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20081     

2‐Methylphenyl 2‐methoxyacridine‐9‐carboxylate

The title compound, C₂₂H₁₇NO₃, crystallizes in the monoclinic space group P2₁/c with four molecules per unit cell. The mol­ecules are arranged in centrosymmetric pairs, joined via the C and attached H atoms in the meta position relative to the methoxy group. These pairs are bonded in the crystalline phase as a result of non‐specific dispersive interactions, and through a network of C—H?O interactions involving the non‐bonded O atom of the carboxy group and, to some extent, the O atom of the methoxy group. The methoxy substituent lies in the plane of the almost planar acridine moiety and is directed towards the phenyl ester group. The phenyl ester group itself is twisted by 35.9 (5)° relative to the mean plane of the acridine moiety.     

One‐Pot Microwave‐Assisted Synthesis of Novel Substituted N‐Dichloroacetyl‐4,5‐dimethyl‐1,3‐oxazolidines

A one‐pot and efficient synthesis of substituted N‐dichloroacetyl‐4,5‐dimethyl‐1,3‐oxazolidines utilizing the reaction of alkamine with aldehyde or ketone in refluxing benzene under microwave irradiation was described. The N‐acylation was followed with dichloroacetyl chloride and NaOH acting as the attaching acid agent. All compounds were characterized by IR, ¹H NMR, ¹³C NMR, and element analysis. Additionally, the absolute configuration of 4a was determined by X‐ray crystallography. All the compounds were tested for their herbicide safeners activity of protecting the maize from the injury of acetochlor.     

Microwave-accelerated Synthesis of Some (±)-1-Aryl-5-chloroisochromans

Solventless one-pot synthesis of some new (±)-1-aryl-5-chloroisochromans by cyclocondensation of 2-(2-chlorophenyl)ethanol with aromatic aldehydes via an acid catalyzed oxa-Pictet-Spengler reaction under microwave irradiation is described.     

Microwave‐assisted synthesis of some 2,4‐thiazolidinedione derivatives

The condensation of 5‐[4′‐(2″‐halo‐ethoxy)benzylidenyl]‐2,4‐thiazolidinediones 2 when separately carried with different 2‐amino thiazoles 3 and different sulphanilamides 4 in DMF, using potassium hydroxide in the presence of a catalytic amount of a phase transfer catalyst, gave new 5‐[4′‐(4″‐aryl‐thiazol‐2″‐yl‐aminoethoxy)‐3′/5′‐substituted benzylidenyl]‐2,4‐thiazolidinediones 5 and 5‐[4′‐(2″/4″‐sulphonamidophenyl aminoethoxy)‐3′/5′‐substituted benzylidenyl]‐2,4‐thiazolidinediones 6 derivatives in good yields, respectively. The structures of all new compounds were established from analytical and spectral data. All the reaction sequences were carried under microwave irradiation, as an efficient tool. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:151–156, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20528     

Phase transfer catalyzed synthesis of 3‐methyl‐4h‐pyrazolo[3,4‐d]isoxazole from 3,5‐dimethyl‐4‐isoxazolyldiazonium tetrafluoroborate

Reaction of 3,5‐dimethyl‐4‐isoxazolyl‐diazonium tetrafluoroborate ( 2 ) with two equivalents of potassium acetate and five mole percent of 18‐crown‐6 in ethanol‐free chloroform produce 3‐methyl‐4H‐pyrazolo[3,4‐d]isoxazole ( 3 ) in good to excellent yield. Pyrazole ( 3 ) was subjected to acylation/aroylation to afford the corresponding 4‐N‐acetyl/aroyl derivatives by reaction with CH₃COCl/ArCOCl in Et₃N.     

The hydroxyl radical reaction rate constant and products of 3,5‐dimethyl‐1‐hexyn‐3‐ol

A bimolecular rate constant,k_DHO, of (29 ± 9) × 10^?12 cm³ molecule^?1 s^?1 was measured using the relative rate technique for the reaction of the hydroxyl radical (OH) with 3,5‐dimethyl‐1‐hexyn‐3‐ol (DHO, HC?CC(OH)(CH₃)CH₂CH(CH₃)₂) at (297 ± 3) K and 1 atm total pressure. To more clearly define DHO's indoor environment degradation mechanism, the products of the DHO + OH reaction were also investigated. The positively identified DHO/OH reaction products were acetone ((CH₃)₂C?O), 3‐butyne‐2‐one (3B2O, HC?CC(?O)(CH₃)), 2‐methyl‐propanal (2MP, H(O?)CCH(CH₃)₂), 4‐methyl‐2‐pentanone (MIBK, CH₃C(?O)CH₂CH(CH₃)₂), ethanedial (GLY, HC(?O)C(?O)H), 2‐oxopropanal (MGLY, CH₃C(?O)C(?O)H), and 2,3‐butanedione (23BD, CH₃C(?O)C(?O)CH₃). The yields of 3B2O and MIBK from the DHO/OH reaction were (8.4 ± 0.3) and (26 ± 2)%, respectively. The use of derivatizing agents O‐(2,3,4,5,6‐pentalfluorobenzyl)hydroxylamine (PFBHA) and N,O‐bis(trimethylsilyl)trifluoroacetamide (BSTFA) clearly indicated that several other reaction products were formed. The elucidation of these other reaction products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible DHO/OH reaction mechanisms based on previously published volatile organic compound/OH gas‐phase reaction mechanisms. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 534–544, 2004     

Microwave‐assisted synthesis of 2‐(2‐pyridyl)azoles. Study of their corrosion inhibiting properties

An efficient and fast procedure for the synthesis of 2‐(2‐pyridyl)azoles is described using ionic liquids as catalysts under microwave irradiation. The X‐ray crystallographic analyses for three of the four synthesized compounds are presented. Potentiodynamic polarization studies were carried out to analyze the electrochemical behavior of the compounds in corrosive acidic media. Of the four derivatives, one compound was detected to be an effective corrosion inhibitor prototype for oil refinery environments.     

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     

4‐(3,5‐Dimethyl‐1H‐pyrazol‐4‐ylmethyl)‐3,5‐dimethyl‐1H‐pyrazol‐2‐ium dihydrogen phosphate: a combined X‐ray and DFT study

The molecular structure of the title salt, C₁₁H₁₇N₄⁺·H₂PO₄⁻, has been determined from single‐crystal X‐ray analysis and compared with the structure calculated by density functional theory (DFT) at the BLYP level. The crystal packing in the title compound is stabilized primarily by intermolecular N—H...O, O—H...N and O—H...O hydrogen bonds and π–π stacking interactions, and thus a three‐dimensional supramolecular honeycomb network consisting of R₄²(10), R₄⁴(14) and R₄⁴(24) ring motifs is established. The HOMO–LUMO energy gap (1.338 eV; HOMO is the highest occupied molecular orbital and LUMO is the lowest unoccupied molecular orbital) indicates a high chemical reactivity for the title compound.     

Microwave‐Assisted Direct Amidation of Ethyl 1‐Phenyl‐5‐hydroxy‐1H‐pyrazole‐4‐carboxylate

Microwave‐assisted treatment of ethyl 5‐hydroxy‐1‐phenyl‐1H‐pyrazole‐4‐carboxylate with excess primary aliphatic amines in 1‐propanol at 140°C and with excess pyrrolidine or piperidine in 2‐methoxyethanol at 180°C produced the corresponding carboxamides in good yields.     

Racemic isopropyl 1,4‐dihydro‐2,6‐dimethyl‐4‐(6‐methyl‐2‐pyridyl)‐3‐nitropyridine‐5‐carboxylate hemi­benzene solvate

This analysis establishes the rotameric orientation of the pyridyl‐ring N atom of the title compound, C₁₇H₂₁N₃O₄·0.5C₆H₆, as antiperiplanar (ap) to the 1,4‐dihydropyridine H‐4, the absence of an intramolecular hydrogen bond between the 1,4‐dihydropyridine NH and the pyridyl‐N atom, and the unusual planarity of the 1,4‐dihydropyridine ring.     

In‐situ cryocrystallization of 1,2‐dimethyl‐3‐nitrobenzene and 2,4‐dimethyl‐1‐nitrobenzene

The crystal structures of 1,2‐dimethyl‐3‐nitrobenzene, C₈H₉NO₂, and 2,4‐dimethyl‐1‐nitrobenzene, C₈H₉NO₂, which are liquids at room temperature, have been obtained through in‐situ cryocrystallization. Weak C—H...O and also π–π interactions are present in both crystal structures.     

An unusual acid: (±)‐3‐benzoyl‐1,2‐dimethyl‐8a‐phenyl‐2‐benzo­thieno­[2,3‐b]pyrrole‐1,2‐dicarboxylic anhydride

The title compound, C₂₇H₂₁NO₄S, is a 2‐benzothieno[2,3‐b]pyrrole derivative with several substituents, present in the crystal as a racemate. The tetra­cyclic fused‐ring system shows a `U‐shaped' mol­ecular architecture, since the two rings flanking the central pyrrolidine ring both point in the same direction.     

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     

Ethyl 4‐do­decyl‐3,5‐di­methyl‐1H‐pyrrole‐2‐carboxyl­ate: intermolecular interactions in an amphiphilic pyrrole

The title compound, C₂₁H₃₇NO₂, is a new amphiphilic pyrrole with a long hydro­carbon chain, which will be used as a precursor for the synthesis of Langmuir–Blodgett films of porphyrins. Molecules related by an inversion centre are joined head‐to‐head into dimers by strong N—H?O hydrogen bonds. The dimers pack in the structure with their carbon chains parallel to one another, thereby forming alternating layers of carbon chains and pyrrole heads. The structure is further stabilized by two weak C—H?π intermolecular interactions, thereby saturating the hydrogen‐bonding capability of the aromatic π‐electron clouds.