New Method for the Synthesis of 2‐Aza‐1,3‐Butadienes

2‐Aza‐1,3‐butadienes have been synthesized from carbonyl compounds and 1,1,1,3,3,3‐hexamethyl‐disilazane in the presence of cobalt‐containing catalysts. The best yields (up to 95%) were achieved in the case of aldehydes branched in the α-position and 2-methylcyclohexanone. In the case of two α,β‐unsaturated ketones, pyridine derivatives were found as the main products.     

Practical One‐Pot Procedure for the Synthesis of 1,2,3,4‐Tetrahydroquinolines by the Imino‐Diels‐Alder Reaction

A novel‐one‐pot procedure for the synthesis of tetrahydroquinolines via the imino‐Diels‐Alder reaction is described. This procedure gives better yields and exhibits better versatility for alkene substrates than the existing hemi‐aminal based methodologies.     

Improved Procedure for the Preparation of cis‐2,4‐Dimethylglutaranhydride

Addition of 2.5 mol% DBU to a mixture of isomeric 2,4‐dimethylglutaric anhydrides in ethyl acetate promotes crystallization‐induced transformation, affording the pure cis‐2,4‐dimethylglutaric anhydride in 87% yield.     

Novel Methods for the Synthesis of 4‐Arylisoquinolinium Perchlorates and 4‐Arylisoquinolin‐1‐ones

2‐Benzylamino‐1‐phenyl‐ethanones 1 were converted to the corresponding isoquinolinium perchlorates 2 in high yields using 70% HClO₄‐FeCl₃ mixture as a cyclization and oxidation reagent. A mild and high yielding method for the oxidation of perchlorates 2 to isoquinolin‐1‐ones 3 involving the treatment of 2 with KOH and K₃[Fe(CN)₆] in THF‐H₂O two‐phase system at room temperature was developed. Compounds 2a–g were shown to be disproportionate to 3 and the corresponding 1,2‐dihydroisoquinoline 4 in the presence of base, which in turn is oxidized by K₃[Fe(CN)₆] to 2.     

Application of Dichlorovinyl Xyloside for the Novel Synthesis of 2,3,4‐Tri‐O‐methyl‐D‐xylono‐1,5‐lactone

A novel synthesis of 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, and its oxidation product 2,3,4‐tri‐O‐methyl‐D‐xylono‐1,5‐lactone, 5, are reported. The new synthesis applies a regioselective Wittig‐like reaction of tetra-O-acetyl-D-xylopyranase, 1, with triphenylphosphine and carbon tetrachloride to yield an O‐dichlorovinyl xyloside protected at C‐1, 2. The protecting group facilitates the permethylation of xylose and is removed under the methylation conditions, to yield tetra-O-acetyl-D-xylopyranase, 3. The anomeric methyl group was removed under mildly acidic conditions to give 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, in good yield. Compound 4 was oxidized using pyridinium chlorochromate to give the title compound, 5, in 95% yield.     

Sydnones as Masked Hydrazines for the Synthesis of 4‐Arylazo‐1,2‐dihydro‐pyrazol‐3‐one Derivatives

A simple and convenient one‐pot synthesis of 4‐(4‐chlorophenylazo)‐5‐methyl‐2‐aryl‐1,2‐dihydro‐pyrazol‐3‐ones (4a–j) has been carried out from 3‐arylsydnones (3a–j) by reaction with 2‐(4‐chlorophenyl)‐hydrazono‐3‐oxo‐butyric acid ethyl ester (2b). The 3‐arylsydnones are used as masked hydrazines in this reaction. Similarly, the 4‐arylazo‐2‐(7‐hydroxy‐4‐methyl‐2‐oxo‐2H‐chromen‐8‐ylmethyl)‐5‐methyl‐1,2‐dihydro‐pyrazol‐3‐ones (7a–j) were synthesized from 3‐[(7‐acetoxy‐4‐methyl‐8‐methylene)coumaryl]sydnone (5). All the newly synthesized compounds exhibited antimicrobial activity greater than the reference drugs used.     

New One‐Pot Procedure for the Synthesis of 2‐Substituted Benzimidazoles

A highly selective synthesis of 2‐substituted benzimidazole derivatives from the reaction of o‐phenylendiamine derivatives and aromatic aldehydes in the presence of an organic salt, NH₄OAc, in absolute ethanol is presented. The products were obtained by evaporating the solvent followed by a simple recrystallization with excellent yields.     

A Facile Method for the Preparation of Pure cis‐2,4‐Pentanediol

Abstract

The isolation of diastereomerically pure cis‐2,4‐pentanediol from a crude mixture of both cis‐ and trans‐2,4‐pentanediols is described through a short procedure involving thermodynamic acetal formation with acetophenone, followed by hydrogenolysis of the acetal protecting group.     

Catalytic Approach for the Synthesis of bis‐Calixarenes

Three new tail‐to‐tail linked biscalix[6]arenes joined via ether linkages have been synthesized. These bis calix[6]arenes have been characterized by ¹H NMR, ¹³C NMR, and mass spectroscopy and elemental analysis.     

Uncatalyzed and Solvent‐Free Process for the Synthesis of 1,4‐Diarylquinoline Derivatives

The uncatalyzed and three‐component reaction of arylaldehyde, malonodinitrile, and 3‐arylamino‐5,5‐dimethylcyclohex‐2‐enone at 160 °C under solvent‐free conditions gave 1,4‐diarylquinoline derivatives in high yields.     

Green Procedure for the Synthesis of Phthalazino[2,3‐b]phthalazine‐5,7,12,14‐tetraones

Different novel phthalazino[2,3‐b]phthalazine‐5,7,12,14‐tetraones were synthesized in a simple and environmentally benign method from the reaction of phthalic anhydrides with semicarbazide or thiosemicarbazide using montmorillonite K‐10 clay as solid heterogeneous acidic catalyst and microwaves under solvent‐free conditions in good yields and short reaction times. Products were characterized by the elemental analysis, IR, NMR, and mass spectrometry.     

Alternative Route for the Synthesis of 6‐Methoxy‐5‐methyl‐α‐tetralone and 6‐Methoxy‐2,5‐dimethyl‐α‐tetralone

The ketoesters 3 and 4, obtained by the condensation of 2‐cyclohexanone carboxylate and 1‐chloro‐3‐pentanone, were heated with 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) to yield the dienones 5 and 6, which on hydrolysis with potassium t‐butoxide and dimethyl sulfoxide afforded tetralin 8. These were converted to tetralone 10 by methylation and oxidation respectively. Further methylation of 10 yielded tetralone 11.     

Generalization of the fourth‐order Hylleraas functional for the case of a non‐Hermitian unperturbed Hamiltonian

Generalization of the fourthorder Hylleraas functional form have been performed for the case of nonHermitian operators. Our new formulas are relevant when the Hermitian Born–Oppenheimer Hamiltonian is decomposed into a nonHermitian unperturbed part and also a nonHermitian perturbation. The results can be used to develop BSSEfree intermolecular perturbation theory up to fourthorder.     

Novel Method for the Synthesis of 6,12‐Dihydro‐2‐Methylindolo[2,3‐ b]Carbazol‐6‐Ones

A novel method for the synthesis of 6,12‐dihydro‐2‐methylindolo[2,3‐b]carbazol‐6‐ones was developed from 1‐oxo‐2,3,4,9‐tetrahydro‐1H‐carbazol‐1‐one through methyl 6‐methyl‐2‐(1‐oxo‐2,3,4,9‐tetrahydro‐1H‐carbazol‐2‐yl)oxoacetate in good yields. This method provides an alternative path for the synthesis of this product using 2‐hydroxy methylene‐2,3,4,9‐tetrahydro‐1H‐carbazol‐1‐one.     

Synthesis of Differently Protected 1‐C‐Methyl‐Ribofuranoses Intermediates for the Preparation of Biologically Active 1′‐C‐Methyl‐Ribonucleosides

Starting from D‐ribose, differently protected 1‐C‐methyl‐D‐ribofuranoses have been prepared as intermediates for the synthesis of variously modified 1′‐C‐methyl‐ribonucleosides, a class of compounds potentially endowed with interesting biological activity.     

QCM‐Based Immunosensor for the Determination of Ochratoxin A

Abstract

A piezoelectric immunosensor based on a competitive format was developed for determination of ochratoxin A (OTA) concentration. Surface modifications via two self‐assembled monolayers (SAMs) were investigated respectively and a better result was obtained with the SAM of 16‐mercaptohexadecanoic acid (16‐MHDA). The quartz crystal microbalance (QCM)‐based immunosensor was fabricated by immobilizing anti‐OTA antibodies onto the surface of the 16‐MHDA‐modified electrode, and allowing competition between free OTA and that conjugated with BSA to occur. The assay exhibited a working range of 50–1000 ng/mL and a detection limit of 16.1 ng/mL. Studies of interference and matrix effects were performed to evaluate the feasibility of the developed immunosensor for the direct analysis of OTA in real samples. Recoveries were conducted at 50, 200, and 1000 ng/g and were determined to be in the range of 142%–76%. The OTA assay is specific. No cross‐reactivates were observed with citrinin.     

Optimizing the Triple‐Potential Waveform for the Pulsed Amperometric Detection of Streptomycin

Abstract

A triple‐potential waveform used for amperometric detection of streptomycin (STP) is investigated. The mobile phase is an aqueous solution of 75 mM phosphoric acid. Waveform parameters are optimized to maximize the signal‐to‐noise ratio (S/N). The potentials of the waveform are designated E1, E2, and E3, and potentials are maintained for time periods t1, t2, and t3. Unlike the normal triple‐potential waveform, the cleaning function is accomplished at negative potential instead of positive potential in our triple‐potential waveform. The detection limit of STP is <0.04 µg mL^?1 (S/N=3). The linearity of STP ranges from 0.1 to 5 µg mL^?1 (r=0.9986). RSD (n=30) of the peak area of STP is 5.8%. The triple‐potential waveform shows low detection limits and long‐term reproducibility.     

One‐Pot Substitution‐Rearrangement Reaction of 2‐Chloroglycidic Ester: Effective Protocol for the Preparation of 3‐Arylsulfenyl‐2‐keto Ester

The one‐pot substitution‐rearrangement reaction of 2‐chloroglycidic ester is reported. Treatment of 2‐chloroglycidic ester with sodium arylthiolate at room temperature results in the formation of 3‐arylsulfenyl‐2‐keto ester in excellent to good yields.     

Study on the New Fluorescence Immunoassays for the 2,4,6‐Trichlorophenol in the Environmental Water

Abstract

This study reported that the hapten of 2,4,6‐trichlorophenol (2,4,6‐TCP) was synthesized by using 2,4,6‐TCP reacted with chloroactic acid in alkaline solution. The hapten was conjugated to bovine serum albumin (BSA) with the modified active ester method to form artificial immune antigen. The anti‐TCP polyclonal antibodies were obtained by using the artificial immuneantigen (TCP‐BSA) to immunize the rabbits. Using the purified antiserum of highest specificity, an antibody‐coated fluoroimmunoassay was developed that shows an IC₅₀ of 4.8 µg/L with a limit of detection of 0.25 µg/L. The antibody showed negligible cross‐reactivity with other phenols, which makes their assays suitable for the selective detection of 2,4,6‐TCP. It shows a good accuracy and suitability to analyze, 2,4,6‐TCP in environmental water.     

Convenient One‐Pot Heterogeneous Catalytic Method for the Preparation of 3,4‐Dihydropyrimidin‐2(1H)‐ones

A new, simple, environmentally friendly synthesis of dihydropyrimidinones from aromatic and aliphatic aldehydes, ethyl acetoacetate, and urea or thiourea using a small‐pore‐size zeolite as catalyst is described. Compared with the classical Biginelli reaction conditions, this method has the advantage of high yield, shorter reaction time, and recyclable and reusable catalyst.