Synthesis of 4‐Arylisocoumarins (=4‐Aryl‐1H‐2‐benzopyran‐1‐ones) through Acidic Hydrolysis of (Z)‐2‐(1‐Aryl‐2‐methoxyethenyl)benzaldehydes,Followed by Oxidation

4‐Arylisocoumarins (=4‐aryl‐1H‐2‐benzopyran‐1‐ones) 6 were prepared from 2‐(1‐aryl‐2‐methoxyethenyl)‐1‐bromobenzenes 1 . Successive treatment of these bromo styrenes with BuLi and 1‐formylpiperidine gave a mixture of (E)‐ and (Z)‐2‐(1‐aryl‐2‐methoxyethenyl)benzaldehydes 2 . Hydrolysis of (Z)‐isomers with conc. HBr, followed by pyridinium chlorochromate (PCC) oxidation of the resulting 1H‐2‐benzopyran‐1‐ol derivatives 4 (and 5 ), afforded the desired products.     

Ritter Reaction of 1‐Aryl‐1‐Fluoro‐2‐Haloethanes

Fluorinated phenethyl bromides 1,2 , and 3 , prove to be totally inert under Ritter reaction conditions in the presence of either SnCl₄ or AgNO₃, due to the strong deactivation by the gem‐difluoro unit. Subjecting 2‐bromo‐1‐fluoro‐1‐phenylethane to SnCl₄ in MeCN at elevated temperatures led to formation of 2‐methyl‐4‐phenyl‐4,5‐dihydrooxazole.     

Preparation of 2‐Arylethynylselanylacetonitriles from 4‐Aryl‐1,2,3‐selenadiazoles

Base decomposition of 4‐(substituted phenyl)‐1,2,3‐selenadiazoles at room temperature resulted in 2‐(substituted phenyl)‐ethynylselenolate anions, which were immediately reacted with bromoacetonitrile to give a series of 2‐(substituted phenyl)ethynylselanylacetonitriles.     

An Efficient Synthesis of New 5‐(1‐Aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles from 1‐Aryl‐1H‐pyrazole‐4‐carbonitriles via [3 + 2] Cycloaddition Reaction

A series of new 5‐(1‐aryl‐1H‐pyrazole‐4‐yl)‐1H‐tetrazoles 4a‐l were synthesized via [3 + 2] cycloaddition reaction from 1‐aryl‐1H‐pyrazole‐4‐carbonitriles 3a‐l , sodium azide and ammonium chloride, using dimethylformamide (DMF) as solvent, in good yields: 64–85%. The structures of these newly synthesized compounds were determined from the IR, ¹H‐ and ¹³C‐NMR spectroscopic data and elemental analyses.     

Selective Synthesis of 2‐Aryl‐1‐benzylated‐1H‐benzimidazoles

An efficient and simple procedure was developed for the green synthesis of various 2‐aryl‐1‐ben‐zylated‐1H‐benzimidazoles in high yields by condensation of o‐phenylenediamine with aldehydes with P₂O₅/SiO₂ as catalyst under solvent‐free and ambient conditions.     

Synthesis of Novel 3‐Acetyl‐2‐Aryl‐5‐(3‐Aryl‐1‐Phenyl‐Pyrazol‐4‐yl)‐2,3‐Dihydro‐1,3,4‐Oxadiazoles

A series of novel pyrazolyl‐substituted 1,3,4‐oxadiazole derivatives ( 4a‐4o ) were prepared by cyclization of the intermediate N′‐((3‐aryl‐l‐phenyl‐pyrazol‐4‐yl)methylene)arylhydrazide with acetic anhydride. The structures of the new compounds were confirmed by IR, ¹H NMR, MS and elemental analysis. Furthermore, preliminary bioassay of some of the title compounds indicated that they exhibited moderate inhibition against HIV‐1 PR.     

Synthesis of 3‐Aryl‐2‐methoxyinden‐1‐one (Z)‐Phenylhydrazones via Hydrobromic Acid‐Mediated Cyclization of 2‐(1‐Aryl‐2‐methoxyethenyl)benzaldehyde Phenylhydrazones

2‐(1‐Aryl‐2‐methoxyethenyl)benzaldehydes 2 , obtained by successive treatment of 1‐(1‐aryl‐2‐methoxyethenyl)‐2‐bromobenzenes 1 with BuLi and 1‐formylpiperidine, were transformed to the corresponding phenylhydrazones 3 on treatment with PhNHNH₂. When these hydrazones were allowed to react with conc. HBr, cyclization, followed by dehydrogenation with air occurred, furnished 3‐aryl‐2‐methoxyinden‐1‐one (Z)‐phenylhydrazones 4 .     

Synthesis and Heterocyclization of 1‐Aryl‐2‐methyl‐4‐oxo‐1,4,5,6‐tetrahydropyridine‐3‐carboxylates

A series of novel isoxazole, dihydropyrazolone, and tetrahydropyridine derivatives were synthesized by the reaction of corresponding ethyl 1‐substituted aryl‐2‐methyl‐4‐oxo‐1,4,5,6‐tetrahydropyridine‐3‐carboxylates with different hydrazines and hydroxylamine. Reaction of tetrahydropyridone with N ,N‐dimethylformamide dimethyl acetal provided 1‐(5‐chloro‐2‐methylphenyl)‐2‐[2‐(dimethylamino)ethenyl]‐4‐oxo‐1,4,5,6‐tetrahydropyridine‐3‐carboxylate, which was cyclized into a bicyclic compound on treatment with ammonium acetate. The structures of all synthesized compounds were confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy data. The structure of 5‐(5‐chloro‐2‐methylphenyl)‐4‐methyl‐2‐phenyl‐2,5,6,7‐tetrahydro‐3H‐pyrazolo[4,3‐c]pyridin‐3‐one was unambiguously assigned by means of X‐ray analysis data.     

4‐Aryl‐2‐ferrocenyl‐ and 2‐Aryl‐4‐ferrocenyl‐2,3‐dihydro‐1,5‐benzothiazepines with Potentially Biological Activities: Synthesis,Characterization, X‐ray Diffraction Studies

A series of novel 4‐aryl‐2‐ferrocenyl‐ and 2‐aryl‐4‐ferrocenyl‐2,3‐dihydro‐1,5‐benzothiazepines 3a , 3b , 3c , 3d , 3e , 3f and 6a , 6b , 6c , 6d , 6e was obtained by the condensation of 1‐aryl‐3‐ferrocenyl‐ and 3‐aryl‐1‐ferrocenyl‐2‐propenones 1a , 1b , 1c , 1d , 1e , 1f and 4a , 4b , 4c , 4d , 4e , respectively, with o‐aminothiophenol in the presence of AcOH and HCl (~64–91%). Their structures were established based on the spectroscopic data and X‐ray diffraction analysis of the compounds 3d , 5a , and 6c .     

Solid‐State [2+2] Photodimerization of 1‐Aryl‐4‐pyridylbutadienes in Cation‐π‐Controlled Crystals

Irradiation of HX (X=CF₃SO₃ or CF₃CO₂) salts of 1‐aryl‐4‐pyridylbutadienes 1 a – 1 c in the solid‐state afforded syn head‐to‐tail dimers in good yields among a number of possible dimers, whereas irradiation of the neutral substrates gave a complex mixture or no products. A comparison of the X‐ray crystal structures of the neutral compounds and the HX salts clarified that their orientation modes are head‐to‐head and head‐to‐tail, respectively. Moreover, while the distances between the two neighboring double bonds of the neutral compounds are relatively far apart from each other, those of HX salts are close together, satisfying Schmidt's requirement. These findings suggested that cation‐π interactions between the pyridinium and aromatic rings are effective for the preorientation of the HX salts of substrates, leading to photodimers in high regio‐ and stereoselectivities.     

Efficient Synthesis of 1‐Aryl‐4‐[(ethoxycarbonyl)oxy]‐1H‐pyrazole‐3‐carboxylates

Two‐step synthesis of N‐aryl 4‐[(ethoxycarbonyl) oxy]‐1H‐pyrazole‐3‐carboxylates is achieved starting from the commercially available ethyl 4‐chloroacetoacetate and aromatic amines. Azo coupling followed by cyclization with ethyl chloroformate–DMAP pair resulted in the formation of new 4‐oxy‐1H‐pyrazole derivatives in high yields.     

Synthesis of 2‐Aryl‐2,3‐dihydro‐3‐sulfanyl‐1H‐isoindol‐1‐ones by Pummerer‐Type Cyclization of N‐Aryl‐2‐(sulfinylmethyl)benzamides

An efficient method for the synthesis of 2‐aryl‐2,3‐dihydro‐3‐sulfanyl‐1H‐isoindol‐1‐ones 1 via Pummerer‐type cyclization of N‐aryl‐2‐(sulfinylmethyl)benzamides 2 is described. Thus, treatment of these sulfinyl‐benzamides 2 , easily prepared from 2‐(bromomethyl)benzoates 3 in three steps, with Ac₂O at ca. 100° resulted in the formation of the desired isoindolones 1 in generally good yields.     

Cyclization vs. Elimination Reactions of 5‐Aryl‐5‐hydroxy 1,3‐Diones: One‐Pot Synthesis of 2‐Aryl‐2,3‐dihydro‐4H‐pyran‐4‐ones

2‐Aryl‐2,3‐dihydro‐4H‐pyran‐4‐ones were prepared in one step by cyclocondensation of 1,3‐diketone dianions with aldehydes. The use of HCl (10%) for the aqueous workup proved to be very important to avoid elimination reactions of the 5‐aryl‐5‐hydroxy 1,3‐diones formed as intermediates. The TiCl₄‐mediated cyclization of a 2‐aryl‐2,3‐dihydro‐4H‐pyran‐4‐one with 1,3‐silyloxybuta‐1,3‐diene resulted in cleavage of the pyranone moiety and formation of a highly functionalized benzene derivative.     

Synthesis,Characterization and Crystal Structure of Some Novel 1‐Aryl‐2‐Thioxo‐2,3‐Dihydro‐1H‐Quinazolin‐4‐Ones

The base catalyzed intramolecular nucleophilic cyclization of 1‐(2‐haloaroyl)‐3‐aryl thioureas ( 1a‐i ), in the presence of DMF afforded the 1‐aryl‐2‐thioxo‐2,3‐dihydro‐1H‐quinazolin‐4‐ones ( 2a‐i ). The structures were confirmed by spectroscopic data, elemental analyses and in case of the 2c by single crystal X‐ray diffraction data. The mechanistic studies support an intramolecular nucleophilic substitution (S_NAr mechanism) rather than intramolecular aromatic substitution (S_RN1 mechanism).     

Fragmentation Mechanism of Trans—α—Aryl—β—enamino Esters

Electron impact-induced fragmentation mechanism of Trans-α-Aryl-β-enamino esters were investigated using mass-analyzed ion kinetic energy (MIKE) spectrometry and high resolution accurate mass data It was found that the main characteristic fragmentations of compounds studied were:an odd electron ion M^ -EtOH was formed by losing a neutral molecule of ethanol;and the skeletal rearrangements took place;and the ring opening reaction happened after losing a carbon monoxide;and the typical McLafferty rearrangement underwent in ester group.The cycliztion reation caused by losing neutral molecule of TsNH2 due to the ortho-effects of substituted group of gromatic ring was also observed.     

BF3‐Oet2/Et3SiH‐Mediated Rearrangement of 4‐Aryl‐5,5‐Diphenylazapan‐4‐Ols

Synthesis of 2‐(2‐arylethyl)‐3,3‐diphenylpyrrolidines has been established starting from different 4‐aryl‐5,5‐diphenylazepan‐4‐ols via boron trifluoride etherate/triethylsilane‐mediated rearrangement.     

Synthesis and Antibacterial Activities of 2‐(1‐Aryl‐5‐Methyl‐1,2,3‐triazol‐4‐yl)‐1,3,4‐Oxadiazole Derivatives

Eighteen novel 2‐(1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐1,3,4‐oxadiazole derivatives and two acylhydrazone intermediate compounds were synthesized by various pathways starting from 1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐formhydrazide ( 1 ). All products were identified by spectroscopic analysis, and 2‐(1‐aryl‐5‐methyl‐1,2,3‐triazol‐4‐yl)‐5‐benzalthio‐1,3,4‐oxadiazole was further validated by X‐ray crystallography. Results from primary antibacterial activity tests indicated that most of the compounds were effective against E. coli, P. aeruginosa, B. subtilis and S. aureus.     

(±)‐2‐Aryl‐2,3‐dihydro‐4(1H)‐quinolinones by a tandem reduction–Michael addition reaction

An efficient synthesis of (±)‐2‐aryl‐2,3‐dihydro‐4(1H)‐quinolinones has been developed from chalcones prepared from 2′‐nitroacetophenone and a series of substituted benzaldehydes. The cyclization sequence is initiated by reduction of the nitro group under dissolving metal conditions using iron powder in concentrated hydrochloric acid. Milder conditions, using acetic acid or acetic acid–phosphoric acid as the reaction medium, were less satisfactory. Procedural details as well as a mechanistic discussion and reaction optimization studies are presented. J. Heterocyclic Chem., (2011).