Synthesis of Novel (p‐Substituted Styryl) Spirobenzopyrans

A series of (p‐substituted styryl) spirobenzopyrans were synthesized by the Wittig reaction of Fisher's bases with 5‐(p‐substituted styryl) salicylaldehyde derivatives. The final spirobenzopyrans were characterized by the ¹H NMR, IR, UV, and GC‐MS analyses.     

Synthesis of 3‐Aryl‐5‐methyl 4‐Substituted [1,2,4]Triazoles

Treatment of N‐substituted acetamides with oxalyl chloride generates imidoyl chlorides, which react readily with aryl hydrazides. Following cyclization, triazoles can easily be obtained in moderate to good yields. 5‐Methyl triazoles can be further functionalized through α‐lithiation and subsequent reaction with an electrophile.     

Y(OTf)3‐Catalyzed,One‐Pot Synthesis of 1,2,4‐Oxadiazole Derivatives

Direct one‐step synthesis of 1,2,4‐oxadiazole from ketones, nitriles, and nitric acid is described using yttrium triflate [Y(OTf)₃] as the catalyst. The salient features of this method include a simple procedure, mild condition, easy purification, and good yields.     

Novel Synthesis and Characterization of N‐Substituted‐calix[4]azacrown Derivatives

Novel calix[4]azacrown derivatives from the reaction between calix[4]amidocrown and the different N‐(4‐bromoacetamidephthalimido)alkanes derivatives, which may be useful intemediate compounds of pseudorotaxane, have been synthesized and structurally characterized by IR, ¹H NMR, ¹³C NMR, MS, and elemental analyses. From their analysis data, it was found that compounds 6a–d adopted a cone conformation.     

Efficient Synthesis of N‐Oxide Derivatives: Substituted 2‐(2‐(Pyridyl‐N‐oxide)methylsulphinyl)benzimidazoles

Different substituted 2‐chloromethylpyridyl derivatives (6a–d) were oxidized with mCPBA to give the respective 2‐chloromethylpyridine‐N‐oxide derivatives (7a–d) at low temperature, which on condensation with 2‐mercapto‐1H‐benzimidazole (8a–c) in the presence of aprotic solvents give the 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfanyl]‐1H‐benzimidazole (9a–d) in good yield. Finally, 9a–d oxidized with mCPBA in chlorinated solvent gives a mixture of 2‐[[(pyridin‐2‐yl‐1‐oxide)methyl]sulfonyl]‐1H‐benzimidazole (3a–d, 10%) and 2‐[[(pyridin‐2‐yl‐1‐oxide) methyl]sulfinyl]‐1H‐benzimidazole (4a–d, 90%) derivatives.     

Novel Synthesis of 3‐Substituted 2‐Thiohydantoins via Aza‐Wittig Reaction on Poly(ethylene Glycol)

A novel method for the liquid‐phase combinatorial synthesis of 3‐substituted‐2‐thiohydantoin has been developed by using poly (ethylene glycol)–supported isothiocyanate. The PEG‐supported isothiocyanate was obtained from the reaction of PEG with bromoacetyl bromide, followed by an aza‐Wittig reaction. Reaction of PEG‐supported isothiocyanate with various aliphatic amines offered 3‐substituted 2‐thiohydantoins in excellent yields with addition, cyclization, and cleavage reactions occurred in one pot.     

Microwave‐Assisted One‐Pot Synthesis of 2‐(Substituted phenyl)‐1H‐benzimidazole Derivatives

A series of 2‐(substituted phenyl)‐1H‐benzimidazole derivatives with various 5‐and 6‐position substituents (‐H, ‐CH₃, ‐CF₃) were synthesized via microwave irradiation using a short synthetic route and Na₂S₂O₅ as oxidant. This simple, fast, and efficient preparation of benzimidazole derivatives has been developed using readily available and inexpensive reagents (aldehydes and 1,2‐phenylenediamines) under solvent‐free conditions.     

Efficient Synthesis of Substituted 2‐Amino‐3‐carbethoxythiophenes

A microwave‐assisted method for the synthesis of a variety of thiophene o‐aminoesters (2a–l) has been developed, starting from an appropriate aldehyde, methyl ketone or acetoacetate ester with ethyl cyanoacetate in the presence of elemental sulfur.     

Efficient Synthesis of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines

A general method for the preparation of 2‐(N‐Substituted)‐2‐imidazolines and 2‐(N‐Substituted)‐1,4,5,6‐tetrahydropyrimidines is described. These heterocycles can be synthesized from their respective anilines with 2‐chloro‐2‐imidazoline or 2‐chloro‐1,4,5,6‐tetrahydropyrimidine, generated in situ from imidazolidin‐2‐one and tetrahydropyrimidin‐2(1H)‐one activated by dimethyl chlorophosphate, in good to excellent yields.     

Synthesis of Novel Asymmetrical 1,4‐Dihydropyridine Derivatives

Asymmetrical 1,4‐dihydropyridine esters 3a and 3i–k were synthesized from the symmetrical precursor 1 through the intermediate 2‐bromomethyl derivative 2. Then, compound 3a was subjected to a different transformation for preparation of 1,4‐dihydropyridine derivatives 3b–h.     

Synthesis of Novel Derivatives of Pyridine‐2,6‐dicarboxylic Acid

Two series of novel derivatives of pyridine‐2,6‐dicarboxylic acid with potential as polydentate ligands were synthesized from pyridine‐2,6‐dicarboxylic acid. All new compounds were characterized by NMR, MS, IR, and EA.     

Synthesis of Substituted 2‐Amino‐cyclobutanones

A series of weakly nucleophilic nitrogen derivatives including carbamates, amides, sulfonamides, and anilines were reacted with 1,2‐bis(trimethylsilyloxy)cyclobutene under acidic conditions to afford various substituted 2‐aminocyclobutanone derivatives 3a–i in modest to excellent yields.     

Efficient Synthesis of 3‐Substituted Coumarins

Abstract

The Mukaiyama's esterification protocol, using 2‐chloro‐1‐methylpyridinium iodide‐triethylamine reagent, has been successfully exploited to provide rapid access to a variety of 3‐substituted coumarins in satisfactory yields.     

Synthesis and Biological Evaluation of Novel Isonucleosides with 1,2,4‐Triazole‐3‐Carboxamide

Novel 1,2,4‐triazole isonucleosides (1 and 2) were efficiently synthesized starting from D‐ribose and D‐xylose, respectively. The key steps were condensation of cyclic sulfate 8 with methyl‐1,2,4‐triazole‐3‐carboxylate and nucleophilic displacement of the tosylate 15 with methyl‐1,2,4‐triazole‐3‐carboxylate, respectively.     

Facile Synthesis of 2‐Substituted 4‐Azaindoles

A novel and efficient strategy for the synthesis of 2‐substituted 4‐azaindoles from 2‐chloro‐3‐nitropyridine through Pd‐catalyzed Sonogashira cross‐coupling, followed by reduction and heteroannulation on t‐BuOK, is reported.     

Synthesis of 2‐(5‐Substituted‐1,3,4‐thiadiazolo‐2‐ylimino)‐4‐thiazolidinones under Microwave Irradiation

Fifteen 2‐(5‐substituted‐1,3,4‐thiadiazolo‐2‐ylimino)‐4‐thiazolidinones were efficiently synthesized from the reaction of ammonium thiocyanate with 2‐chloro‐N‐(5‐substutited‐1,3,4‐thiadiazolo‐2‐yl)acetamides under microwave irradiation. The target compounds were obtained in better yields (75–98%) and shorter time (5 min) than with conventional heating.     

Synthesis of New 5‐Substituted Pyrimidine Acyclonucleosides

Acyclonucleosides of pyrimidine were prepared by condensing appropriately silylated 5‐substituted pyrimidines with an acyclic side chain in the form of an acetylated haloalkoxyalcohol and subsequent removal of the protecting acetyl group in base. Also, acyclonucleosides with a 1‐ethoxymethyl side chain have been investigated. The activity against hepatitis B virus (HBV) has been tested.     

Synthesis of Some Novel 1,3,4‐Oxadiazol‐2‐yl‐4(3H)‐quinazolinones

N‐1‐Aroyl‐2‐{[(3‐methyl‐4(3H)‐quinazolinone‐2‐yl)methyl]anilino} ethano hydrazides (4), prepared from 2‐phenylaminomethyl‐3‐methyl‐4(3H)‐quinazolinone (1), underwent PPA‐catalyzed cyclization the to title compounds 5 in 51–67% yield.     

Convenient Synthesis of Structurally Novel 1,3‐Disubstituted Azetidine Derivatives

A convenient synthesis of structurally novel 1,3‐disubstituted azetidine derivatives is described. The approach involves condensation of an azetidine building block with sulfonylated carbamic acid methyl ester, subsequently followed by quenching the imidoyl chloride with amines. Different derivatives were prepared by substituting benzhydrol as well as benzenesulfonamide as part of the core structure.     

Synthesis of the Substituted 3‐Cyclobutene‐1,2‐diones

A convenient synthesis of the novel squaric acid derivatives is reported. Unsymmetrically substituted 3,4‐diamino‐3‐cyclobutene‐1,2‐diones and 3‐amino‐4‐hydroxy‐3‐cyclobutene‐1,2‐diones were prepared by interaction of diethyl squarate with different nucleophilic reagents such as alkali, primary and secondary amines and amino acids. Substituted 3‐amino‐4‐aryl‐3‐cyclobutene‐1,2‐diones were synthesized by interaction of squaryl dichloride with different arenes followed by arylsquarylation of amines. Efficient procedures were developed for consequent substitution of ethoxy groups in diethyl squarate and chlorine atoms in squaryl dichloride. The synthesized compounds have a great potential of bioactivity and are useful objects for biomedicinal screening.