Convenient Synthesis of 3,5‐Disubstituted Isoxazoles

α,β‐Unsaturated oximes obtained from the corresponding α,β‐unsaturated ketones on treatment with 2 equivalents of manganese dioxide in refluxing chloroform gives 3,5‐disubstituted isoxazoles in good yields.     

Unexpected Microwave Reaction of 1,3‐Disubstituted Imidazolium Salts: A Novel Synthesis of 1,3‐Disubstituted Imidazole‐2‐thiones

Microwave‐promoted reaction of 1,3‐disubstituted imidazolium salts with potassium thioacetate or potassium thiocyanate under solvent‐free conditions provided a rapid and efficient synthesis of 1,3‐disubstituted imidazole‐2‐thiones.     

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.     

Convenient Solid-phase Synthesis of Benzothiazole Derivatives

Resin-bound cyclic malonic ester 1 reacted with aryl isothiocynate, then was treated with bromine, followed by cleavage from the resin under perchloric acid to give benzothiazoles 4.     

Synthesis of Novel Heteroannular Disubstituted Cyclopalladated Ferrocenylimine

Cyclopalladated compounds derived from N-donor ligands have attracted great interest in the last decade due to their novel and outstanding applications in the fields of organic synthesis, catalysis and photochemistry.[1] But among all cyclopalladated ferrocenylimine derivatives reported so far, the palladium was bound to the substituted Cp ring, resulting in a five-membered metallocycle.     

Synthesis of Novel Carbohydrate Acridinone Derivatives with Potential Biological Activities using 1,3‐Dipolar Cycloaddition

Novel 10‐{[3‐(6‐hydroxy‐2,2‐dimethyltetrahydrofuro[2,3‐d][1,3]dioxol‐5‐yl)‐4,5‐dihydro‐5‐isoxazolyl]methyl}‐9(10H)‐acridinone derivatives (13–16) were synthesized by 1,3‐dipolar cycloaddition using the carbohydrate derivative as dipole and different 10‐allyl‐9(10H)‐acridinone derivatives (9–12) as dipolarophiles. The new cycloadducts as well as the dipolarophiles precursors were characterized spectroscopically.     

Simple and Convenient Synthesis of 21‐Thioalkylether Derivatives of Methyl 16‐Prednisolone Carboxylates

The antedrug approach for corticosteroids has been described as a fundamentally sound approach for the development of safer anti‐inflammatory and anti‐asthmatic therapy. However, the derivatization of prednisolone and its congeners have been considered to be major pitfalls, because their syntheses are complicated by the presence of numerous carboxylate esters and hydroxyl functions in the steroid nucleus. A simple and direct synthesis of 21‐thioalkylether derivatives of methyl 16‐prednisolonecarboxylates is described. The 21‐mesylate of the methyl 16‐prednisolonecarboxylate and 9‐fluoro‐17‐dehydro methyl 16‐prednisolonecarboxylate were reacted with Na‐thioalkoxides to furnish the desired thioethers in good yields. A previously published method for the methanolysis of 16‐cyanoprednisolone to methylcarboxylate has been reexamined, and the conditions are explained clearly. The reaction conditions for all these reactions were critical.     

Convenient Synthesis of Indene Derivatives via Intramolecular Friedel-Crafts Cyclization of Tetraaryl Substituted 1,3-Butadienes

A convenient and efficient method for the highly regioselecfive synthesis of indene derivatives 4 and 5 from tetraaryl substituted 1,3-butadienes 3 was described. The method involves an intramolecular Friedel-Crafts cyclization and a corresponding double-bond positional shift of isomers 4 and 5 in the presence of different Lewis acids under mild conditions with higher than 90% yields.     

A Convenient Synthesis of Novel Meldrum＇s Acid C60 Fullerene Derivatives

A series of novel Meldrum＇s acid C60 derivatives were prepared in moderate yields from a convenient one-pot reaction of C60, the Meldrum＇s acid derivatives, 12 and 1,8-diazabicyclo-[5,4,0]-undec-7-ene （DBU） in toluene at room temperature under nitrogen atmosphere. All the new compounds were fully characterized by the spectral data and elemental analysis. A carbene intermediate mechanism was proposed for this reaction.     

A Novel Synthesis of Isoxazole Derivatives

Thenitronesareveryimportantinorganicsynthesis.TheyhavebeenwidelyutilizedasintermediatesfromwhichcomPlexheterocyclicornaturalcompoundsanddrugs"'weresynthesisedsuchasisoxazoline3andoxazine4.However,theconversionofnitronetoisoxazolebythermaldecompositionhasnotbeenreported.Inthispaper,wedevelopanewsyntheticmethodofisoxazolesfromheterocyclicnitronesasfollows:wi.-"'rtXfa.H;b.3,4-O-CH2-o-;c.4-CH3O,d.4-Cl;e.2-Brf.2-Cl,g.3,4-coCH3;h.3-ro2;i.4-so2;j.4-CH3Experiment8lAdriedroundbottomflaskundernit…     

Synthesis of Novel Ferrocenyl-containing Thiazole Derivatives

Ferrocenes and their derivatives have been used in material chemistry, electrochemistry and in nonlinear optics. Recently, increasing interests have been focused on their biological activity1. Ferrocifen is a ferrocene derivative of tamoxifen, will be sub…     

Synthesis of Novel Pyrazolines via 1,3‐Dipolar Cycloadditions of Heterocyclic Isopropenes

An efficient and practical synthesis of novel pyrazoline structures has been achieved through 1,3‐dipolar cycloaddition of the corresponding heterocyclic isopropenes and diazo precursors.     

Convenient Synthesis of 7,8‐Dimethoxytetralin‐2‐one

7,8‐Dimethoxytetralin‐2‐one (1), an important intermediate for the synthesis of compounds possessing biological activity, was synthesized by simple reaction steps from commercially available starting materials.     

Convenient Synthesis of 5‐Aryl Uracils

A convenient one‐step synthesis of 5‐aryl uracils has been developed. The procedure involves heating ethyl 3‐hydroxy‐2‐arylpropenate with urea at 130°C, followed by base‐catalyzed cyclization. The method is simple and high yielding.     

Synthesis of Novel Spin‐Labeled Derivatives of Podophyllotoxin as Potential Antineoplastic Agents

Five novel nitroxyl spin‐labeled ester derivatives of podophyllotoxin have been prepared by reacting the corresponding N‐(1‐oxyl‐2,2,6,6‐tetramethyl‐4‐piperidinyloxycarbonyl) amino acids with the hydroxy group of podophyllotoxin in the presence of dimethylaminopyridine and N,N‐dicyclohexylcarbodiimide and evaluated as potential antitumor agents. All of the target compounds showed more significant cytotoxicity against P‐388 murine leukemia and A‐549 human lung carcinoma in vitro than etoposide.     

Synthesis of Bis‐1,4‐Dihydropyridine Derivatives

Abstract

A series of bis‐1,4‐dihydropyridine derivatives were synthesized by the reaction of p‐phenylenedialdehyde or m‐phenylenedialdehyde and active methylene compounds.     

Synthesis of Novel Spin Labeled Daunomycin Derivatives

The anthracycline antibiotics daunomycin 1 is clinically useful antineoplastic agents, with a broad spectrum of activity. However, it is hampered by a number of undesirable side effects, especially serious cardiotoxicity and this stimulated the search for new anthracyclines with improved pharmacological profiles1-3. In our group, nitroxy radicals were first introduced to daunomycin and two spin labeled daunomycin derivatives have been reported recently4. Now we reported other three new spin la…     

Novel Synthesis of 5‐Substituted‐3‐phenylindole‐2‐(1,2,4‐triazole) Derivatives

Various substituted 3‐phenylindole 2‐carboxylates (1a–c) were prepared according to the literature methods. These carboxylates (1a–c) on reaction with thiosemicarbazide yielded 5‐substituted‐3‐phenylindol‐2‐(1,2,4‐triazole‐3‐thione) (2a–c) on refluxing in pyridine for 8 h. The 5‐substituted‐3‐phenylindole‐2‐[1,2,4‐triazolo‐3‐thioacetic acid] (3a–c) were prepared from 5‐substituted‐3‐phenyl indole‐2‐[1,2,4‐triazole‐3‐thione] (2a–c) on reaction with an appropriate alkylating agent and sodium acetate in acetic acid. Further, (3a–c) were reacted with acetic anhydride to bring about a cyclocondensation reaction to yield 5‐substituted‐3‐phenylindol‐2‐thiazolo(2,3‐b)‐triazole (4a–c). The 5‐substituted‐3‐phenylindole‐2‐[1,2,4‐triazolo‐3‐acetic acid] (3a–c) were reacted with o‐phenylenediamino dihydrochloride in ethylene glycol to yield 5‐substituted‐3‐phenylindole‐1,2,4‐triazolo‐3′‐yl‐thiomethyl)benzimidazoles (5a–c).     

Convenient Synthesis of Bis（oxazoline） Dicarboxylate Derivatives

The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated.Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivatives,which can not be obtained by the general method using MsC1 and Et3N as dehydrating cyclization reagent.