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.     

Convenient Method for Synthesis of Substituted 2‐Amino‐2‐chromenes

Some substituted 2‐amino‐2‐chromenes were synthesized by the reaction of arylidenemalononitriles with 1‐naphthol or 2‐naphthol in the presence of sodium hydroxide as catalyst under solvent‐free condition.     

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.     

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.     

Efficient and Simple Synthesis of Substituted 3‐Phenyl‐7‐methoxybenzopyrans as Pseudo‐Vitamin‐D3 Analogs

An efficient and simple synthesis of substituted 3‐phenyl‐7‐methoxybenzopyrans as pseudo‐vitamin‐D₃ analogs in good yields under mild reaction conditions is described.     

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.     

Synthesis of Some 3‐Substituted Isochromen‐1‐ones

An alternative method for the synthesis of 3‐substituted isocoumarins from homophthalic acid and ester is described.     

Efficient Synthesis of N‐Cyano α and β‐Amino Esters

A versatile method for the synthesis of N‐cyano α and β‐amino esters is described. Reaction of different amino esters with cyanogen bromide in dry ether gave the corresponding N‐cyano α and β‐amino esters in excellent yields.     

An Efficient Synthesis of Heterocyclic Substituted Ureidoalkylphosphonates

Inarecentreport',a-aminoalkylphosphonateswithpyrazoIemoietyshowedverygoodinhibitoryeffectsagainstplantvirus.Inaddition,a-aminoalkylphosphonicacidsserveforinhibitingenZymeactivity,bacterialgrowthandinagrochemistryasantifungalagents,herbicidesandplantregulators'.Thereforeconsideringthewideapplicationsofsuchcompoundsandthebioactivitiesofheterocycliccompoundsandureaderivatives,wedesignedtosynthesizealargevarietyofheterocyclicsubstitutedureidoalkylphosphonates3.Thereportedmethodforsynthesisofsubst…     

First Synthesis of N‐Substituted Amino and N‐Sulfonylaminated Methylthiopyrimidines: Reaction of Dimethyl N‐Cyanodithioiminocarbonate With Substituted Hydrazides

A novel and efficient method for the synthesis of a new variety of methylsulfanylpyrimidines by the reaction of dimethyl N‐cyanodithioiminocarbonate with substituted hydrazides. The synthetic potential of the method is demonstrated.     

Zinc Hydroxyapatite–Catalyzed Efficient Synthesis of 5‐Substituted 1H‐Tetrazoles

Zinc hydroxyapatite (ZnHAP) is an effective heterogeneous catalyst for the (2+3)‐cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles in good yields. The catalyst is recovered and reused for several cycles with consistent activity.     

Efficient One‐Pot Synthesis of 2‐Amino‐4,6‐diarylbenzene‐1,3‐dicarbonitrile under Solvent‐Free Conditions

A facile parallel synthesis of 2‐amino‐4,6‐diarylbenzene‐1,3‐dicarbonitrile derivatives via a one‐pot reaction of aromatic aldehydes, aromatic ketone, and malononitrile under solvent‐free conditions has been developed. This new protocol has the advantages of shorter time, higher yields, lower cost, and environmental friendliness.     

Synthesis of Terminal Amino Substituted Cyclopentadienyl Titanium Complexes

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Efficient Synthesis of Highly Substituted Furan,Thiophene, Pyrrole and 2‐Aminothiazole Derivatives

Ethyl cyanoacetate dimer (1) undergoes bromination with N‐bromosuccinimide (NBS) to afford 3‐amino‐4‐bromo‐2‐cyano‐pent‐2‐enedioic acid diethyl ester (2). This bromo derivative reacts with potassium carbonate, sodium hydrogen sulfide, aromatic amines, ammonium thiocyanate, thiourea, N‐phenylthiourea, and thiosemicarbazide to afford highly substituted furan, thiophene, pyrrole, and 2‐aminothiazole derivatives. Mechanistic explanations as well as structure elucidations are discussed.     

Catalyst‐free Efficient Synthesis of 3‐Thio‐2‐deoxysugar Derivatives in Water

3‐Thio‐ and 3‐dithiocarbamoyl‐2‐deoxy carbohydrate derivatives have been synthesized using water as solvent without using a catalyst. In most of the cases yields obtained were excellent.     

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 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).     

Synthesis of N‐Substituted 4,6‐Dimethyl‐3‐cyano‐2‐pyridones Under Microwave Irradiation

N‐substituted 4,6‐dimethyl‐3‐cyano‐2‐pyridones have been prepared from acetylacetone, N‐substituted cyanoacetamide, and pyperidine as catalyst under microwave irradiation without solvent. The rapid and simple method produced pure products in high yields.     

Facile and Efficient Synthesis of Substituted 1,4‐Dithiafulvalenes from β‐Dicarbonyl Compounds

A facile and efficient synthetic route to substituted 1,4‐dithiafulvalenes has been developed. The precursors 2 may be easily prepared from the reactions of β‐dicarbonyl compounds 1 with CS₂ and 1,2,3‐tribromopropane under mild conditions. The elimination of HBr of 2 in basic media furnishes corresponding acetyl substituted 1,4‐dithiafulvalenes 3 in 85–93% yields. The aldol condensation reaction of 2 with various arylaldehydes affords alkenoyl substituted 1,4‐dithiofulvalenes 4 in high to excellent yields.