The Current Status of Heterocyclic Combinatorial Libraries

DMAP as a new efficient catalyst for the one-pot synthesis of condensed phthalazines

A new, convenient, and efficient method for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones is developed starting from phthalhydrazide, aromatic aldehydes, and malononitrile using 4-N,N-dimethylaminopyridin as catalyst. This modified route provides much higher yields and a simple work-up procedure of products. Also this methodology is of interest due to the use of ethanol as a solvent without use of any toxic metals as catalyst, thus minimizing the cost, the operational hazards, and environmental pollution.

Stereoselective cascade assembling of benzylidenecyanoacetates and 1,3-dimethylbarbituric acid into (1R*,2S*)-1-cyano-5,7-dialkyl-4,6,8-trioxo-2-aryl-5,7-diazaspiro[2.5]octane-1-carboxylates

A new stereoselective cascade reaction of benzylidenecyanoacetates and 1,3-dimethylbarbituric acid by the action of bromine in the presence of a base into substituted (barbituric acid)-5-spirocyclopropanes is described. The yields are in the range of 60%–75%. Nuclear magnetic resonance (NMR) studies indicate that this cascade transformation results in the stereoselective formation of spiro products with trans-configuration of aryl and alkoxycarbonyl substituents in the cyclopropane ring. The products are a perspective class of compounds with prominent pharmacological and physiological activity.

Rhodium-catalyzed malonation of 2-arylquinazolines with 2-diazomalonates: double C–H functionalization

Herein, rhodium-catalyzed malonation of 2-arylquinazolines with diazomalonates was described.

Solid-Phase Synthesis of 1,3,4-Thiadiazole Derivatives via Desulfurative Cyclization of Thiosemicarbazide Intermediate Resin

A 1,3,4-thiadiazole library was constructed by solid-phase organic synthesis. The key step of this solid-phase synthesis involves the preparation of polymer-bound 2-amido-5-amino-1,3,4-thiadiazole resin by the cyclization of thiosemicarbazide resin using p-TsCl as the desulfurative agent, followed by the functionalization of the resin by alkylation, acylation, alkylation/acylation, and Suzuki coupling reactions. Both the alkylation and acylation reactions chemoselectively occurred at the 2-amide position of 2-amido-5-amino-1,3,4-thiadiazole resin and the 5-amine position of 2-amido-5-amino-1,3,4-thiadiazole resin, respectively. Finally, these functionalized 1,3,4-thiadiazole resins were treated with trifluoroacetic acid in dichloromethane, affording diverse 1,3,4-thiadiazole analogs in high yields and purities. The 1,3,4-thiadiazole analogs show a different distribution of physicochemical and biological properties compared with our previously constructed 1,3,4-oxadiazole and 1,3,4-thiadiazole libraries in a range of orally available drug properties.

An Improved Procedure for the Three-Component Synthesis of 1H-Pyrazolo[1,2-B]Phthalazine-5,10-Dione Derivatives Using Basic Ionic Liquid

An efficient and green method for the synthesis of 1 H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives has been achieved through the one-pot, three-component condensation of aromatic aldehydes, malononitrile or ethyl cyanoacetate, and phthalhydrazide in the presence of 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH) as catalyst in EtOH. This reaction does not involve any hazardous organic solvent and toxic catalyst. The ionic liquid can be recovered and recycled for subsequent reactions. Moreover, this protocol has the advantages of easy work-up, short reaction time, mild reaction conditions and environmentally benign procedures compared with the reported methods.

Iodine-mediated synthesis of heterocycles via electrophilic cyclization of alkynes

Syntheses of heterocyclesvia5-exoor 6-endo-digiodocyclizations from alkynes.

Diastereoselective synthesis of cyclopentene spiro-rhodanines containing three contiguous stereocenters via phosphine-catalyzed [3 + 2] cycloaddition or one-pot sequential [3 + 2]/[3 + 2] cycloaddition

5-Spiro-cyclopentene-rhodanine derivatives have been synthesized through two different diastereoselective phosphine-catalyzed cascade reactions in excellent diastereoselectivities and good to excellent yields.

A Highly Efficient Diversification of 2-Amino/Amido-1,3,4-oxadiazole and 1,3,4-Thiadiazole Derivatives via Reagent-Based Cyclization of Thiosemicarbazide Intermediate on Solid-Phase

A 2-amino/amido-1,3,4-oxadiazole and 1,3,4-thiadiazole library has been constructed on solid-phase organic synthesis. The key step on this solid-phase synthesis involves the preparation of polymer-bound 2-amino-1,3,4-oxadiazole and 1,3,4-thiadiazole core skeleton resin by cyclization of thiosemicarbazide with EDC·HCl and p-TsCl, respectively. The resulting core skeleton undergoes functionalization reaction with various electrophiles such as alkyl halides, and acid chlorides to generate N-alkylamino and N-acylamino-1,3,4-oxadiazole, and 1,3,4-thiadiazole resin, respectively. Finally, the 2-amino and 2-amido-1,3,4-oxadiazole and 1,3,4-thiadiazole library was then generated in good yields and high purities by cleavage of the respective resin under trifluoroacetic acid(TFA) in dichloromethane(DCM). The constructed library shows reasonable, oral bioavailability drug properties as determine by using the Lipinski's Rule and similar parameters.

Ceria-Vanadia/Silica-Catalyzed Cascade for C-C and C-O Bond Activation: Green One-Pot Synthesis of 2-Amino-3-cyano-4H-pyrans

We designed a ceria-vanadia/silica (Ce-V/SiO2) heterogeneous catalyst and used it for the green and efficient synthesis of 2-amino-3-cyano-4H-pyran derivatives. The green reaction was a multicomponent one-pot condensation of 5,5-dimethylcyclohexane-1,3-dione, aromatic aldehyde, and malononitrile in an eco-compatible solvent (ethanol). The catalyst was synthesized and fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The reported procedure offers a number of advantages including decreased reaction times, mild conditions, high yields, operational simplicity, and environmentally benign and simple work-up procedures. Furthermore, the catalyst is economical, fully recyclable, and reusable for over five runs while preserving its high activity. The synthesized 2-amino-3-cyano-4H-pyran products can later be used for pharmaceutical purposes.

Catalyst-free tandem Knoevenagel-Michael reaction of aldehydes and pyrazolin-5-one: fast and convenient approach to medicinally relevant 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol)s

Catalyst-free tandem Knoevenagel-Michael reaction of aryl aldehydes and two equivalents of 3-methyl-1-phenyl-2-pyrazolin-5-one results in fast (5 min) formation of medicinally relevant 4,4′-(arylmethylene)bis(1

A mesoporous SBA-15 silica catalyst functionalized with phenylsulfonic acid groups (SBA-15-Ph-SO3H) as a novel hydrophobic nanoreactor solid acid catalyst for a one-pot three-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones and triazolo[1,2-a]indazole-triones

Phenyl sulfonic acid functionalized mesoporous SBA-15 silica was prepared through the silanization of activated mesoporous SBA-15 with diphenyldichlorosilane followed by silylation and sulfonation.

Diversity oriented synthesis and IKK inhibition of aminobenzimidazole tethered quinazoline-2,4-diones, thioxoquinazolin-4-ones, benzodiazepine-2,3,5-triones, isoxazoles and isoxazolines

The derivatization of resin-bound aminobenzimidazole toward the parallel solid-phase synthesis of aminobenzimidazole tethered pharmacologically important heterocycles such as quinazoline-2,4-diones, thioxoquinazolin-4-ones, benzodiazepine-2,3,5-triones, isoxazoles and isoxazolines is reported. All the compounds were tested for IKK inhibition. Only one compound elicited significant inhibition of IKKε, TBK-1 and IKK2.

DABCO-functionalized mesoporous SBA-15: an efficient and recyclable catalyst for the synthesis of spiro-pyranoxindoles as antioxidant agents

A series of spiro-pyranoxindole derivatives were prepared in good yields via a three-component reaction of isatins with activated methylene reagents and kojic acid using 1,4-diazabicyclo[2.2.2]octane (DABCO) immobilized on mesoporous SBA-15 as a heterogenized organocatalyst in aqueous media. The synthesized compounds were evaluated for their antioxidant activity by a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay.

An Efficient Three-Component Synthesis of Trispiropyrrolidines Derivatives through 1,3-Dipolar Cycloaddition Reaction

The synthesis of novel trispiropyrrolidine derivatives has been achieved by a one-pot, three-component 1,3-dipolar cycloaddition reaction of 3-aryl-5-arylmethylenespiro[indole-3’,2-[1,3]thiazolane]-2'(1 H),4-dione, isatin and sarcosine in refluxing toluene which produced the corresponding cycloadducts in good yields. The structures were determined by 1H NMR, IR and elementary analysis.