Ru(II)-Catalyzed C-H Activation and Annulation Reaction via Carbon-Carbon Triple Bond Cleavage.

An unprecedented Ru(II)-catalyzed C-H activation and annulation reaction, which proceeds via C-C triple bond cleavage, is reported. This reaction of 2-phenyldihydrophthalazinediones with alkynes, which works most efficiently in the presence of bidented ligand 1,3-bis(diphenylphosphino)propane, affords good yields of substituted quinazolines.

Facile Diversity-Oriented Synthesis of Polycyclic Pyridines and Their Cytotoxicity Effects in Human Cancer Cell Lines.

A three-component cascade method has been developed for the direct synthesis of polysubstituted pyridines. This strategy provides a very convenient route to pyridines using a variety of ß-bromo-α,ß-unsaturated aldehydes, 1,3-diketones, and ammonium acetate without any additional catalyst or metal salt under mild conditions. A variety of ß-ketoesters and 4-hydroxycoumarin were also used instead of 1,3-diketones for the diverse synthesis of polycyclic pyridines. One of the synthesized pyridines has been unambiguously established by a single crystal XRD study. All of the synthesized pyridine derivatives were evaluated for their antiproliferative properties in vitro against the human cancer cell lines HeLa, Me180, and ZR751. Compounds 4{4,1} and 4{2,4} showed significant cytotoxicity in the human breast cancer cell line ZR751 and cervical cancer cell line Me180, respectively, and a few other compounds were found to have moderate activities.

Carbon-Carbon Bond Cleavage Reaction: Synthesis of Multisubstituted Pyrazolo[1,5-a]pyrimidines.

A new carbon-carbon bond cleavage reaction was developed for the efficient synthesis of multisubstituted pyrazolo[1,5-a]pyrimidines. This base induced reaction of 1,3,5-trisubstituted pentane-1,5-diones and substituted pyrazoles afforded good yields of the pyrazolo[1,5-a]pyrimidines.

Ruthenium-catalyzed decarbonylative addition reaction of anhydrides with alkynes: a facile synthesis of isocoumarins and α-pyrones.

A novel ruthenium catalyzed straightforward and efficient synthesis of isocoumarin and α-pyrone derivatives has been accomplished by the decarbonylative addition reaction of anhydrides with alkynes under thermal conditions.

An efficient route for annulation of pyrimidines to steroids and non-steroids via a base catalyzed one-pot three component reaction.

A facile strategy for the synthesis of steroidal A- and D-ring fused pyrimidines has been accomplished in high yields via a one-pot reaction of steroidal ketones, aromatic aldehydes and amidine derivatives in presence of potassium tert-butoxide in refluxing ethanol. The generality of the reaction was also extended to non-steroidal ketones.

Synthesis of steroidal and nonsteroidal vicinal heterocyclic alcohols, N-(1-cycloalkenyl)heterocycles and their antibacterial studies.

A solvent free steroidal and nonsteroidal epoxide ring opening reaction by nitrogen containing heterocycles under microwave irradiation is described. Some of the epoxide ring opening compounds were converted to their corresponding N-(1-cycloalkenyl)heterocycles via an acid catalyzed dehydration reaction. The antimicrobial activities of the epoxide ring opening compounds and N-(1-cycloalkenyl)heterocyclic compounds were tested by agar diffusion assay. Compounds 6, 9-12, 24 and 27 showed moderate inhibition against the growth of pathogenic bacteria Escherichia coli, Pseudomonas syringae, Bacillus subtilis, Proteus vulgaris and Staphylococcus aureus.

Palladium-catalyzed multi-component synthesis of steroidal A- and D-ring fused 5,6-disubstituted pyridines under microwave irradiation.

The preparation of steroidal A-, D-ring fused 5,6-disubstituted pyridines and nonsteroidal substituted pyridines is described form Pd(OAc)2 catalyzed multi-component reaction of steroidal/nonsteroidal ß-halovinyl aldehyde, alkyne and benzylamine in solvent-free condition under microwave irradiation.

Microwave-promoted and Lewis acid catalysed synthesis of steroidal A- and D-ring fused 4,6-diarylpyridines.

The preparation of novel steroidal heterocycles containing 4,6-diaryl substituted pyridine moiety fused to the 2,3- and 16,17-positions of the steroid nucleus is described. The Michael reaction of steroidal ketones (1a, 1b and 1c) with in situ generated chalcones provided the intermediates 3,5-diaryl-1,5-dicarbonyl steroidal derivatives (4a-s). Subsequently, the intermediates 4a-s were converted to the pyridine derivatives (5a-s) by solid phase reaction with urea in presence of BF3.OEt2 as the catalyst under microwave irradiation. All the synthesized heterosteroids are new compounds and are currently being evaluated for their biological activities.

A microwave promoted solvent-free approach to steroidal quinolines and their in vitro evaluation for antimicrobial activities.

The preparation of A-ring and D-ring fused steroidal quinolines is described from one-pot reaction of steroidal ß-bromovinylaldehydes and arylamines in solvent-free and catalyst-free condition under microwave irradiation. The antimicrobial activities of the compounds were tested by agar diffusion assay and broth macro dilution method. Compounds 7a, 7e and 7g-h showed promising in vitro activity when tested against fungal pathogen Aspergillus niger whereas compounds 7e-h and 7j showed promising activity when tested against fungal pathogen Candida albicans. Compounds 7c and 7f showed potent inhibition against the growth of Gram negative bacteria Pseudomonas aeruginosa and compounds 7e, 7g-h and 7j inhibited the growth of tested Gram positive bacteria Bacillus subtilis and Staphylococcus aureus.

A convenient strategy for the annulation of aryl scaffold to A/B-ring steroids under microwave irradiation.

A facile strategy for the annulation of 2,6-dicyanoaniline moiety to steroidal A/B-ring is described from base catalyzed and microwave-promoted reaction of steroidal 3-keto-2-hydroxymethylenes with malononitrile in high yields. The generality of the reaction has been extended to non-steroidal cyclic and aliphatic ketohydroxylmethylenes.

Zinc triflate: a highly efficient reusable catalyst in the synthesis of functionalized quinolines via Friedlander annulation.

An environmentally friendly and highly efficient procedure for the preparation of quinolines and fused polycyclic quinolines has been developed by a simple Friedlander annulation reaction of 2-aminoaryl ketone with carbonyl compounds in presence of zinc triflate under microwave irradiation and solvent-free conditions. The reaction also proceeds effectively when In(OTf)(3) was used in lieu of Zn(OTf)(2) as the catalyst. The catalyst can be recovered after the reaction and reused efficiently in subsequent runs.

A facile three-component solid phase synthesis of steroidal A-ring fused pyrimidines under microwave irradiation.

The preparation of ring-A fused pyrimidines at the steroidal 2,3-position is herein described. The novel steroidal pyrimidines were prepared from the solid phase three-component reaction of 2-hydroxymethylene-3-keto steroids, arylaldehydes and ammonium acetate under microwave irradiation.

Convenient preparation of A-ring fused pyridines from steroidal enamides.

A facile strategy for the preparation of A-ring fused pyridosteroids has been accomplished in high yields by the reaction of Vilsmeier reagent (chloromethyleneiminium salt) with steroidal A-ring enamides (2- and 3-ene) under thermal conditions. The structure of 6'-chloro-5alpha-cholest [3,2-b]pyridine was determined by X-ray analysis.

A microwave promoted and Lewis acid catalysed solventless approach to 4-azasteroids.

The preparation of 3-oxo-4-azasteroid from A-nor-3,5-secosteroid-3-oic acid is described in a solventless condition catalysed by Lewis acid under microwave irradiation. We utilized urea as an environmentally benign source for the generation of ammonia for the aza cyclization reaction.

Microwave promoted one-pot synthesis of novel A-ring fused steroidal dehydropiperazines.

The preparation of ring-A fused steroidal dehydropiperazine at the 3,4-position is herein described. The novel steroidal dehydropiperazines were prepared from the annulation reaction of ethylenediamine with 3-keto-4-en steroids in a one-pot reaction under microwave irradiation. The key step involves base catalysed aerial oxidation of the C-6 methylene group followed by cyclocondensation of ethylenediamine via Michael addition reaction.

A novel microwave-mediated one-pot synthesis of indolizines via a three-component reaction.

[reaction: see text] The microwave-mediated three-component reaction of acyl bromide, pyridine, and acetylene is catalyzed by basic alumina to give corresponding indolizines in excellent yields in a one-pot reaction.