G. Rajeshwar Reddy

Pd-mediated new synthesis of pyrroles: their evaluation as potential inhibitors of phosphodiesterase 4

A sequential Pd-mediated multi-component reaction followed by Suzuki or Heck or Sonogashira coupling in a single pot has been developed for the synthesis of functionalized pyrroles as potential inhibitors of PDE4.

Iodine catalyzed four-component reaction: a straightforward one-pot synthesis of functionalized pyrroles under metal-free conditions

An iodine-catalyzed four-component reaction of 1,3-dicarbonyl compounds, amines, aldehydes and nitroalkanes afforded polysubstituted pyrroles under a metal free condition. Simplicity, low cost and good yields are the key features of this methodology. The mechanism of this four component process is discussed and structural elaboration of one of the compounds synthesized using Suzuki and Sonogashira coupling is presented.

Construction of a quinoline ring via a 3-component reaction in water: crystal structure analysis and H-bonding patterns of a 2-aryl quinoline

Montmorillonite K-10 mediated green and one-pot synthesis of 2-substituted quinolines has been accomplished via a 3-component reaction of aniline, aldehydes and ethyl 3,3-diethoxypropionate in the presence of air oxygen in water. The crystal structure analysis and H-bonding patterns of one compound prepared are presented.

Yb(OTf)3 mediated MCR: a new and regioselective approach towards polysubstituted pyrroles of pharmacological interest

A regioselective synthesis of 1,2,3,4-tetrasubstituted pyrroles has been achieved via Yb(OTf)3-mediated 3-component reaction of amines, a 1,3-diketone and phenacyl bromide in a single pot. Yb(OTf)3 was identified as a reusable catalyst and a number of pyrrole derivatives were prepared by using this strategy. Single crystal X-ray diffraction study of a representative compound confirmed the substitution pattern on the central pyrrole ring. The crystal structure analysis of the same compound indicated the presence of a sheet-like molecular arrangement along the bc-plane present in the molecule. A possible mechanism for the regioselective formation of 1,2,3,4-tetrasubstituted pyrrole rings is discussed. A number of compounds synthesized showed PDE4 inhibitory properties when tested in vitro and two of them were identified as inhibitors of further interest.

A Pd-mediated new strategy to functionalized 2-aminochromenes: Their in vitro evaluation as potential anti tuberculosis agents

A multi component based synthesis involving palladium catalyzed C-C bond forming reaction has been developed as a new strategy to access systematically modified functionalized 2-aminochromenes. This MCR involves the use of bromobenzaldehyde as a key component and is highlighted by generating a new compound library. Many of these compounds showed Mycobacterium tuberculosis H37Rv chorismate mutase inhibiting properties in vitro representing the lead example of chorismate mutase inhibition by heteroarene based compounds.

Cu-catalyzed coupling-cyclization in PEG 400 under ultrasound: a highly selective and greener approach towards isocoumarins

The combination of CuI–K2CO3-PEG 400 facilitated the coupling-cyclization of o-iodobenzoic acid with terminal alkynes under ultrasound, affording a greener and practical approach towards 3-substituted isocoumarins with remarkable regioselectivity. This inexpensive and Pd and ligand free methodology gave rise to various isocoumarins of potential pharmacological interest.

Montmorillonite K-10 catalyzed green synthesis of 2,6-unsubstituted dihydropyridines as potential inhibitors of PDE4.

Montmorillonite K-10 mediated MCR of anilines, arylaldehydes and ethyl-3,3-diethoxypropionate in water afforded 2,6-unsubstituted dihydropyridines depending on the nature of anilines employed. A variety of dihydropyridines were prepared by using this green methodology in good yields and montmorillonite K-10 was found to be an inexpensive and reusable catalyst. The structure elaboration of a representative compound was carried out under Heck conditions. Some of the compounds synthesized showed significant inhibition of PDE4B when tested in vitro. Docking studies indicated that one of the ester moieties of these compounds played a key role in their interactions with the PDE4B protein.

(Pd/C-mediated)coupling–iodocyclization–coupling strategy in discovery of novel PDE4 inhibitors: a new synthesis of pyrazolopyrimidines

Pyranones fused with a pyrazolopyrimidine moiety were prepared via regioselective construction of pyranone ring using (Pd/C-mediated)coupling–iodocyclization followed by Sonogashira/Heck/Suzuki reactions. The pyrazolopyrimidine based reactant required was obtained via a new H3PO3 mediated condensation reaction. This strategy has led to the discovery of a novel and potentially safe PDE4 inhibitor.

FeF3-catalyzed MCR in PEG-400: ultrasound assisted synthesis of N-substituted 2-aminopyridines

FeF3 catalyzed four component reaction under ultrasound irradiation was explored for the first time to prepare N-substituted 2-aminopyridines in good yields. The methodology involved the use of readily available starting materials and PEG-400 under mild reaction conditions in the presence of air. The one-pot methodology afforded a range of compounds of pharmacological interest indicating its potential in generating a diversity based library of small molecules useful for medicinal chemistry and drug discovery.