Rama Krishna Peddinti

Iodine catalyzed cross-dehydrogenative C–S coupling by C(sp2)–H bond activation: direct access to aryl sulfides from aryl thiols

A novel, efficient and unprecedented green protocol for the formation of C–S bonds has been developed under metal-free conditions. This protocol involves the synthesis of aryl sulfides through the cross-dehydrogenative coupling of readily available aryl thiols with electron-rich species under solvent-free conditions and the corresponding aryl sulfides are obtained in high to quantitative yields. A catalytic amount of inexpensive and non-toxic iodine drives the reaction and no exclusion of air and expensive ligands is required.

An expeditious, highly efficient, catalyst-free and solvent-free synthesis of nitroamines and nitrosulfides by Michael addition

A simple, atom economical, fast and highly efficient green protocol has been developed for the synthesis of nitroamines and nitrosulfides by the Michael addition of amines and thiols to nitroolefins by simple mixing or grinding. This catalyst-free and solvent-free green approach provided the addition products in quantitative yield within minutes at room temperature. This procedure does not require any water quenches, solvent separations and purification steps such as recrystallization and column chromatography.

Glucosamine-Based Primary Amines as Organocatalysts for the Asymmetric Aldol Reaction

Glucosamine derivatives have been synthesized starting from commercially available N-acetyl-D-glucosamine/glucosamine hydrochloride and have been employed successfully as efficient organocatalysts for the direct asymmetric aldol reaction between cyclohexanone and aryl aldehydes having diversified substituents. Furthermore, the anomeric effect of various groups present at the anomeric position on the catalytic activity of these organocatalysts was also studied.

Introduction of a clean and promising protocol for the synthesis of β-amino-acrylates and 1,4-benzoheterocycles: an emerging innovation

A highly efficient, elegant and simple procedure with exceptionally mild conditions has been proposed for the synthesis of β-amino-acrylate derivatives and an array of biologically and pharmaceutically active benzoheterocycles. The protocol offers a valuable alternative to known methods and will find applications in the field of green synthesis. The regio- and stereo-chemistry of the products were established by IR, NMR and single crystal X-ray analysis.

Reversal of polarity in masked o-benzoquinones: rapid access to unsymmetrical oxygenated biaryls.

An unprecedented diacetoxyiodobenzene induced direct arylation of guaiacol derivatives and electron-rich arenes using a Lewis acid as an activator furnishes unsymmetrical biaryls without prefunctionalization of both coupling partners. The addition of electron-rich arenes on the α-position of electrophilic masked o-benzoquinones in an anti-Michael addition fashion affords the highly oxygenated unsymmetrical biaryls in good to excellent yields.

Chemical generation of o-quinone monoimines for the rapid construction of 1,4-benzoxazine derivatives

Highly reactive o-benzoquinone monoimines were chemically generated and successfully trapped with electron-rich olefins that led to the synthesis of hitherto unknown 1,4-benzoxazine derivatives. This unprecedented transformation was achieved by the oxidation of o-aminophenols bearing appropriate functionality on the arene residue with less expensive hypervalent iodine reagent in the presence of vinylic ethers or thioethers.

Role of isothiocyanate conjugate of pterostilbene on the inhibition of MCF-7 cell proliferation and tumor growth in Ehrlich ascitic cell induced tumor bearing mice.

Naturally occurring pterostilbene (PTER) and isothiocyanate (ITC) attract great attention due to their wide range of biological properties, including anti-cancer, anti-leukemic, anti-bacterial and anti-inflammatory activities. A novel class of hybrid compound synthesized by introducing an ITC moiety on PTER backbone was evaluated for its anti-cancer efficacy in hormone-dependent breast cancer cell line (MCF-7) in vitro and Ehrlich ascitic tumor bearing mice model in vivo. The novel hybrid molecule showed significant in vitro anti-cancer activity (IC50=25 ± 0.38) when compared to reference compound PTER (IC50=65 ± 0.42). The conjugate molecule induced both S and G2/M phase cell cycle arrest as indicated by flow cytometry analysis. In addition, the conjugate induced cell death was characterized by changes in cell morphology, DNA fragmentation, activation of caspase-9, release of cytochrome-c into cytosol and increased Bax: Bcl-2 ratio. The conjugate also suppressed the phosphorylation of Akt and ERK. The conjugate induced cell death was significantly increased in presence of A6730 (a potent Akt1/2 kinase inhibitor) and PD98059 (a specific ERK inhibitor). Moreover, the conjugated PTER inhibited tumor growth in Ehrlich ascitic cell induced tumor bearing mice as observed by reduction in tumor volume compared to untreated animals. Collectively, the pro-apoptotic effect of conjugate is mediated through the activation of caspases, and is correlated with the blockade of the Akt and ERK signaling pathways in MCF-7 cells.

BF3·Etherate-Mediated Friedel–Crafts Arylation of 2-Hydroxy-1,4-benzoxazines: Synthesis of 2-Aryl-1,4-benzoxazine Derivatives

BF3·etherate-mediated carbon-carbon bond formation by the Friedel-Crafts arylation of 2-hydroxybenzoxazine derivatives with various electron-rich arenes is reported. The current protocol provides an easy access for the synthesis of a series of densely substituted 2-aryl-1,4-benzoxazine derivatives under mild conditions.

Hypervalent iodine mediated synthesis of carbamate protected p-quinone monoimine ketals and p-benzoquinone monoketals

A simple and efficient method for the synthesis of p-quinone monoimide ketals and p-benzoquinone monoketals by using a hypervalent iodine reagent, diacetoxyiodobenzene, has been developed. These two types of ketals are achieved from a single starting material by varying the reaction conditions.

S-Arylation of thiols with masked o-benzoquinones: synthesis of alkyl aryl/diaryl sulfides

A novel, efficient, and metal-free C–S bond formation of masked o-benzoquinones with thiols is reported. This protocol involves the synthesis of unsymmetrical alkyl aryl/diaryl sulfides in excellent yields under mild and catalyst-free conditions.