B. Satheesh Krishna

PEG-SO3H catalyzed synthesis and cytotoxicity of α-aminophosphonates

One pot three-component PEG-SO(3)H catalyzed reaction of 4-(Pyridin-4-yl)benzaldehyde and triethyl phosphite with various primary amines afforded α-aminophosphonates with high yields by the Kabachnik-Fields reaction. These new structurally diversified set of α-aminophosphonates (4a-j) were evaluated for their anti-tumor activity on human chronic myeloid leukemia cells (K 562), human colon carcinoma cells (Colo 205) along with non-cancerous human embryonic kidney cells (HEK 293). They showed moderate activity on both cancerous cells and non-cancerous cells.

Synthesis of Schiff's bases in aqueous medium: a green alternative approach with effective mass yield and high reaction rates

Abstract Schiffs bases constitute a class of pharmaceutical and medicinally important molecules. The conventional methods for the synthesis of Schiffs bases require long reaction times and use of organic solvents. We report a novel and eco-friendly condensation reaction method permitting the “green synthesis” of various Schiffs bases by stirring 1,2-diaminobenzene with various aromatic aldehydes in water as solvent. This method is experimentally simple, clean, high yielding, green, and with reduced reaction times. The product is purified by simple filtration followed by washing with water and drying processes.

Synthesis, Antimicrobial, and Antioxidant Activity of New α-Aminophosphonates

Abstract A new class of α-aminophosphonates 2–16 has been synthesized by the reaction of equimolar quantities of Schiffs bases with diethyl/dimethyl/diphenyl phosphite in dry toluene under reflux conditions using tetramethylguanidine (TMG) as a catalyst via Pudovik reaction in high yields (78–89%). The structures of the title compounds have been established by elemental; infrared (IR); 1H-, 13C-, and 31P-NMR; and mass spectral data analyses. They were found to possess significant antimicrobial and antioxidant activity. Supplemental materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT

Ionic Liquid–Promoted Phospha-Michael Reaction: Convenient Access to β-Nitrophosphonates

Abstract A convenient and mild procedure is developed for β-nitrophosphonates via phospha-Michael addition of phosphites to nitrostyrene at room temperature in the presence of 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU)–based ionic liquid [DBUH][OAc]. The operational simplicity, convenient workup, and reusability of the ionic liquid make this method attractive. GRAPHICAL ABSTRACT

Efficient synthesis, antioxidant and antimicrobial profiles of 2-(arylamino)- and 2-(heteroarylamino)- 1,3,4,2λ 5 -dioxazaphosphinin-2-ones

Synthesis of 5,6-diphenyl-6H-1,3,4,2λ5-dioxazaphosphinin-2-ones having an amino substituent at phosphorus atom has been accomplished in two steps. It involves the preparation of 2-chloro intermediate and its subsequent reaction with various aromatic or heterocyclic amines in dry tetrahydrofuran and triethylamine at reflux temperature. These compounds were characterized by IR, 1H, 13C, and 31P NMR spectroscopy and mass spectrometry, and elemental analysis. All the title compounds were screened for antioxidant properties by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay, reducing power assay, and lipid peroxidation assay. The tested compounds exhibited potent dose-dependent in vitro antioxidant activity, as well as a significant antimicrobial activity.

Synthesis, Characterization, and Thermogravimetric Studies of a Phosphorus-Containing Dendron Built from 1,5-Diaminonaphthalene at the Core

Abstract A facile divergent synthesis of a phosphorus-containing dendron containing 1,5-diaminonaphthalene is described. The phosphorus-containing dendron, functionalized with a 1,5-diaminonaphthalene unit at the core and phenolic OH groups grafted at the periphery, has been accomplished in a versatile, simple fashion, using Schiffs condensation and nucleophilic substitution reactions with POCl3, 3-hydroxy-benzaldehyde, 4-hydroxy-benzaldehyde, and 3-amino-phenol iteratively. The structures of intermediate dendrons were characterized by infrared, NMR (1H, 13C, and 31P), liquid chromatography–mass spectrometry, and C, H, N analysis. The structure of the final dendron (6) was confirmed by infrared, NMR (1H, 13C, and 31P), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and C, H, N analysis. The thermal stability and degradation of the resulting final dendron was checked by thermal gravitometric analysis/differential thermal analysis. GRAPHICAL ABSTRACT