C. Naga Raju

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, spectral characterization and biological evaluation of phosphorylated derivatives of galanthamine

A series of novel phosphorylated derivatives of galanthamine 6-11 and 12-17 were synthesized in two step process with high yields. In the first step galanthamine 1 was reacted with bis (2-chloroethyl) phosphoramidic dichloride 2/4-nitrophenyl phosphorodichloridate 3 in presence of triethylamine (TEA) in dry tetrahydrofuran (THF) yielded the intermediates 4/5. They were further reacted with various compounds like 2-aminoethanol, ethyleneglycol, ethylenediamine, 2-aminoethanethiol, 2-hydroxyethanethiol, monopotassium dihydrogenphosphate to obtain the title compounds 6-11 and 12-17. The title compounds showed promising antimicrobial, antioxidant activities and was greatly influenced by the presence of different bioactive groups.

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, 1H, 13C, 31P NMR ANALYSIS, AND INSECTICIDAL ACTIVITY OF MEMBERS CONTAINING EXTERNAL P—O OR P—N BONDS IN 6-SUBSTITUTED-2,10-DICHLORO-12H-DIBENZO[d,g][1,3,2]DIOXAPHOSPHOCIN 6-OXIDES

Abstract The synthesis of novel 6-substituted-2,10-dichloro-12H-dibenzo[d,g][1,3,2]dioxaphosphocin 6-oxides is described along with IR, 1H, 13C, and 31P NMR spectral data. Phosphorus couplings of 5 J PH, 2 J POC and 3 J POCC were determined. An appraisal of the data in total did not allow unequivocal differentiation between a boat-boat, boat-chair, distorted boat, or twist boat conformation for the eight-membered ring of the dioxaphosphocin 6-oxides. A few members of this family were evaluated for toxicity in the insect P. americana.

Synthesis and TGA Evaluation of Novel Triphosphate Esters

Several new substituted organo tri/thiotriphosphate esters were synthesized by condensing cyclic oxaza/dioxaphosphorochloridates/ thiochloridates with K2HPO4 in the presence of tetrabutylammonium iodide. The functionality on the phosphate was systematically changed by synthesis, thus allowing evaluation and comparison of a range of phosphate esters with highly varied structural features. They were subjected to thermogravimetric analysis, derivative thermogravimetric analysis, and differential thermal analysis to assess their thermal stability and potential use as flame retardants. It has been found that their thermal degradations, being highly complex and dependent upon a number of molecular structural features, are difficult to rationalize on simple rules.

Microwave Assisted Synthesis of Biologically Active α-Aminophosphonates Catalyzed by Nano-BF3·SiO2 under Solvent-Free Conditions

Abstract An efficient and high-yield synthesis of a class of new α-aminophosphonate derivatives as diethyl α-aryl/2-thienyl-α-[2-(phenylthio)phenylamino]methylphosphonates 6a–j in short reaction times from three component coupling reactions (Kabachnik-Fields reaction) of 2-aminodiphenylsulfide 3, substituted phenyl/heterocyclic aldehydes 4a–j, and diethyl phosphite 5 is reported. The reaction proceeds smoothly in the presence of the catalyst, nano-silica-supported boron trifluoride (BF3·SiO2) without using solvent under microwave irradiation. The title compounds were tested for in vitro antibacterial and antifungal activities at concentrations of 100 and 200 μg/disc. Minimum inhibitory concentrations (MICs) were also examined. Supplementary materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text, figures and tables. GRAPHICAL ABSTRACT

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

Polyethylene Glycol–Promoted Dialkyl, Aryl/Heteroaryl Phosphonates

Abstract A new, straightforward polyethylene glycol–promoted method for Michaelis–Arbuzov rearrangement has been described.

Synthesis, spectral characterization and bioactivity evaluation of novel α-aminophosphonates

GRAPHICAL ABSTRACT ABSTRACT A facile synthesis of novel α-aminophosphonates 5a-j was accomplished by condensation of imines (3a-j) with diethyl phosphite (4) in ethanol at 50–60°C using easily recoverable and reusable catalyst, tetramethyl guanidine (TMG) via pudovik reaction in high yields. All the title compounds were characterized by spectral and elemental analysis. They were further screened for their abilities towards in vitro antibacterial, antifungal and antioxidant activities. The compounds 5g, 5d, 5f exhibited good antibacterial and antifungal activities compared to the standard bactericide, Penicillin and fungicide, Griseofulvin, respectively. The compounds 5h, 5i, 5g, and 5c exhibited good antioxidant activity compared to the standard ascorbic acid.

Syntheses and Antimicrobial Activity of Some Novel 6‐Substituted Dibenzo[d, f][1,3,2]dioxaphophepin‐6‐oxides, Sulfides, and Selenides

Abstract 6‐Substituted‐dibenzo[d, f][1,3,2]dioxaposphepin‐6‐oxides, sulfides, and selenides (5a–i, 6a–d, and 7a–d) were synthesized by reacting 2,2′‐biphenol (1) with phosphorus tribromide in the presence of triethylamine at 0–30°C and subsequent reaction of the monobromide (2) with different Grignard reagents (3) at room temperature. The products (4) were converted to corresponding oxides, sulfides, and selenides (5a–i, 6a–d, and 7a–d) by oxidation with H2O2 at room temperature and refluxing with sulfur and selenium respectively. The chemical structures of all the products were confirmed by analytical, IR, NMR (1H, 13C, and 31P), and mass spectral data. Most of these compounds exhibited moderate antimicrobial activity.