K. Uma Maheswara Rao

The Synthesis and Bioactivity of Dimethyl (2,3- Dihydrobenzo[b][1,4]Dioxin-6-Yl)(Aryl Amino)Methylphosphonates

Abstract A new series of α-aminophosphonates have been synthesized by a one-pot three-component reaction of 2,3-dihydrobenzo[b][1,4]dioxine-6-carbaldehyde, various amines, and dimethyl phosphite by using nano-TiO2 as a catalyst under solvent-free conditions at 50°C. The major advantages of the present method are high yields, short reaction times, recyclable catalyst, and solvent-free reaction conditions. Among these new structurally diversified set of α-aminophosphonates, dimethyl (2,3-dihydrobenzo[b][1,4]dioxin-6-yl)(3-nitrophenylamino) methylphosphonate and dimethyl (2,3-dihydrobenzo[b][1,4]dioxin-6-yl)(4-fluoro-3-nitro-phenyl-amino) methylphosphonate have shown higher antioxidant activity in diphenyl picryl hydrazyl (DPPH) scavenging, reducing power assay, and lipid peroxidation methods. GRAPHICAL ABSTRACT

Synthesis and Bioassay of Alkyl-2-[(5,6-dimethyl-2-sulfido-1,3,4,7,2-dioxadiazaphosphepin-2-yl)amino] Alkyl/Aryl Esters

Synthesis of alkyl-2-[(5,6-dimethyl-2-sulfido-1,3,4,7,2-dioxadi- azaphosphepin-2-yl)amino]alkyl/aryl esters (3a–j) was accomplished via a two-step process. It involves the prior preparation of monochloride intermediate (2) and its subsequent reaction with the amino acid esters in dry tetrahydrofuran in the presence of triethylamine at reflux temperature. These compounds were characterized by infrared (IR), 1H-, 13C-, and 31P-nuclear magnetic resonance (NMR), and mass and elemental analysis and were found to exhibit potent antimicrobial activity.

An improved method for the preparation of alkyl/arylurea derivatives using chlorocarbonylsulfenyl chloride as carbonylating agent

A convenient procedure has been developed for preparation of amine-substituted or monomethylamine-substituted alkyl/arylurea derivatives. The method comprises two steps—reaction of an alkyl/aryl amine with chlorocarbonylsulfenyl chloride in a non-polar solvent to produce an alkyl/arylcarbonylsulfenyl chloride, then reaction of this alkyl/arylcarbonylsulfenyl chloride with ammonia or monomethylamine in a two-phase reaction with a phase-transfer catalyst, to produce the corresponding alkyl/aryl-substituted urea.Graphical AbstractR1, R2: H, methyl, ethyl, propyl, butyl, benzyl, cyclohexyl; R3: H, methyl. A simple, one-pot, rapid, efficient, cost-effective, non-phosgene route for synthesis of alkyl/arylurea derivatives starting with the corresponding alkyl/aryl amine and chlorocarbonylsulfenyl chloride.

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.