Tarun Kumar

Rauhut-Currier reaction of nitroalkenes with vinyl sulfones.

The Rauhut-Currier reaction between nitroalkenes and vinyl sulfones has been successfully carried out for the first time. The reaction proceeds in the presence of an imidazole/LiCl catalyst system in dioxane to provide the adducts possessing a synthetically useful 1-bis-sulfonyl-3-nitroalkene moiety in good to excellent yield. A one-pot transformation of the products to β-sulfonyl-α,β-unsaturated ketoximes has also been demonstrated.

Imidazoles from nitroallylic acetates and α-bromonitroalkenes with amidines: synthesis and trypanocidal activity studies.

Cascade reactions of amidines with nitroallylic acetates and α-bromonitroalkenes provide potentially bioactive imidazoles in good to excellent yields in most cases. While 2,4-disubstituted imidazol-5-yl acetates are formed in the first case, 2,4-disubstituted imidazoles, bearing no substituent at position 5, are the products in the second case. These two series of imidazoles, viz. 2,4,5-trisubstituted and 2,4-disubstituted, were screened for their activity against the protozoan parasite Trypanosoma cruzi which is responsible for Chagas disease. As many as three compounds were as active as the standard benznidazole and two others were 2-3-fold more active highlighting the potential of substituted imidazoles, easily accessible from nitroalkenes, as possible anti-parasitic agents.

One-pot regioselective synthesis of functionalized and fused furans from Morita–Baylis–Hillman and Rauhut–Currier adducts of nitroalkenes

Highly functionalized and fused furans have been synthesized via cascade reactions of Morita–Baylis–Hillman and Rauhut–Currier adducts of nitroalkenes with active methylene compounds. The reactions involving SN2′-intramolecular Michael addition or Michael addition-intra-molecular nucleophilic substitution take place in a regioselective manner to afford synthetically and biologically useful furans in moderate to good yields.

Synthesis of Aminophenanthrenes and Benzoquinolines via Hauser–Kraus Annulation of Sulfonyl Phthalide with Rauhut–Currier Adducts of Nitroalkenes

The Hauser-Kraus reaction of sulfonyl phthalide with nitroalkene derivatives provides access to aminophenanthrenes, including phenanthrene-substituted amino acids and benzoquinolines. The intermediate quinones bearing a key ketoalkyl moiety undergoes facile intramolecular enamine cyclization. Interestingly, enamines derived from primary and secondary amines undergo cyclization via C-centered nucleophilic attack to provide aminophenanthrenes, whereas those derived from ammonia undergo cyclization via N-centered nucleophilic attack leading to benzoquinolines. A one-pot protocol for the direct transformation of phthalides and nitroalkene derivatives to aminophenanthrenes and benzoquinolines has also been developed.

Generation and Trapping of a Cage Annulated Vinylidenecarbene and Approaches to Its Cycloalkyne Isomer

A novel cage-annulated (bis-homocubyl) vinylidenecarbene has been generated and successfully trapped without any intermediacy of its cycloalkyne isomer. The greater kinetic and thermodynamic stability of the vinylidenecarbene vis-à-vis its cycloalkyne isomer has been predicted by DFT B3LYP/6-31G* calculations. The calculated results suggest the prospects of the cycloalkyne becoming amenable for trapping, if generated under suitable experimental conditions, owing to the substantial kinetic energy barrier associated with its possible ring contraction via 1,2-shift to the vinylidenecarbene isomer and marginal ground state energy difference. However, all of our attempts to directly generate and trap the cycloalkyne yielded unsatisfactory results. Attempted generation and trapping of a C2-symmetric bis-vinylidenecarbene from a bis-vinylidenedibromide met with unexpected failure.

Parallelization Issues of Domain Specific Question Answering System on Cell B.E. Processors

A question answering system is an information retrieval application which allows users to directly obtain appropriate answers to a question. In order to deal with an explosive growth of information over internet and increased number of processing stages in answer retrieval, time and processing hardware required by question answering system has increased. The need of hardware is currently served by connecting thousands of computers in cluster. But faster and less complex alternatives can be found as a multi-core processor. This paper presents a pioneer work by identifying major issues involved in porting a general question answering framework on a cell processor and their possible solutions. The work is evaluated by porting the indexing algorithm of our biomedical question answering system, INDOC (Internet Doctor) on cell processors.