Articles written in Journal of Chemical Sciences

    • Synthesis of new 4,6-disubstituted-1,3-oxazinan-2-one analogues

      Arun Jyoti Borah Prodeep Phukan

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      1,3-Oxazinan-2-one analogues are important heterocyclic compounds having significant biological activities. This study reports the synthesis of eight new 4,6-disubstituted -1,3-oxazinan-2-one analogues from corresponding homoallylic carbamates. Homoallylic carbamates were synthesized via a three-component reaction of aldehyde, allyltrimethylsilane and benzyl carbamate in presence of iodine as catalyst. In the next step, homoallylic carbamates were subjected to Sharpless dihydroxylation (racemic) to produce 3,4-dihydroxybutylcarbamate derivatives. This product was then treated with NaH in tetrahydrofuran (THF) to produce the desired 6-(hydroxymethyl)-1,3-oxazinan-2-one in high yield.

    • DFT analysis of the nucleophilicity of substituted pyridines and prediction of new molecules having nucleophilic character stronger than 4-pyrrolidino pyridine


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      Some commonly used 3-substituted, 4-substituted and 3,4,5-substituted pyridines were examinedusing DFT to predict the nucleophilicity behavior based on four different methods known in the literature.HOMO-LUMO energy calculations were done using DFT/B3LYP/6-311G+(d,p) level of theory. To establishthe most suitable nucleophilicity scale for all the ranges of pyridines covered herein, either Hammett substituentconstant (σ) or experimental nucleophilicity values were computed. On the basis of this study, some new4-substituted pyridines with enhanced nucleophilicity have been proposed. Nucleophilic behaviour of a fewpredicted molecules was found to be better than that of 4- pyrrolidino pyridine.

    • Nucleophilicity and CO2 fixation ability of phosphorus, nitrogen and sulfur ylides: insights on stereoelectronic factors from DFT study


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      Nucleophilicity and CO2 fixation ability of the ylides of phosphorous, sulfur and nitrogen havebeen assessed using DFT calculations at M06-2X/6-311++G(d,p)//M06-2X/6-31+G(d) level. Nucleophilicityof 54 ylides and their CO2 adducts have been evaluated using a theoretical nucleophilicity index(N) which shows good linear correlation (R2 = 0.87) with Mayr’s experimental nucleophilicity parameter forthe S-ylides. Two key geometrical parameters, condensed Fukui function (fk-) and Gibbs free energy ofreaction (ΔGr) for the ylide-CO2 adducts have also been calculated. In absence of steric effect around theylidic C-atom and any other secondary interaction, binding energy of the CO2-adducts of all the three types ofylides has a good linear correlation with the nucleophilicity. Nucleophilicity of a P-ylide increases whenelectron-donating groups are introduced as substituents on both P and the ylidic C-atom. An electronwithdrawinggroup on the same sites reduces nucleophilicity. Free ylides have higher nucleophilicity thantheir CO2 adducts.

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