Showing papers by "Subbarayappa Adimurthy published in 2010"

Making Full Use of the Oxidizing Equivalents in Bromate in the Selective Oxidation of Thiols, Sulfides, and Benzylic/Secondary Alcohols into Disulfides, Sulfoxides, and Aldehydes/Ketones

Abstract: The oxidation of thiols to disulfides was achieved in high yields with 6:1 mol ratio of thiol to NaBrO3, while the oxidation of sulfides and benzylic/secondary alcohols to the corresponding sulfoxides and aldehydes/ketones was successfully undertaken with 3:1 mol ratio of substrate to NaBrO3. These ratios correspond to the minimum theoretical requirement of NaBrO3. The reactions were conducted at 0−30 °C, depending upon substrate, and were initiated with catalytic amounts of H+ and Br− (initial Br−/BrO3− = 1:3.5 for thiol oxidation and 1:8 for sulfide and alcohol oxidation). Further, regeneration and reuse of the spent reagent in the aqueous effluent was demonstrated.

HBr−H2O2: A Facile Protocol for Regioselective Synthesis of Bromohydrins and α-Bromoketones and Oxidation of Benzylic/Secondary Alcohols to Carbonyl Compounds under Mild Aqueous Conditions

Abstract: HBr−H2O2 is efficiently activated in water under mild conditions, allowing the bromohydroxylation of various styrenes. HBr−H2O2 is more economic and easy to handle and offers sufficiently high regioselectivity (100%) for bromohydrin synthesis. Further activation of bromohydrin with a catalytic amount of HBr (50 mol %) and H2O2 in water affords α-bromoketones in moderate to good yields in a single step. Oxidation of benzylic/secondary alcohols to the corresponding carbonyl compounds has been achieved with the HBr (10 mol %) and H2O2 efficiently in aqueous dioxane under ambient conditions.

KHSO4: a highly efficient and reusable heterogeneous catalyst for hydroarylation of styrenes

Abstract: Hydroarylation of styrenes with arenes/heteroarenes using KHSO4 (10 mol%) as an efficient heterogeneous catalyst is described. High conversion and selectivity (>99%) were observed for hydroarylation of styrenes with 2-naphthol at reflux temperature of 1,2-dichloroethane. Yields were quantitative with all styrenes. Moderate to good conversions and selectivities were achieved with other aromatics and heteroaromatics under the same conditions. Regeneration and reusability of KHSO4 were demonstrated. Addition of a trace amount of water could help to reactivate the KHSO4 through dispersion and to facilitate the hydroarylation reaction.

Bromide Tolerance in Plants: A Case Study on Halophytes of Indian Coast

Abstract: Many industrial effluents contain occasionally various toxic elements. Many a time, bromide forms a constituent of the effluents especially originating from coastal regions. Plant materials have been effectively employed as tools to remediate this situation. Some halophytes are the best choice for reducing the toxic levels from affected salanised soils. This paper deals with the bromide uptake and its accumulation effect on the growth of Salicornia brachiata, Suaeda nudiflora, and Salvadora persica, the common halophyts of Indian coast. The species were grown with NaBr solution along with other essential nutrients. The growth in S. brachiata, S. nudiflora, and S. persica was more or less same except for some apparent morphological differences in NaBr grown plants as compared to that in NaCl-fed plants. The bromide present in various parts of these plants was determined by simple and eco-friendly techniques for the first time. A reliable spectrophotometric method was developed and employed to estimate the bromide composition in all plant extracts. The bromide levels were about 0.086–0.2 g in the root, 0.175–0.443 g in stem and 0.287–0.432 g in leaves per g of dry plant material and at higher levels it affected the photosynthetic activity. Cultivation of these plants for reclamation of bromide affected soils has been advocated as an alternative.

A process for the eco-friendly preparation of 3, 5-dibromo-4-hydroxybenzonitrile

Abstract: A highly pure 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) has been prepared in high yield from 4-hydroxybenzonitrile using eco-friendly brominating reagent comprising of 2:1 mole ratio of bromide to bromate salts in aqueous acidic medium without any catalyst under ambient conditions with no work up procedure. The product 3,5-dibromo-4-hydroxybenzonitrile was obtained in 91-99% yield with melting point 189-191° C. and more than 99% purity by gas chromatographic analysis without any purification.

A fast and highly efficient method for the synthesis of tertiary amines in aqueous medium

Abstract: A facile and highly efficient method for the synthesis of tertiary amines by the reaction of secondary amines with benzylic bromides and 1,1'-dibromo p/o-xylenes in aqueous dioxane and NaOH is described. The reactions arc dually promoted by the base in short time (15 min.) at ambient conditions in aqueous medium.

A Fast and Highly Efficient Method for the Synthesis of Tertiary Amines in Aqueous Medium.

Abstract: A facile and highly efficient method for the synthesis of tertiary amines by the reaction of secondary amines with benzylic bromides and 1,1'-dibromo p/o-xylenes in aqueous dioxane and NaOH is described. The reactions arc dually promoted by the base in short time (15 min.) at ambient conditions in aqueous medium.