Author
Pramod R. Chopade
Other affiliations: Lehigh University
Bio: Pramod R. Chopade is an academic researcher from Texas Tech University. The author has contributed to research in topics: Methanol & Solvent. The author has an hindex of 3, co-authored 5 publications receiving 176 citations. Previous affiliations of Pramod R. Chopade include Lehigh University.
Topics: Methanol, Solvent, Alcohol, Primary alcohol, Reaction rate constant
Papers
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TL;DR: Water has a high affinity for SmI2 (compared to that of the alcohols), and the onset of coordination at relatively low concentrations channels the reaction through a mechanistically distinct pathway.
Abstract: The effects of proton donors (alcohols and water) on the rate of reduction of acetophenone by SmI2 have been examined utilizing stopped-flow spectrophotometric studies. The rate orders with respect to proton source and the kinetic isotope effects were determined as well. The reaction was first-order in phenol, 2,2,2-trifluoroethanol, methanol, and ethanol and zero-order in 2-propanol and 2-methyl-2-propanol when 25 equiv of proton source were used in the reduction. Methanol, ethanol, 2,2,2-trifluoroethanol, and phenol also showed a direct correlation between the pKa of the alcohol and the rate of reduction. Under the same conditions, water had a fractional rate order of 1.4. Further studies showed that water has a rate order of 1 at lower concentrations ( 80 equiv). These results clearly indicate that the nature of the proton donor and its concentration affects the rates of reduction. Water has a high affinity for SmI2 (compared to that of the alco...
108 citations
TL;DR: It is revealed that solvation plays an important role in substrate reduction by SmI(2) using methanol as a proton source and reduces in THF, DME, and CH(3)CN provided the anti diastereomer predominantly.
41 citations
TL;DR: Reduction of a series of β-hydroxyketones by SmI2/H2O/Et3N provided 1,3-diols in quantitative yields and most reactions provided moderate to excellent diastereoselectivity with syn- diols as the major isomer in most instances.
36 citations
2 citations
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TL;DR: A review, cyclization reactions in natural product synthesis of 4-9 membered and larger rings were discussed.
Abstract: A review, cyclization reactions in natural product synthesis of 4-9 membered and larger rings were discussed. [on SciFinder (R)]
477 citations
303 citations
TL;DR: An overview of the current knowledge of the reagent SmI2 as a reducing agent, in particular with additives that increase its reactivity is given in this article, where the use of various proton sources is covered, as well as the effect of co-solvents.
Abstract: Samarium(II) iodide is a one-electron transfer reagent that has become highly appreciated as a mild and selective reducing agent in recent years. It has been found experimentally that various additives and co-solvents largely control the reactivity of SmI2. This microreview provides an overview of the current knowledge of the reagent SmI2 as a reducing agent, in particular with additives that increase its reactivity. The use of various proton sources is covered, as well as the effect of co-solvents. Furthermore, the very powerful reagent mixture SmI2/H2O/amine is also described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
166 citations
TL;DR: Simple modular di- and tripeptides with a primary amine at the N-terminus catalyze the aqueous asymmetric aldol reaction between unmodified ketones and aldehydes to furnish the corresponding beta-hydroxy ketones with up to 86% ee in water and 99% in aqueously media.
Abstract: Simple modular di- and tripeptides with a primary amine at the N-terminus catalyze the aqueous asymmetric aldol reaction between unmodified ketones and aldehydes to furnish the corresponding β-hydroxy ketones with up to 86% ee in water and 99% ee in aqueos media.
163 citations
TL;DR: Samarium(II) iodide reductants have emerged as powerful single electron donors for the highly chemoselective reduction of common functional groups, which opens up new prospects for unprecedented transformations via radical intermediates under mild regio-, chemo- and diastereoselectives conditions that are fully orthogonal to hydrogenation or metal-hydride mediated processes.
Abstract: Recently, samarium(II) iodide reductants have emerged as powerful single electron donors for the highly chemoselective reduction of common functional groups. Complete control of the product formation can be achieved on the basis of a judicious choice of a Sm(II) complex/proton donor couple, even in the presence of extremely sensitive functionalities (iodides, aldehydes). In most cases, the reductions are governed by thermodynamic control of the first electron transfer, which opens up new prospects for unprecedented transformations via radical intermediates under mild regio-, chemo- and diastereoselective conditions that are fully orthogonal to hydrogenation or metal-hydride mediated processes.
162 citations