- Simplified Method of Ascertaining Steric Effects in Electrophilic Addition Reactions. A Comparison of Bromination, Oxymercuration, and Hydroboration
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Correlations of ionization potentials (IP's) versus relative reactivities of a variety of alkenes toward bromination, oxymercuration, and hydroboration show very good (r=0.83) to excellent (r=0.98) agreement.The use of alkenes having a broad range of steric requirements and electronic effects reveals that bromination is independent of steric effects while oxymercuration and hydroboration each exhibit a natural separation into sterically similar groups, within which alkene IP's correlate with relative reactivities.In hydroboration of allylic compounds, characteristicsof the HOMO influence the regioselectivity as well as the relative reactivity.The data indicate that the transition states of the rate-determining steps of oxymercuration and hydroboration are similar, but both are different from that of bromination.
- Nelson, Donna J.,Cooper, Penny J.,Soundararajan, Raman
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- Method for preparation of 3-methylthiopropanol from 3-methylthiopropanal
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The invention provides a method for preparation of 3-methylthiopropanol from 3-methylthiopropanal by reduction reaction under a solvent or solvent-free condition. The invention further includes purification treatment on the reaction mixture, and the obtained product has purity higher than 99.0%. The preparation method uses a reactive solvent containing 3-methylthiopropanol component, and compared with other organic solvents can effectively increase the yield of 3-methylthiopropanol.
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Paragraph 0032; 0033; 0034; 0035; 0036
(2017/10/28)
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- An immobilized homogeneous catalyst for efficient and selective hydrogenation of functionalized aldehydes, alkenes, and alkynes
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An immobilized cationic rhodium(I) catalyst bearing the diphosphine 1,1′-bis(diisopropylphosphino)-ferrocene (DiPFc, 1) allows efficient and chemoselective hydrogenation of a range of functionalized aldehydes, as well as alkenes and alkynes, under mild conditions. This heterogenized catalyst system is convenient to prepare, is stable to air and moisture over extended periods, and is readily recycled.
- Burk,Gerlach,Semmeril
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p. 8933 - 8939
(2007/10/03)
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- Catalytic Thioether and Thioacetal Formation using Bis(diphenylphosphino)methane Complexes of Platinum (II)
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Bis(dihenylphosphino)methane complexes of platinum (II) catalyze the formation of thioethers from thiols and alkyl halides and of thioacetals from thiols or dithiols and geminal dihalides.
- Page, Philip C. Bulman,Klair, Sukhbinder S.,Brown, Michael P.,Smith, Christopher S.,Maginn, Stephen J.,Mulley, Suzanne
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p. 5933 - 5940
(2007/10/02)
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- Solvomercuration-Demercuration. 9. Oxymercuration-Demercuration of Chloro-, Epoxy-, and Thiomethyl-Substituted Alkenes
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The oxymercuration-demercuration (OM-DM) of allyl, crotyl, 3-buten-1-yl, 4-penten-1-yl, and 5-hexen-1-yl chlorides and methyl sulfides as well as 3,4-epoxy-1-butene, 4,5-epoxy-1-pentene, and 5,6-epoxy-1-hexene has been studied.Allyl chloride undergoes a slow but normal OM to give the Markovnikov oxymarcurial.However, in situ demercuration under the standard conditions (NaOH, NaBH4) gives only allyl alcohol.Fortunately, demercuration with an ethanolic solution of sodium borohydride results in high yields of the chlorohydrin accompanied by small amounts of propylene oxide.In contrast, crotyl chloride fails to give any products resulting from the OM-DM sequence.Thus, 3-buten-2-yl chloride underwent only solvolytic reaction while 2-methylallyl chloride underwent exclusive OM to give, upon DM, the expected Markovnikov chlorohydrin.Similarly, 3-buten-1-yl chloride underwent exclusive hydration under the standard OM-DM conditions.In the case of 4-penten-1-yl chloride, the C1-C5 neighboring-group participation was seen during OM.However, 5-hexen-1-yl chloride showed exclusive hydration to give a 94percent yield of the Markovnikov chlorohydrin.The approximate rates of solvolysis of a series of representative alkyl halides have been determined under the OM conditions.The OM-DM of 3,4-epoxy-1-butene proceeded to give hydrated products although the yield was low, ca. 60percent.On the other hand, 4,5-epoxy-2-pentene gave products arising only from participation of the epoxide ring in the OM stage.Moreover, the yields of these products are very low, only ca. 15percent.By contrast, the OM-DM of 4,5-epoxy-1-pentene proceeds cleanly, giving a 96percent yield of the Markovnikov epoxy alcohol.In the case of 5,6-epoxy-1-hexene, ca. 80percent of the products arise from epoxide participation in the OM stage.With the exception of the crotyl derivative, the (methylthio)alkenes undergo hydration cleanly, although slowly, to give approximately 70-80percent yields of the thio alcohols.The crotyl alkene gave 3-butene-2-ol in only ca. 20percent yield.
- Brown, Herbert C.,Lynch, Gary J.
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p. 930 - 939
(2007/10/02)
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