Electric Literature of 453-20-3, The reaction rate of a catalyzed reaction is faster than the reaction rate of the uncatalyzed reaction at the same temperature.453-20-3, Name is 3-Hydroxytetrahydrofuran, molecular formula is C4H8O2. In a Article£¬once mentioned of 453-20-3
Hydroboration. 71. Hydroboration of Representative Heterocyclic Olefins with Borane-Methyl Sulfide, 9-Borabicyclo<3.3.1>nonane, Dicyclohexylborane, and Disiamylborane. Synthesis of Heterocyclic Alcohols
The hydroboration of representative heterocycles bearing an endocyclic double bond with borane-methyl sulfide (BMS), 9-borabicyclo<3.3.1>nonane (9-BBN), dicyclohexylborane (Chx2BH), and disiamylborane (Sia2BH) was investigated systematically to establish the optimum conditions for the clean and quantitative hydroboration.The hydroboration of 2,3- and 2,5-dihydrofurans with BMS (3:1 molar ratio) at 25 deg C for 1 h affords the trialkylborane, readily oxidized to 3-hydroxytetrahydrofuran in excellent yield.However, preparation of the corresponding dialkylboranes from these olefins using 2 olefin/BMS was not possible even at 0 deg C.Excess hydride and prolongated reaction time cause ring cleavage of the alkylboranes to yield both unsaturated alcohol and the dihydroborated products 1,3- and 1,4-pentanediols.Hydroboration of both 2,3-dihydrothiophene and 2-methyl-4,5-dihydrofuran with BMS proceeds cleanly to the trialkylborane stage, oxidized to the corresponding alcohols in almost quantitative yields.Hydroboration of 3-pyrroline with BMS could not be achieved with the unprotected nitrogen atom.Such hydroboration could be accomplished by protecting the nitrogen atom with the benzyloxycarbonyl group affording the trialkylborane, readily converted to N-(benzyloxycarbonyl)-3-pyrrolidinol in good yield.Conditions for a clean hydroboration of these heterocyclic five-membered olefins with 9-BBN, Chx2BH, and Sia2BH were also established.In all cases clean trialkylboranes were obtained, readily oxidized to heterocyclic alcohols in high yields. 3,4-Dihydropyran, on hydroboration with BMS, followed by oxidation, affords 3-hydroxytetrahydropyran in good yield.However, ring cleavage in this case is greater when compared to 2,3-dihydrofuran. 2-Methoxy- or 2-ethoxy-3,4-dihydro-2H-pyran readily undergo hydroboration with BMS to the trialkylboranes, oxidized to the corresponding trans and cis alcohols in a 7:3 ratio.As the steric requirements of the dialkylborane are increased, more trans alcohol is formed.Thus at 0 deg C, the ratios of trans to cis alcohols were increased from 1:1 to 7:3 and then to 8:2 with 9-BBN, Chx2BH, and Sia2BH, respectively.N-(Benzyloxycarbonyl)-1,2,3,6-tetrahydropyridine is readily hydroborated with BMS, 9-BBN, Chx2BH, and Sia2BH to the corresponding trialkylboranes, readily oxidized to N-(benzyloxycarbonyl)-3- and -4-piperidinols in good yield.Strongly basic groups in the heterocyclic ring can greatly reduce the ease of hydroboration, and the introduction of boron beta to the heteroatom can lead to elimination.However, both problems can be avoided to provide ready hydroboration-oxidation of heterocyclic olefins.
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Reference£º
Tetrahydrofuran – Wikipedia,
Tetrahydrofuran | (CH2)3CH2O – PubChem