• Bulletin of the Korean Chemical Society
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• v.10 no.4
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• pp.382-388
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• 1989

The approximate rates and stoichiometry of the reaction of excess potassium tri-sec-butylborohydride ($K_s-Bu_3BH$) with selected organic compounds containing representative functional groups were determined under the standard conditions (0$^{\circ}C$, THF) in order to define the characteristics of the reagent for selective reductions. Primary alcohols evolve hydrogen in 1 h, but secondary and tertiary alcohols and amines are inert to this reagent. On the other hand, phenols and thiols evolve hydrogen rapidly. Aldehydes and ketones are reduced rapidly and quantitatively to the corresponding alcohols. Reduction of norcamphor gives 99.3% endo- and 0.7% exo-isomer of norboneols. The reagent rapidly reduces cinnamaldehyde to the cinamyl alcohol stage and shows no further uptake of hydride. p-Benzoquinone takes up one hydride rapidly with 0.32 equiv hydrogen evolution and anthraquinone is cleanly reduced to the 9,10-dihydoxyanthracene stage. Carboxylic acids liberate hydrogen rapidly and quantitatively, however further reduction does not occur. Anhydrides utilize 2 equiv of hydride and acyl chlorides are reduced to the corresponding alcohols rapidly. Lactones are reduced to the diol stage rapidly, whereas esters are reduced moderately (3-6 h). Terminal epoxides are rapidly reduced to the more substituted alcohols, but internal epoxides are reduced slowly. Primary and tertiary amides are inert to this reagent and nitriles are reduced very slowly. 1-Nitropropane evolves hydrogen rapidly without reduction and nitrobenzene is reduced to the azoxybenzene stage, whereas azobenzene and azoxybenzene are inert. Cyclohexanone oxime evolves hydrogen without reduction. Phenyl isocyanate utilizes 1 equiv of hydride to proceed to formanilide stage. Pyridine and quinoline are reduced slowly, however pyridine N-oxide takes up 1.5 equiv of hydride in 1 hr. Disulfides are rapidly reduced to the thiol stage, whereas sulfide, sulfoxide, sulfonic acid and sulfone are practically inert to this reagent. Primary alkyl bromide and iodide are reduced rapidly, but primary alkyl chloride, cyclohexyl bromide and cyclohexyl tosylate are reduced slowly.

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.469-475
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• 1993

The approximate rates and stoichiometry of the reaction of excess lithium tris(diethylamino)aluminum hydride (LTDEA) with selected organic compounds containing representative functional groups under standardized condition (tetrahydrofuran, 0$^{\circ}C$) were examined in order to define the characteristics of the reagent for selective reductions. The reducing ability of LTDEA was also compared with those of the parent lithium aluminum hydride (LAH) and lithium tris(dibutylamino)aluminum hydride (LTDBA). In general, the reactivity toward organic functionalities is in order of LAH${\gg}$LTDEA${\geq}$LTDBA. LTDEA shows a unique reducing characteristics. Thus, benzyl alcohol and phenol evolve hydrogen slowly. The rate of hydrogen evolution of primary, secondary, and tertiary alcohols is distinctive: 1-hexanol evolves hydrogen completely in 6 h, whereas 3-hexanol evolves hydrogen very slowly. However, 3-ethyl-3-pentanol does not evolve any hydrogen under these reaction conditions. Primary amine, such as n-hexylamine, evolves only 1 equivalent of hydrogen. On the other hand, thiols examined are absolutely inert to this reagent. LTDEA reduces aldehydes, ketones, esters, acid chlorides, and epoxides readily to the corresponding alcohols. Quinones, such as p-benzoquinone and anthraquinone, are reduced to the corresponding diols without hydrogen evolution. However, carboxylic acids, anhydrides, nitriles, and primary amides are reduced slowly, where as tertiary amides are readily reduced. Finally, sulfides and sulfoxides are reduced to thiols and sulfides, respectively, without evolution of hydrogen. In addition to that, the reagent appears to be an excellent partial reducing agent to convert esters, primary carboxamides, and aromatic nitriles into the corresponding aldehydes. Free carboxylic acids are also converted into aldehydes through treatment of acyloxy-9-BBN with this reagent in excellent yields.

• Bulletin of the Korean Chemical Society
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• v.13 no.5
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• pp.531-537
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• 1992

The approximate rates and stoichiometry of the reaction of excess potassium 2-thexyl-1,3,2-dioxaborinane hydride(KTDBNH) with 55 selected compounds containing representative functional groups under standardized conditions (tetrahydrofuran, TEX>$0^{\circ}C$, reagent : compound=4 : 1) was examined in order to define the characteristics of the reagent for selective reductions. Benzyl alcohol and phenol evolve hydrogen immediately. However, primary, secondary and tertiary alcohols evolve hydrogen slowly, and the rate of hydrogen evolution is in order of $1^{\circ}$> $2^{\circ}$> $3^{\circ}$. n-Hexylamine is inert toward the reagent, whereas the thiols examined evolve hydrogen rapidly. Aldehydes and ketones are reduced rapidly and quantitatively to give the corresponding alcohols. Cinnamaldehyde is rapidly reduced to cinnamyl alcohol, and further reduction is slow under these conditions. The reaction with p-benzoquinone dose not show a clean reduction, but anthraquinone is cleanly reduced to 9,10-dihydro-9,10-anthracenediol. Carboxylic acids liberate hydrogen immediately, further reduction is very slow. Cyclic anhydrides slowly consume 2 equiv of hydride, corresponding to reduction to the caboxylic acid and alcohol stages. Acid chlorides, esters, and lactones are rapidly and quantitatively reduced to the corresponding carbinols. Epoxides consume 1 equiv hydride slowly. Primary amides evolve 1 equiv of hydrogen readily, but further reduction is slow. Tertiary amides are also reduced slowly. Both aliphatic and aromatic nitriles consume 1 equiv of hydride rapidly, but further hydride uptake is slow. Analysis of the reaction mixture with 2,4-dinitrophenylhydrazine yields 64% of caproaldehyde and 87% of benzaldehyde, respectively. 1-Nitropropane utilizes 2 equiv of hydride, one for hydrogen evolution and the other for reduction. Other nitrogen compounds examined are also reduced slowly. Cyclohexanone oxime undergoes slow reduction to N-cyclohexylhydroxyamine. Pyridine ring is slowly attacked. Disulfides examined are reduced readily to the correponding thiols with rapid evolution of 1 equiv hydrogen. Dimethyl sulfoxide is reduced slowly to dimethyl sulfide, whereas the reduction of diphenyl sulfone is very slow. Sulfonic acids only liberate hydrogen quantitatively without any reduction. Finally, cyclohexyl tosylate is inert to this reagent. Consequently, potassium 2-thexyl-1,3,2-dioxaborinane hydride, a monoalkyldialkoxyborohydride, shows a unique reducing characteristics. The reducing power of this reagent exists somewhere between trialkylborohydrides and trialkoxyborohydride. Therefore, the reagent should find a useful application in organic synthesis, especially in the field of selective reduction.

• Bulletin of the Korean Chemical Society
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• v.13 no.2
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• pp.199-207
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• 1992

The approximate rates and stoichiometry of the reaction of excess sodium diethyldihydroaluminate (SDDA) with 68 selected organic compounds containing representative functional groups were examined under standard conditions (THF-toluene, $0^{\circ}C$ in order to compare its reducing characteristics with lithium aluminum hydride (LAH), aluminum hydride, and diisobutylaluminum hydride (DIBAH) previously examined, and enlarge the scope of its applicability as a reducing agent. Alcohols, phenol, thiols and amines evolve hydrogen rapidly and quantitatively. Aldehydes and ketones of diverse structure are reduced rapidly to the corresponding alcohols. Reduction of norcamphor gives 11% exo-and 89% endo-norborneol. Conjugated aldehydes such as cinnamaldehyde are rapidly and cleanly reduced to the corresponding allylic alcohols. p-Benzoquinone is mainly reduced to hydroquinone. Hexanoic acid and benzoic acid liberate hydrogen rapidly and quantitatively, however reduction proceeds very slowly. Acid chlorides and esters tested are all reduced rapidly to the corresponding alcohols. However cyclic acid anhydrides such as succinic anhydride are reduced to the lactone stage rapidly, but very slowly thereafter. Although alkyl chlorides are reduced very slowly alkyl bromides, alkyl iodides and epoxides are reduced rapidly with an uptake of 1 equiv of hydride. Styrene oxide is reduced to give 1-phenylethanol quantitatively. Primary amides are reduced very slowly; however, tertiary amides take up 1 equiv of hydride rapidly. Tertiary amides could be reduced to the corresponding aldehydes in very good yield ( > 90%) by reacting with equimolar SDDA at room temperature. Hexanenitrile is reduced moderately accompanying 0.6 equiv of hydrogen evolution, however the reduction of benzonitrile proceeds rapidly to the imine stage and very slowly thereafter. Benzonitrile was reduced to give 90% yield of benzaldehyde by reaction with 1.1 equiv of hydride. Nitro compounds, azobenzene and azoxybenzene are reduced moderately at $0^{\circ}C$, but nitrobenzene is rapidly reduced to hydrazobenzene stage at room temperature. Cyclohexanone oxime is reduced to the hydroxylamine stage in 12 h and no further reaction is apparent. Pyridine is reduced sluggishly at $0^{\circ}C$, but moderately at room temperature to 1,2-dihydropyridine stage in 6 h; however further reaction is very slow. Disulfides and sulfoxides are reduced rapidly, whereas sulfide, sulfone, sulfonic acid and sulfonate are inert under these reaction conditions.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.285-291
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• 1987

The approximate rates, stoichiometries and products of the reaction of potassium triethylborohydride $(KEt_3BH)$ with selected organic compounds containing representative functional groups under the standard condition $(0^{\circ}C,$ THF) were examined in order to explore the reducing characteristics of this reagent as a selective reducing agent. Primary alcohols, phenols and thiols evolve hydrogen rapidly whereas secondary and tertiary alcohols evolve very slowly. n-Hexylamine is inert to this reagent. Aldehydes and ketones are reduced rapidly and quantitatively to the corresponding alcohols. Reduction of noncamphor gives 3% exo- and 97% endo-norboneol. Anthraquinone is cleanly reduced to 9,10-dihydro-9,10-dihydroxyanthracene stage. Carboxylic acids liberate hydrogen rapidly and quantitatively but further reduction does not occur. Anhydrides utilize 2 equiv of hydride to give an equimolar mixture of acid and alcohol. Acid chlorides, esters and lactones are rapidly and quantitatively reduced to the corresponding alcohols. Epoxides are reduced at moderate rates with Markovnikov ring opening to give the more substituted alcohols. Primary amides liberate 1 equiv of hydrogen rapidly. Further reduction of caproamide is slow whereas benzamide is not reduced. Tertiary amides are reduced slowly. Benzonitrile utilizes 2 equiv of hydride in 3 h to go to the amine stage whereas capronitrile takes only 1 equiv. The reaction of nitro compounds undergo rapidly whereas azobenzene and azoxybenzene are reduced slowly. Cyclohexanone oxime rapidly evolves hydrogen without reduction. Phenyl isocyanate utilizes 1 equiv of hydride to proceed to formanilide stage. Pyridine N-oxide and pyridine is reduced rapidly. Disulfides are rapidly reduced to the thiol stage whereas sulfoxide, sulfonic acid are practically inert to this reagent. Sulfones and cyclohexyl tosylate are slowly reduced. Octyl bromide is reduced rapidly but octyl chloride and cyclohexyl bromide are reduced slowly.

• Applied Chemistry for Engineering
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• v.7 no.5
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• pp.888-901
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• 1996

Oxidations of cyclopentene and of 1-pentene with air have been studied on a V/Mo/P/Al/Ti-mixed oxide catalyst in a fixed bed integral reactor. At high levels of conversion maleic anhydride was in each case produced as the major organic product, along with minor amounts of phthalic anhydride and, only starting from 1-pentene, also of citraconic anhydride. At lower levels of conversion a total of 30 organic products have been identified, some of which may be intermediates on the way from the substrates to the three anhydrides mentioned above. Based on the dependence of selectivities of the organic products on conversion, reaction schemes for the formation of maleic anhydride, phthalic anhydride and citraconic anhydride have been proposed. Oxidation at $310^{\circ}C$ led to increasing conversions and selectivities for maleic anhydride with decreasing space velocities. The highest selectivities for maleic anhydride were obtained at conversion of ca. 100%. Oxidation at a constant space velocity of $2{\cdot}10^4h^{-1}$ led to increasing conversions with increasing temperatures in the range of $300^{\circ}C{\sim}420^{\circ}C$, while the selectivity for maleic anhydride passed through a maximum value of ca. 39% at $370^{\circ}C$ in the oxidation of cyclopentene and a maximum value of ca. 30% at $400^{\circ}C$ in the oxidation of 1-pentene.

• Journal of Life Science
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• v.19 no.9
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• pp.1218-1225
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• 2009

Difractose anhydrides (DFAs) is studied as a sweetener for diabetics because of its structural property. DFAs have four types: DFA I, III, IV (degradation of levan) and V (degradation of inulin). Especially, DFA IV has been shown to enhance the absorption of calcium in experiments using rats. Levan fructotransferase is an enzyme for producing di-d-fructose-2,6':6,2-dianhydride (DFA IV). To identify structural characterization, we purified wild-type and mutants (D63A, D195N and N85S) of levan fructotransferase (LFTase) from Microbacterium sp. AL-210. These proteins were purified to apparent homogeneity by Ni-NTA affinity column, Q-sepharose ion exchange and gel filtration chromatography and detected by SDS-PAGE. They were also analyzed by circular dichroism (CD) measurements, JNET secondary structure prediction, activity measurements at various temperatures, and pH analysis. The optimum pH for the enzyme-catalyzed reaction was pH 7.5 and optimum temperature was observed at $55^{\circ}C$. Along with wild-type LFTase, mutants were analyzed by CD measurement, fluorescence analysis and differential scanning calorimetry (DSC). N85S showed less $\alpha$-helix and more $\beta$ strand than others. Also, N85S showed almost the same curve as wild-type in their steady-state fluorescence spectra, whereas mutant D63A and D195N showed higher intensity than wild-type. The amino acid sequence of wild-type LFTase was compared to the sequences of exo-inulinase from Aspergillus awamori, a plant fructan 1-exohydrolase from Cichorium intybus, and Thermotogo maritime (Tm) invertase and showed a high identity with Exo-inulinase from Aspergillus awamori.