Selective Reduction of Thiol Esters with Sodium Borohydride

A couple of years ago, Fujita and co-workers¹ reported the reduction of 2-thiazoline-2-thiol esters to alcohols with sodium borohydride in aqueous tetrahydrofuran. In connection with an ongoing synthetic project which requires the selective reduction of a stable acid derivative to the alcohol level in the presence of nitrile and ester groups, we examined the reaction of a variety of thiol esters with sodium borohydride. Our results show that the highly reactive (and thus unstable) 2-thiazoline-2-thiol ester derivatives are unnecessary and in fact various types of thiol esters are readily convertible to alcohols under mild conditions which do not effect the reduction of common acid derivatives such as nitrile, ester, and amide.     

Selective Reduction Among Carboxylic Acids with Sodium Borohydride

The selective reduction among carboxylic acids via acyloxyborohydrides derived from sodium borohydride and carboxylic acid mixture is demonstrated.     

Catalytic Reduction of Nitroarenes to Azoxybenzenes With Sodium Borohydride in the Presence of Bismuth

Aromatic nitro compounds have been found to be selectively reduced to azoxy compounds in good yields by NaBH₄ in the presence of bismuth powder.     

A Novel Application of Sodium Borohydride for the Regiospecific and Stereoselective Reduction of Conjugated Alkadiynes

Alkynes, when carrying an α-sulfonyl group, are shown to be stereoselectively reduced to z-alkenes using sodium borohydride under mildly basic conditions.     

BER催化还原一些含氮功能基化合物的研究

用强碱性阴离子交换树脂制备了硼氢阴离子交换树脂还原剂(BER),使其在氯化铜等金属化合物的催化下还原一些芳香硝基、氰基、氮氮双键等含氮功能基化合物.还研究了BER的制备条件:如温度、溶剂、不同金属化合物对还原反应的影响,并初步探讨其反应机理.     

Kinetics of Potassium Ion-Exchange in a Cation-Exchange Resin

The kinetics of the exchange of potassium ions in a cationexchange resin has been studied. The rate measurements have been made by a potentiometric technique, and both the kinetic and the activation parameters of the reaction were determined. The rate-controlling step, at the beginning of the reaction, has proved to be the diffusion of the K⁺ ions through the film surrounding the resin beads.     

The Reduction of Aromatic Aldehydes to Hydrocarbons with Borohydride Exchange Resin (BER)-Nickel Acetate in Methanol

Aromatic aldehydes were reduced to the corresponding hydrocarbons with borohydride exchange resin (BER) - nickel acetate in methanol in excellent yields.     

Quantitative Ion-Exchange TLC of p-Hydroxybenzoic Acid in the Presence of Preservatives

JPC – Journal of Planar Chromatography – Modern TLC - Rapid separation of p-hydroxybenzoic acid from methyl p-hydroxy-benzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate,...     

Selective Reduction of Carboxylic Acid Esters in the Presence of a Five-Membered Cyclic Sulfone

Carboxylic acid esters can be selectively reduced in the presence of five-membered cyclic sulfones using AlH_3. ether in anhydrous THF at cold temperatures.     

Steric Effects in the Reduction of Ketones with Sodium Borohydride

The rates for the reduction of ketones with sodium borohydride are interpreted in terms of two parameters, both derived from force-field calculations; i.e. the strain difference between alcohol and ketone (Δ strain) and the steric hindrance towards approach of the hydride R. Models for the evaluation of R are discussed. With this approach reduction rates over a range of 10⁸ can be rationalized within a factor of 6–10.     

酸性离子交换树脂催化合成二氢香豆素类化合物

以强酸性离子交换树脂为催化剂,由间苯三酚与丙烯酸或取代丙烯酸反应合成了3个二氢香豆素和1个四氢苯并二吡喃酮类化合物,其中5-羟基-3,4,6,7-四氢苯并[1,2-b;5,4-b']二吡喃-2,8-二酮(2a)和3-甲基-5,7-二二羟基-3,4-二氢香豆素(1b)还未见文献报道.取代丙烯酸的反应活性低于丙烯酸,使用甲苯-四氢呋喃混合溶剂代替甲苯单一溶剂可使2a的产率由20%提高到66%.     

Reduction of Solid Benzophenones with Sodium Borohydride

The solvent-free reduction of benzophenone and five substituted benzophenones with sodium borohydride to the corresponding alcohols was studied by thermal analysis, X-ray powder diffractometry, NMR spectroscopy, and scanning electron microscopy. In most cases, the reaction occurs via liquid eutectic phases that are formed between the benzophenone and the resulting benzohydrol. Nevertheless, this reaction can be carried out without the need for a solvent, leading to pure alcohol without side products. In some cases, heating may be necessary to achieve a reasonably short reaction time. In conclusion, this reaction type appears to be feasible as a preparative organic reaction that avoids a solvent.This revised version was published online in November 2005 with corrections to the Cover Date.     

4-Aza-N-Benzyl Bicyclo [2,2,2] Octyl Ammonium Borohydride a Highly Chemoselective Reagent for the Reduction of Aldehydes in the Presence of Ketones

The title compound reduces aldehydes in the presence of ketones with high chemoselectivity in t-butanol under reflux condition in high yields.     

Reduction of Carboxylic Acids by Tetraalkyl Ammonium Borohydride

Tetraalkylammonium borohydride reduces carboxylic acids to the corresponding alcohols in good yields utilizing only stoichiometric quantities of hydride and also in the absence of any Lewis acids.     

Plasma-catalytic Selective Reduction of NO with C2H4 in the Presence of Excess Oxygen

This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250℃ in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650ppm C2H4, 5.8% 02 in N2and GHSV = 12000h^-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma-catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.     

脂肪族酯基选择性还原模型的建立

以不同烷基取代的酯作为模型, 对其进行NaBH4还原研究. 不同取代基酯的起始反应温度和半衰期显示出了明显的差别和一定的选择性; 用B3LYP/6-31++G(d,p)//HF/6-31G(d,p)方法计算得到的过渡态能量与实验得到的活化能变化趋势一致; 实验中观察到了奇偶碳效应; 对NaBH4还原酯基的溶剂影响进行了初步研究.     

Tandem Reduction Studies of Bromo Compounds Using Tetrabutylammonium Borohydride

Tetrabutylammonium borohydride can be used for multifunctional transformations through tandem reductions of halo compounds in THF.     

Microwave-Assisted Solid Reaction: Reduction of Ketones Using Sodium Borohydride

A general and efficient procedure for microwave-assisted reduction of liquid and solid ketones using sodium borohydride without solvents is described. The added support can enhance both the efficiency and chemoselectivity of reduction.