Reduction and N-Alkylation of α-Methylene-indolines with Sodium Cyanoborohydride in Carboxylic Acids

The reaction of α-methylene-indolines with NaCNBH₃ in carboxylic acids at room temperature can yield either 2β,3β-dihydro-indolines or their N-alkyl derivatives as main products with high selectivity, depending mainly on the carboxylic acid and on the reaction time when using a large excess of NaCNBH₃.     

Raney Nickel–Catalyzed Hydrogenation of Unsaturated Carboxylic Acids with Sodium Borohydride in Water

A mild, selective, and green method for the reduction of unsaturated carboxylic acids with sodium borohydride–Raney nickel (W6) system in water is reported. This method is practical and safe and avoids use of organic solvents.     

Simple Reduction of Heteroaromatic Esters to Alcohols Using a Sodium Borohydride–Methanol System

Some heteroaromatic esters were reduced to the corresponding alcohols by using a sodium borohydride–methanol system. The reduction was completed within 0.15–2.0 h in refluxing THF. The alcohol products were isolated after aqueous workup in moderate to excellent yield (48–97%).     

First One-step Enantioselective Reduction of á-Haloacetophenones into Styrene Oxides using Sodium Borohydride in Water

The synthesis of enantiomerically enriched epoxides especially styrene oxides is an interesting challenge1, since they are often valuable building blocks for various fine chemical 2 products and pharmaceuticals such as β2-, β3-, and α1-adrenergic receptor agonists3, . In recent years, 4 there has been a flood of papers describing the synthetical methods of the chiral non-racemic epoxides5, . Here we firstly developed a green, simple and potential epoxidation system by 6 enantioselecti…     

Silica‐Supported Sodium Hydrogen Sulfate Catalyzed Facile Transformation of p‐Hydroxybenzyl Alcohols to p‐Hydroxybenzyl Ethers and Thioethers

Abstract

The heterogeneous catalyst, silica‐supported sodium hydrogen sulfate (NaHSO₄ · SiO₂) has been found to be highly efficient in carrying out the transformation of p‐hydroxybenzyl alcohols at room temperature to p‐hydroxybenzyl ethers and thioethers in very high yields.     

Facile Synthesis of 3‐Hydroxyglutamic Acids via Cyanation of Chiral N‐Acyliminium Cation Derived From (S)‐Malic Acid

Facile synthesis of 3‐hydroxyglutamic acids via cyanation of an N‐acyliminium intermediate derived from (S)‐malic acid is described. The chiral cyclic imide derived from (S)‐malic acid was converted to an acetoxylactam by reduction with sodium borohydride followed by acetylation. The obtained acetoxylactam was treated with trimethylsilyl cyanide in the presence of boron trifluoride etherate to give the corresponding cyanolactam in high yield, even though the diastereoselectivity of the cyanation reaction was moderate. The diastereomers of the cyanolactam were chromatographically separable and were independently converted to (2R,3S)‐ and (2S,3S)‐3‐hydroxyglutamic acids.     

Oxidation of Aldehydes and Ketones into Carboxylic Acids and Esters Using 4‐Amino‐2‐Chloroperbenzoic Acid Supported on Silica Gel

Abstract

4‐Amino‐2‐chloroperbenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of aldehydes and ketones to the corresponding carboxylic acids and esters.     

Sn-Mediated Catalytic Asymmetric Reduction of Carbonyl Groups by Sodium Borohydride(or Sodium Borodeuteride)

Two remarkable reducing agents NaBH_4 (or NaBD_4)/SnCl_2(orSnCl_4·2Et_2O) with chiral ligands are applied to the asymmetricreduction of carbonyl compounds with excellent chemical yieldsand enantioselective excesses.     

Asymmetric Borohydride Reduction of Acetophenone Catalyzed by Chiral Salen-Co(Ⅱ) Complex Using Sodium Borohydride

Development of efficient catalytic asymmetric reactions is the most challenging task in current synthetic chemistry; much effort has been devoted to create the chiral metal complexes of asymmetric catalysis. In the last two decades' many brand-new ligands had been synthesized and their combination with various metal ions has been applied in asymmetric catalysis. However, most ligands have only narrow applications and their use is limited to some reactions. Exceptionally, a few ligands and their metal complexes such as binaphthol, semicollin,and binap show wide applicability. Chiral salen ligand is one of such ligands and their metal complexes are now used as the catalysts for a variety of asymmetric reactions such as epoxidation^[1], aziridination^[2], cyclopropanation^[3], Diels-Alder reaction^[4], asymmetric transfer hydrogenation of aromatic ketones^[5] and kinetic resolution of racemic epoxides^[6] and so on.     

Asymmetric Reduction of Prochiral Ketones with N‐Sulfonylated Amino Alcohols as Catalysts

Novel N‐sulfonylated amino alcohols were synthesized from L‐amino acids and (+)‐camphor, and their application to asymmetric reduction of prochiral ketones with NaBH₄–BF₃ · Et₂O is described.     

Efficient Fixation of Carbon Dioxide by Electrolysis Facile Synthesis of Useful Carboxylic Acids

Electrochemical fixation of atmospheric pressure of carbon dioxide to organic compounds is a useful and attractive method for synthesizing of various carboxylic acids. Electrochemical fixation of carbon dioxide, electrochemical carboxylation, organic halides, organic triflates, alkenes, aromatic compounds, and carbonyl compounds can readily occur in the presence of an atmospheric pressure of carbon dioxide to form the corresponding carboxylic acids with high yields, when a sacrificial anode such as magnesium or aluminum is used in the electrolysis. The electrochemical carboxylation of vinyl bromides was successfully applied for the synthesis of the precursor of nonsteroidal anti-inflammatory agents such as ibuprofen and naproxen. On the other hand, supercritical carbon dioxide （scCO2） has significant potential as an environmentally benign solvent in organic synthesis and it could be used both as a solvent and as a reagent in these electrochemical carboxylations by using a small amount of cosolvent.     

Selective Esterification of Aliphatic Carboxylic Acids in the Presence of Aromatic Carboxylic Acids Over Monoammonium Salt of 12‐Tungstophosphoric Acid

Monoammonium salt of 12‐tungstophosphoric acid [(NH₄)H₂PW₁₂O₄₀] was found to be a practical and useful heterogeneous catalyst for an efficient and selective esterification of aliphatic carboxylic acids with alcohols in the presence of aromatic carboxylic acids. The heteropoly acid–based heterogeneous catalyst has the advantages of a simple workup procedure, water insolubility, and good activity.     

Convenient Synthesis of tert‐Butyl Esters of Indole‐5‐carboxylic Acid and Related Heterocyclic Carboxylic Acids

The tert‐butyl esters of indole‐5‐carboxylic acid and related compounds such as benzofuran‐ and benzothiophene‐5‐carboxylic acid were readily accessed by reacting the appropriate carboxylic acids with tert‐butyl trichloroacetimidate. To obtain the tert‐butyl esters of the 5‐carboxylic acids of 1H‐benzotriazole and 1H‐benzimidazole, position 1 of these heterocycles had to be protected by acetylation prior to reaction with tert‐butyl trichloroacetimidate. Cleavage of the acetyl residue of the obtained intermediates by dilute aqueous NaOH in ethanol led to the desired tert‐butyl 1H‐benzotriazole‐and 1H‐benzimidazole‐5‐carboxylates.     

Efficient CuCl-Catalyzed Selective and Direct Oxidation of β- and γ-Substituted Aliphatic Primary Alcohols to Carboxylic Acids

A new procedure for the selective and direct oxidation of aliphatic primary alcohols having substitution at β- and γ-positions to corresponding carboxylic acids was developed using a catalytic amount of ligand and additive-free CuCl with anhydrous ^t BuOOH in acetonitrile solvent under very mild reaction conditions. This procedure is very simple and mild and works efficiently without any additives at room temperature.     

A New Synthesis of β-Phenylethyl Alcohols and Phenyl-Acetic Acids via Hydroboration of Phenylketene Dihalides

The synthesis of phenylethyl alcohols and phenyl-acetic acids have been carried out by various methods. We now report a simple synthesis for these compounds via the unprecedented hydroboration-oxidation reaction on phenylketene dihalides.     

Trimethylsilyldiazomethane – A Mild and Efficient Reagent for the Methylation of Carboxylic Acids and Alcohols in Natural Products

Summary. Esterification of various naturally occurring carboxylic acids with trimethylsilyldiazomethane proceeds nearly quantitatively under very mild conditions. Furthermore, highly sterically hindered alcohols can be converted directly to the corresponding methyl ethers. Improved methods for the preparation and quantification of this reagent are described.     

N‐Bromosuccinimide: A Facile Reagent for the Oxidation of Benzylic Alcohols to Aldehydes

The oxidation of benzylic alcohols to aldehydes using N‐bromosuccinimide (NBS) under ambient conditions without use of a transition‐metal catalyst has been described.     

Convenient Asymmetric Borane Reduction of Ketones Catalyzed by Simple Amino Alcohols and Corresponding Amino Acids

The catalytic enantioselective borane reduction of ketones is a well-studied theme1. Since the pioneering work of Corey2, a variety of good catalysts have been synthesized through further modification on simple amino alcohols and their corresponding amino acids,3,4 . But when simple amino alcohols were directly used in the reduction their catalytic efficiency was very low. For the first time Buono5 has reported through carefully chosen reaction condition the catalytic efficiency of a simple…     

Sn－Mediated Catalytic Asymmetric Reduction of Carbonyl Groups by Sodium Borohydride （or Sodium Borodeuteride）

Two remarkable reducing agents NaBH₄ (or NaBD₄)/SnCl₂(or SnCl₄·2Et₂O) with chiral ligands are applied to the asymmetric reduction of carbonyl compounds with excellent chemical yields and enantioselective excesses.     

Reduction of Aldehydes and Ketones with Potassium Borohydride as Reductant

A series of aldehydes and ketones were reduced by potassium borohydride in an ionic liquid/water ([bmim]PF6/H2O) biphasic system to afford corresponding alcohol with high purity in excellent yields. The ionic liquid/water biphasic system could promote the chemoselectivity and the substituents such as nitro group and chlorine remained intact. Aromatic ketones were not as active as aromatic aldhydes and cyclic ketones owing to their higher steric hindrance. The ionic liquid could be recycled and reused. This protocol has notable advantages of no need of phase transfer catalyst and organic solvents, mild conditions, simple operation, short reaction time, ease work-up, high yields and recycling of the ionic liquid.