Highly efficient catalytic aerobic oxidations of benzylic alcohols in water

A highly efficient catalytic system without transition metals in water has been developed for aerobic oxidations of benzylic alcohols. The newly developed catalyst system could oxidize benzylic alcohols and heteroaromatic analogues with 1 mol % TEMPO as a catalyst and with a catalytic amount of 1,3-dibromo-5,5-dimethylhydantoin and NaNO2 as cocatalysts. Under the optimal conditions, various alcohols could be converted into their corresponding aldehydes or ketones in high yields.     

Cu(II)-catalyzed selective aerobic oxidation of alcohols under mild conditions

Aerobic Alcohol Oxidation. An efficient four-component system consisting of acetamido-TEMPO/Cu(ClO4)2/TMDP/DABCO in DMSO has been developed for room-temperature aerobic alcohol oxidation. Under the optimal conditions, various alcohols could be converted into their corresponding aldehydes or ketones in good to excellent yields. The newly developed catalytic system could also be recycled and reused for three runs without any significant loss of catalytic activity.     

Transition-Metal-Free TEMPO Catalyzed Aerobic Oxidation of Alcohols to Carbonyls Using an Efficient Br2 Equivalent under Mild Conditions

An effective transition‐metal‐free catalytic system is developed for aerobic oxidations of alcohols. Using catalytic amount of bromide‐bromate coupling, H₂SO₄, and NaNO₂, together with 2,2,6,6‐tetramethylpiperidine N‐oxyl radical (TEMPO) in the presence of air, various alcohols could be converted into the corresponding aldehydes or ketones in good to excellent isolated yields under mild conditions.     

3-BocNH-ABNO-catalyzed aerobic oxidation of alcohol at room temperature and atmospheric pressure

A transition-metal-free catalytic system has been developed for selective transformation of alcohol to aldehydes or ketones. The reactions were performed with 3-(tert-butoxycarbonylamino)-9-azabicyclo[3.3.1]nonane N-oxyl (3-BocNH-ABNO) as the catalyst, NaNO₂ as the co-catalyst, molecular oxygen as the terminal oxidant, and AcOH as the solvent under room temperature. This catalytic system exhibited broad functional group tolerance. A series of alcohol substrates, including primary and secondary benzylic alcohols, heteroaromatic analogues, primary and secondary aliphatic alcohols, could be converted into their corresponding aldehydes and ketones in good conversions and selectivities.     

Organocatalytic Conjugate Addition of Azide Ion to α,β‐Unsaturated Aldehydes

An efficient and simple amine‐catatalyzed azide conjugate addition to α,β‐unsaturated aldehydes has been developed. In the presence of a catalytic amount of tertiary amine with a 1:1 mixture of NaN₃ and 37% HCl in CH₂Cl₂, α,β‐unsaturated aldehydes provided β‐azido aldehydes, which could be transformed into 1,3‐amino alcohols.     

A very mild and chemoselective oxidation of alcohols to carbonyl compounds

Efficient oxidation of primary alcohols and beta-amino alcohols to the corresponding aldehydes and alpha-amino aldehydes can be carried out at room temperature and in methylene chloride, using trichloroisocyanuric acid in the presence of catalytic TEMPO: aliphatic, benzylic, and allylic alcohols, and beta-amino alcohols are rapidly oxidized without no overoxidation to carboxylic acids. Secondary carbinols are slowly oxidized so that the reaction is highly chemoselective. Reaction: see text.     

Catalytic Oxidation of Alcohols to Corresponding Aldehydes or Ketones with TEMPO-Mediated Iodosobenzene in Water in the Presence of a Surfactant

An efficient, facile, and rapid oxidation of alcohols to the corresponding aldehydes or ketones with a stoichiometric amount of iodosobenzene (PhIO) in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl free radical (TEMPO), KBr, and a surfactant, such as SDS (sodium dodecylsulfate), was reported. The oxidation proceeded in water at room temperature to afford aldehydes or ketones in excellent yields and high selectivity without overoxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved with the catalytic system of PhIO/TEMPO/KBr/SDS. A possible mechanism for the oxidation was supposed.     

Highly sustainable catalytic dehydrogenation of alcohols with evolution of hydrogen gas

The catalytic dehydrogenation of alcohols into aldehydes and ketones in the absence of H-acceptors was studied with several transition metal catalysts in order to develop a large-scale procedure. Applying Ru(OCOCF₃)₂(CO)(PPh₃)₂, the so called Robinson catalyst, several secondary alcohols could be dehydrogenated with high selectivity into the corresponding ketones in relatively short reaction times. Highly effective atom utilization could be realized avoiding solvents and giving hydrogen gas as the sole by-product. However, in contrast to Robinson's work the catalytic dehydrogenation of primary alcohols appeared to be problematic due to decarbonylation with concomitant catalyst deactivation and aldol condensation under the strong acid or basic conditions applied.     

Direct organocatalytic asymmetric alpha-chlorination of aldehydes

The direct organocatalytic enantioselective alpha-chlorination of aldehydes has been developed. The reaction proceeds for a series of different aldehydes with NCS as the chlorine source using easily available catalysts such as l-proline amide and (2R,5R)-diphenylpyrrolidine. The alpha-chloro aldehydes are obtained in up to 99% yield and up to 95% ee. The synthetic utility of the enantioselective alpha-chlorination of aldehydes is demonstrated by transformation of the alpha-chloro aldehydes to the corresponding alpha-chloro alcohols (>90% yield) by standard reduction and further transformation to both a terminal epoxide and amino alcohol, both obtained without loss of optical purity. Oxidation of the alpha-chloro aldehydes followed by esterification gave optically active alpha-chloro esters without loss of optical purity. It is demonstrated that these optically active alpha-chloro esters can be converted into nonproteinogenic amino acids in overall high yields, maintaining the enantiomeric excess obtained in the catalytic enantioselective alpha-chlorination step.     

Vanadium-catalyzed selective aerobic alcohol oxidation in ionic liquid [bmim]PF6

A selective aerobic oxidation of alcohols into the corresponding aldehydes or ketones was developed by using two-component system VO(acac)₂/DABCO in the ionic liquid [bmim]PF₆, and the catalysts can be recycled and reused for three runs without any significant loss of catalytic activity.     

N-溴代丁二酰亚胺水相氧化醇类化合物反应研究

以水为反应介质、NBS为氧化剂,在水相无催化剂条件下实现了醇的氧化.芳香醇、脂肪醇都可以达到95%以上的醛(或酮)产率,但该体系对一些含供电子取代基的醇的反应活性不高,选用salen-Co(Ⅲ)配合物作为催化剂,可拓宽反应的底物适用范围.     

Development and application of highly efficient ruthenium-based catalysts for the ring opening metathesis polymerization

Various bisallylic ruthenium(IV) complexes were synthesized and tested as catalysts for the ring opening metathesis polymerization (ROMP) of norbornene. In presence of cocatalysts such as silanes or certain diazoalkanes a significant increase of the catalytic activity could be observed. With these highly efficient systems the ROMP of diolefinic norbornene derivatives (dicyclopentadiene, 5-ethylidene-2-norbornene, norbornadiene) and monomers containing functional groups was achieved (e.g. alcohols, acids, esters, amides, imides, ketones, aldehydes, …).     

Concepts for ligand design in asymmetric catalysis: a study of chiral amino thiol ligands

A series of new chiral sulfur–nitrogen chelate ligands, derived from amino acids, has been synthesised rationally. Fruitless experiments into catalytic asymmetric conjugate additions and desymmetrisation of meso-epoxides led us to analyse our ligands in the catalytic asymmetric addition of diethylzinc to aromatic aldehydes. These latter experiments were successful with chiral benzylic alcohols being obtained in up to 82% enantiomeric excess.     

FeCl3催化Et2Zn与芳香醛的加成反应研究

以FeCl_3作为催化剂, 研究了Et_2Zn与芳香醛的加成反应, 考察了催化剂、溶剂、催化剂与Et_2Zn用量及温度对该反应的影响. 实验结果表明: 在60℃, 1.2当量Et_2Zn, 甲基环戊基醚为溶剂的反应条件下, 10 mol% FeCl_3可以较高效的将各种芳香醛转化为仲醇.     

EFFECT OF MORPHOLOGICAL STRUCTURE OF AMINOMETHYL POLYSTYRENE RESIN ON THE CATALYTIC PROPERTIES OF POLYMERSUPPORTED RUTHENIUM COMPLEXES

Polymer-supported ruthenium complexes ■-Phen-Ru-①,■-Phen-Ru-②,■-Phen-Ru-③,■-Phen-Ru-④, ■-Phen-Ru-⑤,■-Phen-Ru-⑥and ■-Phen-Ru-⑦were prepared using aminomethyl polystyrenes of different morphological structures as supports.A variety of alcohols were oxidized efficiently into the corresponding ketones, carboxylic acids or aldehydes with iodosylbenzene (PhIO) catalyzed by aminomethyl polystyrene-supported ruthenium complexes under mild reaction conditions in acetonitrile.The influences of morphological struct...     

Asymmetric diethylzinc addition and phenyl transfer to aldehydes using chiral cis-cyclopropane-based amino alcohols

A new series of amino alcohols with a chiral cyclopropane backbone have been developed and used in the catalytic asymmetric diethylzinc addition and phenyl transfer to various types of aldehydes. These cyclopropane-based chiral amino alcohols show high enantioselectivity in the addition of organozincs to aromatic and aliphatic aldehydes. For diethylzinc addition to aromatic and aliphatic aldehydes, up to 97% ee and 93% ee are obtained, respectively. For the phenyl transfer to aromatic aldehydes, the best enantioselectivity was 89% ee.     

分子氧氧化醇的研究进展

鉴于分子氧具有经济、环保、易得的优势,本文从均相催化、多相催化以及新材料的角度阐述了近年来液态醇选择氧化到醛酮的进展。着重介绍了过渡金属作为活性组分构成的催化体系,较详细的对新催化材料的研究做了一下归类,并对其在醇的氧化反应中的应用做了介绍,认为传统催化领域的研究仍然具有魅力,同时新材料的开发与运用在未来的具有诱人的前景。     

Nickel‐Catalyzed Direct Coupling of Allylic Alcohols with Organoboron Reagents

The direct coupling of allylic alcohols with arylboronic acids or their derivatives catalyzed by Ni(cod)₂ in the presence of a catalytic amount of base has been developed. A wide variety of allylic substrates or arylboronic acids turned out to be applicable to this catalytic system. The present method does not require the use of ligands for stabilizing the nickel catalyst in most cases or additional activators for activation of allylic alcohols.     

Room-temperature Cannizzaro reaction under mild conditions facilitated by magnesium bromide ethyl etherate and triethylamine

[reaction: see text] A room-temperature convenient Cannizzaro reaction prompted by magnesium bromide ethyl etherate and triethylamine is described for smooth conversion of aromatic aldehydes into their respective alcohols and carboxylic acids. The methodology is applicable to both inter- and intramolecular reactions and could be directed to obtain the carboxylic moiety in the form of an acid, an amide, or an ester compound depending on the selected reaction conditions or workup procedure.     

Chemoselective oxidation of primary alcohols catalysed by Ce(III)-complex intercalated LDH using molecular oxygen at room temperature

Herein we describe the preparation of an efficient heterogeneous catalyst consisting of an anionic Ce(III)-complex immobilized Zn/Al-layered double hydroxide (LDH) and its use in the catalytic liquid phase oxidation of primary alcohols using molecular O(2) at room temperature. Various primary alcohols could be transformed to their corresponding aldehydes in good to excellent yields using the set of optimal conditions. The heterogeneous catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity.