Copper-catalyzed N-alkylation of amides and amines with alcohols employing the aerobic relay race methodology

By employing aerobic oxidation to aldehydes as a more effective alcohol activation strategy, we developed a green Cu-catalyzed N-alkylation method for various amides and amines with alcohols. This reaction is more advantageous than the literature methods for it uses a ligand-free copper catalyst, can be readily carried out under milder aerobic conditions and generates water as the only byproduct. More importantly, based on our mechanistic studies and also supported by the literature, rather than following the previously-proposed mechanisms, we deduce that the newly-proposed relay race process should be the most possible and a more rational mechanism for the reactions, especially under aerobic conditions.     

Na-promoted aerobic oxidation of alcohols to ketones

Aerobic oxidation of a number of diaryl and arylalkyl carbinols to ketones was promoted by Na in THF at room temperature with up to 99% yield. This new oxidation method is also selective with good efficiency for the oxidation of benzylic secondary alcohols but not for a primary alcohol or nonbenzylic secondary alcohols. Under nitrogen, a catalytic amount of Ni or transition metal halides such as CoCl₃, FeCl₃, and NiCl₃ in combination with Na was also found to conduct a dehydrogenation of a secondary alcohol to the corresponding ketone in high yield at room temperature.     

Cobalt phthalocyanine catalyzed aerobic oxidation of secondary alcohols: an efficient and simple synthesis of ketones

A variety of activated and non-activated secondary alcohols have been efficiently oxidized to their corresponding ketones in excellent yields with molecular oxygen using cobalt phthalocyanine as catalyst in the presence of powdered potassium hydroxide.     

Copper-catalyzed oxidative synthesis of 2-oxo-acetamidines from one-pot three-component reaction of aryl methyl ketones,secondary amines and anilines

Some novel 2-oxo-acetamidines were synthesized via one-pot three-component reaction of acetophenones, secondary amines and anilines in presence of CuI as catalyst. The reaction involved in a oxidation process of C (sp³)H bonds of acetophenones in presence of air followed by aminations, and products were obtained in good to excellent yields (70–82%) in simple work-up procedure.     

Novel polyaniline-supported molybdenum-catalyzed aerobic oxidation of alcohols to aldehydes and ketones

[reaction: see text] Oxidation of alcohols to aldehydes and ketones has been studied in high yields using molecular oxygen and a catalytic amount of 1 in toluene under stirring (ca. 100 degrees C). The reactions of primary alcohols are faster compared to secondary alcohols and the catalyst 1 can be recycled without loss of activity.     

Rhodium-catalyzed alkylation of ketones and alcohols with alcohols

An efficient method for direct alkylation of ketones and alcohols through the borrowing hydrogen strategy in the presence of rhodium complexes as catalyst was developed. This transformation is tolerant to various functional substrates and is efficient in C–C coupling of primary and secondary alcohols, which provides an alternative method of the synthesis of functional ketones from simple and commercially available materials.     

Copper-catalyzed methyl esterification of aromatic aldehydes and benzoic alcohols by TBHP as both oxidant and methyl source

A copper-catalyzed synthesis of methyl esters from aromatic aldehydes in the presence of tert-butyl hydrogen peroxide (TBHP) was developed via a radical reaction mechanism. TBHP acts not only as an efficient oxidant, but also as a green methyl source in such transformation. Moreover, this method could also be efficiently extended to the methyl esterification of benzylic alcohols.     

Polyaniline supported vanadium catalyzed aerobic oxidation of alcohols to aldehydes and ketones

Polyaniline supported vanadium complex 1 catalyzes efficiently the oxidation of alcohols to aldehydes and ketones in high yields under molecular oxygen in toluene at ca. 100 °C. The catalyst 1 can be recycled without loss of activity.     

Copper-catalyzed coupling of aryl iodides with aliphatic alcohols

[reaction: see text] A simple and mild method for the coupling of aryl iodides and aliphatic alcohols that does not require the use of alkoxide bases is described. The reactions can be performed in neat alcohol. For more precious alcohols, the etherification was carried out in toluene as solvent using 2 equiv of alcohol. Additionally, the cross-coupling of an optically active benzylic alcohol with an unactivated aryl halide was demonstrated to proceed with complete retention of configuration.     

Synthesis and some transformations of secondary mercaptoethynyl alcohols and ketones of the thiophene series

A number of thienylmercaptoethynyl alcohols, which were oxidized to the corresponding ketones, were synthesized via the Iotsich reaction of thiophene-2-aldehyde with mercaptoethynyl ethers. On reaction with hydrazine the ketones undergo intramolecular cyclization to form substituted pyrazoles. The IR spectra of the compounds obtained are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 33–36, January, 1971.     

Reduction of ketones with secondary alcohols,catalyzed by triphenylphosphine complexes of ruthenium and rhodium

Russian Chemical Bulletin -     

Photolytic generation of ketones from 6-phenanthridinylmethyl ethers of secondary alcohols

Ketones are generated by photolysis (320 nm) of 6-phenanthridinylmethyl ethers of secondary alcohols. The 6-phenanthridinylmethyl group may therefore be utilized as a latent carbonyl function, especially as the 6-phenanthridinyl-methyl group is chemically inert toward hydroboration, Grignard additions, LiAlH₄-reduction, bromination or ozonolysis at other parts of the molecule     

乙酸中碘催化氧化苄醇为相应醛或酮(英文)

本文报道了用I2/NaNO2/4-OH-TEMPO为催化剂,空气为氧化剂,在冰乙酸中催化氧化苄醇的方法.文中考察了催化剂各组分和温度对催化氧化反应的影响,在催化过程中碘替代过渡金属作为4-OH-TEMPO的共催化剂,在选择条件下苄醇氧反应的产物产率达到90%,在反应过程中生成醛或酮.     

Au6Pd/resin催化伯醇和仲醇氧化偶联-转移加氢反应制备酮类化合物

由简单小分子通过 C–C键偶联来构筑复杂多样的大分子是有机合成的重要方向.传统的 C–C键偶联反应一般使用卤代烃和金属有机化合物为底物,具有原子效率低、有害废弃物排放等缺点.因此,迫切需要发展一种绿色高效的 C–C键偶联方法.其中,以醇类化合物作为底物通过“氢转移”(脱氢/aldol缩合/加氢)实现 C–C键偶联的途径受到广泛关注.该方法具有诸多优点：(1)醇类化合物来源广泛、价格低廉、相对安全;(2)只产生 H2和 H2O,没有其它副产物.但由于醇类化合物(特别是仲醇)脱氢困难,该偶联反应条件一般比较苛刻.我们使用 O2来辅助仲醇脱氢,采用离子交换树脂负载的 Au6Pd纳米颗粒为催化剂,实现了温和条件下伯醇和仲醇的偶联反应.而且发现在氧化气氛下,反应过程中发生了“氢转移”现象,产物为饱和酮类化合物.通过设计对照实验并结合 XAFS(X–射线吸收光谱)表征结果,我们揭示了在 Au6Pd/resin催化剂上发生“氢转移”反应的机理. AuPd/resin催化剂采用离子交换–NaBH4还原法制备. TEM照片显示 Au, Pd以及双金属 AuPd纳米颗粒均匀分散在载体上,平均粒径为2–4 nm,而且随着 Au/Pd比例减小, AuPd纳米颗粒的粒径逐渐减小. XRD谱图显示,随着 Au/Pd比例减小, Au(111)衍射峰逐渐向高角度发生偏移,说明 AuPd形成了合金.我们以苯甲醇和(±)-1-苯乙醇氧化偶联为探针反应考察了催化剂的催化性能.结果显示,以 Au/resin和 Pd/resin为催化剂时,产物为不饱和酮.而以 AuPd/resin为催化剂时,转化率显著提高,说明 AuPd之间存在明显的协同作用.而且随着 Au/Pd比例增加,产物逐渐由不饱和酮转变为饱和酮,当 Au/Pd≥6时,产物完全为饱和酮,说明反应过程中发生了“氢转移”.为验证这一推测,我们以苯甲醇和查尔酮为底物在相同条件下反应.结果显示,以 Au/resin和 Pd/resin为催化剂时,查尔酮没有转化.而以 AuPd/resin为催化剂时,查尔酮大部分转化为饱和酮(转化率为91%),验证了反应中发生了“氢转移”的推测.为研究“氢转移”发生的机理,我们采用 XAFS对催化剂价态进行了表征. Pd元素 K边 X射线吸收谱图显示,随着催化剂中 Au/Pd比例的增加,E0值逐渐减小,说明 Pd价态逐渐降低. EXAFS拟合数据表明,随催化剂中 Au/Pd比例增加, Pd–O配位数逐渐减小.基于以上结果推断,在 AuPd/resin催化剂中,随着 Au/Pd比例的增加, Pd的抗氧化能力显著增强,更多的 Pd以 Pd(0)形式存在.结合文献报道结果,我们认为正是催化剂中的 Pd(0)夺取了醇的βC–H后生成了 Pd–H,而 Pd–H是“氢转移”反应的催化剂.另一方面,有文献报道,在氧化气氛下, O2也可以辅助脱除醇的βC–H.为区分 Pd(0)和 O2在脱除醇βC–H中的作用,我们对 Au6Pd/resin在惰性气氛下对伯醇(苯甲醇)或仲醇((±)-1–苯乙醇)转化的催化性能进行了考察.结果显示,苯甲醇可以转化为苯甲酸(收率为23%),而(±)-1–苯乙醇则完全没有转化.这说明伯醇可以直接被催化剂(Pd(0))活化,而仲醇的活化则必须有 O2参与.综上,我们提出伯醇和仲醇氧化偶联反应的机理： Au6Pd/resin催化伯醇转化为醛(同时产生 Pd–H物种),而 O2辅助活化仲醇转化为酮.醛和酮发生 aldol缩合生成α,β不饱和酮,该中间物种被 Pd–H加氢生成饱和产物.     

Copper-catalyzed alkylation of benzoxazoles with secondary alkyl halides

Copper-catalyzed direct alkylation of benzoxazoles using nonactivated secondary alkyl halides has been developed. The best catalyst is a new copper(I) complex (1), and the reactions are promoted by bis[2-(N,N-dimethylamino)ethyl] ether.     

InBr3-catalyzed reduction of ketones with a hydrosilane: deoxygenation of aromatic ketones and selective synthesis of secondary alcohols and symmetrical ethers from aliphatic ketones

An InBr₃-Et₃SiH reducing system was developed to selectively convert aliphatic ketones to a variety of secondary alcohols in moderate to good yields. An initial mixing of InBr₃ and PhSiH₃ was followed by the addition of aliphatic ketones and a solvent to afford the symmetrical ether derivatives.     

Copper-catalyzed oxidative esterification of alcohols with aldehydes activated by Lewis acids

An efficient oxidative esterification of aromatic and aliphatic aldehydes with simple alcohols was accomplished using catalytic amounts of Cu(ClO₄)₂·6H₂O and InBr₃ with tert-hydroperoxide as an oxidant.     

Copper-catalyzed solvent-free redox condensation of benzothiazoles with aldehydes or benzylic alcohols

An efficient and practical method for the construction of 2-aryl- and 2-alkyl-substituted benzothiazoles via a copper-catalyzed redox condensation process between benzothiazoles and aldehydes or benzylic alcohols has been developed. The reaction proceeded under mild reaction conditions using environmentally benign tert-butyl hydroperoxide (TBHP) as the oxidant. A reaction mechanism involving the ring-opening of benzothiazoles initiated by the attack of acyl radical on the thiazole ring and intramolecular condensation is proposed based on the isolation of an anilide disulfide intermediate.