Mild and direct conversion of esters to morpholine amides using diisobutyl(morpholino)aluminum: application to efficient one-pot synthesis of ketones and aldehydes from esters

Morpholine amide intermediates, which are easily prepared by aminolysis of various esters with diisobutyl(morpholino)aluminum, react with organolithium and reducing agents (DIBALH or LDBMA) without isolation of the aminolysis intermediates to give ketones in 83–95% yields and aldehydes quantitatively.     

Facile oxidative conversion of alcohols to esters using molecular iodine

A simple, efficient, and high-yield procedure for the oxidative conversion of alcohols to various types of esters and ketones, with molecular iodine and potassium carbonate was successfully carried out.     

多相 MnOx氮掺杂碳材料催化氮杂环侧链 Csp3-H的氧化反应

sp3杂化的碳氢键氧化成酮是有机合成中一个重要方法.相应的酮产物被广泛应用在医药和天然产物合成中.目前已经开发出多种衍生于含 N杂环酮的药物化合物和具有生物活性的天然产物,例如阿普米定、苯吡胺、氯苯吡胺、曲普利啶、多西拉敏等.传统的含 N杂环侧链氧化生成酮的方法使用化学计量的强氧化剂(如高锰酸钾),不可避免地产生众多的副产物.近年来,均相的过渡金属催化剂被广泛应用于含 N杂环侧链氧化生成酮的反应中.但是 N杂环和过渡金属配位导致催化剂失活,选择性降低.金属的残留也使后处理过程变得繁琐.均相催化剂还存在难以回收利用的缺点.使用多相催化剂可以解决上述问题,因而具有重大的研究意义.目前为止,还很少有文献报道多相催化剂催化含 N杂环侧链氧化生成酮的方法.本文使用硝酸锰和菲啰啉的络合物在氮气氛围中高温焙烧,制备了一系列新型 MnOx-N@C材料.首次应用于 C–H氧化成酮的领域中.以2-苄基吡啶为模板底物,使用叔丁基过氧化氢为氧化剂,我们研究了 MnOx-N@C材料的催化活性.研究发现,在600oC焙烧得到的 MnOx-N@C材料具有最高的催化活性.实验得到最佳的反应条件：0.5 mmol底物,3当量的叔丁基过氧化氢,1 mg MnOx-N@C (600oC)材料. ICP结果表明,1 mg MnOx-N@C (600oC)材料中含有的锰相对于0.5 mmol底物的摩尔分数为0.79 mol%,说明该材料具有很高的催化活性.我们进一步研究了 MnOx-N@C (600oC)材料适用的底物范围,发现它可以催化2,3-环戊烯并吡啶类化合物、苄基吡啶类化合物发生氧化反应生成相应的酮;当反应底物中存在其他可以被氧化的碳氢键时,该材料表现出很高的选择性,可见其具有广泛的底物范围和优异的选择性.对于克级以上规模的底物量, MnOx-N@C仍能表现出很高的催化活性,表明其在有机合成中具有很好的实用性;连续使用6次后,该催化剂依然表现出很高的催化活性.表征结果表明, MnOx-N@C (600oC)材料中 MnOx粒子大小为1.71–6.56 nm;样品中存在 C–N, C=N和吡咯型的 N; Mn的化学态有+2,+3和+4.     

Efficient oxidation of alcohols electrochemically mediated by azabicyclo-N-oxyls

Preparation of azabicyclo-N-oxyls and the electrochemical oxidation of alcohols using them as mediators have been exploited. This oxidation was applicable to a transformation of sterically hindered secondary alcohols into the corresponding ketones in high yields.     

N, O-ligand accelerated zinc-catalyzed transesterification of alcohols with vinyl esters

N-Phenyldiethanolamine (1f) is an efficient ligand for zinc-catalyzed transesterification of alcohols with vinyl acetate (R³ = Me) at room temperature. In the case of using other vinyl esters (R³ = Et, n-Pr, Ph), the corresponding products were easily obtained in the presence of pyridine-type ligand 2 instead of aminoalcohol 1f.     

1,2-Diethoxyethane catalyzed oxidative cleavage of gem-disubstituted aromatic alkenes to ketones under minimal solvent conditions

Aerobic oxidation using pure dioxygen gas as the oxidant has attracted much attention, but its application in synthetic chemistry has been significantly hampered by the complexity of catalytic system and potential risk of high-energy dioxygen gas. By employing 1,2-diethoxyethane as a catalyst and ambient air as an oxidant, an efficient protocol for the construction of various aryl-alkyl and diaryl ketones through oxidative cleavage of gem-disubstituted aromatic alkenes under minimal solvent conditions has been achieved.     

Iodine-mediated Z-selective oxidation of ketones to α,β-unsaturated esters: synthesis and mechanistic studies

The Z-selective oxidation of simple acyclic ketones to Z-2,3-trisubstituted α,β-unsaturated esters is described. Enolates generated under the reaction conditions undergo double iodination followed by a Favorskii-related rearrangement to the unsaturated ester. This reaction represents the first stereoselective one-step transformation of ketones to α,β-unsaturated esters. Mechanistic studies suggest that an electrocyclic reaction governs the Favorskii-related rearrangement.     

Iron-catalyzed benzamide formation. Application to the synthesis of moclobemide

A convenient and user-friendly method to yield benzamides from primary and secondary amines and various benzylic alcohols in the presence of a cheap iron salt (FeCl₂·4H₂O) and tert-butylhydroperoxide (70% in water) as a stoichiometric oxidant is described. Control experiments indicated that this reaction might involve radical species. This method proved to be general, generating a family of 30 benzamides and was applied to the preparative synthesis of anti-anxiety drug moclobemide.     

An effective one-pot conversion of acid chlorides to aldehydes and ketones

Aldehydes and ketones were synthesized from their respective acid chlorides via a one-pot protocol. Morpholine amide intermediates that were readily prepared by the aminolysis of various acid chlorides with diisobutyl(morpholino)aluminum smoothly reacted with the reducing agent LDBMA and the organolithium reagents under mild reaction conditions (0 °C), giving almost excellent product yields of up to 95%.     

Laccase-catalyzed carbon-carbon bond formation: oxidative dimerization of salicylic esters by air in aqueous solution

The laccase catalyzed oxidative dimerization of salicylic esters, a rare example of a laccase-catalyzed carbon-carbon bond formation, was studied. This reaction allows the use of air as stoichiometric oxidant and proceeds in aqueous solution. The preparative scope and the mechanism of the method, which provides a new and convenient access to functionalized biaryls under mild conditions, were investigated.     

Novel C-C bond cleavage under mild, neutral conditions: conversion of electron-deficient aryl alkyl ketones to aryl carboxylic esters

A novel, unique way to cleave the carbon-carbon bond in aryl alkyl ketones under mild, neutral conditions is described. Treatment of aryl alkyl ketones in a refluxing mixture of N,N-dimethylformamide dimethyl acetal and methanol for 16 h provided aryl carboxylic esters. The scope and limitations of the reaction are discussed. Useful yields of the reaction can be obtained with electron-deficient aryl groups, and the yields are higher when the alkyl group is larger than a methyl group. Studies toward elucidation of the reaction mechanism led to a proposed mechanism that is consistent with all the observations.     

Cationic iridium-BINAP complex-catalyzed addition of aryl ketones to alkynes and alkenes via directed C-H bond cleavage

Cationic Ir complex ([Ir(cod)₂]BF₄ + BINAP) catalyzed the addition of ortho-C-H bonds in aryl ketones to alkynes, which gave alkenylated products in good to high yield. Styrene derivatives were good substrates, and the enantioselective addition to norbornene was also described.     

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.     

An efficient method for the reductive conversion of acyclic esters to ethers via a TMS-protected acetal

We report an efficient two step process for the reduction of non-aromatic esters to the corresponding ethers via the intermediate TMS-protected acetal. The acetal formed after the first step can be carried on directly to the subsequent reduction to the ether without purification. The ester reduction step was monitored using in-situ ReactIR for disappearance of the CO peak, allowing for the exact determination of time and equivalents of the reducing agent. Furthermore, use of TMS-imidazole to form the acetal has allowed us to dramatically reduce the overall reaction time required for the two step procedure.     

Catalytic oxidative conversion of alcohols, aldehydes and amines into nitriles using KI/I2-TBHP system

The oxidative conversion of alcohols, aldehydes and amines to give corresponding nitriles in excellent yields was easily achieved by the catalytic amount of KI or I₂ in combination with TBHP as an external oxidant. This non-transition metal catalyst is cost effective and provides easy work-up and separation of the product.     

Direct conversion of primary and secondary carboxylic acids to trifluoromethyl ketones

Primary and secondary carboxylic acids were converted in one step to the corresponding trifluoromethyl ketones by treatment with trifluoroacetic anhydride (TFAA) and pyridine in toluene at 60-100 °C followed by hydrolysis/decarboxylation with water at 45 °C.     

Fragmentation of chloroperoxides: hypochlorite-mediated dehydration of hydroperoxyacetals to esters

Hypochlorites efficiently dehydrate hydroperoxyacetals to furnish the corresponding esters. The reaction, which can be accomplished with stoichometric Ca(OCl)₂ or with catalytic amounts of t-BuOCl, appears to involve formation and heterolytic fragmentation of secondary chloroperoxides, species not previously described in solution chemistry.