An Efficient One-pot Synthesis of β-Amino/β-Acetamido Carbonyl Compounds via ZrCl4-catalyzed Mannich-type Reaction

Zirconium(IV) chloride catalyzed efficient one-pot synthesis of β-amino/β-acetamido carbonyl compounds at room temperature is described. In the presence of ZrCl4, the three-component Mannich-type reaction via a variety of in situ generated aldimines, with various ketones, aromatic aldehydes and aromatic amines in ethanol, led to the formation of β-amino carbonyl compounds and the four-component Mannich-type reaction of aromatic aldehydes with various ketones, acetonitrile and acetyl chloride resulted in the corresponding β-acetamido carbonyl compounds in high to excellent yields. This methodology has also been applied towards the synthesis of dimeric β-amino/β-acetamido carbonyl compounds.     

Synthesis of Quinolines via a Metal‐Catalyzed Dehydrogenative N‐Heterocyclization

Efficient ruthenium‐, rhodium‐, palladium‐, copper‐ and iridium‐catalysed methodologies have been recently developed for the synthesis of quinolines by the reaction of 2‐aminobenzyl alcohols with carbonyl compounds (aldehydes and ketones) or the related alcohols. The reaction is assumed to proceed via a sequence involving initial metal‐catalysed oxidation of 2‐aminobenzyl alcohols to the related 2‐aminobenzaldehydes, followed by cross aldol reaction with a carbonyl compound under basic conditions to afford α,β‐unsaturated carbonyl compounds. These aldehydes or ketones can be also generated in situ via dehydrogenation of the related primary and secondary alcohols. In the final step cyclodehydration of the α,β‐unsaturated carbonyl compound intermediates gives quinolines. Good yields of quinolines were also obtained by reacting 2‐nitrobenzyl alcohols and secondary alcohols in the presence of a ruthenium catalyst. Finally, aniline derivatives afforded also a useful access to quinolines by the reaction with 1,3‐propanediol or 3‐amino‐1‐propanol, or in a three‐component reaction with benzyl alcohol and aliphatic alcohols.     

纳米铝粉促进羰基化合物水相烯丙基化反应

氮气保护条件下,纳米铝在0.1 N NH₄Cl溶液中,能有效地促进羰基化合物与烯丙基溴进行Barbier-Grignard型烯丙基化反应,得到相应高烯丙醇。芳香族醛或酮的烯丙基化产率较高,而脂肪族羰基化合物反应产率低,反应产率受羰基空间位阻影响大,在同样条件下,邻羟基羰基化合物烯丙基化产物主要是赤式-邻二醇。     

Synthesis of Oximes with NH2OH.HCl/DOWEX(R)50WX4 System

The oximation of a variety of carbonyl compounds was efficiently carried out with DOWEX(R)50WX4/NH₂OH·HCl system. The reactions were performed in ethanol to give Z‐aldoximation isomers of aldehydes and E‐oximaton of acetophenone derivatives in a perfect selectively. The oximation of compounds with two carbonyl groups was carried out selectively on one carbonyl moiety. Also, the oximation of aldehydes over ketones has been accomplished successfully by this system.     

Synthesis of β-amino carbonyl compounds via a Zn(OTf)2-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds

A Zn(OTf)₂-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds was described. This one-pot three-component reaction afforded the corresponding β-amino carbonyl compounds, β-amino esters, and β-amino ketones in good to excellent yields. The reaction was also applied for the liquid-phase synthesis of β-amino carbonyl compound library using PEG as a support.     

An Improved Liquid-Phase Synthesis of Simple Alkylpyridines

The synthesis of pyridines from mixtures of aldehydes or ketones NH₃ in the liquid phase has been reinvestigated, using continuous dosage of the carbonyl components to the reaction mixture. The main product from the reaction of acetaldehyde and formaldehyde is 3-methylpyridine ( 6 ), which is also the main product from the reaction of acrolein or a mixture of crotonaldehyde and formaldehyde under the same conditions. The reaction of other aldehydes with formaldehyde give 3,5-dialklypyridines, e.g. 10, 16 . Acetone reacts with either formaldehyde or acetaldehyde to give polysubstituted alkylpyridines. A mechanistic pathway is proposed which accounts for the formation of the observed products.     

Lead(IV) acetate oxidative ring-opening of 2,3-epoxy primary alcohols: a new entry to optically active α-hydroxy carbonyl compounds

The treatment of 2,3-epoxy primary alcohols with lead(IV) acetate (LTA) leads to α-acetoxy aldehydes or α-acetoxy ketones, through the nucleophilic ring-opening of an intermediate oxonium and the subsequent carbon-carbon bond cleavage. This reaction represents a new route to optically active α-hydroxy carbonyl compounds.     

Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C₅₊ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd‐promoted ZnO‐ZrO₂ catalyst. The sequence of reaction steps involved in the C₅₊ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross‐aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C₅₊ ketones and the stability of the catalyst. A yield of >70 % to C₅₊ ketones was achieved over a 0.1 % Pd‐ZnO‐ZrO₂ mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation.     

Predominantly sigma-bonded metal carbonyl cations (sigma-carbonyls): new synthetic,structural, and bonding concepts in metal carbonyl chemistry

Predominantly σ‐bonded metal carbonyl cations (σ‐carbonyls) are conveniently generated in the Lewis superacid SbF₅ or the conjugate Brønsted–Lewis superacid HF? SbF₅, primarily by solvolytic or reductive carbonylations. Thermally stable salts are formed with the fluoroantimonate(V ) ions [SbF₆]^? and [Sb₂F₁₁]^?. The salts are characterised by analytical, structural, spectroscopic and computational methods. Most homoleptic carbonyl cations have very regular geometries, comensurate with their d‐electron configurations: linear (d¹⁰), square planar (d⁸) or octahedral(d⁶). The cations with metals in oxidation states of +2 or +3 are termed “superelectrophilic”. Extended molecular structures form by significant interionic C? F contacts with electrophilic carbon as acceptor. To account for all experimental observations, a conceptually simple synergetic bonding model is proposed. An outlook at anticipated future developments based on very recent results is provided.     

Synthesis of Mannich type products via a three-component coupling reaction

The reactions of alkyl nitriles, acetyl chloride, aldehydes and β-ketoesters or simple ketones was studied for the one-pot synthesis of β-acetamido carbonyl compounds. It was observed that the reaction proceeds in the absence of Lewis acids. However, a Lewis acid catalyzes the reaction and several were tested. It was found that whereas Cu(OTf)₂ is suitable for the coupling of β-ketoesters with aldehydes, Sc(OTf)₃ is the best for ketones. A possible mechanism is proposed based on the isolation and characterization of an intermediate.     

Facile One‐Pot Synthesis of N‐Alkylated Benzimidazole and Benzotriazole from Carbonyl Compounds

An efficient one‐pot N‐alkylation of benzimidazole and benzotriazole from carbonyl compounds and tosylhydrazide has been accomplished via copper powder‐catalyzed N—H bond insertion affording N‐alkylated products in good yields. The reaction can tolerate a wide range of carbonyl compounds, such as aryl, alkyl, heterocyclic and α,β‐unsaturated ketones, and aldehydes.     

Enolizable Carbonyls and N,O‐Acetals: A Rational Approach for Room‐Temperature Lewis Superacid‐Catalyzed Direct α‐Amidoalkylation of Ketones and Aldehydes

An efficient catalytic room‐temperature direct α‐amidoalkylation of carbonyl donors, that is, ketones and aldehydes with unbiased N,O‐acetals, is described. Sn(NTf₂)₄ is an optimal catalyst to promote this challenging transformation at low loading and the reaction shows promising scope. A comprehensive and rational evaluation of this reaction has led to the establishment of an empirical scale of nucleophilic reactivity for a broad set of ketones that should be helpful in the synthetic design and development of carbonyl α‐functionalization methods.     

Generation of perfluoro- and 1-chloropolyfluorobenzocycloalken-1-yl cations and their relative stability

Treatment of perfluorinated benzocyclobutene, indan, and tetralin with SbF₅-SO₂Cl₂, as well as of their 1,1-dichloro analogs with SbF₅, gave 1-chloropolyfluorobenzocycloalken-1-yl cations whose structure was studied by ¹⁹F and ¹³C NMR and confirmed by their transformations into perfluorinated ketones upon hydrolysis. Dissolution of perfluorinated benzocyclobutene, indan, and tetralin in excess SbF5 generated perfluorobenzocycloalken-1-yl cations in equilibrium with their precursors. The relative stability of perfluoro- and 1-chloropolyfluorobenzocycloalken-1-yl cations decreases as the size of the alicyclic fragment increases.     

Allylation of Carbonyl Compounds Mediated by Aluminum/Fluoride Salts in Water

A novel mediator (Al/KF) has been developed and employed in the Barbier‐type alkylations of various aldehydes and ketones with alkyl halide in water. The carbonyl compounds could be effectively converted into corresponding homoallylic alcohol in good yields only when allyl bromides or substituted allyl bromides were used as halides. Aromatic aldehydes could afford homoallylic alcohols in high yields, unfortunately, the allylation of aromatic aldehyde substituted by nitro‐ or amino‐group could not proceed smoothly, and the allylation yields of ketones and aliphatic carbonyl compounds were lower under the same condition. The diastereoselectivity and regioseletivity of the reaction have also been studied, the predominant products preferred the erythro‐ or anti‐isomer in dominant γ‐adduct by using Al/KF mediated allylation of benzaldehydes with cinnamyl bromide and ethyl 4‐bromo‐2‐butenoate in water.     

Solvent-switchable Acetalization by Yb（OTf）3-Catalyzed Procedures

O,O＇Diethyl acetals were prepared in high yields under mild conditions via the reaction of triethyl orthoformate with aldehydes and ketones in absolute ethanol in the presence of as low as 0.1 tool% of Yb（OTf）3. Using the same catalyst in THF-H2O, these O,O＇-diethyl acetals could be converted to the corresponding carbonyl compounds efficiently. This new protection-deprotection protocol presents the advantages of ease of execution, high efficiency and good chemoselectivity.     

A New Glimpse into the CO2‐Philicity of Carbonyl Compounds

We report a theoretical study on non‐conventional structures of 1:1 complexes between carbon dioxide and carbonyl compounds. These structures have never been reported before but are relevant for understanding the solubility of carbonyl compounds in supercritical CO₂. The work is based on the results of ab initio calculations at the MP2 and CCSD(T) levels using aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets. Investigated systems include aldehydes, ketones and esters, together with some fluorinated derivatives. The results are interpreted in terms of natural bond orbital analyses. Harmonic vibrational frequency calculations have also been done in order to compare them with available experimental data. We show for the first time that complexes where CO₂ behaves globally as a Lewis base are stable in the case of ketones and esters, but not in the case of aldehydes, and their stability is similar to that of traditional complexes in which CO₂ behaves as a Lewis acid. This finding considerably modifies the concept of CO₂‐philicity and may have important ramifications in the development of green reactions in supercritical CO₂.     

Metal and solvent‐free cyanosilylation of carbonyl compounds with tris(pentafluorophenyl)borane

A highly effective method of the cynaosilylation of aldehydes and ketones with TMSCN in the presence of catalytic amount of B(C₆F₅)₃ [tris(pentafluorophenyl)borane] has been developed. Cyano transfer from TMSCN to carbonyl group proceeds at room temperature under solvent‐free conditions. Various alehydes and ketones have been converted into the corresponding trimethylsilylether within short reaction times with excellent yield under mild conditions. Copyright © 2008 John Wiley & Sons, Ltd.     

Zirconium borohydride piperazine complex, an efficient, air and thermally stable reducing agent

A zirconium borohydride piperazine complex (Ppyz)Zr(BH₄)₂Cl₂, obtained by the reaction of an ethereal solution of ZrCl₄ and LiBH₄ with piperazine is a stable, selective and efficient reducing agent. (Ppyz)Zr(BH₄)₂Cl₂ reduces aldehydes, ketones, silylethers, α,β-unsaturated carbonyl compounds and esters. The reactions were performed in diethyl ether at room temperature or under reflux, and the yields of the corresponding alcohols were excellent. The selective reduction of aldehydes in the presence of ketones and complete regioselectivity in the reduction of α,β-unsaturated carbonyl groups were observed.     

Efficient One‐Pot Synthesis of β‐Acetamido Carbonyl Compounds Using Fe3O4 Nanoparticles

A new, one‐pot condensation of aldehydes, enolizable ketones and esters, AcCl, and MeCN, in the presence of Fe₃O₄ nanoparticles (nano‐Fe₃O₄) as an efficient catalyst, for the preparation of β‐acetamido carbonyl compounds at room temperature is described.     

Chemoselectivity in the Reaction of 2‐Diazo‐3‐oxo‐3‐phenylpropanal with Aldehydes and Ketones

The chemoselectivity in the reaction of 2‐diazo‐3‐oxo‐3‐phenylpropanal ( 1 ) with aldehydes and ketones in the presence of Et₃N was investigated. The results indicate that 1 reacts with aromatic aldehydes with weak electron‐donating substituents and cyclic ketones under formation of 6‐phenyl‐4H‐1,3‐dioxin‐4‐one derivatives. However, it reacts with aromatic aldehydes with electron‐withdrawing substituents to yield 1,3‐diaryl‐3‐hydroxypropan‐1‐ones, accompanied by chalcone derivatives in some cases. It did not react with linear ketones, aliphatic aldehydes, and aromatic aldehydes with strong electron‐donating substituents. A mechanism for the formation of 1,3‐diaryl‐3‐hydroxypropan‐1‐ones and chalcone derivatives is proposed. We also tried to react 1 with other unsaturated compounds, including various olefins and nitriles, and cumulated unsaturated compounds, such as N,N′‐dialkylcarbodiimines, phenyl isocyanate, isothiocyanate, and CS₂. Only with N,N′‐dialkylcarbodiimines, the expected cycloaddition took place.