Synthesis of β-hydroxymalonates: the direct aldol addition of malonates to aldehydes in the presence of SiCl4 and i-Pr2EtN

The direct aldol addition of malonates to aromatic, hetero-aromatic and unsaturated aldehydes leading to β-hydroxymalonates is described. The stability of these products, the trimethyl silyl protection of the hydroxyl group as well as the role of both SiCl₄ and i-Pr₂EtN in attaining the final products are also discussed.     

Direct ethoxycarbonyldifluoromethylation of aromatic compounds using Fenton reagent

Direct ethoxycarbonyldifluoromethylation of aromatic compounds by BrCF₂CO₂Et was investigated using Fenton reagent in dimethylsulfoxide. Various five-membered hetero-aromatic compounds, benzene derivatives and uracil having ethoxycarbonyldifluoromethyl group were obtained catalytically with the combination of ferrocene and H₂O₂ at room temperature. The ethoxycarbonyldifluoromethylation occurred at the position predicted by the trend of the electrophilic substitution of aromatic compounds. When para-substituted aniline derivatives were used as a substrate, the one-pot synthesis of 3,3-difluoro-2,3-dihydroindole-2-one derivatives was achieved through the ethoxycarbonyldifluoromethylation at the ortho-position to the amino group and the consecutive intramolecular amidation of the amino group and the adjacent ethoxycarbonyldifluoromethyl group.     

Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P2O5/SiO2 under heterogeneous conditions

A convenient and efficient procedure for the Friedel-Crafts acylation of aromatic compounds with carboxylic acids in the presence of P₂O₅/SiO₂ is described. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields of the products are the advantages of this method.     

Esr studies on the reactive character of the radical anions,so−2, so−3 and so−4 in aqueous solution

The reactive characteristics of the oxy anion radicals of sulphur, SO^?₂, SO^?₃ and SO^?₄ were investigated by use of the rapid-mixing flow technique coupled with electron spin resonance (ESR) which can detect the radicals having a lifetime of 5–100 msec. The SO^?₂ reduced the aromatic nitro compounds to the corresponding anion radicals, but did not abstract the hydrogen from the saturated compounds nor add to the unsaturated compounds. The SO^?₃ could add to the compounds having CC bond, but did not abstract the hydrogen from the saturated compounds nor reduce the aromatic nitro compounds. The SO^?₄ could abstract the hydrogen from the saturated compounds and also add to the unsaturated compounds having CC bond, but did not reduce the aromatic nitro compounds. These differences of the reactivity towards the organic substrates were discussed on the basis of the difference in the distribution of the unpaired electron density of each radical anion.     

Reductive esterification of aromatic aldehydes using Zn/Ac2O/imidazole or Zn/Yb(OTf)3/(RCO)2O system

Benzaldehydes are reduced by metallic zinc in the presence of Ac₂O and imidazole, giving the corresponding benzyl acetates in good yields. Reductive esterification of aromatic aldehydes is also carried out via gem-diacetoxy compounds. Carbonyl compounds are readily converted to the gem-diacyloxy compounds in excellent yields on treatment with 2 molar amounts of acid anhydride and 10 mol% of Yb(OTf)₃ in MeCN at room temperature. Thus-formed diacyloxy compounds derived from aromatic aldehydes are reduced in situ by metallic zinc to afford the corresponding esters.     

Hf[N(SO2C8F17)2]4-catalyzed Friedel-Crafts acylation in a fluorous biphase system

In a fluorous biphase system, Hf[N(SO₂C₈F₁₇)₂]₄ complex (1 mol %) catalyzes Friedel-Crafts acylation of aromatic compounds such as anisole, toluene and chlorobenzene, and the corresponding aromatic ketones are obtained in satisfactory to high yields. The catalyst is selectively soluble in lower fluorous phase and can be easily recovered by simple phase separation. Furthermore, the catalyst can be reused without decrease of activity in most cases.     

硫酸亚铈催化的芳香化合物与苄基醇、烯丙醇类化合物以及苄基氯的傅-克烷基化反应研究

硫酸亚铈作为一种便宜的和有效的催化剂催化芳香化合物与苄基醇、烯丙醇类化合物和苄基氯的傅-克烷基化反应. 在1～10 mol%的硫酸亚铈存在下, 芳香化合物分别与苄基醇、烯丙醇类化合物和苄基氯能够顺利有效地进行傅-克烷基化反应. 此外, 催化剂能回收, 再次使用三次也没有明显地失去催化活性.     

Synthesis, characterization, and crystal structures of n-alkyldiorganodithiophosphates RS2P(OC6H4)2

Treatment of KS₂P(OC₆H₄)₂ (1) with five n-alkyl halides afforded the stable n-alkyldithiophosphate compounds RS₂P(OC₆H₄)₂ (2–6). Single crystal X-ray analysis revealed that the PS₂ fragment in 1 displays an isobidentate coordination pattern; compounds 2–4 display a monodentate binding pattern. The crystal packing of title compounds is stabilized by cation-π, weak hydrogen bonding C–H---O, as well as aromatic non-bonded interactions.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid, H5[PMo10V2O40]

The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

Chiral trans-carboxylic trifluoromethyl 2-imidazolines by a Ag2O-catalyzed Mannich-type reaction

Trifluoromethyl aldimines derived from α-amino esters have proven to be very good starting materials to obtain the title compounds. A Ag₂O-catalyzed Mannich-type/cyclization cascade reaction starting from suitable α-isocyano acetates leads to enantiopure valuable trans-carboxylic trifluoromethyl substituted 2-imidazolines by a highly stereoselective addition without the need to add organocatalysts.     

Metal carbonyl complexes of 3,5-dimethylaceheptylene. Synthesis and molecular structures of (C14H8Me2)Mn2(CO)6 and (C14H8Me2)Fe3(CO)8

The reactions of the non-alternant polycyclic aromatic hydrocarbon 3,5-dimethylaceheptylene, C₁₄H₈Me₂, with various transition metal carbonyls and the molecular geometry of the compounds (C₁₄H₈Me₂)Mn₂(CO)₆ and (C₁₄H₈Me₂)Fe₃(CO)₈ is shown.     

HClO4-SiO2 catalyzed stereoselective synthesis of β-amino ketones via a direct Mannich-type reaction

The HClO₄-SiO₂ catalyzed three-component, one-pot Mannich reaction of ketones, aromatic aldehydes and aromatic amines is carried out in ethanol to afford the corresponding β-amino ketones in good yields and high stereoselectivities in favor of the anti-isomer. Three new compounds are reported.     

Regioselective bromination of aromatic compounds with Br2/SO2Cl2 over microporous catalysts

A new selective brominating system Br₂/SO₂Cl₂/zeolite, has been discovered. Partially cation-exchanged Ca²⁺-Y zeolite efficiently catalyzes the selective para-bromination of neat chlorobenzene (CB) by Br₂/SO₂Cl₂ affording a CB conversion of ∼89% and a para-selectivity of ∼97%. During the bromination reaction, SO₂Cl₂ oxidizes HBr, prevents its accumulation within the zeolite pores and yields a more active brominating species. The Ca²⁺-Y catalyst was found to be stable under the bromination conditions, and can easily be regenerated by calcination. The Br₂/SO₂Cl₂/Ca²⁺-Y brominating system could be applicable to other activated aromatic compounds such as o-xylene, toluene and fluorobenzene.     

Nitric acid in the presence of P2O5 supported on silica gel—a useful reagent for nitration of aromatic compounds under solvent-free conditions

A variety of aromatic compounds are nitrated to parent nitro aromatic compounds under solvent-free conditions using 65% nitric acid in the presence of P₂O₅ supported on silica gel is described. This methodology is useful for nitration of activated and deactivated aromatic rings.     

POCl3-mediated synthesis of hydrolysis-prone 2-trifluoroethylbenzimidazoles

Loss of a trifluoromethyl group has been observed as an unproductive side reaction in the formation of 2-trifluoroethylbenzimidazoles. A hydrolytic mechanism for this transformation is proposed that is consistent with evidence for the identity of reaction intermediates. Cyclodehydration with POCl₃ suppresses hydrolysis of the trifluoromethyl group and provides 2-trifluoroethylbenzimidazoles in good yields.     

An efficient synthesis of diarylmethanes via InCl3·4H2O-catalyzed dehydration of electron-rich arenes with trioxane

A facile, efficient and environmentally benign procedure for the synthesis of diarylmethanes via the reaction of arenes with trioxane catalyzed by InCl₃·4H₂O was developed. The reactions of aromatic compounds bearing electron-donating group proceeded smoothly affording the corresponding diarylmethanes in good to excellent yields.     

Molybdenum pentachloride (MoCl5) or molybdenum dichloride dioxide (MoO2Cl2): advanced catalysts for thioacetalization of heterocyclic, aromatic and aliphatic compounds

A new, convenient and mild method for thioacetalization of heterocyclic, aromatic and aliphatic compounds catalyzed by MoCl₅ or MoO₂Cl₂ is described. This novel method is important for the synthesis of the difficult to prepare heterocyclic thioacetals such as the pterin thioacetals and it offers significant advantages such as high conversion, short reaction times and simplicity in operation.     

SnCl2-catalyzed three-component one-pot Mannich-type reaction: efficient synthesis of β-aminocarbonyl compounds

Abstract  

SnCl₂-catalyzed three-component one-pot Mannich reaction of acetophenone or p-chloroacetophenone with different aromatic aldehydes and aromatic amines in ethanol at ambient temperature gave the corresponding β-aminocarbonyl compounds in good to excellent yields. Four new compounds are reported for the first time.     

η2-acylcarbonylvanadium-verbindungen

Substituted vanadium carbonyl compounds with η²-bonded acyl ligands (η²-RCO)V(CO)₃

(

= ditertiary phosphines or arsines: dppe, dppp, dppm, diars, arphos, dpase) have been prepared by photochemical reaction of [V(CO)₄

] with various substituted benzoyl chlorides and cyclopropanylcarbonyl chloride.Effects of aromatic substituents and

upon the thermal stability of the η²-acylcarbonylvanadium compounds are discussed. IR ν(CO) force constants and ⁵¹V NMR signals are linearly correlated with Hammett's σ constants of the aromatic substituents.The preparation of V(CO)₂Cl(diars)₂ is described.     

Highly chemoselective reduction using a Rh/C-Fe(OAc)2 system: practical synthesis of functionalized indoles

Here, we report a highly effective and chemoselective method of preparing substituted indoles from (E)-2-nitropyrrolidinostyrenes via hydrogenation in the presence of a rhodium catalyst doped by additives such as Ni(NO₃)₂·6H₂O, Fe(OAc)₂ or Co(acac)₃. These hydrogenation conditions may also be applied to other substrates. Aromatic nitro compounds and olefins can be selectively reduced in the presence of aromatic benzyl ethers, aromatic halides and aromatic aldehydes.