A straightforward preparation of fluorine-containing 1,2-dihydropyrimidines and pyrimidines with 2,2-dihydropolyfluoroalkylaldehydes

The reactions of 2,2-dihydropolyfluoroalkylaldehydes with ammonia and enol ethers or carbonyl compounds are described. In the presence of zinc chloride, all reactions took place readily in THF at 50 °C to give fluorine-containing 1,2-dihydropyrimidines in moderate to good yields. Dehydrogenation of the resulting fluorine-containing 1,2-dihydropyrimidines with tetrachloro-1,4-benzoquinone (TCBQ) or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) at room temperature afforded the corresponding fluorine-containing pyrimidines in good yields.     

Reactions of 2,2-dihydropolyfluoroalkylaldehydes with amines: a facile synthetic method for fluoroalkyl enaminoketones

Reactions of 2,2-dihydropolyfluoroalkylaldehydes (1) with amines (2) were studied. Both aliphatic amines and electron-deficient aromatic amines readily reacted with 1 in acetonitrile and water under reflux to give fluoroalkyl enaminoketones (3) in high yields, while no condensed products were obtained by reactions of 1 with electron-rich aromatic amines under similar conditions. In the presence of triethylamine, however, the reaction of 1 with electron-rich aromatic amines at room temperature gave 3 in low yields.     

The reaction of 2-fluoroalkyl-1-iodoethylenes with arylamines: a facile method for the synthesis of fluoroalkylated quinolines and enaminoketones

The reaction of 2-fluoroalkyl-1-iodoethylenes with arylamines (1) and the subsequent acid promoted transformation of the products were described. In the presence of ZnCl₂ and triethylamine, 1 reacted readily with various p-substituted anilines in HMPA under a vacuum of 60-70 mmHg to give the corresponding enaminoaldehydes (2) as a mixture of E- and Z-isomers. Cyclization of 2, without further purification in refluxing toluene, catalyzed by strong acids such as p-toluene sulfonic acid and trifluoromethanesulfonic acid gave 2-fluoroalkylquinolines (3) in good yields, while fluoroalkylated enaminoketones (4) were obtained predominantly when 2 was treated with acids in aqueous THF solution. A possible mechanism was proposed for the formation of 3 and 4.     

An indium-TMSCl promoted reaction of diphenyl diselenides and aldehydes: novel routes to selenoacetals and alkyl phenyl selenides

The reaction of diphenyl diselenides with aldehydes in the presence of In-TMSCl has been investigated. Aliphatic aldehydes provide the corresponding selenoacetals, whereas aromatic aldehydes lead predominantly to alkyl phenyl selenides under the same reaction conditions. This constitutes a new approach for the synthesis of selenoacetals and selenides from aldehydes.     

A ruthenium-catalyzed one-pot method for α-alkylation of ketones with aldehydes

Ketones react with an array of aldehydes in dioxane at 80 °C in the presence of a catalytic amount of RuCl₂(PPh₃)₃ along with KOH to give the corresponding α-alkylated ketones in moderate to good yields. A reaction pathway involving base-catalyzed cross-aldol reaction between ketones and aldehydes to form α,β-unsaturated ketones and regioselective reduction of carbon-carbon double bond of α,β-unsaturated ketones is proposed for this catalytic process.     

Titanium-mediated cross-coupling reactions of imines with ketones or aldehydes: an efficient route for the synthesis of 1,2-amino alcohols

The cross-coupling reactions of imines with ketones using Ti(OⁱPr)₄/c-C₅H₉MgCl reagent lead to 1,2-amino alcohols after hydrolysis. The coupling reactions with aldehydes could also afford 1,2-amino alcohols, however, in some cases, aziridines were obtained as major products in a stereoselective manner.     

An indium-TMSCl promoted reaction of diphenyl diselenide and diorganyl disulfides with aldehydes: novel routes to selenoacetals, thioacetals and alkyl phenyl selenides

The reactions of diphenyl diselenide and dialkyl disulfides with aldehydes in the presence of In-TMSCl have been investigated. Aliphatic aldehydes provide the corresponding selenoacetals and aromatic aldehydes lead predominantly to benzyl phenyl selenides on reaction with diphenyl diselenide. However, the reaction of dimethyl disulfide and diphenyl disulfide with both aromatic and aliphatic aldehydes produce dithioacetals. This provides a novel route to the synthesis of selenoacetals, thioacetals and selenides from aldehydes.     

Catalytic hydroboration of aldehydes and ketones with sodium hydride: Application to chemoselective reduction of aldehydes over ketones

Sodium hydride-promoted catalytic hydroboration of aldehydes and ketones with pinacolborane (HBpin) was examined, and 10?mol% of NaH was found to cause the HBpin to participate in hydroboration in a convenient and efficient manner at mild reaction conditions. Further chemoselective hydroboration of aldehyde over ketone functionality was also analyzed. In addition, no hydroboration was observed form ester, acyl chloride, amide, nitrile, alkene, alkyne, alkyl halide and epoxide functional groups indicate that present system (HBpin, NaH) is highly selective for aldehydes and ketones.     

Studies on the reaction of unsymmetrical trifluoromethyl 1,2-phenylenediamine with various ketones leading to novel fluorinated heterocycles

Unsymmetrical 1,2-phenylenediamine on reaction with various ketones resulted in a number of fluorinated heterocycles such as benzimidazoles, quinoxalines and spiro benzimidazoles in high yields. The role of substituents in diamine in its reaction with various ketones and on the nature of product formation has been studied in detail.     

A novel system for the synthesis of nitriles from aldehydes using aqueous ammonia and sodium dichloroiodate

A simple and mild method for the conversion of varieties of aldehydes to the corresponding nitriles using aqueous ammonia and aqueous sodium dichloroiodate reagent at room temperature is discussed. Advantages of this system are short reaction time, easy work-up and moderate to good yields.     

碲氢化钠与苯并咪唑盐的反应和醛的合成新方法

自1975年Barton首次制备了碲氢化钠以来,由于它是一种温和的选择性还原剂和良好的亲核试剂,并具有试剂易得、后处理方便等优点,在有机合成中的应用得到了迅速发展[1-5].例如,Barton等[1]用碲氢化钠对吡啶盐和异喹啉盐的季铵化的碳氮双键在碱性乙醇溶液中还原脱卤能生成加氢衍生物.本文则首次报道碲氢化钠对苯并咪唑盐还原脱卤生成苯并咪唑烷的反应.其合成路线如图示1所示:     

A novel carbocatalytic hydride transfer strategy for efficient reduction of structurally different aldehydes and ketones in water

Reduced graphene oxide (rGO)–NaBH₄ is reported as mild and efficient catalyst-system for chemo-/regioselective reduction of structurally different aliphatic, aromatic as well as α,β-unsaturated aldehydes and ketones in water. The rGO was prepared by reducing graphene oxide using Tulsi leaf extract as bio-reductant. Operational simplicity, ambient reaction condition, high yield of pure products (80–97%), no by-product formation, no use of column chromatography for purification are the salient features of the envisaged protocol. Furthermore, the recovered TRGO was recycled and reused for subsequent reductions up to five times without any loss in activity.     

3,3,6,6-Tetrachloro-2,2-dihydroxycyclohexanone as a synthetic equivalent of unavailable 3-chloro-6-hydroxy-1,2-benzoquinone: first synthesis of 4-chloro-1-hydroxyphenazines

3,3,6,6-Tetrachloro-2,2-dihydroxycyclohexanone has been found to be an excellent synthetic equivalent of unavailable 3-chloro-6-hydroxycyclohexa-1,2-benzoquinone. Reactions with 1,2-phenylenediamines provide hitherto unattainable 4-chloro-1-hydroxyphenazines in fair to high yields.     

Direct Leuckart-type reductive amination of aldehydes and ketones: a facile one-pot protocol for the preparation of secondary and tertiary amines

A high-yielding and facile one-pot Leuckart-type reaction for rapid access to a number of 2° and 3° amines is described.     

Development of a sensitive fluorescent derivatization reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethoxy-carbonylhydrazine and its application for determination of aldehydes from alcoholic beverage using high-performance liquid chromatography with fluorescence detection and enhance mass spectrometric identification

A pre-column derivatization method for the sensitive determination of aldehydes using the tagging reagent 1,2-benzo-3,4-dihydrocarbazole-9-ethoxy-carbonylhydazine (BCEC) followed by high-performance liquid chromatography with fluorescence detection and enhance mass spectrometric identification has been developed. The chromophore of fluoren-9-methoxy-carbonylhydrazine (Fmoc-hydrazine) reagent was replaced by 1,2-benzo-3,4-dihydrocarbazole functional group, which resulted in a sensitive fluorescence derivatizing agent BCEC. BCEC can easily and quickly label aldehydes. The maximum excitation (333 nm) and emission (390 nm) wavelengths were essential no change for all the aldehyde derivatives. The fluorescence intensity was substantially affected by the solvents, being higher in organic than protic solvents. Derivatives are sufficiently stable to be efficiently analyzed by high-performance liquid chromatography. The derivatives showed an intense protonated molecular ion corresponding m/z [M + (CH₂)_n − 1]⁺ (M: molecular mass of BCEC, n: corresponding aldehyde carbon atom numbers) under positive-ion mode. The collision-induced dissociation of protonated molecular ion formed products at m/z = 245.7.0, m/z = 263.7 and m/z = 217.7, and corresponding the cleavage of CH₂OCO, CH₂OCO and NCH₂CH₂ bonds, respectively. Studies on derivatization demonstrated excellent derivative yields in the presence of trichloroacetic acid (TCA) catalyst. Maximal yields close to 100% were observed with a 10- to 15-fold molar reagent excess. Separation of the derivatized aldehydes has been optimized on ZORBAX Eclipse XDB-C₈ column with aqueous acetonitrile in conjunction with a binary gradient elution. Excellent linear responses were observed at the concentration range of 0.08-16.65 μmol/L with coefficients of >0.9999. Estimated detection limits for the aldehydes, obtained by successive dilution of a derivatized standard solution containing 16.65 μmol/L of each aldehyde (at a signal-to-noise ratio = 3:1), are from 3.75 to 16.65 fmol.     

Amberlyst-15 as a novel and recyclable solid acid for the coupling of aromatic aldehydes with homopropargyl alcohol

Aldehydes undergo smooth condensation with homopropargyl alcohol in the presence of Amberlyst-15^® under mild conditions to afford the corresponding β-butynyloxy enones in excellent yields with a high degree of selectivity.     

A novel three-component reaction for the synthesis of 1,2-dihydroisoquinolines via the reaction of isoquinoline and isocyanides with strong CH-acids in water

A straightforward and efficient method for the synthesis of 1,2-dihydroisoquinolines via the one-pot, three-component reaction of an isocyanide, isoquinoline and a strong CH-acid in water without using any catalyst at 70 °C is reported. The method offers several advantages including high yields of products and an easy work-up procedure.     

Sulfamic acid:An efficient,cost-effective and green catalyst for crossed-aldol condensation of ketones with aromatic aldehydes under solvent-free

Aromatic aldehydes undergo crossed-aldol condensation with ketones in the presence of catalytic amount of sulfamic acid(SA) to afford the correspondingα,β-unsaturated aldol products under solvent-free conditions in good to high yields at 45-80℃.     

A novel alpha-arylation of ketones,aldehydes, and esters via a photoinduced SN1 reaction through 4-aminophenyl cations

4-Aminophenyl cations (expediently generated by photolysis of 4-chloroaniline and its N,N-dimethyl derivative by photolysis in MeCN) added to enamines and gave the corresponding alpha-(4-aminophenyl) ketones in satisfactory yields. The yields of the same ketones were increased when silyl enol ethers were used in the place of enamines. The alpha-arylation of silyl enol ethers of aldehydes occurred with lower yields and only with the N,N-dimethyl derivative. The procedure was successful with ketene silyl acetals giving in a single step a good yield of alpha-(4-aminophenyl)propionic(acetic) esters, known intermediates for the preparation of analgesic compounds. The reaction of the aryl cation with Danishefsky's diene gave the arylated beta-methoxy enone. The method is complementary to the recently developed palladium-catalyzed alpha-arylation and occurs under neutral conditions.     

Three-component bimetallic (Pd/In) mediated cascade allylation of C=X functionality: Part 1. Scope and Class 1 examples with aldehydes and ketones

A new general three-component Pd/In bimetallic cascade reaction with four synthetic variants involving aryl iodides, allenes and C=X compounds affording homoallylic alcohols/amines as products is described and exemplified for Class 1 processes (intermolecular Pd-intermolecular In steps). Remarkable increases in yield and reaction rates were observed in the presence of amine additives. Excellent diastereoselection is exhibited when 2-hydroxycyclohexanone is employed, and semi-empirical and ab initio calculations are used to rationalise the observed syn:anti diastereoselectivity.