Construction of 3,9-diazatetraasteranes and 3,9-diazatetracyclododecanes by photocycloaddition reaction of 1,4-dihydropyridines: Experimental and theoretical investigation

A photocycloaddition reaction of ethyl 1,4-diaryl-1,4-dihydropyridine-3-carboxylate for the construction of 3,9-diazatetraasteranes (P₁) and 3,9-diazatetracyclododecanes (P₂) is reported for the first time. The types of reaction product clearly differ with solvent, regardless of the irradiation wavelength. The difference in P₁ and P₂ lies in the second step of the intramolecular [2 + 2] photocyclization. In order to further investigate this phenomenon and gain a deeper understanding of the photochemical behavior of 1,4-dihydropyridines, DFT and TDDFT theoretical calculations are performed. The results provide a good explanation for the formation of 3,9-diazatetraasteranes and 3,9-diazatetracyclododecanes.     

3,9-二氮杂四星烷类化合物的合成研究

对3,9-二氮杂四星烷(3,9-二氮杂六环[6.4.0.0^2,7.0^4,11.0^5,10]十二烷)的合成进行了系统地研究. 以1,4-二氢吡啶为原料, 研究了溶剂、溶液浓度、光源、照射波长及光照时间等因素对[2＋2]环加成反应的影响, 得到了一系列3,9-二氮杂四星烷化合物, 并用IR, ¹H NMR, ¹³C NMR, MS和HRMS对其结构进行了表征.     

Reductive Studies on 3-Oxidopyrylium-alkene [5 + 2] Cycloadducts: Access to Some Hydroxy Cycloheptenoids

The scope of nickel boride as a versatile reducing reagent is extended to the 3-oxidopyrylium-alkene [5 + 2] cycloadducts. In this report, we demonstrate that nickel boride is capable of one-pot 1,2- and 1,4-reduction of enones present in the cycloadducts in good yields. Subsequent elaboration of the cycloadducts towards synthesis of functionalized cycloheptenoid derivatives devoid of the oxa-bridge is also explored.

Microwave-Accelerated Ruthenium-Catalyzed [2π + 2π] Cycloadditions of Dimethylacetylene Dicarboxylate with Norbornenes

An efficient and convenient procedure has been developed for the ruthenium-catalyzed [2π + 2π] cycloadditions of dimethylacetylene dicarboxylate with norbornenes. Reaction is significantly accelerated in microwave conditions, while the commonly used benzene solvent was replaced by environmentally benign tetrahydrofuran.

De novo synthesis of 1,4-dihydropyridines and pyridines

An efficient and general method for the synthesis of 1,4-dihydropyridines and pyridines based on a lithiation/isomerization/intramolecular carbolithiation sequence is reported. This procedure provides an efficient, divergent, and straightforward entry to a wide range of polysubstituted dihydropyridines and pyridines starting from readily available N-allyl-ynamides.     

Novel synthetic route to 1,4-dihydropyridines from β-amino acrylates by using titanium(IV) chloride under facile conditions

The reactions of Boc-β-amido- and β-amino acrylates, in which the CC possesses both nucleophilic and electrophilic sites, were investigated under acidic conditions. The trifluoroacetic-acid induced cyclization of the β-amido acrylates to the corresponding oxazolidin-2-ones involves a rarely seen nucleophilic attack of the carbamate carbonyl group. The cyclotrimerization of β-amino acrylates to N-substituted 1,4-dihydropyridines was observed in the presence of a Lewis acid. High yields of 1,4-dihydropyridines (70–83%) were readily obtained by using substoichiometric amount TiCl₄ under mild condition. The cyclotrimerization is presumably occurring via a Hantzsch related mechanism involving three addition/elimination reactions of the amphiphilically reactive CC.     

Studies on the photochemical oxidation of N,N-diacyl-1,4-dihydropyrazine derivatives

The photochemical oxidation of N,N-diacyl-1,4-dihydropyrazines was investigated by irradiation from a medium-pressure mercury lamp. The main products of the photooxygenation were isolated and unambiguously confirmed by ¹H NMR spectra, ¹³C NMR spectra, H-H, C-H correlation spectra, high-resolution mass spectrometry, and single-crystal x-ray diffraction analysis. The complicated NMR spectra of main products were studied by variable-temperature NMR experiments. The mechanism of the photooxygenation of N,N-diacyl-1,4-dihydropyrazines is suggested to be a [2 + 2] cycloaddition of oxygen to the double bond.     

Blue Photoluminescent Dimeric Cu(I) Dithiophosphates Bridged by a Flexible Ligand 1,2-Bis(4-Pyridyl)Ethane

The title compound {Cu[S₂P(OC₂H₅)₂](bpe)} _n (1) is constructed from flexible ligand bpe (bpe = 1,2-bis(4-pyridyl)ethane) and the Cu[S₂P(OC₂H₅)₂], which was characterized by single crystal structure determination, elemental analysis, XRD, and IR spectra. X-ray diffraction studies revealed that polymeric compound 1 consists of dinuclear module to form 1-D chains with the intramolecular Cu···Cu interactions (ca. 2.63 Å). This interaction may show a profound influence on the observed blue luminescence emission spectrum for 1. Crystal data for 1 at 293(2) K: Space group P ? 1, a = 9.277(3), b = 10.504 (4), c = 31.801(1) Å, α = 92.849(3), β = 90.401(2), γ = 114.547(7)°, V = 2813.9(2) ų, Z = 2, R ₁ = 0.041.     

FeCl3 · 6H2O-Catalyzed Acceleration of the Acylation of Sodium Azide with N-Acylbenzotriazoles

Catalyzed by ferric chloride hexahydrate (FeCl₃ · 6H₂O), the acylation of sodium azide with N-acylbenzotriazoles was greatly accelerated in a mixed solvent of acetone and water. Thus, good to excellent yields of a variety of acyl azides were obtained at room temperature in a short time. Furthermore, because of the complete conversion of N-acylbenzotriazoles and the easy removal of the by-product, purification by column chromatography was no longer required, which made the protocol suitable for large-scale preparation.

Catalytic Synthesis of Fused 1,4-Dihydropyridines and 1,4-Dihydropyridine Derivatives Using Preyssler Heteropolyacids Catalyst

An efficient and convenient method for the synthesis of 1,4-dihydropyridines from β-dicarbonyl compounds, aldehydes, and ammonium acetate and the synthesis of fused 1,4-dihydropyridines from dimedone in the presence of Preyssler heteropolyacid catalyst are reported under reflux conditions with good to excellent yields. Preyssler heteropolyacid catalyst is easily prepared, stable (up to 300 °C), reusable, efficient, green and inexpensive.     

A convenient method for the synthesis of substituted 2-alkylthio-3-cyano-4,6-dimethyl-5-phenylcarbamoyl-1,4-dihydropyridines

Substituted 2-alkylthio-3-cyano-4,6-dimethyl-5-phenylcarbamoyl-1,4-dihydropyridines were obtained by successive reaction of acetaldehyde with cyanothioacetamide and acetoacetanilide, -chloracetamide or phenacyl bromide in the presence of piperidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 345–347, March, 2000.     

Stereocontrolled Oxyselenation Studies on 1,4-Dihydropyridines: Synthesis of Trans-2-hydroxy (or Alkoxy) 3-Phenylseleno-1,2,3,4-tetrahydropyridines

In view of the versatile chemistry and important applications of organoselenium compounds, the introduction of selenium and oxygen functionalities to 1,4-dihydropyridines 4a–d has been achieved. Thus, the natural tendency of 1,4-dihydropyridines 4a–d to undergo biomimetic oxidation to afford pyridinium salts can be switched off through the use of reagents that interact electrophilically with the enamine moiety present in the system. Electrophilic interaction of N-phenylselenophthalimide (N-PSP) with N-alkyl-1,4-dihydropyridines 4a–d in the presence of tetrahydrofuran/H₂O and alcohol (methanol or ethanol) stereoselectively leads to the corresponding trans-2-hydroxy (or alkoxy) 3-phenylseleno-1,2,3,4-tetrahydropyridines 5a–k in satisfactory yields (40–90%).

Palladium-catalyzed [5+2] oxidative annulation of N-Arylhydrazones with alkynes through CH activation to synthesize Benzo[d][1,2]diazepines

An efficient and novel method using palladium catalyst for the synthesis of benzo[d][1,2]diazepines by [5 + 2] annulation of N-arylhydrazones with alkynes has been developed. This methodology undergoes through eight membered palladacycle serving as a backbone for the formation of CC/CN bond to provide benzodiazepine derivatives in moderate to good yield.     

Chemoselective Reduction and Transesterification of α-Keto Propargylic Esters Mediated by NaBH4 and CeCl3 · 7H2O

An efficient one-pot synthesis of α -hydroxy propargylic esters by chemoselective reduction followed by transesterification using NaBH₄ in combination with CeCl₃ · 7H₂O is described.

RuCl3-DCHA Catalyst System: A Selective Aerobic Oxidation of Primary Benzylic Alcohols Under Mild Conditions

The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl₃ · 3H₂O–dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl₃ · 3H₂O–DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments.     

Three-Component Reaction of 4-Methylpyridine with Alkyl Propiolates and Secondary Phosphine Chalcogenides

The reaction between 4-methylpyridine, alkyl propiolates, and secondary phosphine oxides proceeded as N-vinylation-C-phosphorylation with stereo- and regioselective formation of (E)-N-ethenyl-C²- phosphoryl-1,2-dihydropyridines [when using bis(2-phenylethyl)phosphine oxide] or (E)-N-ethenyl-C⁴- phosphoryl-1,4-dihydropyridines (when using diphenylphosphine oxide). The process occurred at 60–62°C within 3 h to give functional dihydropyridines in 40–82% yield. Under similar conditions, bis(2-phenylethyl) phosphine sulfide and selenide reacted with alkyl propiolates preferably by nucleophilic PH-monoaddition at the triple bond.     

Platinum(II)‐Catalyzed Intramolecular Cyclization of o‐Substituted Aryl Alkynes through sp3 C?H Activation

Ring leader : PtCl₂ catalyzes intramolecular cyclization of o‐isopropyl or o‐benzyl aryl alkynes to give substituted indene derivatives with good yields and high selectivity. This reaction appears to proceed through an sp³ C? H activation and 1,4‐hydrogen migration pathway (see scheme).

     

Synthesis of Quinolines from N-Tosyl-1-azadienes

A route to aryl-substituted quinolines from N-tosyl 1-azadienes is described. The key steps are a [4 + 2] cycloaddition with benzyne followed by base treatment of the 1,4-dihydroquinoline product. The N-tosyl 1-azadienes were prepared from readily accessible cinnamaldehyde and chalcone substrates by condensation with p-TsNH₂.

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