An efficient one-pot, two-step synthesis of 4-substituted 1-heteroarylpiperazines under microwave irradiation conditions

A highly efficient one-pot, two-step microwave procedure has been developed for the synthesis of 4-substituted 1-heteroarylpiperazines. Microwave heating of heteroaryl chlorides with 1,4-diazabicyclo[2.2.2]octane (DABCO) at 160 °C for 15 min yielded 1-heteroaryl-4-(2-chloroethyl)piperazines, which could be further reacted with various nucleophiles, again under microwave irradiation conditions, to give an array of 4-substituted 1-heteroarylpiperazines in good to excellent yields.     

新型碱性离子液体催化剂高效催化合成吡喃酮[2,3-d]嘧啶酮和[2,3-d]嘧啶衍生物

制备了碱性离子液体1,1'-(丁烷-1,4-二基)双(1,4-二氮杂二环[2.2.2]辛烷-1-ium)羟化物,并采用红外光谱、1H核磁共振谱和pH值分析对其进行了表征.然后将它用于室温研磨条件下高效催化合成吡喃酮[2,3-d]嘧啶酮和[2,3-d]嘧啶.该法步骤简单,反应时间短,产物收率高,无需柱色谱分离,原料易得,且可回收利用.     

DABCO catalyzed reaction of various nucleophiles with activated alkynes leading to the formation of alkenoic acid esters, 1,4-dioxane, morpholine, and piperazinone derivatives

The reaction of acids, alcohols, acylamides, 1,2-diols, 1,2-diamines or amino alcohols with activated alkynes catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) was systematically investigated. A series of unsaturated alkenoic acid esters or heterocycles were formed in the reaction of monobasic or dibasic nucleophiles in excellent yields, respectively.     

Ab Initio Study of H-Bond Dynamics in Three-Component Crystals Comprising (DABCOH+)n Polycationic Chains

In this work, the dynamic character of hydrogen-bond (H-bond) networks in two three-component crystals comprising polycationic chains was described. The first studied system was 1,4-diazabicyclo[2.2.2]octan-1-ium (DABCOH⁺) sulfamate monohydrate, known for its large negative linear compressibility. The second analyzed material was the newly obtained polar salt co-crystal: 1,4-diazabicyclo[2.2.2]octan-1-ium sulfamate urea. X-ray diffraction measurements enabled us to study the H-bond systems in both crystals using the graph set analysis. Obtained structures served as the initial models for Born-Oppenheimer molecular dynamics computations. A detailed study of intermolecular interactions and power spectra was conducted. The analysis of time and space correlations between the changes in H-bonds enabled the detection of proton transfer occurring in both systems at 300 K. Further study of those dynamic phenomena was done using the Energy Decomposition Analysis for selected trajectory fragments. Our work should improve the understanding of dielectric and ferroelectric properties of hybrid organic-inorganic materials.     

Does the DABCO-catalysed reaction of 2-hydroxybenzaldehydes with methyl acrylate follow a Baylis-Hillman pathway?

Evidence is presented which supports the intermediacy of dipolar Baylis-Hillman-type adducts in the synthesis of coumarin and chromene derivatives from the reaction of 2-hydroxybenzaldehydes with methyl acrylate in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO).     

Two novel phase transition materials based on 1-isopropyl-1,4-diazabicyclo[2.2.2]octan-1-ium

Two novel phase transition materials,[C₉H₂₀N₂] [Na(BF₄)₃] (1) and[C₉H₂₀N₂] [(PF₆)₂] (2), were synthesized based on 1-isopropyl-1,4-diazabicyclo[2.2.2]octan-1-ium with sodium tetrafluoroborate and hexafluorophosphoric acid, respectively. Differential scanning calorimetry measurements detected that 1 and 2 underwent reversible phase transitions, which were confirmed by dielectric measurements. Single crystal X-ray diffraction data suggested that compound 1 changed from a high temperature phase with a space group of P6₃ to a low temperature one with a space group of P2₁/c, and that compound 2 transformed from the space group of Pbca at room temperature to P2₁/c at low temperature. Formation of hydrogen bonds and distortion of 1,4-diazabicyclo[2.2.2]octane rings may drive the transitions.     

Sulfonylation of 1,4-Diazabicyclo[2.2.2]octane: Charge-Transfer Complex Triggered C−N Bond Cleavage

A novel charge-transfer complex triggered sulfonylation of 1,4-diazabicyclo[2.2.2]octane (DABCO) with mild reaction conditions has been developed. The formation of a charge-transfer complex between electron-withdrawing (hetero)aryl sulfonyl chloride and DABCO allows the synthesis of N-ethylated piperazine sulfonamide in good yields. The reaction has a high functional group tolerance. Spectroscopic studies confirmed the charge-transfer complex formation between sulfonyl chlorides and DABCO, which facilitates the C−N bond cleavage of DABCO.     

Rhodium-catalyzed formylation of organomercurials: application to efficient polyol synthesis

The rhodium-catalyzed formylation of organomercurials-a new transformation of organomercurials-is reported. The addition of 0.50 equiv of 1,4-diazabicyclo[2.2.2]octane (DABCO) was found to promote the reaction, and it is postulated that the DABCO acts as a ligand for mercury. Several examples are presented to document the scope of the reaction. This reaction was developed in the context of a larger program focused on the development of efficient strategies for the synthesis of polyol-derived natural products, and an efficient (8 steps) synthesis of Tolypothrix pentaether that employs this methodology is reported.     

Dual nucleophilic catalysis with DABCO for the N-methylation of indoles

DABCO is an extremely active catalyst for the methylation of indoles in conjunction with dimethyl carbonate (DMC). This green chemistry is highly effective and produces N-methylindoles in nearly quantitative yields. The reaction sequence consists of competing alkylation and acylation pathways and involves 1,4-diazabicyclo[2.2.2]octane (DABCO) dually as a nucleophilic catalyst, ultimately resulting in a single product: the N-methylated indole.     

DABCO-促进新型呋喃并[3,2-c]喹啉酮类化合物的合成

在1,4-二氮杂二环[2.2.2]辛烷(DABCO)促进下,以水为反应介质,通过3-溴乙酰基-4-羟基-1-甲基-2-喹啉酮与芳香醛的亲核取代、分子内环化及消除的串联反应,合成了9个新型的呋喃并[3,2-c]喹啉酮类化合物,其结构经~1H NMR,~(13)C NMR,IR,MS(ESI)和元素分析表征。     

DABCO-Catalyzed Multicomponent Reaction for Synthesis of Benzo[a]carbazoles

DABCO (1,4-diazabicyclo[2.2.2]octane) catalyzed a multicomponent reaction using the starting precursor 2,3,4,9-tetrahydro-1H-carbazol-1-one, malononitrile, and aromatic/heteroaromatic aldehyde.     

Reaction of 1-arylmethylidenepyrazolidin-1-azomethine imines with aryl ketenes

A reaction of aryl ketenes with 1-arylmethylidenepyrazolidin-1-azomethine imines, generated by the diaziridine ring opening in 6-aryl-1,5-diazabicyclo[3.1.0]hexanes catalyzed with Et2O·BF3, leads to 1,2-bis(phenylacetyl)pyrazolidine, 2-arylacetyl-1-arylidenepyrazolidin-1-ium chlorides, or a representative of 1,5-diazabicyclo[3.3.0]octan-2-ones, viz., 4-(4-eth-oxyphenyl)-3,3-diphenyl-1,5-diazabicyclo[3.3.0]octan-2-one, depending on the reaction conditions and the structure of the starting compounds. A mechanism suggested earlier for the transformation of 1,5-diazabicyclo[3.1.0]hexanes in the reaction with ketenes was confirmed.     

Synthesis of Spiro Dihydrofurans and 1,8-Dioxo-xanthenes via DABCO Catalyzed Tandem Reaction of Aldehyde with Cyclohexane-1,3-dione and Dimedone

The 1,4-diazabicyclo[2.2.2]octane(DABCO) catalyzed reaction of cyclohexane-1,3-dione or dimedone with various aldehydes in acetonitrile resulted in the polysubstituted tetraketones, spiro dihydrofurans or 1,8-dioxo-xanthenes derivatives as main products respectively according to the structure of reactants and reaction conditions.     

DABCO-mediated substitution of vinylic iodides: synthesis of β-cyano Baylis-Hillman acetates

Nucleophilic substitution of vinyl β-iodo Baylis-Hillman acetates using 1,4-diazabicyclo[2.2.2] octane (DABCO) and then KCN, provides a stereoselective method for the synthesis of the corresponding β-cyano Baylis-Hillman acetates in high yields.     

Synthesis of substituted chromenes through the DABCO-catalyzed reaction of but-3-yn-2-one and methyl propiolate with salicyl N-tosylimines (DABCO = 1,4-diazabicyclo[2.2.2]octane)

The DABCO-catalyzed (DABCO = 1,4-diazabicyclo[2.2.2]octane) reaction of but-3-yn-2-one and methyl propiolate with salicyl N-tosylimines yields highly functionalized chromenes and has been thoroughly investigated; the rational mechanism for the reaction has been demonstrated on the basis of 1H NMR spectroscopic investigation.     

A simple and convenient synthesis of [1,2,4]triazolo/benzimidazolo ‎quinazolinone and [1,2,4]triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine derivatives catalyzed by ‎DABCO-based ionic liquids

DABCO-based ionic liquids were utilized for the preparation of [1,2,4]triazolo/benzimidazolo quinazolinone and [1,2,4]triazolo[1,5-a]pyrimidine derivatives in the adequate procedures. These methods involve three-component reaction between aldehydes, β-diketones and 3-amino-1,2,4-triazole or 2-aminobenzimidazole in the presence of 1,4-disulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium chloride ([DABCO](SO₃H)₂(Cl)₂) and 1,4-disulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium dihydrogen sulfate ([DABCO](SO₃H)₂(HSO₄)₂) as reusable and economical catalysts at 100 °C. These methods also show eco-friendly characters by elimination of solvent. Any by-product was not prepared through this method, and products were separated by a simple workup procedure. The other noticeable benefits of these procedures are excellent yields, short reaction times, mild reaction conditions and use of available and inexpensive materials.     

Easy Conversion of Dimethyl α-(Bromomethyl)fumarate into Functionalized Allyl Ethers Mediated by DABCO

New functionalized allyl ethers were obtained in good yields following the mild selective reaction of different alcohols with allyl bromide in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) and a catalytic amount of triethylamine (TEA) at room temperature.     

Base-mediated stereospecific synthesis of aryloxy and amino substituted ethyl acrylates

The stereospecific synthesis of aryloxy and amino substituted E- and Z-ethyl-3-acrylates is of interest because of their potential in the polymer industry and in medicinal chemistry. During work on a copper-catalyzed cross-coupling reaction of ethyl (E)- and (Z)-3-iodoacrylates with phenols and N-heterocycles, we discovered a very simple (nonmetallic) method for the stereospecific synthesis of aryloxy and amino substituted acrylates. To study this long-standing problem on the stereoselectivity of aryloxy and amino substituted acrylates, a series of O- and N-substituted nucleophiles was allowed to react with ethyl (E)- and (Z)-3-iodoacrylates. Screening of different bases indicated that DABCO (1,4-diazabicyclo[2.2.2]octane) afforded successful conversion of ethyl (E)- and (Z)-3-iodoacrylates into aryloxy and amino substituted ethyl acrylates in a stereospecific manner. Herein are the details of this DABCO-mediated stereospecific synthesis of aryloxy and amino substituted E- or Z-acrylates.     

SYNTHESIS,CHARACTERIZATION, AND CRYSTAL STRUCTURE OF A NOVEL DECAVANADATE Mg(H2O)6(C6H14N2)2V10O28·8H2O

Journal of Structural Chemistry - A novel decavanadate salt Mg(H2O)6(C6H14N2)2V10O28·8H2O is obtained by the reaction of vanadium oxide and 1,4-diazabicyclo [2.2.2] octane (DABCO). The title...     

On the effect of 1,4-diazabicyclo[2.2.2]octane on the singlet-oxygen dimol emission: photosensitized generation of (1O2)2

Time-resolved singlet-oxygen dimol luminescence has been recorded upon laser-pulsed photosensitization of singlet oxygen by 2-acetonaphthone or 1-H-phenalen-1-one in perfluorobenzene, perdeuterobenzene, and perdeuteroacetonitrile. It is shown that 1,4-diazabicyclo[2.2.2]octane (DABCO) does not enhance radiative properties of the dimol species generated by the photosensitization. Instead, DABCO strongly reduces the singlet-oxygen dimol luminescence. Rate constants for the quenching of the dimol luminescence by DABCO have been determined for the three solvents used.