Catalytic Amount Of DBU Research Articles

Stereodivergent Synthesis of Chiral Hydrobenzofuranpyrrolidines by Catalytic Asymmetric Dearomative Cyclization and Controlled Epimerization

A rapid and straightforward way to access stereoisomeric sets of products bearing multiple stereogenic centers is still a significant challenge in asymmetric catalysis. We present herein our experimental studies on the stereodivergent synthesis of chiral hydrobenzofuran‐fused pyrrolidines with three stereogenic centers via organocatalytic asymmetric dearomative cyclization and epimerization process. Chiral bifunctional thiourea catalyst could successfully promote the enantioselective dearomatization cyclization of 2‐nitrobenzofurans with o‐hydroxy aromatic aldimines, which enabled the synthesis of (3S,3aR,8bR)‐hydrobenzofuran[3.2]pyrrolidines in 79‐92% yields with >20:1 stereoselectivities and 93‐99% enantio‐ selectivities. While catalytic amount of DBU could induce the direct intramolecular epimerization of (3S,3aR,8bR)‐hydrobenzofuran[3.2] pyrrolidines to its diastereomers (3R,3aR,8bR)‐hydrobenzofuran[3.2] pyrrolidines in 72‐87% yields without loss of stereoselectivities. The mechanistic pathways of the epimerization process were investigated by a series of control experiments study. This work provides an alternative and forward solution for the stereodivergent preparation of functionalized pyrrolidines with potential bioactivities.

Metal-Free Catalyzed Oxidation/Decarboxylative [3+2] Cycloaddition Sequences of 3-Formylchromones to Access Pyrroles with Anti-Cancer Activity.

An efficient and direct approach to pyrroles was successfully developed by employing 3-formylchromones as decarboxylative coupling partners, and facilitated by microwave irradiation. The protocol utilizes easily accessible feedstocks, a catalytic amount of DBU without any metals, resulting in high efficiency and regioselectivity. Notably, all synthesized products were evaluated against five different cancer cell lines and compound 3l selectively inhibited the proliferation of HCT116 cells with an IC50 value of 10.65 μM.

Intermolecular direct catalytic cross-Michael/Michael reactions and tandem Michael/Michael/aldol reactions to linear compounds

Catalytic cross-Michael/Michael reactions of nitroalkenes and ethyl acrylate with pronucleophiles including thiols, dimethyl methylmalonate, and 2-nitropropane to linear three-component products were developed by using a catalytic amount of DBU in DMSO. Tandem sulfa-Michael/Michael/aldol reactions of a thiol, a nitroalkene, ethyl acrylate, and an aldehyde proceeded to give a linear four-component product. The high nucleophilicity of in situ-formed nitronate anions and ester enolates in DMSO was important for the present multi-component cascade reactions using pronucleophiles that had protons with relatively high acidity.

Ketones as Electrophile in Nitroaldol Reaction: Synthesis of β,β-Disubstituted- 1,3‑dinitroalkanes and Allylic Nitro Compounds

β,β-Disubstituted-1,3-dinitro compounds were obtained exclusively with an overall yield of 83% through a domino nitroaldol/elimination/1,4-addition process, when excess nitromethane was added to cyclohexanone or butanone using DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), as a basic catalyst. On the other hand, β-nitroalcohols could be obtained in 30-84% yield, when nitromethane reacts with different aliphatic ketones in stoichiometric amounts, in the presence of catalytic amounts of K2CO3(s), Amberlyst®-A21 or TBAF.3H2O (tetra-n-butylammonium fluoride trihydrate)/THF (tetrahydrofuran). In addition, a new and versatile route to obtainment of allylic nitro compounds, by treatment of acetylated nitroalcohols and aldehydes in catalytic amounts of DBU or TBAF.3H2O, via a one-pot elimination/nitroaldol reaction sequence, was developed.

Synthesis of 2-bromomethyl-2,3-dihydrobenzofurans from 2-allylphenols enabled by organocatalytic activation of N-bromosuccinimide

Activation of NBS in acetic acid and a catalytic amount of DBU promotes an intramolecular oxybromination of 2-allylphenols to produce highly aggregated value and densely functionalized 2-bromomethyl-2,3-dihydrobenzofurans.

Access to 2‐Amino‐3‐Arylthiophenes by Base‐Catalyzed Redox Condensation Reaction Between Arylacetonitriles, Chalcones, and Elemental Sulfur

AbstractA straightforward access to 2‐amino‐3‐arylthiophenes has been developed via one‐pot two‐step three‐component reaction of arylacetonitriles, chalcones and elemental sulfur. The first step consists of a DBU‐catalyzed formation of Michael adduct between arylacetonitriles and chalcones. The second step is a cascade of DABCO‐catalyzed sulfuration of the Michael adduct with elemental sulfur followed by an oxidative cyclization to afford thiophenes. Compared to the Gewald reactions and related transformations which are limited in acetonitriles bearing a methylene group activated by an α‐substituted electron withdrawing group as substrates, our method can be applied to a wide range of arylacetonitriles and requires only catalytic amounts of DBU and DABCO. The developed reaction opens an access to 3‐aryl‐2‐aminothiophenes complementary to classical Gewald reactions with high degree of structural diversity and atom efficiency.magnified image

An efficient and novel protocol for the synthesis of spiro[1,3]oxazino[5,6-c]quinoline derivatives by one-pot, three-component reaction

One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic amount of DBU in H2O/EtOH (1:1) at 50 °C produced the 4-aroyl-5′-methyl-3,4-dihydro-2′H-spiro[[1,3]oxazino[5,6-c]quinoline-2,3′-isoxazol]-5(6H)-one derivatives containing spiro[1,3]oxazino[5,6-c]quinoline moiety in 82–89% yield. The high yields of products, easy work-up, and availability of starting materials are the main advantages of this synthetic strategy.

Highly syn-Selective Elimination of Peterson anti-Adducts to Give Z-α,β-Unsaturated Esters

Peterson adducts have been known to stereospecifically give syn-elimination products upon treatment with base except when the product olefin is in conjugation with an electron-withdrawing group. The missing piece has been put in place by using a catalytic amount of DBU, by which syn-elimination could be effected to provide the thermally less stable Z-olefin from the anti-adduct with high selectivity.

Mono‐ and bifunctional six‐membered cyclic carbonates synthesized by diphenyl carbonate toward networked polycarbonate films

ABSTRACTThe synthesis of six‐membered cyclic carbonates from diols utilizing less toxic and easily‐handled diphenyl carbonate (DPC) is carried out based on the reactivity and selectivity at different conditions. Commercially‐available neopentylglycol (NPG) or di(trimethylolproapane) (DTMP) react effectively with DPC at 140°C and converted to their corresponding monofunctional NPG‐carbonate (NPGC) or bifunctional DTMPC‐carboante (DTMPC), respectively. The selectivity of these carbonates changes depending on a feed ratio of DPC and these diols. After a NPG/DPC mixture with the DPC/NPG feed ratio of 4 was heated at 140°C for 48 h, the NPGC is isolated with a yield of 74%. A 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU)‐catalyzed ring‐opening polymerization (ROP) of NPGC with DTMPC can form effectively networked structures. By only drying of THF solutions containing NPGC, DTMPC, and a catalytic amount of DBU at 60°C for 12 h, the ROP efficiently proceeds and networked polycarbonate films with well transparency and flexibility are easily obtained. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41956.

Synthesis of 3,3-disubstituted oxindoles by one-pot integrated Brønsted base-catalyzed trichloroacetimidation of 3-hydroxyoxindoles and Brønsted acid-catalyzed nucleophilic substitution reaction

Treatment of 3-hydroxyoxindoles with trichloroacetonitrile (1.3 equiv.) and a catalytic amount of DBU (0.1 equiv.) followed by addition of nucleophiles (1.5 equiv.) and diphenylphosphoric acid (0.2 equiv.) afforded the 3,3-disubstituted oxindoles in good to excellent yields. DFT computations supported the notion that the reaction went through the 1-alkyl-2-oxo-2H-indol-1-ium intermediate.

Novel peripherally tetra-substituted octacationic metal-free and metallophthalocyanines: Synthesis, spectroscopic characterization and aggregation behaviours

In this study, new 1,3-bis[3-(diethylamino)phenoxy]propan-2-ol 1 and phthalonitrile derivative 3 bearing 1,3-bis[3-(diethylamino)phenoxy]propan-2-ol substituent at peripheral position have been synthesized. The synthesis, characterization of the tetra-4-(2-[3-(diethylamino)phenoxy]-1-{[3-(diethylamino)phenoxy]methyl}ethoxy) substituted metal-free 4 and metallophthalocyanines 5, 6, 7, (MPcs, M=Ni, Co, Cu) are reported for the first time. These new metal-free and metallophthalocyanines 4–7 were converted into water soluble quaternized products by the reaction with methyl iodide 4a–7a. The metal-free phthalocyanine 4 was prepared from phthalonitrile derivative 3 in n-pentanol with a catalytic amount of 1,8-diazabicyclo[5.4.0]undec-7ene (DBU). Metallophthalocyanines 5–7 were prepared by cyclotetramerization of 3 with the corresponding metal salts (NiCl2, CoCl2, CuCl2) in n-pentanol with a catalytic amount of DBU. The aggregation behaviours of the phthalocyanine complexes were studied in different solvents and concentrations. The new compounds have been characterized by using UV–vis, IR, 1H NMR, 13C NMR, MS spectroscopic data and elemental analysis.

The Synthesis and Microbiological Activity of New 4-Chloropyridin-2-yl Derivatives

Synthesis of 4-chloropicolinamidrazone derivatives starting from 4-chloropicolinamide is described. The desired compounds were formed by reactions of methyl 4-chloropicolinohydrazonamide or 4-chloro-N'-methylpicolinohydrazonamide with suitable counter partners (carbon disulfide, alkyl halides, aldehydes, ketones, carbohydrazonamides or isothiocyanates) or via 4-chloropicolinimidate, obtained by a convenient method from nitrile with catalytic amount of DBU. Selected products were screened for bacteriostatic and tuberculostatic activity.

DBU-Catalyzed Addition Reactions of Sulfonylimidates

Sulfonylimidates react with various types of N-protected imines in the presence of a catalytic amount of DBU to afford β-aminosulfonylimidates in high yields and high anti-selectivities. The experimental procedure is described in detail.

ChemInform Abstract: Sulfonylimidates as Nucleophiles in Catalytic Addition Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Solvent‐Free Synthesis of Quinazoline‐2,4(1H,3H)‐diones Using Carbon Dioxide and a Catalytic Amount of DBU.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

An Efficient Synthesis of 7,8‐Dihydropyrimido[5,4‐d]pyrimidines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

DBU-Mediated Mild and Chemoselective Deprotection of Aryl Silyl Ethers and Tandem Biaryl Ether Formation

An efficient method for the selective cleavage of aryl ­silyl ethers is established using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). With either 1.0 or 0.10 equivalent of DBU, smooth de­silylation of various aryl silyl ethers was accomplished selectively in the presence of alkyl silyl ethers and other base-sensitive groups such as acetate and ester. In addition, direct transformation of aryl silyl ethers into biaryl ethers using a catalytic amount of DBU was possible through tandem desilylation and SNAr reaction with ­activated aryl fluorides.

Synthesis of the Parent and Substituted Tetracyclic ABCD Ring Cores of Camptothecins via 1-(3-Aryl-2-propynyl)- 1,6-dihydro-6-oxo-2-pyridinecarbonitriles

A new synthetic pathway to the parent and substituted ABCD ring cores of the camptothecin family of alkaloids was developed. The N-alkylation of 1,6-dihydro-6-oxo-2-pyridinecarbonitrile (2) with 3-bromo-1-phenylpropyne provided 3a using Curran's protocol. Treatment of 3a with a catalytic amount of DBU (5 mol %) at 110 degrees C for 12 h produced indolizino[1,2-b]quinolin-9(11H)-one (6a), the parent ABCD ring core of camptothecin, in essentially quantitative yield.

Synthesis of 3‐Benzyl‐2‐hydroxy‐7,8‐dihydro‐6H‐quinolin‐5‐ones from Baylis—Hillman Adducts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of 3-Benzyl-2-hydroxy-7,8-dihydro-6H-quinolin-5-ones from Baylis-Hillman Adducts

2-Hydroxy-7,8-dihydro-6H-quinolin-5-one skeleton is a useful backbone for the synthesis of numerous biologically interesting compounds such as carbostyrils (2-hydroxyquinolines) or huperzine A analogues, which have shown biological activities including non-steroidal antiinflammatory activity, acetylcholinesterase (AChE) inhibitory activity and antimalarial activity. During the studies on the chemical transformation of the Baylis-Hillman adducts toward synthetically useful heterocyclic compounds we envisioned that we could synthesize 3-benzyl-5-methoxycarbostyril derivatives 5. Our synthetic rationale for 5a is depicted in Scheme 1. Reaction of the Baylis-Hillman acetate 1 and cyclic enaminone 2 would provide the tetrahydroquinoline-2,5-dione skeleton 3 via SN2' type reaction of cyclic enaminones to the BaylisHillman acetates followed by amide bond formation. We thought that the following iodine-assisted oxidative aromatization of cyclohexenone moiety and base-catalyzed isomerization of lactam moiety would afford the desired 3benzyl-5-methoxycarbostyril derivative 5. The reaction of Baylis-Hillman acetate 1a and 3-amino-2cyclohexenone (2a) in refluxing ethanol in the presence of catalytic amount of acetic acid gave 3-benzylidene-4,6,7,8tetrahydro-1H,3H-quinoline-2,5-dione (3a) as the major product (52%) together with small amounts of 4a (< 10%). The reaction could also be conducted in n-butanol without acetic acid catalyst in a similar pattern. But, when we used nbutanol as the solvent, 4a was observed as the major product on TLC presumably due to the effect of higher reaction temperature than in EtOH. But, 3a was not changed completely into 4a even after heating for a long time. Thus we examined the conditions for the effective transformation of 3a into 4a and we found a suitable condition fortunately. Conversion of 3a into 4a could be carried out easily with catalytic amounts of DBU in THF at room temperature (reflux for the conversion of 3g into 4g, entry 7 in Table 1). Thus, we prepared 4a-c according to the following procedures: reaction of 1a-c and 2a in refluxing n-BuOH, separation of 3 and 4 as a mixtures, and finally DBU treatment to form 4a-c as the final products (entries 1-3 in Table 1). It is interesting to note that the easiness for the conversion