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A new and efficient strategy for the stereoselective synthesis of tetrahydropyridino- and deazepanopyrrolo[1,2- c ]imidazolidines has been developed. Annulation of acylethynylpyrroles with six- and seven-membered cyclic imines (MeCN/THF, 20–25 °C, 24–72 h) leads to tetrahydropyrrolo[1′,2′:3,4]imidazo[1,2- a ]pyridines and hexahydropyrrolo[1′,2′:3,4]imidazo[1,2- a ]azepines with (E)-acylethenyl moiety in 28–96% yields. [ABSTRACT FROM AUTHOR]

The mechanisms of reactions between electron‐deficient acetylenes, specifically acylpyrrolylacetylenes, and 1‐pyrrolines were examined using a DFT B2PLYP‐D3/6‐311++G**//B3LYP/6‐31+G* approach. The study was focused on the interaction of 1‐phenyl‐3‐(1H‐pyrrol‐2‐yl) prop‐2‐yn‐1‐one with 5‐methyl‐3,4‐dihydro‐2H‐pyrrole, and was aimed at a clearer understanding of the reaction progress. The reaction pathway for the synthesis of a dipyrroloimidazole derivative comprising three five‐membered nitrogen‐containing heterocycles is compared to one typical for N‐substituted acylethynylpyrroles, which involves opening the pyrroline ring to form δ‐keto aminoenones. An explanation is presented for the high level of deuterium exchange during the reaction in deuterated methanol. Also, the impact of trace water in acetonitrile was assessed. A ring‐opening mechanism is proposed, involving the 1‐pyrroline molecule as a base. The photochemical isomerization process of the end product is also examined. [ABSTRACT FROM AUTHOR]

Catalyst-free nucleophilic substitution of hydrogen in quinolines under the action of available acylethynylpyrroles occurs at 80–110 °C in MeCN or toluene to stereoselectively afford 2-(E-2-acylethenylpyrrolyl)quinolines with a yield up to 78%. This unexpected cross-coupling proceeds apparently via the redox ring-opening of the intermediate quinoline/acylethynylpyrrole cycloadduct. Thus, we produced the first example of intramolecular SNH substitution of hydrogen in quinoline using the pyrrole nucleophile with 1,2-transfer of the acylethenyl substituent in the intermediate [2 + 3]-cycloadduct. This intermediate was isolated in the case of 1-methylisoquinoline wherein the [2 + 3]-cycloadduct was found to be stable. In general, the reaction mechanism was also supported using a high-level correlation electron pair approximation approach LPNO-CEPA/1/CBS utilizing M06-2X/Def2-TZVPP geometry. [ABSTRACT FROM AUTHOR]

Available pyrrolylalkynones with tetrahydroindolyl, cycloalkanopyrrolyl, and dihydrobenzo[g]indolyl moieties, acylethynylcycloalka[b]pyrroles, are readily annulated with Δ1-pyrrolines (MeCN/THF, 70 °C, 8 h) to afford a series of novel pyrrolo[1′,2′:2,3]imidazo[1,5-a]indoles and cyclohepta[4,5]pyrrolo[1,2-c]pyrrolo[1,2-a]imidazoles functionalized with an acylethenyl group in up to an 81% yield. This original synthetic approach contributes to the arsenal of chemical methods promoting drug discovery. Photophysical studies show that some of the synthesized compounds, e.g., benzo[g]pyrroloimidazoindoles, are prospective candidates for TADF emitters of OLED. [ABSTRACT FROM AUTHOR]

Acylethynylpyrroles, now readily available by the cross-coupling of pyrroles with acylbromoacetylenes in solid Al2O3 media, in the presence of 1-methylimidazole underwent unprecedentedly easy (40–45 °C) cyclodimerization into bis(acylmethylidene)dipyrrolo[1,2-a:1′,2′-d]pyrazines in up to 51% yield. Some other organic and inorganic basic catalysts can also trigger this cyclodimerization, but less efficiently. [ABSTRACT FROM AUTHOR]

The ring-opening/functionalization of 1-pyrrolines by cyano-acetylenes or acetylenic ketones (20–80 °C, MeCN, H2 O) affords δ-keto aminoacrylonitriles and δ-keto aminoenones, mostly as the Z -isomers, in up to 85% yields. The synthesis involves C(2)–N bond cleavage in the intermediate hemiaminal resulting from the intermediate 1,3(4)-dipolar 1-pyrroline/acetylene complexes and water. [ABSTRACT FROM AUTHOR]

Electron-deficient propargylic alcohols (EWG = CN, C(O)Ph, CO2Me, C(O)NH2) under catalyst-free mild conditions are annulated with Δ1-pyrrolines to afford functionalized hexahydropyrrolo[ 2,1-b]oxazoles, mostly in 19–93 % yield. The synthesis is stereoselective with respect to disposition of functionalized ethenyl group relative to the condensed heterocyclic system thus formed in most cases. This methodology provides a simple one-pot access to a novel family of synthetically and pharmaceutically prospective. [ABSTRACT FROM AUTHOR]

Chemoselective and atom-economical methods for the synthesis of ferrocene diethenyl ethers have been developed via direct base-catalyzed addition of 1,1′-bis(hydroxymethyl)ferrocene to various acetylenes. This ferrocene diol has been shown to be capable of adding to acetylene (KOH/DMSO, 70–80 °C, 1–3 h), propyne (KOH/DMSO, 70 °C, 12 h), phenylethyne (KOH/DMSO, 20–25 °C, 48 h), alkylpropiolates (DABCO, 10 mol%/CH2 Cl2 , 20–25 °C, 0.5 h), and acylacetylenes (DABCO, 1 mol%/CH2 Cl2 , 20–25 °C, 0.5 h) to afford the corresponding diethenyl ethers in 73–98% yields. [ABSTRACT FROM AUTHOR]

BACKGROUND Methyl vinyl ether (MVE), which polymers and copolymers are widely used in industry and medical chemistry, is produced mainly through base‐catalysed vinylation of methanol with acetylene under pressure. The most well‐known and sustainable acetylene source is calcium carbide. Significant economic benefits can be achieved by using calcium carbide as the source of acetylene directly in the industrial production of MVE. RESULTS: Eco‐friendly and operationally simple method for vinylation of methanol, one of a major objects of C1 chemistry, using calcium carbide in water in the presence of potassium or sodium carbonates (140–150 °C, 1‐L steel rotating autoclave, maximum autogenic pressure 18–30 atm) has been developed and realized on 10‐g scale. The major co‐product of this reaction is a mixture of calcium hydroxide and calcium carbonate with minor content of potassium or sodium carbonates, which can be safely used for improving acidic soils. CONCLUSION: Novel efficient method for vinylation of methanol with calcium carbide in water in the presence of alkali metal carbonates has been developed. The method allows avoiding acetylene gas under pressure that demands special equipment and safety measures. The major advantages of this technology are also availability and low cost of the catalysts. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The reaction of 3 H -indoles with tertiary propargylic alcohols to give functionalized dihydrooxazolo[3,2- a ]indoles in good to excellent yields has been developed. This metal- and solvent-free, one-pot tandem assembly proceeds under mild conditions (22–60 °C) and is regio- and stereoselective: either the Z - or E -isomers (relative to the double bond) are alternatively formed depending on other functionalized substituents on the propargylic alcohols. [ABSTRACT FROM AUTHOR]