Acylethynylpyrroles undergo facile (rt, MeCN or MeOH, 24–72 h) catalyst-free annulation with 1-pyrrolines to afford acylmethylenetetrahydrodipyrrolo­[1,2-a:1′,2′-c]­imidazoles in up to 93% yield and 90% E-stereoselectivity of the olefin moiety.

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New catalytic systems CsFMOH (M = Li, Na) were developed for the synthesis of alkyl vinyl ethers comparable in efficiency to cesium alcoholates. The addition of primary and secondary alcohols to acetylene occurs in the presence of these systems at the atmospheric (DMSO, 100°C) or at enhanced (without solvent, 135 140°C) acetylene pressure and affords alkyl vinyl ethers in up to 93% yield. * For communication XII see [1]. The systematic investigation of alcohols vinylation with acetylenes discovered by A.E. Faworsky [2] and further developed by W. Reppe [3] and M.F.Shostakovskii [4] provide deeper theoretical insight into the nucleophilic additions to the triple bond [5] and constant refining of the synthesis of vinyl ethers of versatile structures [3 12].Here the main trend in stimulating vinilation reaction is the application of superbasic systems, like alkali metal hydroxidepolar solvent lacking hydroxy groups (DMSO, N-methylpyrrolidone, HMPA) [5, 712], or alkali metal alcoholateLewis base (Crown ether)solvent lacking hydroxy groups (hydrocarbon) [13,14].We report here on the application of highly basic systems CsFMOH and CsFMOHDMS (M = Li, Na) as efficient catalysts to alcohols vinylation.In [15,16] it was shown by an example of 1-heptanol vinylation under enhanced and atmospheric acetylene pressure in the presence of alkali metal hydroxides that the catalysts under investigation fit to the following series according to the decreasing efficiency:The comparison of the catalytic activity of KOH hydrates (2KOH·H 2 O and KOH·H 2 O) confirmed the known [4,7] negative effect of water on the vinylation process. Consequently, the use of anhydrous alkali metal hydroxides, first of all of CsOH would considerably accelerate the vinylation of the hydroxy compounds. However the preparation of anhydrous cesium and rubidium is a laborious process. Usually azeotropic removal of water is used with an appropriate high-boiling solvent (octane, toluene). The present article contains findings evidencing the possibility of a successful application to the vinyl ethers synthesis of a catalytic system CsFMOH (M = Li, Na) where the anhydrous CsOH is formed directly in the course of vinylation. This system possesses significant advantages compared to traditional vinylation catalysts like sodium and potassium hydroxides.The high catalytic efficiency of the system developed is apparently due predominantly to the exchange between the lithium or sodium hydroxides and cesium fluoride resulting in cesium hydroxide and sparingly soluble lithium or sodium fluorides.The nature of the alkali metal cation in the MOH (where M = Li, Na) used in the catalytic couple CsF MOH did not virtually affect the rate of vinylation in keeping with the preliminary occurrence of the exchange reaction and with the actual catalysis of alcohol vinylation by the arising cesium hydroxide. The formation of sparingly soluble lithium and sodium fluorides shifts the exchange equilibrium to the right. Therewith the better solubility in alcohols of NaOH compared to...

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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

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