Cyclization of 1-Aryl-5-Phenylpent-4-en-2-yn-1-Ones to 2,3-Dihydropyran-2-Ones in Trifluoromethanesulfonic Acid
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Cyclization of 1-aryl-5-phenylpent-4-en-2-yn-1-ones to 2,3-dihydropyran-2-ones in trifluoromethanesulfonic acid Anna S. Zalivatskaya1,2, Aleksander А. Golovanov2,3, Aleksander V. Vasilyev1,2* 1
Saint Petersburg State Forest Technical University, 5 Institutskiy Pereulok, Saint Petersburg 194021, Russia; е-mail: [email protected] 2 Institute of Chemistry, Saint Petersburg State University, 7/9 University Embankment, Saint Petersburg 199034, Russia 3 Togliatti State University, 14 Belorusskaya St., Togliatti 445020, Russia Submitted June 3, 2020 Accepted July 17, 2020
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(7), 953–956
Under the action of an excess of trifluoromethanesulfonic acid, 1-aryl-5-phenylpent-4-en-2-yn-1-ones cyclize intramolecularly to 6-aryl2-phenyl-2,3-dihydropyran-4-ones. The reaction proceeds at room temperature for 1 h with 50–60% yields. Keywords: conjugated enynones, dihydropyranones, trifluoromethanesulfonic acid, carbocations, cyclization.
Various conjugated enynones are valuable compounds for organic synthesis. Three important linearly or crossconjugated functional fragments are present in their structure (multiple double and triple carbon–carbon bonds, as well as a carbonyl group), that allow them to undergo a variety of synthetic transformations. Nowadays, the number of works devoted to the methods of synthesis of organic compounds based on the enynone transformations has increased.1 Nevertheless, linearly conjugated pent-4-en2-yn-1-ones 1 (Scheme 1) remain the least studied among all possible conjugated enynones, probably due to the complicated methods of their synthesis. It is known from the literature data that 1,5-diarylbut4-en-2-yn-1-ones interact at the C-3 atom of the acetylenic bond to form dienone structures in reactions with S-nucleophiles (Scheme 1).2 Enynones that do not contain aryl substituents at the carbonyl group interact with nucleophiles in a similar way. For example, an intramolecular cyclization with the participation of the alkoxycarbonyl group and the C-3 atom of the triple bond of enynes, catalyzed by gold complexes in the presence of AcOH, has been described3,4 (Scheme 1). Nucleophilic silylation of enynones and their carboxy analogs, catalyzed by copper(II) complexes, occurs at the C-3 and C-5 atoms of the enynone system, leading to the corresponding bisilyl derivatives (Scheme 1).5 In contrast, the reactions of enynones 1 with electrophilic reagents proceed at the C-2 0009-3122/20/56(7)-0953©2020 Springer Science+Business Media, LLC
atom of the acetylene bond. Thus, intramolecular reactions have been presented in which C-2 atom of the triple bond acts as a nucleophilic center, which ultimately leads to various carbocycles6 (Scheme 1). Scheme 1. Literature data on synthetically significant transformations of linearly conjugated pent-4-en-2-yn-1-ones 1
Until now, the conversion of pent-4-en-2-yn-1-ones 1 under the action of various electrophilic reagents, such as Brønsted or Lewis acids, has not been systematically 953
Chemistry of Heteroc
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