title: Studies on tellurium-containing heterocycles. Part 20. Reactions of 2-benzoselenopyrylium salts and 2-benzotelluropyrylium salts with nucleophiles: formation of 1-functionalized 1H-isoselenochromenes and 1H-isotellurochromenes.
abstract: The reactions of the 2-benzoselenopyrylium (1A) and 2-benzotelluropyrylium cations (1B) with a variety of nucleophiles have been investigated. LiAlH(4), sodium alkoxide (NaOMe, NaOi-Pr and NaOt-Bu), diethylamine, n-butylamine and acetone reacted with 1 to give the 1H-isochromenes (2) and the corresponding 1-substituted products (4-9) under mild conditions in almost good to high yields. The 1-alkyl(phenyl)isoselenochromenes (10-13) and 1-benzylisochromenes (18A, 18B), which were produced by the reaction of the salts 1 with Grignard reagents, were converted to the corresponding 1,3-disubstituted 2-benzopyrylium salts (14-17, 19) by treatment with triphenylcarbenium tetrafluoroborate (Ph(3)C(+) BF(4)(-)), respectively. The 1-benzylselenopyrylium salts (19A) and 1-benzyltelluropyrylium salts (19B) exist in the solvent as an equilibrium mixture of the salts (19) and the corresponding (Z)-benzylidene compounds (20).
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa 920-1181, Japan. h-sashida@hokuriku-u.ac.jp
authors.forename: Haruki
authors.initials: H
authors.lastname: Sashida
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ohyanagi
mesh_terms: D000147:Acids, Heterocyclic / Q000737:chemistry*; D017607:Aluminum Compounds / Q000737:chemistry; D001578:Benzopyrans / Q000737:chemistry*; D006574:Heterocyclic Compounds, 2-Ring / Q000737:chemistry*; D007202:Indicators and Reagents; D018020:Lithium Compounds / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D018036:Selenium Compounds / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013691:Tellurium / Q000737:chemistry*
chemical_list: C488443:2-benzoselenopyrylium; C488444:2-benzotelluropyrylium; D000147:Acids, Heterocyclic; D017607:Aluminum Compounds; D001578:Benzopyrans; D006574:Heterocyclic Compounds, 2-Ring; D007202:Indicators and Reagents; D018020:Lithium Compounds; D018036:Selenium Compounds; C042073:lithium aluminum hydride; D013691:Tellurium