title: Synthesis and structure of m-terphenyl thio-, seleno-, and telluroethers.
abstract: Several routes for the synthesis of m-terphenyl thio-, seleno-, and telluroethers were investigated. m-Terphenyl iodides react with diphenyl diselenides or ditellurides (CsOH·H(2)O, DMSO, 110 °C) to give the desired compounds in 19-84% yield which significantly extends the previously reported such reactions because o-benzyne cannot be an intermediate as previously suggested. However, the most general synthetic route was that involving reaction of 2,6-diaryl Grignard reagents with sulfur, selenium, or tellurium electrophiles. The m-terphenyl thio-, seleno-, and telluroethers were characterized spectroscopically and, in one case, by single-crystal X-ray analysis. Certain of these compounds showed atropisomerism and barriers for interconversion of isomers were determined by variable-temperature NMR spectroscopy. The barriers for interconverting the syn and anti atropisomers increase on going from the analogous S to Se to Te compounds. Calculations on this isomerization revealed that the barriers are due to rotation about the aryl-aryl bond and that the barriers for rotation about the aryl-chalcogen bond are much lower.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States.
authors.forename: Uzma I
authors.initials: UI
authors.lastname: Zakai
authors.forename: Anna
authors.initials: A
authors.lastname: Błoch-Mechkour
authors.forename: Neil E
authors.initials: NE
authors.lastname: Jacobsen
authors.forename: Leif
authors.initials: L
authors.lastname: Abrell
authors.forename: Guangxin
authors.initials: G
authors.lastname: Lin
authors.forename: Gary S
authors.initials: GS
authors.lastname: Nichol
authors.forename: Thomas
authors.initials: T
authors.lastname: Bally
authors.forename: Richard S
authors.initials: RS
authors.lastname: Glass