title: Development of a mild and versatile directed cycloaddition approach to pyridines.
abstract: The aza-Diels-Alder cycloaddition of 1,2,4-triazines with alkynes offers a rapid and convenient method for the synthesis of highly substituted pyridines, but often requires harsh conditions and long reaction times. The present study offers a solution to these limitations by use of a temporary tether established by a Lewis acid-base complexation of in situ generated alkynylboranes and triazines bearing a Lewis basic donor. The cycloaddition reactions take place within 20 min at 40 °C and provide direct access to a broad range of pyridines with complete and predictable regiocontrol. The carbonboron bond can be further functionalised by cross-coupling allowing further functionality to be introduced after cycloaddition.
authors.affiliation: Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, S3 7HF (UK).
authors.forename: Sylvestre P J T
authors.initials: SP
authors.lastname: Bachollet
authors.forename: Jérôme F
authors.initials: JF
authors.lastname: Vivat
authors.forename: Dean C
authors.initials: DC
authors.lastname: Cocker
authors.forename: Harry
authors.initials: H
authors.lastname: Adams
authors.forename: Joseph P A
authors.initials: JP
authors.lastname: Harrity
keywords: boranes; cycloadditions; pyridines; regioselectivity; triazines