title: Studies in sigmatropic rearrangement: synthesis of a [6,6]pyranothiopyran ring system by sequential claisen rearrangement and pyridine hydrotribromide mediated regioselective "6-Endo" cyclization.
abstract: [reaction: see text] 4-(4'-Aryloxybut-2'-ynylthio)[1]benzopyran-2-ones are refluxed in chlorobenzene to afford 4-aryloxymethylthiopyrano[3,2-c][1]benzopyran-5(2H)-ones which are subsequently subjected to heating in o-dichlorobenzene in the presence of N,N-diethylaniline and then treated with pyridine hydrotribromide to give [6,6]pyranothiopyrans in almost quantitative yield.
authors.affiliation: Department of Chemistry, University of Kalyani, West Bengal, India. kcm@klyuniv.ernet.in
authors.forename: K C
authors.initials: KC
authors.lastname: Majumdar
authors.forename: U K
authors.initials: UK
authors.lastname: Kundu
authors.forename: S K
authors.initials: SK
authors.lastname: Ghosh