title: Hetero-Diels-Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles.
abstract: Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels-Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.
authors.affiliation: Department of Organic and Applied Chemistry, University of Łódź, Tamka 12, PL 91-403 Łódź, Poland.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Mlostoń
authors.affiliation: Department of Organic and Applied Chemistry, University of Łódź, Tamka 12, PL 91-403 Łódź, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Grzelak
authors.affiliation: Center of Molecular and Macromolecular Studies PAS, Sienkiewicza 112, PL 90-363 Łódź, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Mikina
authors.affiliation: Department of Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Anthony
authors.initials: A
authors.lastname: Linden
authors.affiliation: Department of Chemistry, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Heinz
authors.initials: H
authors.lastname: Heimgartner
keywords: dimethyl acetylenedicarboxylate (DMAD); hetero-Diels–Alder reactions; high pressure reactions; methyl propiolate; thioketones; thiopyrans