Selenophen - 2 - yl - substituted thiocarbonyl ylides – at the borderline of dipolar and biradical reactivity

The reactions of aryl (selenophen-2-yl) thioketones with CH2N2 occur with spontaneous elimination of N2, even at low temperature (-65°), to give regioselectively sterically crowded 4,4,5,5tetrasubstituted 1,3-dithiolanes and/or a novel type of twelve-membered dithia-diselena heterocycles as dimers of the transient thiocarbonyl S-methanides. The ratio of these products depends on the type of substituent located at C(4) of the phenyl ring. Whereas the formation of the 1,3-dithiolanes corresponds to a [3 + 2] cycloaddition of an intermediate thiocarbonyl ylide with the starting thioketone, the twelvememberd ring has to be formed via dimerization of the ’thiocarbonyl ylide’ with an extended biradical structure. DOI: https://doi.org/10.1002/hlca.201500050 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-110376 Accepted Version Originally published at: Mloston, Grzegorz; Urbaniak, Katarzyna; Linden, Anthony; Heimgartner, Heinz (2015). Selenophen2-yl-substituted thiocarbonyl ylides – at the borderline of dipolar and biradical reactivity. Helvetica Chimica Acta, 98(4):453-461. DOI: https://doi.org/10.1002/hlca.201500050 M-309/HCA_25.02.2015 Prof. Dr. H. Heimgartner Tel. 044 635 4282 Fax 044 635 6836 e-mail: [email protected] Selenophen-2-yl Substituted Thiocarbonyl Ylides – at the Borderline of Dipolar and Diradical Reactivity by Grzegorz Mlostoń* a ), Katarzyna Urbaniak a ), Anthony Linden b ), and Heinz Heimgartner* b ) a ) University of Łódź, Department of Organic and Applied Chemistry, Tamka 12, PL91-403 Łódź (phone: +48 42 6355761; fax: +48 42 6655162; e-mail: [email protected]) b ) University of Zürich, Department of Chemistry, Winterthurerstrasse 190, CH-8057 Zürich (phone:+41 44 6354282; fax: +41 44 6356812; e-mail: [email protected]) Dedicated to Professor Christian Robl, Friedrich-Schiller-Universität Jena, on the occasion of his 60 th birthday