title: Perfluoroalkyl-substituted thiophenes and pyrroles from donor-acceptor cyclopropanes and heterocumulenes: synthesis and exploration of their reactivity.
abstract: A methyl 2-trifluoromethyl-2-siloxycyclopropanecarboxylate was smoothly deprotonated by lithium diisopropylamide and reacted with carbon disulfide and methyl iodide to afford a dihydrothiophene derivative. The crucial step in this transformation is a ring-expansion of the anionic intermediate by [1,3] sigmatropic rearrangement. The dihydrothiophene was converted into the corresponding 5-trifluoromethylthiophene derivative by phosphoryl chloride in refluxing pyridine. A one-pot version of the reaction sequence efficiently provided the thiophene in good yield. Analogously, aryl- and alkyl-substituted isothiocyanates instead of carbon disulfide afforded the corresponding trifluoromethyl-substituted pyrroles in moderate to very good overall yields. Explorative reactivity studies with the methylthio-substituted thiophene and pyrrole derivatives demonstrate that they are precursors of a range of interesting trifluoromethyl-substituted products, including new members from the thienothiophene and thienopyrrole class.
authors.affiliation: Institut für Chemie und Biochemie, Freie Universität Berlin , Takustrasse 3, D-14195 Berlin, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gladow
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Reissig
mesh_terms: D003521:Cyclopropanes / Q000737:chemistry*; D015394:Molecular Structure; D011090:Polyenes / Q000138:chemical synthesis* / Q000737:chemistry; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013876:Thiophenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D003521:Cyclopropanes; D011090:Polyenes; D011758:Pyrroles; D013876:Thiophenes