title: Regioselective Oligomerization of 3-(Alkylsulfanyl)thiophenes with Ferric Chloride.
abstract: The action of FeCl(3) on 3-(alkylsulfanyl)thiophenes (3-(alkylthio)thiophenes) leads to the one-step formation of regioregular alpha-conjugated oligothiophenes, from trimer to octamer, depending on the solvent used and on the length of the alkyl chain. The regiochemistry of these oligomers is characterized by one inner head-to-head linkage between adjacent rings and by a variable number of lateral head-to-tail junctions. The reaction of ferric chloride with the head-to-head and head-to-tail bis(methylsulfanyl)-2,2'-bithiophenes gives the corresponding tetramers, while the reaction with the tail-to-tail counterpart affords a high molecular weight insoluble material. With the aid of theoretical calculations, these results are interpreted on the basis of the joint effects of the orienting power of the substituents and of the stability of the radical cations formed during the oxidative process.
authors.affiliation: I.Co.C.E.A., Area Ricerca C.N.R., Via Gobetti 101, 40129 Bologna, Italy, Dipartimento di Chimica, Universita' di Modena, Via Campi 183, 41100 Modena, Italy, and Dipartimento di Chimica G. Ciamician, Universita' di Bologna, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Barbarella
authors.forename: Massimo
authors.initials: M
authors.lastname: Zambianchi
authors.forename: Rosanna
authors.initials: R
authors.lastname: Di Toro
authors.forename: Martino
authors.initials: M
authors.lastname: Colonna
authors.forename: Dario
authors.initials: D
authors.lastname: Iarossi
authors.forename: Francesca
authors.initials: F
authors.lastname: Goldoni
authors.forename: Alessandro
authors.initials: A
authors.lastname: Bongini