title: Difunctionalisation of arenes and heteroarenes by directed metallation and sulfoxide-magnesium exchange.
abstract: The aryl sulfoxide moiety allows an expedient two-step difunctionalisation of readily available diaryl sulfoxides. Highly functionalised 1,2,4-trisubstituted arenes and difunctionalised heteroarenes (furans, thiophenes, benzofurans and pyridines) were prepared in a two-step sequence, triggered by an aryl sulfoxide group. In the first step, the sulfoxide moiety acts as a metallation-directing group, allowing smooth ortho-magnesiation with TMPMgCl⋅LiCl (TMP=tetramethylpiperidine). After a quenching reaction with an electrophile, the resulting sulfoxide is converted into a second magnesium reagent with iPrMgCl⋅LiCl (sulfoxide-magnesium exchange), which can be trapped with various electrophiles. Highly chemoselective TMPMgCl⋅LiCl and iPrMgCl⋅LiCl are compatible with a broad range of functional groups (e.g., F, Cl, CF(3) , CN, CO(2) tBu, alkynyl, ethers, thioethers). Large-scale reactions (25-40 mmol) and the preparation of fully functionalised furans and thiophenes are also reported.
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr 5-13, Haus F, 81377 München, Germany.
authors.forename: Laurin
authors.initials: L
authors.lastname: Melzig
authors.forename: Christian B
authors.initials: CB
authors.lastname: Rauhut
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Naredi-Rainer
authors.forename: Paul
authors.initials: P
authors.lastname: Knochel