title: Azaphilic versus Carbophilic Coupling at C=N Bonds: Key Steps in Titanium-Assisted Multicomponent Reactions.
abstract: Consecutive C- and N-arylation of N-heterocyclic nitriles is mediated by titanium(IV) alkoxides. The carbo- and azaphilic arylation step may be separated by choosing the order in which the two equivalents of aryl transfer reagent are added. In the course of this transformation, the ancillary N-heterocycle acts as both a directing anchor group and electron reservoir. In the selectivity-determining step, the selectivity is governed by a choice between (direct) C- and Ti-arylation; the latter opens up a reaction pathway that allows further migration to the nitrogen atom. The isolation of metal-containing aggregates from the reaction mixture and computational studies gave insights into the reaction mechanism. Subsequently, a multicomponent one-pot protocol was devised to rapidly access complex quaternary carbon centers.
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany).
authors.forename: Torsten
authors.initials: T
authors.lastname: Roth
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany).
authors.forename: Hubert
authors.initials: H
authors.lastname: Wadepohl
authors.affiliation: Institut Charles Gerhardt, CNRS 5253, cc 1501, Université de Montpellier, Place Eugène Bataillon, 34000 Montpellier (France). eric.clot@umontpellier.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Clot
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg (Germany). lutz.gade@uni-heidelberg.de.
authors.forename: Lutz H
authors.initials: LH
authors.lastname: Gade
keywords: heterocycles; metallacycles; multicomponent reactions; synthetic methods; titanium