title: Deprotonation of benzoxazole and oxazole using lithium magnesates.
abstract: The first deprotonations of oxazole and benzoxazole using lithium magnesates are described. The reactions occurred in tetrahydrofuran at room temperature using 1/3 equiv of lithium tributylmagnesate. As 2-lithiooxazole and 2-lithiobenzoxazole, lithium tri(2-oxazolyl)magnesate and lithium tri(2-benzoxazolyl)magnesate very rapidly and completely isomerized to the more stable 2-(isocyano)enolate and 2-(isocyano)phenolate type structures, respectively, a result shown by NMR analysis. The isolation of 2-substituted oxazoles and benzoxazoles in medium to good yields after electrophilic trapping was interpreted in two ways: (1) the equilibration between the open and closed structures is faster than the trapping of the open isomers, and the closed isomers are more reactive than the open ones, or (2) the open isomers react with electrophiles in a intramolecular Passerini type reaction. The nonreactivity of the 2-(isocyano)enolate type structure toward anisaldehyde in the absence of lithium bromide makes the intramolecular Passerini type reaction more plausible.
authors.affiliation: Laboratoire de Chimie Organique Fine et Hétérocyclique, UMR 6014, IRCOF, CNRS, Université et INSA de Rouen, Place E. Blondel BP 08, 76131 Mont-Saint-Aignan Cedex, France.
authors.forename: Omar
authors.initials: O
authors.lastname: Bayh
authors.forename: Haçan
authors.initials: H
authors.lastname: Awad
authors.forename: Florence
authors.initials: F
authors.lastname: Mongin
authors.forename: Christophe
authors.initials: C
authors.lastname: Hoarau
authors.forename: Laurent
authors.initials: L
authors.lastname: Bischoff
authors.forename: François
authors.initials: F
authors.lastname: Trécourt
authors.forename: Guy
authors.initials: G
authors.lastname: Quéguiner
authors.forename: Francis
authors.initials: F
authors.lastname: Marsais
authors.forename: Fernando
authors.initials: F
authors.lastname: Blanco
authors.forename: Belén
authors.initials: B
authors.lastname: Abarca
authors.forename: Rafael
authors.initials: R
authors.lastname: Ballesteros