title: A new method for the preparation of non-terminal alkynes: application to the total syntheses of tulearin A and C.
abstract: Lactones are known to react with the reagent generated in situ from CCl4 and PPh3 in a Wittig-type fashion to give gem-dichloro-olefin derivatives. Such compounds are now shown to undergo reductive alkylation on treatment with organolithium reagents RLi to furnish acetylene derivatives bearing the substituent R at their termini (R=Me, n-, sec-, tert-alkyl, silyl); the reaction can be catalyzed with either Cu(acac)2 or Fe(acac)3 /1,2-diaminobenzene. Two alkynol derivatives prepared in this way from readily accessible lactone precursors served as the key building blocks for the total syntheses of the cytotoxic marine macrolides tulearin A (1) and C (2). The assembly of these fragile targets hinged upon ring closing alkyne metathesis (RCAM) followed by a formal trans-reduction of the resulting cycloalkynes via trans-hydrosilylation/protodesilylation.
authors.affiliation: Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr (Germany).
authors.forename: Konrad
authors.initials: K
authors.lastname: Lehr
authors.forename: Saskia
authors.initials: S
authors.lastname: Schulthoff
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ueda
authors.forename: Ronaldo
authors.initials: R
authors.lastname: Mariz
authors.forename: Lucie
authors.initials: L
authors.lastname: Leseurre
authors.forename: Barbara
authors.initials: B
authors.lastname: Gabor
authors.forename: Alois
authors.initials: A
authors.lastname: Fürstner
keywords: alkynes; hydrosilylation; iron catalysis; metathesis; molybdenum; natural products