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  • Title: A new method for the preparation of non-terminal alkynes: application to the total syntheses of tulearin A and C.
    Author: Lehr K, Schulthoff S, Ueda Y, Mariz R, Leseurre L, Gabor B, Fürstner A.
    Journal: Chemistry; 2015 Jan 02; 21(1):219-27. PubMed ID: 25367701.
    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.
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