科研之友
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<jats:title>Abstract</jats:title><jats:p>Although molybdenum alkylidyne complexes such as <jats:bold>1</jats:bold> endowed with triarylsilanolate ligands are excellent catalysts for alkyne metathesis, they can encounter limitations when (multiple) protic sites are present in a given substrate and/or when forcing conditions are necessary. In such cases, a catalyst formed in situ upon mixing of the trisamidomolybenum alkylidyne complex <jats:bold>3</jats:bold> and the readily available trisilanol derivatives <jats:bold>8</jats:bold> or <jats:bold>11</jats:bold> shows significantly better performance. This two‐component system worked well for a series of model compounds comprising primary, secondary or phenolic ‐OH groups, as well as for a set of challenging (bis)propargylic substrates. Its remarkable efficiency is also evident from applications to the total syntheses of manshurolide, a highly strained sesquiterpene lactone with kinase inhibitory activity, and the structurally demanding immunosuppressive cyclodiyne ivorenolide A; in either case, the standard catalyst <jats:bold>1</jats:bold> largely failed to effect the critical macrocyclization, whereas the two‐component system was fully operative. A study directed toward the quinolizidine alkaloid lythrancepine I features yet another instructive example, in that a triyne substrate was metathesized with the help of <jats:bold>3</jats:bold>/<jats:bold>11</jats:bold> such that two of the triple bonds participated in ring closure, while the third one passed uncompromised. As a spin‐off of this project, a much improved ruthenium catalyst for the redox isomerization of propargyl alcohols to the corresponding enones was developed.</jats:p>
- 出版日期2016-6-13
