Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim/Ruhr, Germany.
J Am Chem Soc. 2010 Aug 18;132(32):11045-57. doi: 10.1021/ja104800w.
Triphenylsilanolate ligands were found to impart excellent reactivity and outstanding functional group tolerance on molybdenum alkylidyne complexes, which catalyze alkyne metathesis reactions of all sorts. The active species either can be obtained in high yield by adaptation of the established synthesis routes leading to Schrock alkylidynes or can be generated in situ from the molybdenum nitride complex 11, which itself is readily accessible in large quantity from inexpensive sodium molybdate. Complexation of the active silanolate complexes 12 and 24 with 1,10-phenanthroline affords complexes 15 and 25, respectively, which are stable in air for extended periods of time. Although these phenathroline adducts are per se unreactive vis-a-vis alkynes, catalytic activity is conveniently restored upon exposure to MnCl(2). Therefore, the practitioner has the choice of different alkyne metathesis (pre)catalysts, which are easy to handle yet broadly applicable and exceedingly tolerant. A host of representative inter- as well as intramolecular alkyne metathesis reactions, including applications to a considerable number of bioactive and, in part, labile natural products, shows the remarkable scope of these new tools. Moreover, it was found that the addition of molecular sieves (5 A >or= 4 A >> 3 A) to the reaction mixture significantly improves the chemical yields while simultaneously increasing the reaction rates. This benefit is ascribed to effective binding of 2-butyne, which is released as the common byproduct in reactions of alkynes bearing a methyl end-cap. Thus, alkyne metatheses can now be performed at ambient temperature with neither the need to apply vacuum to drive the conversion nor recourse to tailor-made substrates. The structures of representative examples of this new generation of alkyne metathesis catalysts in the solid state were determined by X-ray analysis.
三苯硅醇盐配体被发现能赋予钼烷基卡宾配合物极好的反应活性和出色的官能团耐受性，这些配合物可催化各种炔烃的交叉复分解反应。活性物种可以通过适应现有的合成路线来获得，这些路线可得到施罗克卡宾，也可以从本身容易大量获得的廉价钼酸钠的氮化钼配合物 11 原位生成。将活性硅醇盐配合物 12 和 24 与 1,10-菲咯啉络合，分别得到配合物 15 和 25，它们在空气中长时间稳定。尽管这些菲咯啉加合物本身与炔烃反应没有活性，但暴露于 MnCl2 时，催化活性很容易恢复。因此，使用者可以选择不同的炔烃交叉复分解（预）催化剂，这些催化剂易于处理，但应用广泛且具有极高的耐受性。大量具有代表性的分子间和分子内炔烃交叉复分解反应，包括对许多生物活性的应用，以及部分不稳定的天然产物，展示了这些新工具的显著应用范围。此外，人们发现将分子筛（5 A≥4 A＞3 A）添加到反应混合物中可以显著提高化学产率，同时提高反应速率。这一好处归因于对末端带有甲基的炔烃反应的常见副产物 2-丁炔的有效结合。因此，现在可以在环境温度下进行炔烃交叉复分解反应，既不需要应用真空来推动转化，也不需要使用定制的底物。通过 X 射线分析确定了这一代新型炔烃交叉复分解催化剂的代表性实例在固态下的结构。
