Anorganische Chemie II-Katalysatordesign, Universität Bayreuth , 95440 Bayreuth, Germany.
J Am Chem Soc. 2015 Oct 14;137(40):12804-7. doi: 10.1021/jacs.5b09510. Epub 2015 Oct 1.
Since alcohols are accessible from indigestible biomass (lignocellulose), the development of novel preferentially catalytic reactions in which alcohols are converted into important classes of fine chemicals is a central topic of sustainable synthesis. Multicomponent reactions are especially attractive in organic chemistry as they allow the synthesis of large libraries of diversely functionalized products in a short time when run in a combinatorial fashion. Herein, we report a novel, regioselective, iridium-catalyzed multicomponent synthesis of pyrimidines from amidines and up to three (different) alcohols. This reaction proceeds via a sequence of condensation and dehydrogenation steps which give rise to selective C-C and C-N bond formations. While the condensation steps deoxygenate the alcohol components, the dehydrogenations lead to aromatization. Two equiv of hydrogen and water are liberated in the course of the reactions. PN5P-Ir-pincer complexes, recently developed in our laboratory, catalyze this sustainable multicomponent process most efficiently. A total of 38 different pyrimidines were synthesized in isolated yields of up to 93%. Strong points of the new protocol are its regioselectivity and thus the immediate access to pyrimidines that are highly and unsymmetrically decorated with alkyl or aryl substituents. The combination of this novel protocol with established methods for converting alcohols to nitriles now allows to selectively assemble pyrimidines from four alcohol building blocks and 2 equiv of ammonia.
由于醇可以从不可消化的生物质（木质纤维素）中获得，因此开发新型优先催化反应，将醇转化为重要的精细化学品类别是可持续合成的核心课题。多组分反应在有机化学中特别有吸引力，因为它们允许以组合方式在短时间内合成具有不同功能化的大型文库。在此，我们报告了一种新颖的、区域选择性的、铱催化的从脒和多达三种（不同的）醇合成嘧啶的多组分反应。该反应通过缩合和脱氢步骤进行，导致选择性的 C-C 和 C-N 键形成。虽然缩合步骤使醇成分脱氧，但脱氢导致芳构化。在反应过程中释放出 2 当量的氢气和水。最近在我们实验室开发的 PN5P-Ir-夹钳配合物最有效地催化了这一可持续的多组分过程。总共合成了 38 种不同的嘧啶，收率高达 93%。新方案的优点是其区域选择性，因此可以直接获得高度不对称地用烷基或芳基取代基装饰的嘧啶。将该新方案与将醇转化为腈的现有方法相结合，现在可以从四个醇构建块和 2 当量的氨选择性地组装嘧啶。
