Development of Methods for Novel Construction of Ring Compounds by Environmentally Benign Transition Metal Catalysts

开发具有高催化性能的新型过渡金属配合物，对于开发原子经济性高、环境友好的合成方法具有重要意义。在本研究中，我们首次通过选择性置换Ru(η^6-1，3，5-环辛三烯)(η^2-二甲基富马酸二甲酯)_2(1)中的1，3，5-环辛三烯(COT)或富马酸二甲酯(DMFM)配体，成功地合成了含芳烃、对苯二酚、三齿吡啶和马来酰亚胺的新型Ru(0)配合物。与之形成鲜明对比的是，类似的Ru(0)配合物Ru(η^4-1，5-环辛二烯)(η^6-1，3，5-环辛三烯)(2)与马来酰亚胺通过钴配体和马来酰亚胺在Ru上的氧化环化反应得到了新型的二价环戊烷配合物(3)，这可能实现新型过渡金属催化的[6 2]共环反应。代表性的例子包括1)1)Ru催化的异氰酸酯、炔烃和一氧化碳的[2 21]共环化反应使多取代马来酰亚胺的快速合成成为可能，2)Rh催化的异氰酸酯和炔烃的环共三聚反应通过控制异氰酸酯和炔烃的摩尔比选择性地生成2-吡啶酮和2，4-吡啶二酮，3)Ru催化的环丁烯和缺电子烯烃通过C-C键裂解/脱氢直接合成取代酚，以及4)不同烯烃的选择性共二聚和共三聚反应，以及通过苯环中间体选择性地进行乙烯的三聚反应。所有反应都以高原子效率进行，并且得到功能单体，没有副产物的形成。

The creation of novel transition metal complexes which show high catalytic performance is essential for development of highly atom-economical and environmentally benign synthetic methods. In this study, we first succeeded in preparation of novel Ru (0) complexes bearing arenes, p-quinones, tridentate pyridyl ligands, and maleimides via selective displacement of either1,3,5-cyclooctatriene (cot) or dimethyl fumarate (dmfm) ligands in Ru (η^6-1,3,5-cyclooctatriene) (η^2-dimethyl fumarate)_2 (1). In sharp contrast, a similar Ru (0) complex, Ru (η^4-1,5-cyclooctadiene) (η^6-1,3,5-cyclooctatriene) (2) smoothly reacted with maleimides to give novel divalent ruthenacyclopentane complexes (3) via oxidative cyclization of a cot ligand and maleimides on the ruthenium, which may realize the development of novel transition-metal catalyzed [6+2] cocyclization reaction.Based on the above described stoichiometric reactions, novel methods for construction of various ring compounds using environmentally benign ruthenium and rhodium catalysts have been developed in this study. Representative examples include 1) first ruthenium-catalyzed [2+2+1] cocyclization of isocyanates, alkynes, and carbon monoxide enables the rapid synthesis of polysubstituted maleimides, 2) rhodium-catalyzed cyclocotrimerization of isocyanates and alkynes leading to the selective formation of 2-pyridones and pyrimicline-2,4-diones by controlling the molar ratio of isocyanates and alkynes, 3) rhodium-catalyzed direct synthesis of substituted phenols from cyclobutenones and electron-deficient alkenes via C-C bond cleavage/dehydrogenation, and 4) selective codimerization and cotrimerization of different alkenes, as well as selective trimerization of ethylene, via ruthenacyclic intermediates. All reactions proceed with high atom-efficiency and give functional monomers without the formation of byproducts.