描述了钯催化形成二芳基醚的一般方法。富含电子的、庞大的芳基二烷基膦配体,其中两个烷基是叔丁基或 1-金刚烷基,是转化成功的关键。使用氢化钠或磷酸钾作为碱,在 100 °C 的甲苯中,可以将各种缺电子、电子中性和富电子的芳基溴化物、氯化物和三氟甲磺酸酯与各种酚结合。膦配体庞大而碱性的性质被认为是提高二芳基醚从钯中还原消除的速率的原因。
A New Biarylphosphine Ligand for the Pd-Catalyzed Synthesis of Diaryl Ethers under Mild Conditions
作者:Luca Salvi、Nicole R. Davis、Siraj Z. Ali、Stephen L. Buchwald
DOI:10.1021/ol202955h
日期:2012.1.6
A new bulky biarylphosphine ligand (L8) has been developed that allows the Pd-catalyzed C–O cross-coupling of a wide range of aryl halides and phenols undermilderconditions than previously possible. A direct correlation between the size of the ligand substituents in the 2′, 4′, and 6′ positions of the nonphosphine containing ring and the reactivity of the derived catalyst system was observed. Specifically
The combination of 2-phosphino-substituted N-arylpyrroles or related indoles (cataCXium®P) and Pd(OAc)2 allows for efficient cross-coupling reactions of aryl chlorides and phenols to give diarylethers. A variety of aryl and heteroaryl chlorides can be coupled with substituted phenols showing unprecedented catalyst turnover numbers.
One aspect of the present invention relates to novel reaction conditions that allow the efficient synthesis of diaryl ethers from arenes bearing a leaving group and arenols under relatively mild conditions. Another aspect of the present invention relates to the dramatic effects of acidic activators on Ullmann-type couplings involving electron-poor and/or relatively insoluble substrates.
Polyarylene thioethers are easily prepared by an oxidative polymerization of an aromatic compound of the formula (I)
wherein R¹, R², R³ and R⁴ are each independently a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group, and Y is a hydrogen atom or a group of the formula (II)
wherein R⁵, R⁶, R⁷ and R⁸ are each independently a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group and X is -O-, -S-, a methylene group or an ethylene group with a sulfidizing agent in the presence of an acid and an oxidizing agent, or in the presence of an acid, a catalyst for oxidative polymerization and oxygen, or in the presence of a Friedel-Crafts catalyst.