Versatile Friedel-Crafts-type alkylation of benzene derivatives using a molybdenum complex/ortho-chloranil catalytic system.
Versatile Friedel-Crafts-type alkylation of benzene derivatives using a molybdenum complex/ortho-chloranil catalytic system.
复制标题
DOI：
10.1002/chem.200801105
复制
发表时间：
2008-11
期刊：
影响因子：
--
通讯作者：
Yoshihiko Yamamoto;Kouhei Itonaga
中科院分区：
文献类型：
--
作者：
Yoshihiko Yamamoto;Kouhei Itonaga
在有机氧化剂邻氯苯腈存在下，各种钼配合物催化苯衍生物与烯烃和醇的Friedel-Craft型烷基化反应。利用[Mo(CO)(6)]和两个当量的邻氯苯酚在80℃时催化降冰片烯和对二甲苯的氢芳基化反应，而[Cr(CO)(6)]和[W(CO)(6)]不能催化相同的反应，这表明钼源的重要性。以钼(II)配合物[CpMoCl(CO)(3)](Cp=环戊二烯)为预催化剂时，反应效果最好。以苯乙烯、环己烯和1-己烯为烯烃底物也发生了氢芳基化反应。根据邻位/对位选择性和马可夫尼科夫选择性，提出了亲电取代机理。在[CpMoCl(CO)(3)]/邻氯苯酚催化体系中，仲醇、苄醇或烯丙醇参与了具有相似选择性的苯烷基化反应，进一步证实了我们的假设。
A variety of molybdenum complexes catalyze Friedel-Crafts-type alkylation reactions of benzene derivatives with alkenes and alcohols in the presence of an organic oxidant, o-chloranil. The utilization of [Mo(CO)(6)] and two equivalents of o-chloranil catalytically furnished the hydroarylation product of norbornene with p-xylene at 80 degrees C, whereas [Cr(CO)(6)] and [W(CO)(6)] failed to catalyze the same reaction, thus indicating the importance of the molybdenum source. The best results were obtained when a molybdenum(II) complex [CpMoCl(CO)(3)] (Cp=cyclopentadienyl) was used as a precatalyst. The hydroarylation reactions also took place with styrenes, cyclohexenes, and 1-hexene as olefin substrates. The electrophilic-substitution mechanism was proposed on the basis of the ortho/para selectivities and the Markovnikov selectivities observed for the hydroarylation products. Our hypothesis was further corroborated by the fact that in the presence of the [CpMoCl(CO)(3)]/o-chloranil catalytic system, secondary, benzylic, or allylic alcohols participated in the alkylation of benzenes with similar selectivities.