铁助力铬：反，反 - 二烯基费歇尔卡宾配合物的邻位苯并环化反应
Iron in the service of chromium: the ortho-benzannulation of trans,trans-dienyl Fischer carbene complexes.
作者信息
Lian Yiqian, Wulff William D
机构信息
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
出版信息
J Am Chem Soc. 2005 Dec 14;127(49):17162-3. doi: 10.1021/ja0540268.
Chromium Fischer carbene complexes with trans,trans-dienyl substituents on the carbene carbon will react with diiron nonacarbonyl to give 2-alkoxycyclohexa-2,4-dienone iron tricarbonyl complexes and/or 2-alkoxyphenols in excellent yields. In the presence of silica gel or base, the cyclohexadienone complex will suffer loss of the iron and aromatization to give 2-alkoxyphenols. The formation of 2-alkoxyphenols from dienyl chromium carbene complexes is a known process (ortho-benzannulation) that only occurs with certain cis,trans-dienyl complexes. Control experiments show that trans,trans-dienyl chromium carbene complexes do not undergo conversion to 2-alkoxyphenols in the absence of an iron source. The process most likely occurs either via coordination of the dienyl unit in the chromium carbene complex to an iron tricarbonyl group and then loss of the chromium or via direct trans-metalation of the carbene ligand to give an iron carbene complex and then internal coordination to the dienyl unit such that cis to trans isomerization of the alpha,beta-double bond occurs.
在卡宾碳上带有反式、反式二烯基取代基的铬费歇尔卡宾配合物会与二铁壬羰基反应，以优异的产率生成2-烷氧基环己-2,4-二烯酮三羰基铁配合物和/或2-烷氧基苯酚。在硅胶或碱存在下，环己二烯酮配合物会失去铁并发生芳构化，生成2-烷氧基苯酚。由二烯基铬卡宾配合物形成2-烷氧基苯酚是一个已知的过程（邻位苯并环化），仅在某些顺式、反式二烯基配合物中发生。对照实验表明，在没有铁源的情况下，反式、反式二烯基铬卡宾配合物不会转化为2-烷氧基苯酚。该过程最有可能通过铬卡宾配合物中的二烯基单元与一个三羰基铁基团配位，然后失去铬，或者通过卡宾配体的直接金属转移，生成一个铁卡宾配合物，然后内部与二烯基单元配位，使得α,β-双键发生顺反异构化来进行。
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