Iron-mediated preparation of vinylcyclopropanecarboxylates: scope, mechanism, and applications.
Iron-mediated preparation of vinylcyclopropanecarboxylates: scope, mechanism, and applications.
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DOI：
10.1021/jo020421u
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发表时间：
2003-01
期刊：
影响因子：
--
通讯作者：
Y. Yun;K. Godula;Yeyu Cao;W. Donaldson
中科院分区：
文献类型：
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作者：
Y. Yun;K. Godula;Yeyu Cao;W. Donaldson
三羰基（1-甲氧基羰基戊二烯基）铁（1+）阳离子（1a）通过攻击与Fe(CO)(3)基团相对的配体表面的C2生成三羰基（戊二烯基）铁配合物2。配合物2的氧化得到产率高的乙烯基环丙烷羧酸酯。一般来说，环丙烷环的相对立体化学反应反映了构型保留的还原消去。在C2取代基较大（即2b）的情况下，环丙烷的主要产物9b表示在C3处反转的环闭合。提出了一种涉及初始氧化（戊二基）铁物种的π -sigma- π重排的机制来解释这些结果。对乙烯基环丙烷羧酸酯产物中乙烯基上氘标记的立体化学进行了研究，结果与所提出的机理一致。将合成乙烯基环丙烷羧酸酯的方法应用于2-（2′-羧基环丙基）甘氨酸(+)-22和(-)-23以及环丙烷三酯(-)-26的合成。
The addition of stabilized carbon nucleophiles to tricarbonyl(1-methoxycarbonylpentadienyl)iron(1+) cation (1a) proceeds via attack at C2 on the face of the ligand opposite the Fe(CO)(3) group to generate tricarbonyl(pentenediyl)iron complexes 2. Oxidation of complexes 2 affords vinylcyclopropanecarboxylates in good yield. In general, the relative stereochemistry about the cyclopropane ring reflects reductive elimination with retention of configuration. In cases where the C2 substituent is bulky (i.e., 2b) the major cyclopropane product 9b represents ring closure with inversion at C3. A mechanism involving pi-sigma-pi rearrangement of the initially oxidized (pentenediyl)iron species is proposed to account for these results. Experiments which probe the stereochemistry of deuterium labeling in the vinyl group of the vinylcyclopropanecarboxylate products were carried out, and these results are consistent with the proposed mechanism. This methodology for the preparation of vinylcyclopropanecarboxylates was applied to the synthesis of 2-(2'-carboxycyclopropyl)glycines (+)-22 and (-)-23 and the cyclopropane triester (-)-26.