ELECTRONIC AND STERIC CONTROL IN CARBON HYDROGEN INSERTION REACTIONS OF DIAZOACETOACETATES CATALYZED BY DIRHODIUM(II) CARBOXYLATES AND CARBOXAMIDES
ELECTRONIC AND STERIC CONTROL IN CARBON HYDROGEN INSERTION REACTIONS OF DIAZOACETOACETATES CATALYZED BY DIRHODIUM(II) CARBOXYLATES AND CARBOXAMIDES
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DOI：
10.1021/ja00056a021
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发表时间：
1993-02-10
影响因子：
15
通讯作者：
PEARSON, MM
中科院分区：
文献类型：
--
作者：
DOYLE, MP;WESTRUM, LJ;PEARSON, MM
二铑(II)催化剂上的羧酸盐和甲酰胺配体可以在重氮乙酸酯的碳-氢插入反应中提供巨大的区域控制。 2,3,4-三甲基-3-戊基重氮乙酰乙酸酯 (1) 通过插入伯和叔 C-H 键而与四（全氟丁酸）二铑 (II) 形成统计分布 (61:39) 的 γ-内酯产物，而四乙酰胺二铑 (II) 仅观察到叔 C-H 插入。使用 2-甲基-2-辛基重氮乙酰乙酸酯 (3) 获得了类似的结果，其中二级和一级 C-H 键之间存在插入竞争，并且电子因素控制区域选择。然而，对于 2-甲基-3-异丙基-3-庚基重氮乙酰乙酸酯 (2) 和 2-甲基-1-苯基-2-丙基重氮乙酰乙酸酯 (4)，C-H 插入的产物分布对于二铑 (II) 配体是不变的；插入二级 C-H 键优于插入 2 (95:5) 的三级 C-H，插入一级 C-H 键优于插入 4 (70:30) 的苄基二级 C-H 键。在这种情况下，可以通过MM2计算进行分析，区域选择性由构象偏好决定，其中C-H插入选择性可以像2和4中发现的那样随机。当只有一个C-H键位点可用于插入形成五元环产物时，从四乙酸二铑(II)催化的反应中仅观察到一种γ-内酯，并且该产物不一定是假定的电子偏好预测的产物。
Carboxylate and carboxamide ligands on dirhodium(II) catalysts can provide enormous regiocontrol in carbon-hydrogen insertion reactions of diazoacetate esters. Whereas 2,3,4-trimethyl-3-pentyl diazoacetoacetate (1) forms gamma-lactone products from insertion into primary and tertiary C-H bonds in a statistical distribution (61:39) with dirhodium(II) tetrakis(perfluorobutyrate), only tertiary C-H insertion is observed with dirhodium(II) tetraacetamide. Similar results are obtained with 2-methyl-2-octyl diazoacetoacetate (3), where competition for insertion exists between secondary and primary C-H bonds and electronic factors govern regioselection. However, with 2-methyl-3-isopropyl-3-heptyl diazoacetoacetate (2) and 2-methyl-1-phenyl-2-propyl diazoacetoacetate (4), product distributions from C-H insertion are invariant with the dirhodium(II) ligands; insertion into a secondary C-H bond is favored over tertiary C-H insertion with 2 (95:5), and insertion into a primary C-H bond is preferred to benzylic secondary C-H insertion with 4 (70:30). In such cases, which are amenable to analyses by MM2 calculations, regioselectivity is determined by conformational preferences for which C-H insertion selectivity can be as random as that found with 2 and 4. When only one C-H bond site is available for insertion to form a five-membered ring product, only one gamma-lactone is observed from reactions catalyzed by dirhodium(II) tetraacetate, and that product is not necessarily the one predicted by presumed electronic preferences.