Monomeric Cinchona Alkaloid-Based Catalysts for Highly Enantioselective Bromolactonisation of Alkynes.
Monomeric Cinchona Alkaloid-Based Catalysts for Highly Enantioselective Bromolactonisation of Alkynes.
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DOI：
10.1002/chem.201604003
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发表时间：
2016-12
期刊：
影响因子：
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通讯作者：
M. Wilking;C. Daniliuc;U. Hennecke
中科院分区：
文献类型：
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作者：
M. Wilking;C. Daniliuc;U. Hennecke
金鸡纳生物碱二聚体（DHQD）2 PHAL已被证明是一种广泛适用的催化剂不对称卤化。然而，该催化剂不必是二聚的，并且制备了一类单体奎尼丁和奎尼丁衍生的催化剂，其在末端炔酸的溴化内酯化中通常显示出上级选择性。机理研究表明，这些有机催化剂作为主体分子，可以结合羧酸为基础的基板作为客人与大量的结合常数。基于这些发现，有人提出，这类催化剂是双功能的性质，活化的卤化剂，以及亲核试剂在亲电卤化反应。
The cinchona alkaloid dimer (DHQD)2 PHAL has been shown to be a broadly applicable catalyst for asymmetric halogenations. However, this catalyst does not have to be dimeric and a class of monomeric quinidine and quinine-derived catalysts was prepared, often showing superior selectivity in bromolactonisations of terminal alkynoic acids. Mechanistic investigations show that these organocatalysts act as host molecules that can bind carboxylic acid-based substrates as guests with substantial binding constants. Based on these findings, it is proposed that this class of catalysts is bifunctional in nature activating the halogenating agent as well as the nucleophile in electrophilic halogenation reactions.