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Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition.
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2020-03-13 , DOI: 10.1002/anie.202001634
Fabian M Hörmann 1 , Christoph Kerzig 2 , Tim S Chung 1 , Andreas Bauer 1 , Oliver S Wenger 2 , Thorsten Bach 1
Affiliation  

Chiral eniminium salts, prepared from α,β‐unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a ruthenium‐catalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49–74 % yield), with high diastereo‐ and enantioselectivities. Ru(bpz)3(PF6)2 was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet‐energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co‐catalyst. In the catalytic reactions, Ru(bpy)3(PF6)2 was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy)3 showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion.

中文翻译:


从钌配合物到手性烯胺离子的三重态能量转移:通过[2+2]光环加成对映选择性合成环丁烷甲醛。



由 α,β-不饱和醛和手性脯氨酸衍生的仲胺制备的手性烯胺盐在可见光照射下发生钌催化的 (2.5 mol%) 分子间 [2+2] 光环加成至烯烃,水解后产生具有高非对映选择性和对映选择性的手性环丁烷甲醛(17 个例子,产率 49-74%)。 Ru(bpz) 3 (PF 6 ) 2被用作钌催化剂,激光闪光光解研究表明该催化剂仅通过三重态能量转移(敏化)起作用。采用手性仲胺助催化剂设计了催化系统。在催化反应中,使用了Ru(bpy) 3 (PF 6 ) 2 ,激光闪光光解实验表明它经历了电子和能量转移。然而,实验证据支持这样的假设:能量转移是唯一有效的猝灭机制。使用Ir(ppy) 3的对照实验显示对烯胺离子的分子间[2+2]光环加成没有催化作用。
更新日期:2020-03-13
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