Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35043, Marburg, Germany.
Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095-1569, USA.
Angew Chem Int Ed Engl. 2019 Oct 7;58(41):14462-14466. doi: 10.1002/anie.201905647. Epub 2019 Aug 30.
3-(2-Formylphenyl)-1-pyrazol-1-yl-propenones undergo an asymmetric photorearrangement to benzo[d]cyclopropa[b]pyranones with up to >99 % ee, which is catalyzed by a bis-cyclometalated rhodium catalyst in the presence of visible light. Mechanistic experiments and DFT calculations support a mechanism in which a photoexcited catalyst/substrate complex triggers an intramolecular hydrogen-atom transfer followed by a highly stereocontrolled hetero-Diels-Alder reaction. In this reaction scheme, the rhodium catalyst fulfills multiple functions by 1) enabling visible-light π→π* excitation of the catalyst-bound enone substrate, 2) facilitating the hydrogen-atom transfer, and 3) providing the asymmetric induction for the hetero-Diels-Alder reaction.
3-(2-甲酰基苯基)-1-吡唑-1-基丙烯酮在双环金属铑催化剂和可见光的存在下，经不对称光重排反应生成苯并[d]环丙[b]吡喃酮，对映过量高达>99%。该反应的机理实验和密度泛函理论（DFT）计算支持以下反应机理：光激发的催化剂/底物络合物引发分子内氢原子转移，随后发生高度立体选择性的杂[4+2]环加成反应。在该反应方案中，铑催化剂通过以下 3 种途径实现多种功能：1）使催化剂结合的烯酮底物的可见光π→π*激发，2）促进氢原子转移，3）为杂[4+2]环加成反应提供不对称诱导。
