Lim Suk Hyun, You Hayeon, Kim Min-Ji, Wee Kyung-Ryang, Cho Dae Won
Department of Chemistry, Yeungnam University, Gyeongsan, Gyeongbuk 38541, Republic of Korea.
Department of Advanced Materials Chemistry, Korea University, Sejong 30019, Republic of Korea.
J Org Chem. 2024 Sep 20;89(18):13150-13166. doi: 10.1021/acs.joc.4c01287. Epub 2024 Sep 3.
Triplet energy transfer (EnT)-promoted photochemical pathways, arisen by visible light and its photosensitizers, have gained significant attention as a complementary strategy for initiating organic transformations in photochemical reactions that are unlikely to occur through a single electron transfer (SET) process. In the present study, we investigated the triplet EnT-promoted 1,3-dipolar cycloaddition reactions of -(trimethylsilyl)methylphthalimide with electron-deficient alkynyl and alkenyl dipolarophiles. The triplet excited state of -(trimethylsilyl)methylphthalimide, promoted by the triplet EnT from thioxanthone (TXA) photosensitizer, underwent sequential intramolecular SET and carbon-to-oxygen migration of the silyl group to form azomethine ylide. This generated ylide cycloadded to alkynes or alkenes to regioselectively and stereospecifically produce a nitrogen-containing benzopyrrolizidine scaffold with multiple stereogenic centers. Crucially, the stereoselectivity of these cycloaddition reactions (i.e., endo versus exo addition) was influenced by the nature of the dipolarophiles.
由可见光及其光敏剂引发的三重态能量转移（EnT）促进的光化学途径，作为一种补充策略，在通过单电子转移（SET）过程不太可能发生的光化学反应中引发有机转化，已受到广泛关注。在本研究中，我们研究了（三甲基硅基）甲基邻苯二甲酰亚胺与缺电子炔基和烯基亲偶极体的三重态EnT促进的1,3-偶极环加成反应。由噻吨酮（TXA）光敏剂的三重态EnT促进的（三甲基硅基）甲基邻苯二甲酰亚胺的三重态激发态，经历了连续的分子内SET和硅基的碳到氧迁移，形成了甲亚胺叶立德。这种生成的叶立德与炔烃或烯烃发生环加成，区域选择性和立体选择性地生成具有多个立体中心的含氮苯并吡咯里西啶骨架。至关重要的是，这些环加成反应的立体选择性（即内型与外型加成）受亲偶极体性质的影响。
