Jiang Yishu, Yang Muwen, Wu Yue, López-Arteaga Rafael, Rogers Cameron R, Weiss Emily A
Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208-3113, USA.
Lead contact.
Chem Catal. 2021 Jun 17;1(1):106-116. doi: 10.1016/j.checat.2021.02.001. Epub 2021 Mar 2.
The use of visible-light photosensitizers to power [2+2] photocycloadditions that produce complex tetrasubstituted cyclobutanes is a true success of photochemistry, but the scope of this reaction has been limited to activated , -unsaturated carbonyls. This paper describes selective intermolecular homo- and hetero-[2+2] photocycloadditions of terminal and internal aryl conjugated dienes - substrates historically unsuited for this reaction because of their multiple possible reaction pathways and product configurations - through triplet-triplet energy transfer from CdSe nanocrystal photocatalysts, to generate valuable and elusive aryl vinylcyclobutanes. The negligible singlet-triplet splitting of nanocrystals' excited states allows them to drive the [2+2] pathway over the competing [4+2] photoredox pathway, a chemoselectivity not achievable with any known molecular photosensitizer. Reversible tethering of the cyclobutane product to the nanocrystal surface results in near quantitative yield of the product. Flat colloidal CdSe nanoplatelets produce cyclobutanes coupled at the terminal alkenes of component dienes with up to 89% regioselectivity.
使用可见光光敏剂来驱动[2+2]光环加成反应以生成复杂的四取代环丁烷是光化学领域的一项重大成就，但该反应的范围一直局限于活化的α,β-不饱和羰基化合物。本文描述了通过CdSe纳米晶体光催化剂的三重态-三重态能量转移，实现末端和内芳基共轭二烯的选择性分子间同-[2+2]和异-[2+2]光环加成反应——由于其多种可能的反应途径和产物构型，这些底物在历史上并不适合该反应——从而生成有价值且难以捉摸的芳基乙烯基环丁烷。纳米晶体激发态可忽略不计的单重态-三重态分裂使其能够驱动[2+2]反应途径，而非竞争性的[4+2]光氧化还原途径，这是任何已知分子光敏剂都无法实现的化学选择性。环丁烷产物与纳米晶体表面的可逆连接导致产物几乎定量生成。扁平的胶体CdSe纳米片在组分二烯的末端烯烃处生成环丁烷，区域选择性高达89%。
