Department of Chemistry, PhotoGreen Lab , Viale Taramelli 12, 27100 Pavia, Italy.
J Org Chem. 2017 Jul 7;82(13):6592-6603. doi: 10.1021/acs.joc.7b00610. Epub 2017 Jun 21.
The reactivity of α,n-didehydrotoluenes (DHTs) in protic media (organic/aqueous mixtures) was explored by means of a combined computational and experimental approach. These intermediates were generated via a photoinduced double elimination process occurring in (chlorobenzyl)trimethylsilanes and led to the formation of a varied products distribution, depending on the isomer tested. Irradiation of ortho- and para-derivatives resulted, respectively, in the formation of triplet α,2- and α,4-DHTs, whose diradical reactivity led to both radical and polar products. On the other hand, irradiation of the meta-precursor led to the singlet α,3-DHT isomer. The latter showed a marked preference for the formation of polar products and this was rationalized, as supported by computational evidence, via the involvement of a zwitterionic species arising through interaction of the nucleophilic solvent with the benzylic position of the DHT.
通过组合计算和实验方法探索了α，n-去氢甲苯（DHTs）在质子介质（有机/水混合物）中的反应性。这些中间体是通过（氯苄基）三甲基硅烷中发生的光诱导双消除过程产生的，导致形成不同的产物分布，具体取决于测试的异构体。对位和邻位衍生物的辐照分别导致三重态α，2-和α，4-DHT 的形成，其自由基的反应性导致自由基和极性产物的形成。另一方面，对间位前体的辐照导致单重态α，3-DHT 异构体的形成。后者表现出对极性产物形成的明显偏好，这可以通过计算证据来合理化，这是通过与 DHT 的苄基位置相互作用的两性离子物种的参与来支持的。
