Lal Anu, Sureshan Kana M
School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram Kerala 695551 India
Chem Sci. 2025 Jun 18. doi: 10.1039/d5sc02327k.
This study investigates the reactivity of constitutional isomers of acylated -hydroxybenzotriazole (HOBt) in solid-state photocycloaddition reactions. To understand the difference in solid-state reactivity of the isomers, we have synthesized two isomeric - and -acyl derivatives of HOBt acylation with anthracene-9-carboxylic acid. Both -anthr-9-oyl oxy-benzotriazole 1 and its -acyl isomer 2 crystallized with the face-to-face arrangement of their anthracene units, with a separation of 3.8 Å between them, satisfying Schmidt's criteria, suggesting that they can undergo a topochemical [4 + 4] photocycloaddition reaction. Upon irradiation using blue light (456 nm), the isomer 2 underwent a quantitative [4 + 4] cycloaddition reaction yielding the dimer D2. However, isomer 1 did not undergo [4 + 4] cycloaddition; instead, it underwent a photochemical [4 + 2] cycloaddition with molecular oxygen, eventually yielding anthraquinone (AQ). The dimer D2 underwent a retro-cycloaddition reaction to revert back to the isomer 2. While isomers give the same product in solution-state reactions, our study establishes that isomers can react differently in the solid state and can give different products.
本研究考察了酰化羟基苯并三唑（HOBt）的构造异构体在固态光环加成反应中的反应活性。为了理解这些异构体在固态反应活性上的差异，我们合成了HOBt的两种异构的α-和β-酰基衍生物——用蒽-9-羧酸进行酰化。α-蒽-9-酰氧基苯并三唑1及其β-酰基异构体2均以蒽单元面对面排列的方式结晶，它们之间的间距为3.8 Å，满足施密特准则，这表明它们能够发生拓扑化学[4 + 4]光环加成反应。用蓝光（456 nm）照射时，异构体2发生定量的[4 + 4]环加成反应生成二聚体D2。然而，异构体1未发生[4 + 4]环加成；相反，它与分子氧发生光化学[4 + 2]环加成反应，最终生成蒽醌（AQ）。二聚体D2发生逆环加成反应又变回异构体2。虽然异构体在溶液态反应中得到相同的产物，但我们的研究表明，异构体在固态时反应方式不同，且能得到不同的产物。
