Solid state double [2 + 2] photochemical reactions in the co-crystal forms of 1,5-bis(4-pyridyl)-1,4-pentadiene-3-one: establishing mechanism using single crystal X-ray, UV and 1H NMR
作者:Ramkinkar Santra、Kumar Biradha
DOI:10.1039/c0ce00612b
日期:——
Double [2 + 2] photochemical reaction of 1,5-bis(4-pyridyl)-1,4-pentadiene-3-one (1P) was observed with 100% yield in four co-crystal forms of 1P with the hydrogen bonding template molecule phloroglucinol (PG) or 5-methoxy resorcinol (MR). The crystal structure of compound 1P does not have the required geometry to produce the double [2 + 2] reaction product, but it gives a single [2 + 2] reaction product with 15% yield upon time restricted irradiation. All the reactions in co-crystals of 1P resulted in the stereospecific exo–exotetrapyridyl tricyclo[6.2.0.03,6]-decane. 1H NMR and the UV-vis spectroscopic studies clearly established a stepwise mechanism for this reaction through the formation of monocyclobutane intermediate. One co-crystal form of 1P with PG and another co-crystal form of 1P with resorcinol were found to be unreactive due to different reasons. Furthermore the mechanochemical grinding products of 1P with RN or MR have exhibited similar structural and reactivity correlations with those crystallized from solution.
观察到 1,5-双(4-吡啶基)-1,4-戊二烯-3-酮 (1P) 发生双 [2 + 2] 光化学反应,四种具有氢键的 1P 共晶形式产率 100%模板分子间苯三酚(PG)或5-甲氧基间苯二酚(MR)。化合物1P的晶体结构不具有产生双[2 + 2]反应产物所需的几何形状,但它在限制时间的照射下产生单[2 + 2]反应产物,产率为15%。 1P 共晶中的所有反应均产生立体特异性外-外四吡啶基三环[6.2.0.03,6]-癸烷。 1H NMR 和紫外-可见光谱研究通过形成单环丁烷中间体清楚地建立了该反应的逐步机制。一种1P与PG的共晶形式和另一种1P与间苯二酚的共晶形式被发现由于不同的原因而没有反应性。此外,1P 与 RN 或 MR 的机械化学研磨产物表现出与从溶液中结晶的产物相似的结构和反应性相关性。