Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Saclay, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
Institute of Chemical and Engineering Sciences (ICES), Agency for Science, Technology and Research (A*STAR), 8, Biomedical Grove, Neuros, #07-01, Singapore, 138665, Singapore.
Chemistry. 2020 Apr 9;26(21):4682-4689. doi: 10.1002/chem.201905597. Epub 2020 Mar 19.
In this study, a very simple technique to perform efficiently photodimerization of some vinylpyridines is reported. By irradiating a stirred mixture of several stilbazoles with solid oxalic acid dihydrate dispersed in a nonpolar (i.e., cyclohexane) or moderately polar (benzene, dichloromethane, dioxane) solvent, the corresponding dimeric cyclobutane adducts were obtained in high yields and excellent regio- and stereoselectivities. The strategy could also be applied successfully to oily, waxy, or even insoluble stilbazoles. Moreover, the oxalic acid loading could be lowered to substoichiometric amounts. When further optimizations were needed, our strategy was found to be highly flexible to identify other oligocarboxylic acids as alternative additives to improve, or even overturn, the regioselectivity. Oxalic acid and other oligocarboxylic acids were found to be capable of orienting more than 50 stilbazoles toward photodimerization under these conditions.
在这项研究中，报道了一种非常简单的技术，可有效地进行几种乙烯基吡啶的光二聚反应。通过辐照搅拌的混合物，其中包含分散在非极性（例如环己烷）或中等极性（苯、二氯甲烷、二恶烷）溶剂中的固态草酸二水合物和几个斯特尔巴唑，以高收率和优异的区域和立体选择性得到相应的二聚环丁烷加合物。该策略也可成功应用于油性、蜡状甚至不溶性的斯特尔巴唑。此外，草酸的负载量可以降低到亚化学计量。当需要进一步优化时，发现我们的策略非常灵活，可以识别其他寡羧酸作为替代添加剂来提高甚至反转区域选择性。在这些条件下，发现草酸和其他寡羧酸能够使 50 多种斯特尔巴唑定向进行光二聚反应。
