Roy Vishal Jyoti, Sen Partha Pratim, Raha Roy Sudipta
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
J Org Chem. 2021 Dec 3;86(23):16965-16976. doi: 10.1021/acs.joc.1c02111. Epub 2021 Nov 2.
Thioesters play a crucial role in biological systems and serve as important building blocks for organic synthesis. Herein, Eosin Y and TBHP mediated photochemical cross dehydrogenative coupling (PCDC) between feedstock aldehydes and thiols has been described at room temperature to synthesize thioesters. This thioesterification protocol proceeds smoothly to give the desired products in good to excellent yields by the suitable PCDC of both alkyl/aryl- aldehydes with a variety of alkyl/aryl-thiols and generates water and BuOH as green byproducts. This method is also found to be scalable with good efficiency. Mechanistic investigations reveal that under this photochemical condition, the formation of acyl radical can be achieved from aldehyde. This acyl radical was further intercepted with an intermediate disulfide, generated in situ via the dehydrogenation of thiol to give the desired thioester. Moreover, disulfides, which are relatively easier to handle, also provided good to excellent yields in the optimized reaction condition. This protocol was further extended toward the more challenging direct transformation of alcohols to thioesters.
硫酯在生物系统中起着至关重要的作用，并且是有机合成的重要构建单元。在此，已描述了在室温下，曙红Y和叔丁基过氧化氢介导的原料醛与硫醇之间的光化学交叉脱氢偶联（PCDC）反应以合成硫酯。通过各种烷基/芳基醛与各种烷基/芳基硫醇的合适PCDC反应，该硫酯化反应顺利进行，以良好至优异的产率得到所需产物，并生成水和丁醇作为绿色副产物。该方法还具有良好的可扩展性和效率。机理研究表明，在这种光化学条件下，醛可形成酰基自由基。该酰基自由基进一步与通过硫醇脱氢原位生成的中间体二硫化物反应，得到所需的硫酯。此外，相对易于处理的二硫化物在优化的反应条件下也能提供良好至优异的产率。该反应方案进一步扩展到更具挑战性的醇直接转化为硫酯的反应。
