Nitro-Spirocyclization of Biaryl Ynones with tert-Butyl Nitrite: Access to NO2‑Substituted Spiro[5,5]trienones

A metal/peroxide-free involved simple cascade 6-exo-trig spirocyclization of tert-butyl nitrite with biaryl ynones has been finished, which resulted in various NO2-modified spiro[5,5]trienones with good regioselectivity/yields. A variety of scaled-up experiments, reduction/epoxidation operations, and mechanistic studies were performed to verify the merits and spirocyclization process of this radical system. Finally, the structure of the spirocycles was confirmed by single-crystal X-ray diffraction.本研究完成了无金属/无过氧化物参与的亚硝酸叔丁酯（tert-butyl nitrite）与联芳基炔酮的简便级联6-exo-trig螺环化反应，得到一系列兼具良好区域选择性与产率的硝基修饰螺[5,5]三烯酮类化合物。为验证该自由基体系的优势及螺环化反应历程，我们开展了多组放大实验、还原/环氧化操作及机理研究。最终，通过单晶X射线衍射（single-crystal X-ray diffraction）确证了目标螺环化合物的结构。