Search

Manganese (Mn) is the third most abundant transition metal on Earth and is known for its exceptional biocompatibility. The development of novel catalytic mode for Mn is of great significance to advancing organic synthesis. In this study, the first manganese (Mn)‐catalyzed [2+2+2] cycloaddition of alkynes is achieved with the aid of visible‐light photoredox catalysis. Photoredox catalysis is proposed to promote the transformation by in situ reduction of high‐valent Mn(II) complex to Mn(0) species, thereby initiating the reaction. Additionally, a photooxidation‐induced reductive ellimination step is also suggested. This system is further distinguished by its notable tolerance towards both terminal and internal alkynes as counterparts of diynes. [ABSTRACT FROM AUTHOR]

Herein, we report a highly efficient Sonogashira‐type cross‐coupling reaction of heteroaryl halides with terminal alkynes under mild transition‐metal‐free conditions using PPh3 and Cs2CO3/NEt3, A wide range of functional groups was tolerated under optimized conditions. Furthermore, the protocol could be extended to the Suzuki‐type cross‐coupling of heteroaryl halides with phenylboronic acid, achieving the corresponding products in good to excellent yields. A test reaction on gram scale delivered the product in reasonably high yield and thus has the potential of promising applications in drug discovery and functional materials. [ABSTRACT FROM AUTHOR]

Herein, the first example of visible‐light‐driven, cobalt‐catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using Ir[dF(CF3)ppy]2(dtbbpy)]PF6 as photosensitizer, CoBr2/n‐Bu3P as proton‐reducing catalyst, and i‐Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over‐reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single‐electron transfer process and controlling the stereoselectivity via an energy transfer process. [ABSTRACT FROM AUTHOR]