Synthesis of a Trivalent P‐Chloro‐Dithienophosphole and Its Reactivity with Organometallic Reagents

Abstract

P‐chloro‐dithieno[3,2‐b:2′,3′‐d]phosphole was synthesized and isolated from the reaction of an aminophosphole and HCl. Developed to act as a common starting material for P‐functionalized phospholes, the compound exhibits a surprising reactivity by generating dimeric biphospholes. Despite this apparent sensitivity, when reacting with organolithium and Grignard reagents, a series of differently P‐functionalized dithieno[3,2‐b:2′,3′‐d]phospholes was accessible. Unexpectedly, organolithium reagents showed reduced reactivity with the chlorophosphole, limiting yields of the desired products due to the competing dimerization. Nonetheless, P‐functionalized phospholes were isolated from reactions of the title compound with both Grignard and organolithium reagents in yields equivalent to, or higher, than by previous methods. A bithiophene‐bridged bisphosphole system was also successfully synthesized without the necessity of generating a bis(dichlorophosphino) reagent. Finally, the isolated P‐functionalized phospholes were analyzed for their photophysical properties. In general, these compounds are strong absorbers in the UV/Vis range of the optical spectrum. The phospholes' emissions were consistent with several previously reported, however, with low quantum yields.