Synthesis of Donor–Acceptor-Type Benzo[<i>b</i>]phosphole and Naphtho[2,3‑<i>b</i>]phosphole Oxides and Their Solvatochromic Properties

A series of donor–acceptor-type benzo­[b]­phosphole and naphtho­[2,3-b]­phosphole oxides have been synthesized through metal-catalyzed reactions as key steps: that is, (1) cobalt- and copper-catalyzed multicomponent coupling of an arylzinc reagent, an alkyne, and dichlorophenylphosphine to assemble the electron-deficient benzophosphole or naphthophosphole oxide core and (2) palladium-catalyzed cross-coupling to introduce an electron-donating substituent to the “benzo” or “naphtho” moiety. These donor–acceptor molecules are strongly fluorescent, showing weak to strong solvatochromism depending on the electron-donating substituent.