Direct Iodination of Electron-Deficient Benzothiazoles: Rapid Access to Two-Photon Absorbing Fluorophores with Quadrupolar D-?-A-?-D Architecture and Tunable Heteroaromatic Core

Direct iodination of benzothiazoles under strong oxidative/acidic conditions leads to a mixture iodinated heteroarenes with 1–2 major components, which are easily separable and structures depend on the I2 equivalents used. Among unexpected but dominant products were identified 4,7-diiodobenzothiazoles rare substitution pattern for SEAr reactions this scaffold. These employed in synthesis 4,7-bis(triarylamine-ethynyl)benzothiazoles — new class highly efficient quasi-quadrupolar fluorophores displaying large two-photon absorption cross sections (540–1374 GM) near-infrared region.