Improved, Odorless Access to Benzo[1,2-d;4,5-d']- bis[1,3]dithioles and Tert -butyl Arylsulfides via C-S Cross Coupling

Benzo[1,2-d;4,5-d']bis[1,3]dithioles are important building blocks within a range of functional materials such as fluorescent dyes, conjugated polymers, and stable trityl radicals. Access to these is usually gained via -butyl aryl sulfides, the synthesis of which requires the use of highly malodorous -butyl thiol and relies on S Ar-chemistry requiring harsh reaction conditions, while giving low yields. In the present work, S- -butyl isothiouronium bromide is successfully applied as an odorless surrogate for -butyl thiol. The C-S bond formation is carried out under palladium catalysis with the thiolate formed in situ resulting in high yields of -butyl aryl sulfides. The subsequent formation of benzo[1,2-d;4,5-d']bis[1,3]dithioles is here achieved with scandium(III)triflate, a less harmful reagent than the usually used Lewis acids, e.g., boron trifluoride or tetrafluoroboric acid. This enables a convenient and environmentally more compliant access to high yields of benzo[1,2-d;4,5-d']bis[1,3]dithioles.