Dediazoniative functionalization of chromen-4-one and chromen-2-one diazonium-BF4 salts in BMIM-ILs. direct access to the -F, -I, -OSO (CF3)=NTf, and N(Tf)(2) derivatives, and facile synthesis of chromenone azo-dyes by coupling to activated arenes

摘要

Chromenone-diazonium-BF4 salts were isolated as stable powders by diazotization of the 7 -aminoderivatives with NaNO2/HBF4. The 7-Fluoro-derivatives were synthesized by fluorodediazoniation in [BMIM][PF6], while the 7-iodo-derivatives were obtained by iododediazoniation with TMSIfiBMIMI [PF6]. Further iodination with NIS furnished the 2,7-di-iodo derivative. Dediazoniation in [BMIM][Tf2N] gave the corresponding chromenone-OSO(CF3)=NTf compounds as major products, along with chromenone N(Tf)2 and the 7-fluoro-derivatives. Chromenone-diazonium salts undergo facile diazocoupling with isomeric trimethoxybenzenes and dimethylaniline at r.t in aqueous EtOH or in [BMIM] [PF6] to give azo-dyes. (C) 2020 Elsevier Ltd. All rights reserved.