Unexpected formation of α-formylated BOPHY in the reaction with copper salts

Abstract

We report the unexpected oxidation of the α-methyl into an α-formyl group in the BOPHY core promoted by Cu(I) alkynide. The newly synthesized formyl derivatives offer great potential as precursors for various post-functionalizations of BOPHYs due to the presence of the formyl group. Half-BOPHYs with the α-formyl group were also obtained as by-products. The α-formyl-derived BOPHY absorbs at 461 nm with a fluorescence quantum yield of 75%. All the target molecules were characterized experimentally by various spectroscopic techniques and X-ray diffraction analyses, and theoretically by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations.