We synthesized a stable π-expanded o-quinodimethane derivative (2) through the photochemical dearomative cycloaddition of corannulene with an isolable dialkylsilylene (1). Compound 2 was isolated as a dark blue solid with a flat bowl shape, in stark contrast to corannulene. Structural and spectroscopic properties, as well as computational studies, reveal that compound 2 exhibits a small yet significant diradical character (y0 = 0.11). The presented results pave the way for further exploration of quinoid chemistry.
