Experimental and computational studies of naphtho[2,3-c]tropone: a highly polarized novel troponid system

Irradiation of 6,7-(2′,3′-naphtho)bicyclo[3.2.0]hepta-3,6-dien-2-one (10) in a rigid glass at −196°C leads to the formation of hitherto unknown naphtho[2,3-c]tropone (3), which exhibits a characteristic UV–vis absorption extending to 700 nm and undergoes rapid [π12+π14] dimerization upon thawing the glass. NICS(1) values calculated for a series of benzo- and naphtho-fused tropones suggest that aromatic character of the tropone ring in 3 is significantly increased relative to the parent system.