Kinetic stabilization of the o-quinoidal 3,4-benzotropone system was investigated. The parent 3,4-benzotropone 1 undergoes rapid [π8 +
π10] dimerization in fluid solution even at −78 °C while triptycene-fused derivative 5 having a tert-butyl group at the C(6) position of the tropone moiety was found to be stable indefinitely under similar conditions. The relative importance of the triptycene moiety and the tert-butyl group in 5 for the kinetic stabilization was evaluated.