The reaction of o-aminobenzaldehyde with cyclic 1, 2-diketones provided 3, 3'-annelated derivatives of 2, 2'-biquinoline. The reaction with 1, 2-cyclododecanedione stopped at the monocondensation stage. High-resolution NMR spectra demonstrate that the dimethylene- and trimethylene-bridged systems are undergoing rapid conformational inversion at room temperature while the tetramethylene-bridged system is conformationally rigid. The ...