Synthesis, molecular structure and fluxional behavior of (R)-7-p-tolyldinaphtho[2,1-b;1′,2′-d]stibole: the first isolated example of optically active group 15 dinaphthoheteroles

The condensation of dibromo-p-tolylstibane with 2,2′-dilithio-1,1′-binaphthyl 3, generated in situ from optically active 2,2′-dibromo-1,1′-binaphthyl (R)-(+)-2 by treatment with tert-butyllithium, afforded optically active (R)-(−)-7-p-tolyldinaphtho[2,1-b;1′,2′-d]stibole 1c, which is fluxional in the NMR time scale at elevated temperatures. The energy barrier (ΔG‡) resulting from the flipping of the two naphthalene rings was estimated to be 85±1 kJ mol−1 and its half life (t1/2) for racemization was determined to be 5.2 h in benzene at 20°C.