Synthesis and fluxional behavior of dinaphtho[2,1-b;1′,2′-d]-siloles and -germoles, involving the first example of optically active group 14 dinaphthoheterols

Abstract 7-Substituted dinaphtho[2,1-b;1′,2′-d]-siloles 2 and -germoles 3, involving the first isolated example of optically active group 14 dinaphthoheteroles, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate. They are fluxional in the NMR time scale at elevated temperatures, and the energy barriers (ΔG‡) for racemization arising from the flipping of the two naphthalene rings are estimated to be 76–77±2 kJ mol−1 for siloles 2b–d and 80±2 kJ mol−1 for germole 3b. The half-life (t1/2) for racemization of the optically active silole (R)-2b prepared from optically active (R)-DBBN by the same procedure is determined to be 7.2 h in benzene at 19°C.