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'-binaphth yl 3, generated in situ from optically active a,2'-dibromo-1,1'-binaphthyl (8)-(+)-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 th e NMR time scale at elevated temperatures. The energy barrier (DeltaG(doubl e dagger)) resulting from the flipping of the two naphthalene rings was est imated to be 85 +/- 1 kJ mol(-1) and its half life (t(1/2)) for racemizatio n was determined to be 5.2 h in benzene at 20 degreesC. (C) 2001 Elsevier S cience Ltd. All rights reserved.