Facile Access to Organostibines via Selective Organic Superbase Catalyzed Antimony-Carbon Protonolysis.

The selective formation of antimony-carbon bonds via organic superbase catalysis under metal- and salt-free conditions is reported. This novel approach utilizes electron-deficient stibine, Sb(CF), to give upon base-catalyzed reactions with weakly acidic aromatic and heteroaromatic hydrocarbons access to a range of new aromatic and heteroaromatic stibines, respectively, with loss of CHF. Also, the significantly less electron-deficient stibines, PhSbCF and PhSb(CF) smoothly underwent base-catalyzed exchange reactions with a range of terminal alkynes to generate the stibines of formulae PhSb(C≡CPh), and PhSbC≡CR [R=CH, CH-NO, COOEt, CHCl, CHNEt, CHOSiMe, Sb(CH)], respectively. These formal substitution reactions proceed with high selectivity as only the CF groups serve as a leaving group to be liberated as CHF upon formal proton transfer from the alkyne. Kinetic studies of the base-catalyzed reaction of PhSbCF with phenyl acetylene to form PhSbC≡CPh and CHF suggested the empirical rate law to exhibit a first-order dependence with respect to the base catalyst, alkyne and stibine. DFT calculations support a pathway proceeding via a concerted σ-bond metathesis transition state, where the base catalyst activates the Sb-CF bond sequence through secondary bond interactions.