Facile Access to Organostibines via Selective Organic Superbase Catalyzed Antimony‐Carbon Protonolysis
Abstract 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(C 6 F 5 ) 3 , 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 C 6 HF 5 . Also, the significantly less electron‐deficient stibines, Ph 2 SbC 6 F 5 and PhSb(C 6 F 5 ) 2 smoothly underwent base‐catalyzed exchange reactions with a range of terminal alkynes to generate the stibines of formulae PhSb(C≡CPh) 2 , and Ph 2 SbC≡CR [R=C 6 H 5 , C 6 H 4 ‐NO 2 , COOEt, CH 2 Cl, CH 2 NEt 2 , CH 2 OSiMe 3 , Sb(C 6 H 5 ) 2 ], respectively. These formal substitution reactions proceed with high selectivity as only the C 6 F 5 groups serve as a leaving group to be liberated as C 6 HF 5 upon formal proton transfer from the alkyne. Kinetic studies of the base‐catalyzed reaction of Ph 2 SbC 6 F 5 with phenyl acetylene to form Ph 2 SbC≡CPh and C 6 HF 5 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‐C 6 F 5 bond sequence through secondary bond interactions.