In the transition-metal catalyzed functionalizations of unactivated alkenes, the efficiency and selectivity of these processes could be improved by introducing directing groups into the alkene substrates. Utilization of thioether as directing group is of great interest, since thioethers are important substructures in diverse natural products, pharmaceuticals, polymers and functional materials, and easily accessible from a number of synthetic pathways. 7 However, due to the poisonous character of sulfides in deactivating transition metal catalysts and the easy C-S bond cleavage under these circumstances, 8 successful usages of thioether to promote and direct reaction processes are still limited. 9 In the area of alkene hydrosilylations, Van Vranken et al revealed the necessity of thioether in accelerating hydrosilylation of olefins under platinum catalysis. 10 However, only one example of hydrosilylating 1,1disubstituted alkene substrate was presented in their work, and allylic sulfides were demonstrated to react sluggishly under this hydrosilylation condition. Shimada reported the efficient iridium-catalyzed hydrosilylation of various sulfur-containing olefins, but with no investigation on 1,1-disubstituted alkenes. Meanwhile, we disclosed the generality of iridium catalysis in hydrosilylating unactivated 1-substituted alkenes, and likewise probed its efficiency towards sterically hindered disubstituted terminal alkenes. The substrate involving thioether group showed its specificity in affording hydrosilylation product. Encouraged by the promising applications of this type of structure and corresponding synthetic methods in manufacturing new interesting materials, as well as our findings that the interaction between a heteroatom (O, N, S) and iridium catalyst can effectively enhance diverse hydrosilylation processes, here we showed our investigations on the thioether-facilitated hydrosilylation of steric 1,1-disubstituted alkenes under a simple iridium catalytic system (c, Scheme 1). A variety of substrates, including allylic and homoallylic sulfides, were hydrosilylated with high efficiency and selectivity. Control experiments revealed the necessity of thioether in promoting this process. a The mixture of 1a (0.20 mmol, 1.0 eq.), silane (0.30 mmol, 1.5 eq.) and catalyst (0.04 mmol, 2 mol %) in solvent (1.00 mL, 0.2 M) was stirred at room temperature for 4 h. b NMR Yield using dimethylsulfone as internal standard. We began our research by using sulfur-containing 1,1disubstituted alkene 1a as the model substrate and PhMe2SiH as the silyl source (Table ). A few simple commercial iridium catalysts were first screened with DCM as the solvent under room temperature, during which a 89% NMR yield of desired product was observed with the utilization of [Ir(COD)Cl]2 (entries 1-4, Table ). The yield was optimized to 95% by using 1,4-dioxane instead of DCM (entries 6, Table ). 1 H NMR control experiment showed this process completed within 2 hours, with observation of trace amount of by-products (Supplementary Figure ). Considering that both the steric effect of the hydrosilanes and the different electronic property of the Si-H bond of them might influence the hydrosilylation process, we next examined the hydrosilane scopei. Decreased yields were obtained with the utilization of Ph2MeSiH, Ph3SiH, BnMe2SiH and Et3SiH (entries 8-11, Table ). The by-product from alkene hydrogenation was confirmed as the major through GC/MS and 1 H NMR analysis (Supplementary Figure ). Usage of (EtO)3SiH gave no desired product as well (entry 12, Table ). The difference is that besides a little partial consumption via side reactions, most of the alkene substrate remained unchanged in this case (Supplementary Figure ). A variety of powerful non-precious-metal catalytic systems have been developed recently for hydrosilylation of 1,1-disubstituted alkenes, including the valuable asymmetric hydrosilylation protocols. The cobalt/isocyanide system reported by Nagashima aroused our interest due to its simple condition and high catalytic activity toward -methylstyrene derivatives. However, treatment of the sulfur-containing alkene 1a with the Co(OAc)2/CNAd catalyst gave no desired hydrosilylation product, which might be caused by the deactivation of cobalt catalyst in the presence of sulfur unit (entries 13 & 14, Table ).