Development of a General Method for the Hiyama–Denmark Cross-Coupling of Tetrasubstituted Vinyl Silanes

General conditions for the Hiyama–Denmark cross-coupling of tetrasubstituted vinyl silanes and aryl halides are reported. Prior reports of Hiyama–Denmark reactions of tetrasubstituted vinyl silanes have required the use of vinyl silanols or silanolates, which are challenging to handle, or internally activated vinyl silanes, which lack structural generality. Now, unactivated tetrasubstituted vinyl silanes, bearing bench-stable tetraorganosilicon centers, and aryl halides can be coupled. The key to this discovery is the identification of dimethyl­(5-methylfuryl)­vinylsilanes as bench stable and easily prepared cross-coupling partners that are readily activated under mild conditions in Hiyama–Denmark couplings. These palladium-catalyzed cross-couplings proceed well with aryl chlorides, though aryl bromides and iodides are also tolerated, and the reactions display high stereospecificity in the formation of tetrasubstituted alkenes. In addition, only a mild base (KOSiMe3) and common solvents (THF/DMA) are required, and importantly, toxic additives (such as 18-crown-6) are not needed. We also show that these conditions are equally applicable to Hiyama–Denamrk coupling of trisubstituted vinyl silanes.本研究报道了四取代乙烯基硅烷与芳基卤化物的Hiyama–Denmark交叉偶联（Hiyama–Denmark cross-coupling）通用反应条件。此前针对四取代乙烯基硅烷的Hiyama–Denmark反应报道，均需使用难以操控的乙烯基硅醇或硅醇盐，或是缺乏结构普适性的内部活化型乙烯基硅烷。本研究实现了带有实验室稳定四有机硅中心的未活化四取代乙烯基硅烷与芳基卤化物的交叉偶联。本发现的核心在于，鉴定出二甲基(5-甲基呋喃基)乙烯基硅烷可作为实验室稳定且易于制备的交叉偶联底物，其可在Hiyama–Denmark偶联的温和条件下轻松活化。该钯催化交叉偶联反应对芳基氯表现出优异的适配性，同时也可兼容芳基溴与芳基碘，且在生成四取代烯烃的过程中展现出极高的立体专一性。此外，该反应仅需使用温和碱（三甲基硅醇钾，KOSiMe3）与常用溶剂（四氢呋喃/THF、N,N-二甲基乙酰胺/DMA），且无需添加有毒助剂（如18-冠-6/18-crown-6），这点尤为关键。本研究同时证明，该反应条件同样适用于三取代乙烯基硅烷的Hiyama–Denmark交叉偶联。