Heterogeneous-Gold-Catalyzed Acceptoriess Cross-Dehydrogenative Coupling of Hydrosilanes and Isocyanic Acid Generated in situ from Urea

摘要

Cross-coupling reactions (e.g., Suzuki, Negishi, Heck, Stille, Kumada, and Buchwald-Hartwig reactions) are of paramount importance and have proven useful for the design of molecules. Although cross-coupling reactions can precisely construct new C—C, C~X, and X—X bonds (X = heteroatom), they usually utilize preactivated substrates (e.g., halides, tosylates, and triflates) and require transmetalation steps, which concurrently generate at least stoichiometric amounts of metal salts as wasted Recently, cross-dehydrogenative coupling reactions by direct activation of OH or X-H bonds have been emerging as synthetic tools because they are more atom efficient and environmentally benign than classical cross-coupling reactions. To date, several efficient cross-dehydrogenative coupling reactions using hydrogen acceptors (oxidants) such as tert-butyl hydroperoxide, hydrogen peroxide, and molecular oxygen have been developed. Acceptoriess cross-dehydrogenative coupling reactions have also been developed. Quite recently, we have also reported C—N (terminal alkynes and amides), P—N (if-phosphonates and amides) Si~N (hydrosilanes and indoles), and Si~C (hydrosilanes and terminal alkynes) bond-forming reactions by cross-dehydrogenative coupling strategy. Herein, we successfully developed a novel green synthetic route to silyl isocyanates through heterogeneous-gold-catalyzed, acceptorless cross-dehydrogenative coupling of hydrosilanes and isocyanic acid (generated by in situ thermolysis of urea) [Eq.(l)].