Ru 3 (CO) 12 -catalyzed dehydrogenative Si N coupling of indoles with hydrosilanes without additive
作者:Wenchao Zhai、Bin Li、Baiquan Wang
DOI:10.1016/j.tet.2018.01.024
日期:2018.3
An efficient Ru3(CO)12-catalyzed dehydrogenative SiN coupling reaction of indoles, pyrrole, and carbazole with hydrosilanes is reported. The reaction does not need any external additive. This catalytic reaction has a wide substrate range, excellent functional group tolerance, and high to excellent reaction efficiency. Gram-scale synthesis demonstrates the practicability of this synthetic method.
Zinc catalysis: Zinc triflate in a nitrile solvent behaved as an effective catalyst for dehydrogenative N‐silylation with a variety of indoles and hydrosilanes (see scheme). The addition of pyridine greatly accelerated the N‐silylation reaction to produce N‐silylindoles exclusively in high to excellent yields.
to the corresponding C-silylation in the case that the nitrogen atom of indoles has a substituent. Pyrrole, carbazole, arylamine, and thiophene substrates other than indoles undergo the dehydrogenative N- and/or C-silylation as well. Mechanistic studies showed that the role of the zinc Lewis acid is to activate the hydrosilane. The rate-determining step of the present reaction was found to be involved
In the presence of Rh(2)(OAc)(4) (OAc = acetate) and TBA(2)WO(4) (TBA = tetra-n-butylammonium), the N-silylation of indole derivatives with hydrosilanes efficiently proceeded to give the corresponding N-silylated indoles in high yields. Pyrrole and carbazole were also N-silylated with the combined catalysts.