Palladium-Catalyzed Amidation Using Tert-Butyl Carbamate And Hiyama Cross-Coupling Reaction Of 2-Trimethylsilylpyridine With Aryl Bromindes

The palladium-catalyzed Buchwald-Hartwig amidation of aryl(Het) halides with tert-butyl carbamate and Hiyama cross-coupling reaction using 2-trimethylsilylpyridine were studied in this thesis as follows:Ⅰ. The palladium-catalyzed Buchwald-Hartwig amidation of aryl(Het) halides with tert-butyl carbamate1. Tert-butyl carbamate and 3-bromoanisole were chosen as the model reaction to examine the influence of catalysts, ligands, bases, solvents and temperature. The results showed that the combination of 3 mol% Pd(OAc)2/9 mol% XPhos with Cs2CO3 as base and 1,4-dioxane as solvent at 100℃is optimum condition (Scheme 1).2. Under the optimized reaction conditions, a series of aryl and heteroaryl halides substrates were investigated for this reaction. It was found that all of them could be converted into the corresponding products in moderate to excellent yields (Scheme 2).Ⅱ. The palladium-catalyzed Hiyama cross-coupling reaction using 2-trimethylsilylpyridine1.2-Trimethylsilylpyridine and 4-bromobenzonitrile were chosen as the model reaction to examine the influence of catalysts, ligands, reaction time, solvents and activators. The combination of Pd(OAc)2/SPhos with 0.1 eq. TBAF (1 M in THF) and 1.0 eq. Ag2O as activator,2.0 ml DMF as solvent at 90℃for 18 h was chosen as reaction condition (Scheme 3).2. Aryl bromides were investigated for this reaction under the chosen reaction conditions. It was found that aryl bromides with electron-withdrawing substituents at para-position, desired products can be obtained in moderate yields. If substituents at ortho-position, the product only can be detected by GC-MS. 2-Trimethylsilylpyridine is a challenging substrate and the study is in progress (Scheme 4).