N-Arylation And σ-Bond Cleavage Tandem Reactions

Transition metal-catalyzed N-arylation tandem reactions are one of the most important methods for the construction of the carbon-nitrogen bonds, and have received considerable attention due to their successful uses in the prepartion of N-ary1 compounds in pharmaceuticals, crop-protection chemicals, and materials. On the other hand, the carbon-carbon, carbon-oxygen or carbon-sulfurσ-bond cleavage tandem rections are also effective methods for the formation of new compounds. The dissertation mainly discusses the N-arylation tandem reaction andσ-bond cleavage tandem reactions. The main contents are included:(1) N-Arylations of the nitrogen-containing heterocycles with trimethoxysilanes has been developed for the synthesis of aryl-substituted nitrogen-containing heterocycles. We found that a catalytic amount of copper powder combined with a catalytic amount FeCl3 was the most effective for the N-arylation reaction. Moreover, the Cu/FeCl3 catalytic system was compatible with a wide range of both nitrogen-containing heterocycles and trimethoxysilanes:in the presence of Cu, FeCl3 and TBAF, a variety of nitrogen-containing heterocycles were coupled with trimethoxysilanes smoothly in moderate to good yield. It is noteworthy that the reaction was carried out under solvent-free conditions. The presence of oxygen or argon disfavored the reaction, and the best results were obtained under air atmosphere.(2) A novel one-pot multicatalytic route to the synthesis of 3-methyleneindolin-2-ones involving a sequential copper-catalyzed N-arylation and palladium-catalyzed C-H functionalization process was presented. In the presence of Cul, Pd(OAc)2 and ligand (N,N’-dimethylethane-1,2-diamine), a variety of propiolamides underwent the cascade reaction with iodides to afford the corresponding 3-methyleneindolin-2-ones in moderate yields.(3) We have developed a TEMPO-promoted copper on iron-catalyzed oxidative route to cleaving the carbon-carbonσ-bond in a-amino carbonyl compounds using O2 terminal oxidant under reusable conditions. In the presence of Cu on Fe, TEMPO and O2. a variety of a-amino carbonyl compounds underwent the cleavage reaction to afford the corresponding formylamides and acids in good yields. The results showed that copper on iron catalyst can be reusable, and the activity of copper on iron catalyst was not obviously decreased after five runs. It is noteworthy that copper on iron catalyst also displays high catalytic activity:the maximal TONs up to 51,000.(4) The synthesis of enol phosphates was described by base-mediated tandem reactions of a-arlyoxyacetophenones with phosphonates. In the presence of Cs2CO3, a variety of a-arlyoxyacetophenones smoothly underwent the sequential O-P bond-forming/C-0 bond cleavage/isomerization tandem reaction with phosphonates at room temperature, providing the corresponding enol phosphates in moderate to excellent yields. Enol phosphate compounds are important because they often display a multitude of robust biologically important properties serving as pharmacological agents, as well as are used as versatile intermediates in organic synthesis. Importantly, this method is simple and mild with a wide range of substrates compatibility, which makes the applications of enol phosphates more attractive in organic synthesis.(5) A selective method for the synthesis of (E)-vinyl sulfones was presented by palladium-catalyzed conjugate addition to electron-deficient alkynes with 1,2-bis(phenylsulfonyl)ethane. In the present of Pd(OAc)2 and N,N-dimethylethane-1,2-diamine,1,2-bis(phenylsulfonyl)ethane underwent the carbon-sulfur bond cleavage, followed by conjugate addition to a variety of electron-deficient alkynes afforded the corresponding (E)-vinyl sulfones in moderate to good yields. It is noteworthy that the sulfone resource, is prepared in situ from 1,2-bis(phenylsulfonyl)ethane through a C-S bond cleavage. The structures of products were determind as (E)-isomers by X-ray single-crystal diffraction analysis.(6) A simple method for the synthesis of phenylsulfonyl-butan-1-ones was described by base-mediated tandem reactions of ketones with 1,2-bis(phenylsulfonyl)ethane. In the presence of KOtBu, 1,2-bis(phenylsulfonyl)ethane underwent the carbon-sulfur bond cleavage, followed by Michael addition to numerous ketones afforded the corresponding phenylsulfonyl-butan-1-ones in moderate to good yields. Notably, this method is simple and mild with a wide range of substrates compatibility...