24257-23-6Relevant articles and documents
Nickel-Catalyzed Asymmetric Hydrogenation of Cyclic Alkenyl Sulfones, Benzo[ b]thiophene 1,1-Dioxides, with Mechanistic Studies
Liu, Gongyi,Tian, Kui,Li, Chenzong,You, Cai,Tan, Xuefeng,Zhang, Heng,Zhang, Xumu,Dong, Xiu-Qin
supporting information, p. 668 - 675 (2021/02/06)
A highly efficient catalytic system based on the cheap transition metal nickel for the asymmetric hydrogenation of challenging cyclic alkenyl sulfones, 3-substituted benzo[b]thiophene 1,1-dioxides, was first successfully developed. A series of hydrogenation products, chiral 2,3-dihydrobenzo[b]thiophene 1,1-dioxides, were obtained in high yields (95-99%) with excellent enantioselectivities (90-99% ee). According to the results of nonlinear effect studies, deuterium-labeling experiments, and DFT calculation investigations, a reasonable catalytic mechanism for this nickel-catalyzed asymmetric hydrogenation was provided, which displayed that the two added hydrogen atoms of the hydrogenation products could be from H2 through the insertion of Ni-H and subsequent hydrogenolysis.
Direct Arylations of Heteroarenes with Benzenesulfonyl Chlorides Using Pd/C Catalyst
Mao, Shuxin,Shi, Xinzhe,Soulé, Jean-Fran?ois,Doucet, Henri
, p. 91 - 97 (2019/12/30)
The reactivity of heteroaromatics in direct arylation with benzenesulfonyl chlorides using 10 % Pd/C as catalyst was explored. With (benzo)thiophenes, (benzo)furans, pyrroles and selenophenes, high yields in arylated heteroarenes were obtained. These arylations were performed using only 5 mol-% Pd/C and Li2CO3 as inexpensive base. The regioselectivities are similar to those observed with homogeneous palladium catalysts. Better yields were obtained with electron-deficient benzenesulfonyl chlorides than with the electron-rich ones. Notably, useful substituents such as bromo or iodo on the benzenesulfonyl chloride were tolerated, as no cleavage of the C–Br or C–I bonds was observed under these conditions. The use of Pd/C presents several advantages compared to the previously employed homogeneous palladium catalysts, as it can be easily removed by filtration at the end of the reaction. The major side-products of the reaction are HBr associated to Li2CO3. Therefore, this new protocol affords a very attractive synthetic scheme in terms of cost, simplicity and low environmental impact for the access to arylated heteroaromatics.
Synthesis of C2 Substituted Benzothiophenes via an Interrupted Pummerer/[3,3]-Sigmatropic/1,2-Migration Cascade of Benzothiophene S-Oxides
He, Zhen,Shrives, Harry J.,Fernández-Salas, José A.,Abengózar, Alberto,Neufeld, Jessica,Yang, Kevin,Pulis, Alexander P.,Procter, David J.
supporting information, p. 5759 - 5764 (2018/04/10)
Functionalized benzothiophenes are important scaffolds found in molecules with wide ranging biological activity and in organic materials. We describe an efficient, metal-free synthesis of C2 arylated, allylated, and propargylated benzothiophenes. The reaction utilizes synthetically unexplored yet readily accessible benzothiophene S-oxides and phenols, allyl-, or propargyl silanes in a unique cascade sequence. An interrupted Pummerer reaction between benzothiophene S-oxides and the coupling partners yields sulfonium salts that lack aromaticity and therefore allow facile [3,3]-sigmatropic rearrangement. The subsequently generated benzothiophenium salts undergo a previously unexplored 1,2-migration to access C2 functionalized benzothiophenes.
