Unsaturated malonyl esters underwent Pd-catalyzed intramolecular allylic alkylation to give 4-vinyl-substituted γ-lactones. In contrast to the previously studied cyclization of malonamides, this reaction could only be achieved with a substrate incorporating a judiciously positioned silicon moiety, which directs the ionization toward the desired η 3 -allyl-palladium complex. The resulting 4-[dimeth
engaged into Hiyama couplings with various iodoarenes, to give the corresponding 4-(α-styryl)-γ-lactones. The use of a specifically substituted iodoarene generated an advanced tetracyclic lactone intermediate incorporating rings A−D of lignans belonging to the podophyllotoxin family. Subsequent electrophilic aromatic substitution with a variety of electron-rich arenes afforded the target picropodophyllin
photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cation via visible-light photoredox catalysis.
光氧化还原和极性反转催化的协同组合使硅烷与 H 2的析氢交叉偶联成为可能O、醇、酚和硅烷醇,它们分别以中等至极好的收率提供相应的硅烷醇、单甲硅烷基醚和二甲硅烷基醚。在仅存在有机光催化剂 4-CzIPN 和硫醇 HAT 催化剂的情况下,Si-H 和 O-H 的脱氢交叉偶联顺利进行,底物范围广,官能团相容性好,不需要任何金属、外部氧化剂和质子还原剂,这与之前报道的光催化析氢交叉偶联反应不同,后者通常需要质子还原助催化剂,如钴络合物。从机制上讲,生成甲硅烷基阳离子中间体以促进交叉偶联反应,因此代表了一种前所未有的生成甲硅烷基阳离子的方法通过可见光光氧化还原催化。
Asymmetric Cu<sup>I</sup>-Catalyzed Insertion Reaction of 1-Aryl-2,2,2-trifluoro-1-diazoethanes into Si–H Bonds
An asymmetric copper(I)-catalyzed Si-H insertionreaction of 1-aryl-2,2,2-trifluoro-1-diazoethanes in dimethyl carbonate as a green solvent alternative was developed. A C2-symmetric copper(I) diimine complex enabled the asymmetric insertionreaction to give enantioenriched (1-aryl-2,2,2-trifluoroethyl)silanes with excellent stereoselectivities (up to 98:2 er). Successful conversion of the silanes into