949495-04-9Relevant articles and documents
Regioselective Crossed Aldol Reactions under Mild Conditions via Synergistic Gold-Iron Catalysis
Chen, Hao,Jean, Jonathan,Shan, Chuan,Shi, Xiaodong,Teng, Shun,Wang, Jin,Wojtas, Lukasz,Ye, Xiaohan,Yi, Yaping,Yuan, Teng,Zhao, Pengyi
, p. 1420 - 1431 (2020)
A synergistic gold-iron (Au-Fe) catalytic system was developed for sequential alkyne hydration and vinyl Au addition to aldehydes or ketones. Fe(acac)3 was identified as an essential co-catalyst in preventing vinyl Au protodeauration and facilitating nucleophilic additions. Effective C–C bond formation was achieved under mild conditions (room temperature) with excellent regioselectivity and high efficiency (1% [Au], up to 95% yields). The intramolecular reaction was also achieved, giving successful macrocyclization (16–31 ring sizes) with excellent yields (up to 90%, gram scale) without extended dilution (0.2 M), which highlights the great potential of this new crossed aldol strategy in challenging target molecule synthesis. Effective construction of the C–C bond is one of the most important tasks in organic synthesis. Whereas aldol condensation is a classic C–C bond-forming transformation, it requires other chemical promoters, such as strong base and reactive acidic catalysts. As a result, the overall transformation is limited in terms of ideal atom economy and environmentally friendly operation. With the discovery of a gold-iron (Au-Fe) synergistic catalysis system, here we describe a new approach to facilitating alkyne hydration and sequential vinyl Au addition to carbonyls. This approach gives the C–C bond-forming products in excellent yields, wide substrate scope, and great functional-group compatibility under mild conditions. This protocol can also be applied to macrocyclization without extended dilution. This C–C bond-forming strategy could facilitate challenging molecule synthesis in chemical, biological, and medicinal research. We report a synergistic gold-iron (Au-Fe) catalytic system to access vinyl Au reactivity by avoiding frequently occurring protodeauration. Fe(acac)3 was identified as an essential co-catalyst, facilitating vinyl Au addition to aldehydes. A broad substrate scope was obtained under mild conditions (room temperature) with excellent regioselectivity and high efficiency (1% [Au], up to 95% yields). This protocol offers a practical solution for achieving macrocyclization (16–31 ring sizes, up to 90%, gram scale) without extended dilution, highlighting the synthetic utility in complex molecular synthesis.
Synergetic oxidation of ethylbenzene to acetophenone catalyzed by manganese(II) complexes bearing pendant iodophenyl groups
Yang, Yiwen,Zhong, Wei,Nie, Binmei,Chen, Jiangmin,Wei, Zhenhong,Liu, Xiaoming
, p. 136 - 142 (2017/11/10)
Five tetradentate ligands, L1–5, bearing the moiety of bis(pyridin-2-ylmethyl)amine (1) and their complexes with Mn(II) were prepared. All the compounds and metal complexes were appropriately characterized. The five manganese(II) complexes (3a–e) are of the formula, [Mn(II)LxCl2] (x = 1-5), as suggested by the crystal structure of complexes 3b and 3c. All the ligands except for L3 possess two iodobenzene groups via an ether linkage (except for L1) with various lengths. By using oxone as an oxidant, the catalytic activity of these complexes on the oxidation of ethylbenzene to acetophenone in acetonitrile/water at room temperature was studied. Our results showed that the pendant iodophenyl groups play a synergetic role with the metal center in the catalysis, and complex 3b possesses the most appropriate length of the linkage between the iodobenzene group and the metal center. EPR and FTIR data suggest that the metal center of the active species should be Mn(IV) after the oxidation of oxone under the reaction conditions. A catalytic mechanism was also proposed based on the experimental observations.
Synthesis of large ring macrocycles (12-18) by recyclable palladiumComplexed dendrimers on silica gel catalyzed intramolecular cyclocarbonylation reactions
Lu, Shui-Ming,Alper, Howard
, p. 5908 - 5916 (2008/02/13)
Intramolecular cyclocarbonylation reactions with palladium-complexed dendrimers on silica gel as catalysts are very effective for the synthesis of twelveto eighteen-membered ring macrocycles. This process can tolerate a wide variety of functional groups,
