40150-57-0Relevant academic research and scientific papers
Evaluating aryl esters as bench-stable C(1)-ammonium enolate precursors in catalytic, enantioselective Michael addition-lactonisations
Young, Claire M.,Taylor, James E.,Smith, Andrew D.
, p. 4747 - 4752 (2019)
An evaluation of a range of aryl, alkyl and vinyl esters as prospective C(1)-ammonium enolate precursors in enantioselective Michael addition-lactonisation processes with (E)-trifluoromethylenones using isothiourea catalysis is reported. Electron deficient aryl esters are required for reactivity, with 2,4,6-trichlorophenyl esters providing optimal product yields. Catalyst screening showed that tetramisole was the most effective isothiourea catalyst, giving the desired dihydropyranone product in excellent yield and stereoselectivity (up to 90 : 10 dr and 98 : 2 er). The scope and limitations of this process have been evaluated, with a range of diester products being generated after ring-opening with MeOH to give stereodefined dihydropyranones with excellent stereocontrol (10 examples, typically ～90 : 10 dr and >95 : 5 er).
Rh-Catalyzed Chemoselective [4 + 1] Cycloaddition Reaction toward Diverse 4-Methyleneprolines
Cai, Wangshui,Wu, Junxian,Zhang, Haowei,Jalani, Hitesh B.,Li, Guigen,Lu, Hongjian
, p. 10877 - 10891 (2019/09/12)
An efficient synthesis of 4-methyleneproline derivatives has been developed through an Rh-catalyzed [4 + 1] cycloaddition strategy using 3-methyleneazetidines and diazo compounds. The reaction proceeds under very mild conditions with a high degree of chemoselectivity, and competing experiments revealed that it is the preferred reaction, dominant over the C-H insertion, O-H insertion, and olefin cyclopropanation reactions which are commonly observed in Rh carbene chemistry. This method can incorporate the proline ester scaffold in pharmaceuticals and natural products. The intramolecular version of the reaction effectively provides proline-fused small to medium-sized tricyclic heterocycles. Gram-scale reactions, one-time addition of diazo compounds, and a minimum catalyst loading of 0.1 mol %, proceeded smoothly, implying their practicality.
