3 years ago

L-Pyroglutamic Sulphonamide as Hydrogen-Bonding Organocatalyst: Enantioselective Diels–Alder Cyclization to Construct Carbazolespirooxindoles

L-Pyroglutamic Sulphonamide as Hydrogen-Bonding Organocatalyst: Enantioselective Diels–Alder Cyclization to Construct Carbazolespirooxindoles
Hua Yang, Ji-Wei Ren, Jun-An Xiao, Jing Wang, Hao-Yue Xiang, Jun Li, Xiao-Qing Chen
Hydrogen-bonding organocatalysts L-pyroglutamic sulphonamides were readily synthesized for the first time by fully exploiting the potentials of L-pyroglutamic acid. The newly designed catalyst was successfully applied in catalyzing asymmetric Diels–Alder cyclization of methyleneindolinones with 2-vinyl-1H-indoles to efficiently assemble carbazolespirooxindoles in excellent stereoselectivity (up to 99% ee, >20:1 dr) and yields (up to 99%). Mechanistic studies disclosed that the well-designed hydrogen-bonding modes between L-pyroglutamic sulphonamide and substrates were crucial for stereocontrol in the cyclization.

Publisher URL: http://dx.doi.org/10.1021/acs.joc.7b00733

DOI: 10.1021/acs.joc.7b00733

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