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Highly enantioselective Michael addition of pyrazolin‐5‐ones to nitroolefins catalyzed by cinchona alkaloid derived 4‐methylbenzoylthioureas
Author(s) -
Yang Mengchen,
Zhang Min,
Wang Zhenyu,
Tang Li,
Chen Wenbin,
Ban Shurong,
Li Qingshan
Publication year - 2018
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23003
Subject(s) - cinchona , chemistry , enantioselective synthesis , cinchona alkaloids , michael reaction , alkaloid , catalysis , organic chemistry , organocatalysis , stereochemistry , combinatorial chemistry
Abstract Cinchona alkaloid‐derived 4‐methyl/nitro benzoylthioureas were synthesized, which smoothly catalyzed the asymmetric Michael addition of pyrazolin‐5‐ones to nitroolefins. The results showed that electronic effects of substituents in the benzene ring of benzoylthioureas have subtle influences on their catalytic abilities and electron donating methyl group is favored than electron withdrawing nitro group. Preliminary Hartree‐Fock calculations revealed that in the catalytic cycle, hydrogen bond energies of the complex formed with 4‐methylbenzoylthioureas are about 0.19 to 1.56 kcal/mol higher than with the corresponding 4‐nitrobenzoylthioureas. 4‐Methylbenzoylthioureas were identified as the most effective catalysts that promoted asymmetric Michael addition of pyrazolin‐5‐ones to nitroolefins to give the S ‐ or R ‐products with high enantioselectivities.