Origin of asymmetric induction in bicyclic guanidine-catalyzed thio-Michael reaction: a bifunctional mode of Lewis acid-Brønsted acid activation.
In addition to a bifunctional Brønsted acid activation mode, an unconventional bifunctional mode of Lewis and Brønsted acid activations was revealed in a DFT study of bicyclic guanidine-catalyzed thio-Michael reaction. This activation mode provides an alternate reaction pathway for the C-S bond forming step and influences the final stereochemical outcome. The calculated turnover frequencies of the R- and S-products, based on the energetic span model, are in good accord with the observed high stereoselectivity toward the S-product.
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
Bokun
B
Cho
Choon-Hong
CH
Tan
Ming Wah
MW
Wong
D000143:Acids / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000737:chemistry*; D002384:Catalysis; D019791:Guanidine / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis* / Q000737:chemistry
D000143:Acids; D001643:Bridged Bicyclo Compounds; D013438:Sulfhydryl Compounds; D019791:Guanidine