Use of Bifunctional Ureas to Increase the Rate of Proline-Catalyzed α-Aminoxylations
作者:Sarah L. Poe、Andrew R. Bogdan、Brian P. Mason、Jeremy L. Steinbacher、Suzanne M. Opalka、D. Tyler McQuade
DOI:10.1021/jo802461w
日期:2009.2.20
The rate of the proline-catalyzed alpha-ammoxylation of aldehydes is significantly increased in the presence of a bifunctional urea. Structure-activity relationship data indicate that both an amine and a urea are crucial for rate enhancement. The evidence presented herein suggests that this rate enhancement originates from the hydrogen bonding interaction between the bifunctional urea and an oxazolidinone intermediate to increase the rate of enamine formation. Proline derivatives that are incapable of forming oxazolidinones exhibit no rate enhancement in the presence of the bifunctional urea. The rate enhancement is general for a variety of aldehydes, and the faster reactions do not reduce yields or selectivities.
Enantioselective Total Synthesis of (+)-Hagen's Gland Lactones
作者:Santosh J. Gharpure、Laxmi Narayan Nanda、Manoj Kumar Shukla
DOI:10.1002/ejoc.201101328
日期:2011.11
Enantioselectivesynthesis of Hagen's gland lactone is described. The enantiomerically enriched diol was prepared by organocatalytic α-oxidation of the aldehyde. The other key reactions involved a highly diastereoselective intramolecular cyclopropanation of vinylogous carbonates to furnish donor–acceptor-substituted cyclopropanes and their ring opening and iodolactonization followed by reduction.
Prolinate Salts as Catalysts for α-Aminoxylation of Aldehyde and Associated Mechanistic Insights
作者:Yujiro Hayashi、Nariyoshi Umekubo、Taku Hirama
DOI:10.1021/acs.orglett.7b01433
日期:2017.8.18
Potassium and tetrabutylammonium prolinate salts are efficient catalysts in the α-aminoxylation reaction of aldehydes and nitrosobenzene, to afford synthetically useful chiral α-aminoxylated aldehydes in nearly enantiomerically pure form. This is the first reaction in which prolinate is more reactive and enantioselective than proline. Because of its higher reactivity, the catalyst loading can be reduced