1140966-35-3Relevant academic research and scientific papers
Chiral phosphoric acid-catalyzed enantioselective three-component Povarov reaction using enecarbamates as dienophiles: Highly diastereo- and enantioselective synthesis of substituted 4-aminotetrahydroquinolines
Dagousset, Guillaume,Zhu, Jieping,Masson, Geraldine
supporting information; experimental part, p. 14804 - 14813 (2011/11/04)
A chiral phosphoric acid (5)-catalyzed three-component Povarov reaction of aldehydes 2, anilines 3, and enecarbamates 4 afforded cis-4-amino-2-aryl(alkyl)- 1,2,3,4-tetrahydroquinolines 1 in high yields with excellent diastereoselectivities (>95%) and almost complete enantioselectivities (up to >99% ee). The reaction was applicable to a wide range of anilines bearing electron-donating (OMe) and electron-withdrawing groups (e.g., Cl, CF 3, NO2) and allowed, for the first time, aliphatic aldehydes to be employed in the enantioselective Povarov reaction. With β-substituted acyclic enecarbamates, 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines with three contiguous stereogenic centers were produced in excellent diastereo- and enantioselectivities (87 to >99% ee). A detailed study of the active catalytic species allowed us to reduce the catalyst loading from 10% to 0.5% with no deterioration of enantiomeric excess. In addition, mechanistic studies allowed us to conclude unequivocally that the Povarov reaction involving enecarbamate as dienophile proceeded via a stepwise mechanism. The key role of the free NH function of the enecarbamate in the success of this transformation was demonstrated. NMR experiments indicating the catalyst-substrate interaction as well as a linear correlation between catalyst and product ee's were also documented.
