1373354-22-3Relevant academic research and scientific papers
Enantioselective 1,3-Dipolar Cycloaddition Reactions of C-Carboxy Ketonitrones and Enals with MacMillan Catalysts: Evidence of a Nonconcerted Mechanism
Ben Ayed, Kawther,Laurent, Mathieu Y.,Martel, Arnaud,Selim, Khalid B.,Abid, Souhir,Dujardin, Gilles
, p. 6763 - 6774 (2017/12/15)
Highly diastereo- and enantioselective 1,3-dipolar cycloadditions between functional ketonitrones and β-substituted enals are promoted by MacMillan imidazolidinium organocatalysts. A study of the reaction scope shows that high selectivities are conserved if the N-protecting group or the ester function is varied. However, the reaction is sensitive to steric interactions with the C substituent of the nitrone. In all cases, the reaction proceeds with high exo selectivity. In most cases, a third diastereomer, incompatible with a concerted mechanism, was also observed, albeit in minute amounts. DFT calculations suggest that the cycloaddition proceeds in a nonconcerted fashion by an initial oxa-Michael-type addition of the nitrone to the double bond followed by a cyclization. This mechanism explains the formation of the observed minor diastereomers. In addition, the diastereo- and enantioselectivities of the reaction were shown to be intermediately thermodynamically controlled, and the diastereomeric ratio is modulated by the kinetics of iminium hydrolysis.
The asymmetric organocatalytic 1,3-dipolar cycloaddition of alkyl pyruvate-derived nitrones and α,β-unsaturated aldehydes
Weselinski, Lukasz,Kalinowska, Eleonora,Jurczak, Janusz
, p. 264 - 270 (2012/06/15)
The catalytic asymmetric 1,3-dipolar cycloaddition of pyruvate-derived nitrones to α,β-unsaturated aldehydes was investigated in the presence of various chiral amines. Highly functionalized isoxazolidines containing a quaternary stereocenter were obtained in moderate yields with up to 92% ee. To the best of our knowledge, this is the first example of an enantioselective 1,3-dipolar cycloaddition of ketonitrones. The model product was subsequently transformed into a 2-pyrrolidinone derivative in two steps.
