365456-23-1Relevant articles and documents
Visible light photocatalytic asymmetric synthesis of pyrrolo[1,2-: A] indoles via intermolecular [3+2] cycloaddition
Casado-Sánchez, Antonio,Domingo-Legarda, Pablo,Cabrera, Silvia,Alemán, José
supporting information, p. 11303 - 11306 (2019/09/30)
The intermolecular diastereoselective and enantioselective synthesis of pyrrolo[1,2-a]indoles is developed through a [3+2] cycloaddition between silyl-indole derivatives and α,β-unsaturated N-acyl oxazolidinones by merging photocatalysis and Lewis acid catalysis.
The role of achiral pyrazolidinone templates in enantioselective Diels-Alder reactions: Scope, limitations, and conformational insights
Sibi, Mukund P.,Stanley, Levi M.,Nie, Xiaoping,Venkatraman, Lakshmanan,Liu, Mei,Jasperse, Craig P.
, p. 395 - 405 (2007/10/03)
We have evaluated the role of achiral pyrazolidinone templates in conjunction with chiral Lewis acids in room temperature, enantioselective Diels-Alder cycloadditions. The role of the fluxional N(1) substituent was examined, with the bulky 1-naphthylmethyl group providing enantioselectivities up to 99% ee, while templates with smaller fluxional groups gave lower selectivities. High selectivities were also observed in reactions of 7d with chiral Lewis acids derived from relatively small chiral ligands, suggesting the pyrazolidinone templates are capable of relaying stereochemical information from the ligand to the reaction center. Lewis acids capable of adapting square planar geometries, such as Cu(OTf)2, Cu(ClO4)2, and Pd(ClO4)2, were found to be particularly effective at providing high selectivities. Additionally, substitution at the C-5 position of the pyrazolidinone templates has been shown to be critical for optimal selectivity. Reactions of the optimal pyrazolidinone appended with a number of common dienophiles and various dienes demonstrate the utility of this achiral template. Furthermore, catalytic loadings could be lowered to 2.5 mol % with essentially no loss in selectivity, π-π interactions were evaluated as a means to explain the unusually high selectivity observed at room temperature. Finally, non-C2-symmetric ligands were employed as a test to determine if chiral relay was operative.
Chiral Lewis Acid Catalysis in Nitrile Oxide Cycloadditions
Sibi, Mukund P.,Itoh, Kennosuke,Jasperse, Craig P.
, p. 5366 - 5367 (2007/10/03)
We describe examples of highly regio- and enantioselective nitrile oxide cycloadditions to unsaturated alkenes using substoichiometric amounts of a chiral Lewis acid. Pyrazolidinones proved to be effective achiral templates in the cycloadditions providing
Exo Selective Enantioselective Nitrone Cycloadditions
Sibi, Mukund P.,Ma, Zhihua,Jasperse, Craig P.
, p. 718 - 719 (2007/10/03)
We have developed a novel method for accessing exo adducts with high enantioselectivity in nitrone cycloadditions to enoates. Pyrazolidinones proved to be effective achiral templates in the cycloadditions, providing exo adducts typically in >15:1 selectivity and 90-98% ee. The use of Lewis acids that form square planar complexes, such as copper triflate, was important for obtaining high exo selectivity. Copyright
Enantioselective conjugate addition of hydroxylamines to pyrazolidinone acrylamides
Sibi, Mukund P.,Liu, Mei
, p. 4181 - 4184 (2007/10/03)
(Matrix Presented) Chiral relay templates provide amplification of selectivity in conjugate addition reactions. Reversal of stereochemistry of the product isoxazolidinones has also been demonstrated by a simple change of the Lewis acid.
