AcOLeDMAP and BnOLeDMAP: Conformationally Restricted Nucleophilic Catalysts for Enantioselective Rearrangement of Indolyl Acetates and Carbonates
摘要:
The rate of indotyl O- to C-acetyl or carboxyl rearrangement is accelerated by the electron-withdrawing N-diphenylacetyl group (DPA) using the conformationally restricted chiral catalysts AcOLeDMAP (12b) and BnOLeDMAP (13b). Highly enantioselective conversion to quaternary C-acetylated and C-carboxylated oxindoles is observed, even for substrates containing branched substituents. The rearrangement of the carboxylate substrates 19 occurs with complementary enantiofacial selectivity using catalyst 13b compared to the acetyl migrations of 16 catalyzed by 12b. Access to N-unsubstituted oxindoles is demonstrated by DPA cleavage with Et2NH.
Enantioselective Photochemical Rearrangements of Spirooxindole Epoxides Catalyzed by a Chiral Bifunctional Xanthone
作者:Mark M. Maturi、Alexander Pöthig、Thorsten Bach
DOI:10.1071/ch15280
日期:——
The title compounds were shown to undergo an enantioselective photochemical rearrangement to 3-acylindolin-2-ones (16–33 % ee). A xanthone, which is tethered via an anellated oxazole to a chiral 1,5,7-trimethyl-3-azabicyclo[3.3.1]nonan-2-one scaffold, efficiently catalyzed this reaction at λ 366 nm, presumably by triplet sensitization. The observed enantioselectivity can be explained by hydrogen bonding