ABSTRACT
An organocatalytic enantio- and diastereoselective synthesis of hexahydropyrrolo[2,3-b]indole-containing tetrasubstituted α-amino allenoates, exhibiting both axial and central chirality, has been accomplished via cascade dearomatization-cyclization reaction. The γ-addition to ß,γ-alkynyl-α-imino esters provides a library of densely substituted highly enantioenriched allenes in high yields and excellent stereoselectivities. In addition, the scope of this methodology has been extended to tryptophol as well. A scale-up reaction and synthetic transformations of the products were performed to demonstrate the practical usefulness of this approach.
ABSTRACT
Herein we report the first use of p-quinone diimide for the aminative dearomatization of 2,3-disubstituted indoles to furnish C3 aza-quaternary chiral indolenines. This approach, which proceeds via an electrophilic 1,6-addition of p-quinone diimide, allows the synthesis of an array of optically active aza-quaternary indolenines with high yields and excellent enantioselectivities. A one-pot approach of the same has also been established to further improve the synthetic accessibility of this protocol.
ABSTRACT
A highly efficient chiral phosphoric acid-catalyzed enantioselective Friedel-Crafts addition of indolizine to cyclic N-sulfonyl imine has been established. The newly developed protocol, which probably proceeds via a monoactivation reaction pathway, allows the access of enantioenriched sulfonamide functionalized indolizines with excellent yields (up to 99%) and enantioselectivities (up to 99%). Moreover, the synthetic utility of this protocol has been explored with some chemical transformations.
