Organocatalytic Regio- and Enantioselective Allylic Alkylation of Indolin-2-imines with MBH Carbonates toward 3-Allylindoles

Organocatalytic Stereodivergent Dearomatization and N-Acylation of 2-Amino-3-subsituted Indoles

Organocatalytic chemo- and enantioselective reactions of 2-amino-3-subsituted indoles have been achieved for the first time. Via asymmetric allylic alkylation of Morita-Baylis-Hillman carbonates, organocatalytic enantioselective dearomatization of 2-amino-3-subsituted indoles afforded an array of enantioenriched 3,3-disubstituted indolin-2-imines bearing a quaternary carbon stereocenter in 34-79% yields with 61-91% ee. With Boc2O as reaction partner, the organocatalytic enantioselective N-acylation of 2-amino-3-subsituted indoles was established to furnish C-N axially chiral products in 22-98% yields with 73-92% ee.

Eco-friendly K-10 Clay-Mediated [3 + 3] Spiroannulation of Morita-Baylis-Hillman Adduct of Isatin with Anthracene: Synthesis of Green Fluorophore Compounds

An easy and simple spiroannulation of the Morita-Baylis-Hillman adduct of isatin derivatives with anthracene was achieved in moderate-to-good yields (37-75%). The spiroderivatives synthesized in this work exhibited green fluorescence properties. The reaction occurred in metal-free eco-friendly K-10 clay-mediated conditions. The final products have multiple structural features such as 3-spirooxindole, fluorophoric anthracene, phenanthracene, phenalene, and perylene cores.

Chiral Phosphine Catalyzed Allylic Alkylation of Benzylidene Succinimides with Morita-Baylis-Hillman Carbonates

Owing to their unique chemical properties, α-alkylidene succinimides generally act as versatile synthons in organic synthesis. Compared with well-established annulations, nucleophilic alkylations of α-alkylidene succinimides are very limited. Accordingly, an organocatalytic allylic alkylation of α-benzylidene succinimides with Morita-Baylis-Hillman (MBH) carbonates was established. In the presence of a chiral phosphine catalyst, α-benzylidene succinimides reacted smoothly with MBH carbonates under mild conditions to furnish a series of optical active succinimides in high yields and enantioselectivities. Different from the reported results, the organocatalytic enantioselective construction of pyrrolidine-2,5-dione frameworks bearing contiguous chiral tertiary carbon centers was achieved via this synthetic strategy. Scaling up the reaction indicated that it is a practical strategy for the organocatalytic enantioselective alkylation of α-alkylidene succinimides. A possible reaction mechanism was also proposed.