Cooperative Tertiary Amine/Chiral Iridium Complex Catalyzed Asymmetric [4+3] and [3+3] Annulation Reactions

Abstract

Asymmetric reactions merging organocatalysis and metal catalysis significantly broaden the scope of organic synthesis.N evertheless,t he accomplishment of stereoselective annulations combining two types of dipole species,i ndependently generated from the activations of organocatalysts and metal complexes,s till remains as ac hallenging task. Now, Morita-Baylis-Hillman carbonates from isatins and carbamate-functionalized allyl carbonates could be chemoselectively activated by achiral Lewis basic tertiary amines and chiral iridium complexes.T he zwitterionic allylic ylides and 1,4-pallyliridium dipoles formed in situ are assembled in ah ighly stereoselective [4+ +3] annulation pattern. Similar cooperative catalytic strategy could be applied for the reactions of Morita-Baylis-Hillman carbonates and vinyl aziridines,furnishing an asymmetric [3+ +3] annulation reaction also with excellent stereocontrol. Scheme 1. Lewis base and transition-metal activations trategies for MBH derivatives and cooperative catalysis.

Stereoselective synthesis and applications of spirocyclic oxindoles

“…Du and Chen have collaboratively reported an asymmetric Ir catalysed [4 + 3]-cycloaddition between an MBH carbonate and π-allyl precursor (Scheme 85). 428 The π-allyl precursor includes a vinylogous leaving group i.e. vinyl-OBoc, ethylene oxazinanones or vinyl aziridines (for six-membered rings) which forms an asymmetric Ir-allyl complex to react with the DABCO activated MBH carbonate.…”

Transition‐Metal‐Catalyzed Cycloaddition Reactions to Access Seven‐Membered Rings

“…In 2019, Cheng and co‐workers disclosed an efficient cooperative catalytic system combining Lewis basic tertiary amine catalysts and iridium complexes for assembling 4‐azepanes 124 with excellent regio‐, chemo‐ and stereoselectivity (Scheme 32). [40] The two highly reactive zwitterionic species, tertiary amine‐tethered allylic ylides 125 a and π‐allyliridium complex‐based 1,4‐dipoles 125 b , generated in situ through activation of isatin‐derived Morita‐Baylis–Hillman carbonates 122 and carbamate‐functionalized allylic carbonates 123 , were coupled together in a [4+3] pattern.…”

Transformations of Modified Morita‐Baylis‐Hillman Adducts from Isatins Catalyzed by Lewis Bases

“…Although the asymmetric [4+3] annulation reaction of MBH adducts catalyzed by a Lewis base has not been realized yet, the transformation under the cooperative catalysis of Lewis base and iridium complex with high stereoselectivities was first disclosed by us . Isatin derived MBH adducts 2 and carbamate‐functionalized allyl carbonates 111 could be chemoselectively activated by DABCO and chiral iridium complex C20 , respectively (Scheme ).…”