Ir‐Catalyzed Enantioconvergent Synthesis of Diversely Protected Allenylic Amines Employing Ammonia Surrogates

Abstract

The first iridium catalyzed, enantioconvergent amination of allenylic carbonates is reported. This process utilizes various commercially available carbamates and sulfonamides to generate allenylic amines including commonly employed protected groups (Boc, Fmoc, Cbz, Ts, Ns) in 62–82 % yield and 87–98 % ee. The products generated through this scalable procedure serve as effective linchpins for the rapid, enantiospecific synthesis of a wide range of complex structures.

Construction of Vicinal Quaternary Centers via Iridium-Catalyzed Asymmetric Allenylic Alkylation of Racemic Tertiary Alcohols

“…Jacobsen has reported that chiral hydrogen-bond donor–acceptor catalysts facilitate asymmetric allylation of tertiary propargylic carbocations in 2018 . Our group entered this area with the substitutions of racemic secondary allenylic alcohols by amines and organozinc reagents using a chiral Ir–bis­(phosphoramidite,olefin) complex. − More recently, we demonstrated that η 2 -coordination of the allene motifs in racemic tertiary allenylic alcohols to a chiral Ir­(I) catalyst led to ionization and generation of an intermediate, metal-bound tertiary carbocation that underwent stereoselective reduction …”

Ammonia surrogates in the synthesis of primary amines

“…71 Carreira and co-workers reported the Ir-catalyzed synthesis of allenylic amines. 72 The reaction successfully worked with virtually all available PG-NH 2 reagents, and in all cases, the enantiomeric excess was good to excellent. Furthermore, the reaction scope was broad, and the authors demonstrated the potential of the intermediates by performing various transformations, including deprotection, to obtain the primary amine (Fig.…”

Recent advances in iridium-catalyzed enantioselective allylic substitution using phosphoramidite-alkene ligands

“…Amination of ra c-allenylic carbonate was also reported by Carreira (Scheme 33). 84 Allenylic carbonate 75 reacted with ammonia equivalents such as BocNH 2 , FmocNH 2 , CbzNH 2 , TsNH 2 , and NsNH 2 to give allenylic amines 76 in high enantioselectivities. Transformation of the products to useful chiral heterocyclic building blocks was possible by the combined reactivity of the allenes and amine moieties.…”