Construction of Polycyclic γ-Lactams and Related Heterocycles via Electron Catalysis

Abstract

Cascade radical cyclization of 1,6-enynes for the construction of biologically important polycyclic γ-lactams and related heterocycles is reported. In these radical cascade processes, three new C–C bonds are formed and transition metals are not required to run these sequences. The mild reaction conditions, broad substrate scope, and the importance of the heterocyclic products render the approach valuable.

Enantioselective One‐pot Synthesis of 3‐Azabicyclo[3.1.0]hexanes via Allylic Substitution and Oxidative Cyclization

“…To realize the one‐pot synthesis of bicyclic pyrrolidine derivatives 1 , the preparation of the key intermediate, 1,6‐enyne 4 a became our initial focus. Intermediate 4 a was readily obtained through the allylic substitution of propargyl amine 2 a with Morita‐Baylis‐Hillman adduct 3 a mediated by a Lewis base (LB) catalyst (Table ) .…”

Radical Cyclization of 1,n‐Enynes and 1,n‐Dienes for the Synthesis of 2‐Pyrrolidone

“…In 2016, Studer and co‐workers developed a versatile method for the synthesis of 2‐pyrrolidinone derivatives via a cascade radical cyclization of 1,6‐enynes and anilines using lithium iodide (LiI) as the initiator (Scheme 1). [15] This reaction formed three new C−C bonds in one‐step without the need for transition metals. While determining the optimal conditions for the synthetic transformation, they found that the absence of initiators or the addition of transition metal salts, such as CuI and FeI 2 , resulted in unsatisfactory yields.…”

Intramolecular cyclization of N-allyl propiolamides: a facile synthetic route to highly substituted γ-lactams (a review)

“…It consists of the following key steps: (i) initial formation of diazonium salt A via reaction of aniline 50 with isoamyl nitrite; (ii) interaction of A with LiI to afford the aryl radical B; (iii) chemoselective radical addition of B to the activated alkene of N-allyl propiolamides 49 to give tertiary alkyl radical C; (iv) 5-exo cyclization of radical C leading to vinyl radical D; (v) intramolecular cyclization of radical D onto the arene produces the cyclohexadienyl radical E; (vi) deprotonation of E with alcoholate derived from isoamyl nitrite to afford arene radical anion F; and (vii) oxidation by liberating an electron gives polycyclic g-lactam product 51. 48…”