Formal [4 + 2] cycloaddition of imines with alkoxyisocoumarins

Abstract

A new preparation of δ-lactams is reported. In the presence of a Lewis acid promoter, alkoxyisocoumarins engage a range of N-aryl and N-alkyl imines to form δ-lactams with a pendent carboalkoxy substituent. A sulfonamide-thiourea catalyst enables the synthesis of these products in moderate to good enantioselectivities.

Formal [3 + 2] cycloaddition of azomethine ylides generated in situ with unactivated cyclic imines: A facile approach to tricyclic imidazolines derivatives

“…The reaction can be performed in DCE and CHCl 3 in similar yields (entries 6-7). Other solvents, such as dioxane, Et 2 O, THF, and EtOAc also afforded product 4a in good yield (entries [8][9][10][11]. Whereas other solvents such as toluene, acetonitrile and methanol generated product 4a in moderate yields (entries 12-14).…”

“…[8] In 2018, Seidel and co-workers demonstrated [4 + 2] cycloaddition of both acyclic and cyclic imines with alkoxyisocoumarin to give δ-lactams in good yield. [9] While Thasana and co-workers developed a cascade cyclization between 1-substituted 3,4-dihydroisoquinolines and coumarin derivatives conveniently to afford the oxaazabicyclo[3.3.1]nonane framework. [10] In 2014, the first enantioselective inverse electron demand imino Diels-Alder reaction is described by Waldmann and co-workers between electron-poor chromone dienes and cyclic imine.…”

Enantioselective Synthesis of Oxindole‐Derived α‐Aryl‐β‐Amino Acid Derivatives and δ‐Lactams with Homophthalic Anhydrides

“…that, an amide‐thiourea could efficiently promote the enantioselective synthesis of lactames with high enantio‐ and diastereoselectivities from a range of simple imines . Recently, a new δ‐lactam preparation from alkoxyisocoumarins and aldimines has been developed, which enables the production of δ‐lactams with a pendent carboalkoxy substituent . However, in these reported examples, only aldimines could be employed as the electrophilic reaction partners.…”

“…[15] It was later found by Seidel et al that, an amide-thiourea could efficiently promote the enantioselective synthesis of lactames with high enantio-and diastereoselectivities from a range of simple imines. [17] However, in these reported examples, only aldimines could be employed as the electrophilic reaction partners. [17] However, in these reported examples, only aldimines could be employed as the electrophilic reaction partners.…”

“…[16] Recently, a new δ-lactam preparation from alkoxyisocoumarins and aldimines has been developed, which enables the production of δ-lactams with a pendent carboalkoxy substituent. [17] However, in these reported examples, only aldimines could be employed as the electrophilic reaction partners. Ketimines, on the other hand, are less explored.…”