Expedient Synthesis of Dihydroisoquinolines by Cascade Annulation of Nitrovinylbenzoquinone

Abstract

1,2‐Dihydroisoquinolines are important building blocks of many natural products and phamarceuticals. In continuation of our ongoing research on transformations of quinone derivatives, herein we present a catalyst‐free cascade annulation of β‐enamino esters with 2‐(2‐nitrovinyl)‐1,4‐benzoquinone, which allowed for the synthesis of various novel 1,2‐dihydroisoquinoline derivatives in moderate to good yields (60 %–99 %). This method is applicable to a wide variety of β‐enamino esters. The structure of one product was determined by an x‐ray crystal analysis. Moreover, a plausible mechanism was proposed.

Annulations involving p-benzoquinones: stereoselective synthesis of fused, spiro and bridged molecules

“…The formal [3+3] annulation of 2-(2-nitrovinyl)-1,4-benzoquinones 39 and β-enamino esters 40 was realized by Zhang's group to produce novel 1,2-dihydroisoquinoline derivatives 41 under catalyst-free conditions. 72 The enamine moiety of β-enamino esters served as 1,3-dipolar species. β-Enamino esters containing alkyl and aryl functionalities responded in this reaction well (yields 60–99%).…”