Phosphine‐Catalyzed [3+2] Cycloaddition and Vinylation of Indole‐Derived α,α‐Dicyanoolefins with γ‐Substituted Allenoates

Abstract

A phosphine-catalyzed [3 + 2] cycloaddition of γsubstituted allenoates with α,α-dicyanoolefins has been established, affording indole-incorporated highly functionalized cyclopentenes. In addition, the vinylation of indole-derived α,α-dicyanoolefins has also been realized under the same reaction conditions by switching to indole-derived α,αdicyanoolefins without protective group at N-1 position.with Morita-Baylis-Hillman carbonates affording bicyclic imides with good yields and enantioselectivities. [13] Inspired by recent achievements on allenoates-based cycloadditions, [8][9][10][11][12] we have also developed a strightforward and atomeconomic catalystfree [2 + 2 + 2] annulation of dihydroisoquinolines and allenoates accessing a diverse range of novel dimeric tetrahydroisoquinoline derivatives. [14] On the basis of our previous work and studies of [3 + 2] cycloadditions of allenoates with α,αdicyanoolefins from other groups, we hypothesized that the indole moiety could be easily incorporated into cyclopentene by using indole derived α,α-dicyanoolefins and allenoates as starting material in the presence of phosphine. Herein, we report our development of synthesis of indole-incorporated highly functionalized cyclopentenes through phosphine catalyzed [3 + 2] cycloaddition of γ-substituted allenoates with α,αdicyanoolefins as well as the N-functionalization of indolederived α,α-dicyanoolefins (Scheme 1). 2 3 4 5 6 7 8