Carbene-Catalyzed Construction of Carbazoles from Enals and 2-Methyl-3-oxoacetate Indoles

Abstract

Direct and rapid construction of carbazoles has been successfully developed via carbene-catalyzed oxidative formal [4 + 2] annulation of enals with 2-methyl-3-oxoacetate indoles. This metal-free reaction features a broad substrate scope, features good functional-group tolerance, proceeds under mild conditions, and can be easily scaled up.

Access to Highly Functionalized Indanes from Arynes and α,γ-Diketo Esters

“…Representative methods include transition metal-catalyzed direct difunctionalization of aryl halides and transition metal-free direct difunctionalization of arynes. , Owing to arynes possessing several advantages, such as ease of availability, high reactivity, transition metal-free, and mild reaction conditions, the use of arynes for the direct difunctionalization of arenes has received considerable attention. As part of our ongoing interest in the synthesis of carbo- and heterocycles, we envisaged that a new strategy for the synthesis of highly functionalized indanes might be achieved from the reaction of arynes and α,γ-diketo esters under mild conditions. Actually, there are two possible reaction pathways when α,γ-diketo esters were employed in aryne chemistry.…”

Synthesis of polysubstituted arenes through organocatalytic benzannulation

“…In 2018, Fu and co-workers extended the b-position activation strategy to the reaction of 2-methyl-3-oxoacetate indoles 134 with enals 49 to access multi-substituted carbazoles 135 (Scheme 38). 65 The best reaction efficiency was achieved by using Cat. 9 as the catalyst in THF.…”

A Benzannulation Strategy for Rapid Access to Quinazoline-2,4-diones via Oxidative N-Heterocyclic Carbene Catalysis

“…In this context, Lupton and co-workers reported an elegant NHC-catalyzed [4+2] annulation of α,β-unsaturated acyl fluorides and silyl dienol ethers for the synthesis of 1,3-cyclohexadienes in which the reaction proceeds via the generation of α,β-unsaturated acylazoliums. , Moreover, a benzannulation approach for the synthesis of multisubstituted arenes from dienals and 1,3-diketones was uncovered by Chi and co-workers . In 2016, the groups of Wang and Ye independently reported the NHC-catalyzed [4+2] annulation of enals with α-cyano-β-methylenones for the efficient construction of benzonitriles . Inspired by these works, and in light of our interest in NHC catalysis proceeding via α,β-unsaturated acylazoliums, , herein we demonstrate the benzannulation approach to quinazoline-2,4-diones.…”