Enaminones as Synthons for a Directed C−H Functionalization: Rh^III‐Catalyzed Synthesis of Naphthalenes

Abstract

The use of enaminones as effective synthons for a directed C-H functionalization is reported. Proof-of-concept protocols have been developed for the Rh(III) -catalyzed synthesis of naphthalenes, based on the coupling of enaminones with either alkynes or α-diazo-β-ketoesters. Two inherently reactive functionalities (hydroxy and aldehyde groups) are integrated into the newly formed cyclic framework and a broad range of substituents are tolerated, rendering target products readily available for further elaboration.

Branched C=C and C−N Bond Cleavage on Enaminones toward the Synthesis of 3‐Acyl Quinolines

“…[13] However,t he most populart ransformation model in such known reactionsa re the condensations initiatedb yt he nucleophilic amino group and/ or the nucleophilic a-C(sp 2 )ÀHb ond. Although other transformations,s uch as C(sp 2 )ÀHc oupling reactions [14] and C=C bond-based cycloaddition reactions, [15] are also occasionally disclosed; the overall diversity of transformationm odelsi ne naminones is not yet abundant.R ecently,w eh ave identified that the C=Cd ouble bond in N,N-disubstituted enaminones is able to undergo af ull cleavage to offer C1 buildingb lock in the construction of pyridines. [16] Under the inspiration of this cleavage model of the C=Cd ouble bond, we envisioned that an alternative synthetic methodf or the synthesis of quinolines might also be designed by employing such bond cleavage as ak ey transformation (Scheme 1).…”

A comprehensive overview of directing groups applied in metal-catalysed C–H functionalisation chemistry

“…The group of Zhu used enaminone starting materials for the synthesis of naphthalene derivatives using either α-diazo-β-ketoesters ( Scheme 3F ) or alkynes ( Scheme 4H ) as coupling partners. 92 In case of α-diazo-β-ketoesters as coupling partners the initial step is an alkylation and good FG tolerance on the substrate was observed. Synthetically useful yields between 50–85% were reported and various alkyl residues including cyclopropyl can be in position R 2 .…”

“…The group of Zhu used enaminone starting materials for the synthesis of naphthalene derivatives using either alkynes ( Scheme 4H ) or α-diazo-β-ketoesters ( Scheme 3F ) as coupling partners. 92 In the case of alkynes, only 1,2-diphenylacetylene was used as reaction partner but good FG tolerance on the substrate was observed and synthetically useful yields between 50–85% were reported. According to the proposed mechanism, the initial step is a Rh-catalysed alkenylation.…”

Recent developments in chemical reactivity of N,N-dimethylenamino ketones as synthons for various heterocycles

“…Proof-of-concept protocols have been developed for the Rh III-catalyzed synthesis of naphthalenes, based on the coupling of enaminones 1 with either alkynes 153 or a-diazo-b-ketoesters 154. Two inherently reactive functionalities (hydroxy and aldehyde groups) are integrated into the newly formed cyclic framework and a broad range of substituents are tolerated, rendering target products 155, 156 readily available for further elaboration (Scheme 49) 71.…”