Acetylide Ion (C₂²⁻) as a Synthon To Link Electrophiles and Nucleophiles: A Simple Method for Enaminone Synthesis

Abstract

Friendly competition: A three‐component reaction system composed of calcium carbide, an aryl aldehyde, and an amine gave enaminones or propargylamines (see picture) in a predictable manner through competitive pathways. The system enables the cost‐efficient synthesis of a variety of enaminones from readily accessible small molecules and demonstrates the versatility of the acetylide ion, which can be used to bridge electrophiles and nucleophiles.

Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology

“…The three‐component reaction between acetylene and aldehydes (AAA coupling) or haloalkanes (AHA coupling) in the presence of a secondary amine gave rise to a broad variety of aminopropynes (Scheme ) . In the case of coupling reactions with benzaldehydes and bulky secondary amines, the reaction predominantly proceeded through enaminone formation . Propargylamine was only observed among the reaction products in a few cases of a typical AAA reaction.…”

Using Calcium Carbide as an Acetylene Source for Cascade Synthesis of Pyrrolo[2,3‐b]quinoxalines via Copper‐Free Sonogashira Coupling Reaction

“…This strategy was successfully applied for the synthesis of enaminones and propargylic amines through the three‐component coupling reaction of CaC 2 , aryl aldehydes, and amines as well as a convenient method for the preparation of propargyl alcohols by reacting CaC 2 with aldehydes and ketones in the presence of 50 mol‐% of cesium carbonate in aqueous DMSO at 60 °C . Novel protocols have already been developed for the synthesis of various functional molecules such as propargylamines, diarylethynes, triazoles, and enaminones from calcium carbide. The use of ethynylmagnesium bromide has also been reported recently as a commercial acetylene surrogate in the Kumada–Negishi ‐type coupling reactions .…”

Organocatalytic activation of isocyanides: N-heterocyclic carbene-catalyzed enaminone synthesis from ketones

“…The proposed methodology provides an unprecedented synthetic route to enaminones via C–C bond formation. Although various synthetic strategies have been developed for the preparation of enaminones, 9 the limited scope and relatively low availability of reagents are significant drawbacks to these procedures. Herein, we report a novel organocatalytic enaminone synthesis from isocyanides and ketones with excellent functional group tolerance.…”