Rapid access to unsymmetrical tolanes and alkynones by sequentially palladium-catalyzed one-pot processes

Abstract

Alkynones as well as unsymmetrically substituted tolanes (diarylalkynes) can be rapidly generated in a one-pot fashion via sequential palladium catalysis. Terminal alkynes, formed in situ by protecting-group free palladium-catalyzed coupling of aryl iodides with ethynyl magnesium bromide, are subsequently transformed by Sonogashira coupling with aryl halides or aroyl chlorides to furnish unsymmetrically substituted alkynes in good to excellent yields.

Heterocycles by Consecutive Multicomponent Syntheses via Catalytically Generated Alkynoyl Intermediates

“…While the previous approaches are directly founded on the coupling of monosubstituted alkynes a more direct pathway represents the coupling of aryl halides and ethynylmagnesium bromide and then acid chlorides as presented in Kumada-Sonogashira sequence V [34]. Thereby, the unsymmetrically substituted alkynones are easily accessible with a broadened substrate scope.…”

Solid State and Aggregation Induced Emissive Chromophores by Multi‐component Syntheses

“…Just very recently we disclosed a coupling-couplingaddition-cyclocondensation four-component synthesis of pyrazoles (Scheme 4), [28] taking advantage of the sequentially Pdcatalyzed Negishi-Kumada-Sonogashira reaction from aryl iodides, ethynyl magnesium bromide, and aroyl chlorides, [29] generating the crucial ynones, followed by concluding cyclocondensation.…”

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

“…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 . It was further demonstrated in these protocols that, unlike the traditional methods, multiple protection and de‐protection steps could be avoided with the direct usage of calcium carbide.…”

“…The use of ethynylmagnesium bromide has also been reported recently as a commercial acetylene surrogate in the Kumada-Negishi-type coupling reactions. [13] [14] It was further demonstrated in these protocols that, unlike the traditional methods, multiple protection and deprotection steps could be avoided with the direct usage of calcium carbide. This greatly reduced the number of synthetic steps, resulting in a more efficient and greener organic synthesis.…”