The Unprecedented Cobalt-Catalysed Oxidative Glaser Coupling under Reductive Conditions

Abstract

The cobalt-catalysed Glaser-type coupling of terminal alkynes was achieved utilising nitrobenzene as a stoichiometric oxidising agent under reductive conditions. The proposed electron transfer from zinc powder to a nitrobenzene coordinated to the cobalt centre initiates the coupling of the coordinated alkynes. Other aryl-, alkenyl-, alkyl-, and silylacetylenes besides phenylacetylene could also be coupled to generate the 1,3-diynes in moderate to very good yields.

Fast, Ligand‐ and Solvent‐Free Synthesis of 1,4‐Substituted Buta‐1,3‐diynes by Cu‐Catalyzed Homocoupling of Terminal Alkynes in a Ball Mill

“…Similar reactions in a microwave preferentially gave rise to the cross‐coupling product 2 k 9. 32, 37c In comparison with the Co‐catalyzed procedure (CoBr 2 , Zn, nitrobenzene, P(O i Pr) 3 ),37c the absence of a defined coordination sphere allows the formation of the statistical mixture of products only. These results indicate that either greater than stoichiometric amounts of copper initiate the cross‐coupling or both modes of activation pass through different activation pathways.…”

Synthesis of N-[5-alkoxy-2(5H)-furanonyl] amino acid propargyl esters

“…The target compounds possessing multiple bioactive moieties will afford a basis for the activity test of potential drug molecules. Terminal alkynes are widely used in click reaction [23][24][25][26][27], Glaser coupling reaction [38][39][40][41], Sonogashira reaction [42][43][44][45], dimerization [46], even different kinds of addition reactions to C-O and C-N bonds [47][48][49][50]. Thus, the obtained propargyl esters are also important intermediates for more 2(5H)-furanone derivatives with polyfunctional groups.…”

Copper‐catalyzed homo‐ and cross‐coupling reactions of terminal alkynes in ethyl lactate

“…On the basis of the originally employed palladium/copper and other bicatalyst systems for oxidative couplings of terminal alkynes, numerous efforts have been made to explore easy, low‐cost and efficient new procedures to run these reactions. The employment of a single alternative transition metal catalyst such as palladium, copper, nickel and cobalt in the reactions has been found to be an improved protocol in terms of atom economics. In addition, discovering new oxidants constitutes another frontier of the modern Glaser reaction.…”