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

Abstract

The bio-based chemical ethyl lactate (EL) has been discovered to be an excellent medium for the Glaser-type homo-and crosscoupling reactions of terminal alkynes. Good to excellent yields of conjugate diynes have been obtained under ligand-free and mild heating conditions in the presence of CuI and molecular oxygen.

Catalyst Free Synthesis of Bis(Indolyl)Methanes and 3,3‐Bis(Indolyl)oxindoles in Aqueous Ethyl Lactate

“…In recent years, ethyl lactate (EL) has been introduced as a possible environmentally safe solvent in organic synthesis due its intrinsic characteristics such as low price, less toxicity, good biodegradability, high stability as well as solubility to both water and organic compounds . Literature survey shows that EL has been used in some organic transformations such as coupling reactions, cycloaddtion reaction, multi‐component reactions, light induced synthesis, and stereoselective synthesis . Therefore, it is worth emphasizing that the development of an efficient and rapid synthetic route for the preparation of biologically and drug active molecules by combining the synthetic efficiency of ultrasonic‐assisted organic reactions and advantages of EL as reaction medium under catalyst free conditions is highly desirable and deserves significant attention.…”

Magnetic copper ferrite catalyzed homo‐ and cross‐coupling reaction of terminal alkynes under ambient atmosphere

“…In order to show the merits and limitations of the present work in comparison with other reported catalytic systems in the literatures, we summarized some of results for the synthesis of 1,2‐diphenylethyne via homo‐coupling of phenylacetylene in Table . As can be seen in this table, the present catalytic system is an equally or more efficient to those previously reported in this reaction, since the use of precious metal catalyst, [12, 15,] high reaction temperature, or the employment of unrecyclable catalysts can be avoided.…”

“…The oxidative homocoupling reaction of terminal alkynes (Glaser‐Hay reaction) was one of the classical protocols for the synthesis of symmetrical conjugated 1,3‐diynes . Various catalytic systems have been developed for this reaction using O 2 or air as the oxidant, including the use of Cu, Pd, Ag, Au and bimetallic Pd/Cu, Pd/Ag and Fe/Cu . Some heterogeneous catalysts, like silica/chitosan core–shell hybrid‐microsphere‐supported CuI, copper nanoparticles supported on silica coated maghemite, copper immobilized on functionalized silica, polymer‐supported copper, Cu(I) immobilized on functionalized SBA‐15, immobilized copper in MCM‐41, mesoporous silica‐supported copper, copper immobilized on nano‐silica triazine dendrimer, copper‐impregnated magnetite have also been successfully employed to promote this reaction.…”

Recent advances in copper-catalyzed C–H bond amidation

“…The C(sp)–H bond in terminal alkynes is more acidic than equivalent alkane and alkene C–H bonds, and the alkynylation reactions by making use of direct transformations on the alkyne C–H bonds such as Sonograshira, Glaser couplings were extensively studied and utilized [ 69 – 72 ]. Under the inspiration of these well-known reaction models, the amidation reaction based on the activation of alkyne C–H bonds were also implemented.…”