Alkyne coupling, copper catalysis

Recently, Pal et al. found that (.S )-prolinol could facilitate the coupling reaction of terminal alkynes with 3-iodoflavone under palladium-copper catalysis in aqueous DMF to give 3-alkynyl substituted flavones of potential biological interest (Eq. 4.17). The coupling of iodobenzene with terminal alkynes at room temperature in water without any cosolvent was completed within 30 minutes, affording the desired product in good yield.36... 

A number of syntheses of di- and polyacetylenes has been reported. 1-Iodo-l-alkynes couple with terminal acetylenes under palladium-copper catalysis to give 1,3-diynes thus y-iodopropargyl alcohol and phenylacetylene afford compound 30. Oxidative coupling of 1 -alkynes to yield symmetrical 1,3-diynes is brought about by air and copper(I) chloride in the presence of N, A -tetramethylethylenediamine (equation Trialkylsilyl sub-... 

Oxidative addition of alkenyl halides, triflates, and other esters to zerovalent palladium compounds has been long known as a viable route to palladium(ii)-alkenyl complexes. Stereospecific coupling reactions involving mono- and (E)- or (Z)-dihalo-alkenes with palladium-copper catalysis under modified Sonogashira conditions are quite versatile and useful. These proceed through oxidative addition of the alkenyl halide via palladium(ii) alkenyl complexes, followed by coupling with a nucleophile (usually an alkynylcopper reagent obtained in situ with co-catalytic copper(i) from terminal alkynes in the presence of, in this case, a base like piperidine instead of diethylamine). ... 

In the same year, Chi et al. developed an enantioselective oxidative coupling of tertiary amines with ahphatic aldehydes by combination of copper catalysis and aminocatalysis (Scheme 2.6) [31]. Both A -Aryl tetrohydroisoquinolines and simple A-Aryl tertiary amines can undergo this enantioselective alkylation reaction. Soon afterwards, organocatalytic enantioselective CDC reaction of ethers with aliphatic aldehydes [32] and Cu-catalyzed asymmetric CDC reaction of iV-carbamoyl tetrahydroisoquinohnes with terminal alkynes [33] were reported. 

Somewhat related to cross-coupling reactions, the carbomagnesiation of terminal alkenes was shown to proceed efficiently in the presence of [(IMes)AgCl] and 1,2-dibromoethane, which was used as an oxidant. The hydroboration of terminal alkynes was also achieved using [(NHC)Ag] catalysts, and with higher regioselectivity compared to copper catalysis conditions. 

The coupling of terminal alkynes with aryl or vinyl halides under palladium catalysis is known as the Sonogashira reaction. This catalytic process requires the use of a palladium(0) complex, is performed in the presence of base, and generally uses copper iodide as a co-catalyst. One partner, the aryl or vinyl halide, is the same as in the Stille and Suzuki couplings but the other has hydrogen instead of tin or boron as the metal to be exchanged for palladium. 

Palladium(0)-catalysed coupling of an orf/to-halophenolic ether (thioether) with a terminal alkyne (or with an alkynylboronic ester ) and ring closure promoted with an electrophile - iodine has been most often used - is an excellent method to make both benzothiophenes °° ° and benzofurans. ortfto-AIkynyl-phenols can be comparably closed with palladium catalysis in the presence of copper(II) halides to give the corresponding 3-halo-benzofurans, ° and ortfto-alkynyl pyridin-2- and -3-yl acetates likewise ring close with iodine, generating furopyridines. ... 

Joint catalysis by tin(IV) chloride and zinc chloride induces coupling of the acetal 114 with the alkyne 115 to give the propargyl ether 116. Allyl halides condense with terminal alkynes in DMF in the presence of copper(I) iodide, potassium carbonate and tetrabutylammonium chloride under phase-transfer conditions to afford eneynes, e.g. equation 19. Palladium-catalysed coupling reactions of 1-bromoallenes with terminal acetylenes have been reported for the first time thus acetylene and the allenes 117 (R R = Me or Et) in triethylamine in the presence of tetrakis(triphenylphosphine)palladium and... 

A three-component cross-coupling of A-tosylhydrazones, terminal alkynes and allyl halides yields allyl allenes, using copper(I) catalysis a copper carbene migratory insertion is proposed. 27... 

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