Acetylides, cross-coupling with terminal

The Pd-catalyzed coupling of o-haloanilines and terminal alkynes tends to produce either the 2-(l-alkynyl)aniline or mixtures of the alkynylanilines and the corresponding indoles [17,18]. However, iV-benzyl-2-iodoaniline has recently been cross-coupled with terminal alkynes to afford the corresponding ben-zylindoles using a Pd zeolite catalyst (Eq. 14) [39]. One can also employ stoichiometric amounts of copper acetylides to effect this transformation [22-24]. 

Z-selective cross-coupling of terminal alkynes with isocyanides to exclusively yield (Z)-l-aza-l,3-enyne products has been achieved for the first time using a constrained geometry catalysts [Y(C5Me4Si(Me2)NR)(Alk) (THF)X] (Aik = R, dimethylaminobenzyl R = lBu, Ph, 2,4,6-Me3C6H2. The intermediate was shown to be the acetylide-bridged dimer [Y(C5Me4Si (Me2)NR)(p-C=CPh)]2.41 [24]... 

Cross-coupling reactions with Zn acetylenides are the most convenient and selective routes to terminal acetylenes. In this reaction Zn is markedy superior to other metals, including Sn (24).116 The higher reactivity of Zn acetylides allowed assembly of hexaethynylbenezenes in two steps, with the last three groups introduced at the second stage by the Negishi reaction (25).117... 

Wang et al. have discovered that ultrafme Ni powder in the presence of Cul, PPh3, and KOH promotes coupling of terminal alkynes with aryl and alkenyl iodides in high yields [65], Recent developments have shown, moreover, that the use of co-catalysts (Cu, Zn, Al, etc.) to facilitate the formation of the acetylides is not always required and that cross-coupling reactions of acetylenes and aryl halides can be performed successfully with Pd-based catalysts alone, even with difficult substrates [48, 66]... 

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