Alkyne, homo-/cross-couplings

Another recent development in the field of palladium-catalyzed reactions with alkynes is a novel multicomponent approach devised by the Lee group. Starting from a-bromovinyl arenes and propargyl bromides, the assembly ofeight-membered car-bocycles can be realized via a cross-coupling/[4+4] cycloaddition reaction. The authors also presented the combination of a cross-coupling and homo [4+2], hetero [4+2], hetero [4+4] or [4+4+1] annulation leading to various cyclic products [147]. 

Homo- and cross-couplings of alkyne promoted by metallic catalysts are versatile reactions for carbon-carbon bond formation and have been utilized to synthesize functional hyperbranched polymers. 

Some of the most useful synthetic transformations of terminal alkynes involve intermolecular and intramolecular homo- and cross-coupling reactions between their. sp-carbon centers, leading to butadiyne or polyyne derivatives. The two most widely used and practical systems are (i) oxidative homocoupling reactions, i.e. Glaser and Eglington reactions and (ii) heterocoupling reactions, i.e. Chodkiewicz-Cadiot coupling of a terminal alkyne with a haloalkyne. 

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