Palladium Alkyne Activation

Palladium-Copper Catalyzed Alkyne Activation as an Entry... 

Water as a green solvent has been successfully applied as a reaction medium for palladium-catalyzed carbonylative Sonogashira reactions (Scheme 5.11) [36]. Instead of using alkynes, activated acetylenes stibanes can also be applied as coupling partners in carbonylations. An example is the palladium-catalyzed carbonylative Sonogashira coupling of alkynyl stibanes with aryl iodides that was published by Kakusawa and Kurita in 2006 [37], The reaction was carried out under 1 bar of CO in DMAc using 5 mol% of Pd(OAc)2 and 20 mol% of PPhs. 

This palladium-catalyzed activation of alkynes toward nucleoplulic attack can also be adapted to oxygen nucleophiles, providing a route to benzofurans. Cacchi has demonstrated this in the Pd(OAc)2/CuISonogashira coupling/cydization of 2-halophenols with terminal alkynes (Scheme 6.8) [11]. This protocol has since... 

The formation of 2-alkenyl-substituted furans was observed in the palladium-catalyzed cross-coupling reactions between benzyl, aryl, or allyl bromides and conjugated ene-yne-ketones. This reaction involved oxidative addition, alkyne activation-cyclization, palladium carbene migratory insertion, P-hydride elimination, and catalyst regeneration (13JA13502). 

Pd-catalyzed reactions involving attack on palladium-alkene, palladium-alkyne, and related -TT-complexes by carbon nucleophiles are discussed in Sect. V.2.3. Complexation of alkenes and alkynes to palladium(II) compounds activates alkenes and alkynes to nucleophilic attack. In general, when Pd(II) salts are employed, stoichiometric quantities of Pd... 

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