Development and applications of highly selective palladium-catalyzed monocoupling reactions of (cyclo)alkenes and 1,3-alkadienes bearing two or three electrophilic sites and bis(enol triflates) with terminal alkynes

The motivation for writing this review with 558 references, which covers the literature up to the end of September 2012, is to fill a part of this gap by illustrating highly selective Pd/Cu-catalyzed and Cu-free Pd-catalyzed monoalkynylation reactions of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) with terminal alkynes. However, Pd-catalyzed selective monocoupling reactions of 1-alkynes with (hetero)aryl halides or pseudohalides with two identical or different electrophilic sites will not be covered. Moreover, Pd-catalyzed monocoupling reactions of 1-alkynes with non-conjugated diene systems bearing an electrophilic site on each carbon–carbon double bond have also been considered to be beyond the scope of this review. In addition to describing and commenting on the aforementioned monoalkynylation reactions of (cyclo)alkenes and 1,3-dienes with two or three identical or different electrophilic sites and bis(enol triflates), emphasis has been placed on the use of Pd-catalyzed monoalkynylations of (cyclo)alkenes and 1,3-butadienes bearing two or three identical or different electrophilic sites and bis(enol triflates) as key steps of the syntheses of core structures and models of enediyne antitumor antibiotics, pharmacologically active compounds, and bioactive naturally occurring compounds including insect sex pheromone components, and fungal and plant metabolites. Moreover, the review has been focused on the formation of disubstituted acetylenic derivatives by one-pot site-selective Pd-catalyzed consecutive alkynylation reactions of di(pseudo)halogenated olefinic substrates with two different terminal alkynes. Where appropriate, the reasons for the observed stereo-, site-, and/or chemoselectivities of the reported Sonogashira-type monoalkynylation reactions have been mentioned and discussed.