Michail Christodoulou

Divergent reactivity of terminal alkynes under transition metals catalysis

The use of the intramolecular transition-metals catalyzed reactions on arenes tethered to an unsaturated system represents a useful method to obtain heterocyclic systems, with the advantage of using the non-activated substrates, thus avoiding the requirement for a halogen substituent. Moreover, the activation of a multiple bond offers the possibility of obtaining different regioisomeric products.

On poly-functionalized substrates it is possible to observe divergent reactivity depending on the different transition-metal catalysts used.

Starting from substituted arenes bearing a carbamate group and a C-C triple bond, the use of palladium catalysis resulted in an intramolecular hydroamination reaction providing benzofused heterocycle systems, the ring-size of which depends on the carbon atom of the triple bond involved in the nucleophilic attack. The use of a different transition-metal catalyst, such as platinum salts, gave a different reactivity and through an hydroarylation process the formation of substituted benzopyrane derivatives was observed. In this case, the reaction involves the terminal carbon of the triple bond through a selective 6-endo-dig cyclization. In the case of aryl substrates bearing double unsaturated pendants, tandem or domino processes were reported.