This work is aimed to describe the development of a method for the selective gem-dimerization of terminal acetylenes. In the case of the model reaction of phenylacetylene (1a), the reaction conditions were optimized through the choice of catalyst, solvent, temperature and reaction time. Various aromatic and aliphatic acetylenes were used as starting substrates. Data on the temperature sensitivity of enynes can be traced in the literature, prompting us to analyze stability of the selected products. We have developed a method for isolating and purifying the resulting products, which were characterized by NMR techniques. With the gem-enynes prepared in this way, we tested their usefulness for the Heck reaction. Using the stable enyne 2f* and 4-iodotoluene (4a), we were able to prepare the desired trisubstituted product in the presence of a PEPPSI Pd-tzNHC complex.
|
