Side by side: Direct cis addition of bromoalkynes 1 to various alkynes 2 was found to proceed in the presence of a PdII catalyst to give difunctionalized enyneproducts3. The method is facile for the synthesis of bromo alkenynes. Furthermore, an unusual mechanism is proposed.
Using inexpensive and safe EtOCS2K as a thiol surrogate and tetrabutylphosphonium bromide and H2O as a mixed solvent, the reaction provided a range of substituted thiophenes in moderate to good yields. In addition, 2,3,4,5-tetrasubstituted thiophenes were able to be prepared under mild reaction conditions by electrophilic heterocyclization with NH4I and EtOCS2K in good yields.