Synthesis of 6-ethynylpurine derivatives

A series of 6-(arylethynyl)purine derivatives are synthesized from the corresponding 6-halopurines via sequential and ‘one-pot’ Sonogashira-coupling reactions. The nature of the acetylene source was found to have a profound influence on the efficiency of the process. In sequential couplings, 2-methyl-but-3-yn-2-ol was found to be an efficient acetylene surrogate, while in the ‘one-pot’ reaction, 1-ethynyl-cyclohexanol gave superior results.