A site selective C-H arylation of free-(NH2) adenines with aryl chlorides: application to the synthesis of 6,8-disubstituted adenines.

An efficient site selective method for the direct arylation of free-(NH2) adenines 1 to provide a range of C-8 arylated adenines 3 in excellent yields is described. This process based on the use of Pd(OH)2/C as the catalyst and a stoichiometric amount of CuI under ligandless conditions is general. It allows the coupling to proceed with a variety of aryl halides, including for the first time cheaper and less reactive aryl chlorides. The extension of this process for the sequential preparation of non-symmetrical C8/N6-arylated adenines 4 is also reported.