Pentafluoronitrobenzene a novel scaffold for the solid-phase synthesis of 2,4,6-substituted-3,5-difluoronitrobenzene libraries

The use of pentafluoronitrobenzene as a scaffold for solid-phase synthesis of 2,4,6-substituted-3,5-difluoronitrobenzenes is described. The scaffold is amenable to the synthesis of structurally diverse combinatorial libraries. Primary and secondary amines can be introduced to the scaffold via three successive nucleophilic aromatic substitutions under increasingly forcing conditions. The synthesis of a 36-member validation library is described as follows. Displacement of the para-fluorine was achieved in solution with a set of primary and secondary amines. Following purification, the para-substituted scaffold was attached to an amino acid-loaded hydroxymethylbenzyloxypolystyrene resin via a second substitution of one of the ortho-fluorines. The final reactive ortho-fluorine was then displaced by a second set of amines. After cleavage from the solid support the library was furnished in good overall purity, as determined by LCMS.