The synthesis of cyclic, branched, and bicyclic oligonucleotides was performed by copper-catalyzed azide−alkyne cycloaddition assisted by microwaves in solution and on solid support. For that purpose, new phosphoramidite building blocks and new solid supports were designed to introduce alkyne and bromo functions into the same oligonucleotide by solid-phasesynthesis on a DNA synthesizer. The bromine