Methods for the formation of sulfurized oligonucleotides are provided. The methods allow for the formation of phosphorothioate linkages in the oligonucleotides or derivatives, without the need for complex solvent mixtures and repeated washing or solvent changes. Oligonucleotides having from about 8, and up to about 50, nucleotides can be sulfurized according to the methods of the invention with higher yields than have been previously reported.