The chemical synthesis of oligonucleotides (ONs) is central to modern molecular biology, diagnostics and nucleic acid therapeutics. While demand for high-quality ONs is increasing, the conventional synthetic method has long-standing efficiency challenges. Widely adopted P(III)-phosphoramidite-based ON synthesis requires an oxidation step after every nucleotide coupling cycle and uses moisture-sensitive building blocks, adding complexity to the workflow and slowing the process.