This invention relates to a process for preparing an oligonucleotide 5′-triphosphate. The process comprises the steps of: (a) synthesizing an oligonucleotide having a 5′ hydroxyl moiety; (b) reacting the 5′ hydroxyl moiety with a reagent of formula I: to convert the 5′ hydroxyl moiety to a 5′-H-phosphonate, wherein R1 and R2 are each independently selected from the group consisting of haloalkyl, aryl, substituted aryl, heteroaryl, substituted heteroaryl, cycloalkyl, substituted cycloalkyl, heterocycle, and substituted heterocycle, acyl, phosphoryl, substituted alkyl acyl, substituted heteroalkyl acyl, substituted aryl acyl or substituted heteroaryl acyl, substituted alkyl phosphoryl, substituted heteroalkyl acyl, substituted aryl phosphoryl, and substituted heteroaryl phosphoryl; (c) activating the H-phosphonate of step (b) by reacting the H-phosphonate with a silylating agent, a halogenated oxidizing agent, a nitrogen-containing heteroaryl, or a combination thereof, to form an activated H-phosphonate; and (d) treating the oligonucleotide having an activated H-phosphonate from step (c) with a poly(alkylammonium)pyrophosphate.