In order to overcome this issue, we turned to mechanochemistry. Protocols in which reagents are subjected to intimate mixing and grinding using ball mills have become increasingly popular in recent years, affording reaction products that cannot be obtained using traditional solution-based methods. Additionally, the use of mechanochemistry obviates the need for solvent and can give short reaction times, good scalability, and even opportunities for in situ reaction monitoring. Mechanochemical protocols have been applied to phosphorylate natural and synthetic polymers. Ball-milling reactions were conducted in a shaker mill using steel jars and ball bearings, using commercial hydride sources and thoroughly dehydrated phosphates. All watersoluble phosphorus-containing products were quantified by 31 P NMR analysis of an aqueous extract of the solid reaction mixture, and percentage yields and recovery rates of extraction are based on total P content in the phosphate input. The reaction of Na3P3O9 with three equivalents of NaH (H:P = 1:1) led to the formation of the desired product in short reaction times (within 60 min) with almost complete consumption of the starting material (Table ). Other major products included pyrophosphate and orthophosphate. Control experiments confirmed that these phosphate materials did not appear simply by ball-milling Na3P3O9 alone under otherwise identical conditions, although Na3P3O9 was partially converted to a variety of cyclic and linear phosphates (see SI). d Parenthesized value includes phosphite in free and phosphorylated forms when phosphorylated phosphites were observed.