Nature Communications, Published online: 04 September 2026; doi:10.1038/s41467-026-77482-4 Herein the authors report the development of a class of phosphites featuring an N–O–P linkage, namely dialkyl phthalimidyl phosphites, which serve as efficient radical trapping reagents. These are applied in the cobalt-catalyzed Markovnikov hydrophosphonylations of unactivated alkenes.