2,2,6,6-Tetramethylpiperidine-1,4-diol is related to 4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (H956500), which is a free radical scavenger. 2,2,6,6-Tetramethylpiperidine-1,4-diol has also been shown to be an in vitro and in vivo radioprotector. It is used as a reagent in stereoselective preparation of tetrasubstituted triarylated olefins via Pd-catalyzed sequential oxidative Heck arylation of alkenes with arylboronic acids using nitroxides as oxidants.