MoOPH, also known as oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide), is a reagent used in organic synthesis.

[2] It is an electrophilic source of oxygen that reacts with enolates and related structures, and thus can be used for alpha-hydroxylation of carbonyl-containing compounds.

This reagent was first utilized by Edwin Vedejs as an efficient alpha-hydroxylating agent in 1974 and an effective preparative procedure was later published in 1978.

[4] MoOPH is synthesized from molybdenum trioxide by oxidation with hydrogen peroxide and addition of the HMPA and pyridine ligands:[4]

Due to MoOPH's steric bulk, preferential attack at the O–O bond occurs from the less hindered enolate face in the absence of stereoelectronic factors.

[9] Common byproducts of the alpha-hydroxylation tend to include overoxidation to the corresponding dicarbonyl or intermolecular aldol reaction of the starting material.

Procedures to prevent side reactions include the inverse addition of the enolate to MoOPH or careful control of the temperature (-78 to -20 °C).

Notable miscellaneous reactions include MoOPH’s ability to oxidize alkylboranes directly to the alcohol with net stereo-retention.