MoOPH, also known as oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide), is a reagent used in organic synthesis. It contains a molybdenum(VI) center with multiple oxygen ligands, coordinated with pyridine and HMPA ligands. 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. Other reagents used for alpha-hydroxylation via enol or enolate structures include Davis oxaziridine, oxygen, and various peroxyacids (see Rubottom oxidation). 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.
3D model (JSmol)
|Molar mass||g·mol−1 434.25|
|Melting point||103–105 °C (217–221 °F; 376–378 K) (dec)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
In the case of sulfones, alpha-hydroxylation leads directly to the ketone or aldehyde.
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.
MoOPH has also been shown to oxidize N-trimethylsilyl amides directly to the hydroxamic acid.
- Edwin Vedejs (April 15, 2001). Oxodiperoxymolybdenum(pyridine)(hexamethylphosphoric triamide). E-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.ro022. ISBN 978-0471936237.
- "HYDROXYLATION OF ENOLATES WITH OXODIPEROXYMOLYBDENUM(PYRIDINE)(HEXAMETHYLPHOSPHORIC TRIAMIDE), MoO5·Py·HMPA(MoOPH): 3-HYDROXY-1,7,7-TRIMETHYLBICYCLO[2.2.1]HEPTAN-2-ONE". Organic Syntheses. 64: 127. 1986. doi:10.15227/orgsyn.064.0127.
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