Mechanism of Oxidation of Phenylacetylenes with Peroxymonophosphoric Acid. Oxirene as Intermediate Interconvertible to Ketocarbene

Article abstract of DOI:10.1021/ja00365a039

Peroxymonophosphoric acid (H3PO5) is shown to be an effective oxidant for acetylenes.Phenylacetylenes, (R = Ph, H, and Me), afford diketones (PhCOCOR), benzoic acid, and rearranged acids (PhRCHCO2H).The relative migratory aptitude is in the order of H >> Me > Ph, which is in agreement with the order of H >> Ph ca.Me for the Wolf rearrangement of α-diazo ketones.However, the oxidation of acetylenes in MeOH-MeCN does not yield α-methoxy ketones, while the decomposition of α-diazo ketones affords significant amounts of the O-H inserted products.GLC or GC-MS analysis shows that the acetylene oxidation affords no detectable amounts of products derived from ketocarbene.Oxirene intermediate, formed by the electrophilic oxidation of acetylenes, may be oxidized to diketones or may rearrange without involvement of ketocarbenes.Hence, ketocarbene-ketocarbene interconversions should proceed via an intermediate (e.g., 16) other than oxirene-like ones.