A new strategy for alkane oxidation with O2 using N-hydroxyphthalimide (NHPI) as a radical catalyst

A practical catalytic method to convert alkanes into the corresponding oxygen-containing compounds with O-2 under mild conditions using N-hydroxyphthalimide (NHPI) in the presence or absence of a transition metal was developed. Thus, cyclohexane was successfully converted into adipic acid in good conversion and selectivity by a combined catalytic system consisting of NHPI and Mn(acac)(2). Lower alkane such as isobutane was converted into t-butyl alcohol (83%) under 10 atm of air by NHPI-Co(OAc)(2) system. Alkylbenzene such as toluene was oxidized to benzoic acid in high yield (81%) under normal temperature and pressure of dioxygen in the presence of a catalytic amount of NHPI and Co(OAc)(2). ESR measurements showed that phthalimide-N-oxyl generated from NHPI under dioxygen atmosphere is a key species in this oxidation and functions as a radical catalyst.