Facile Intramolecular O–14 C-7 Acetyl Transfer in Opiate 14-Acetate Esters

We have recently reported the facile conversion of naloxone la and naltrexone lb to the corresponding tri-acetates 2.¹In an effort to convert 2 to the 14-acetate ester 3, we attempted to selectively hydrolyze 2 in dilute NaOH solution at 23 °C. However, the product that was produced in high yield was not the expected ester 3, as it exhibited an IR carbonyl absorption (1631 cm^-1) corresponding to a β-diketone. Also, its NMR spectrum contained a methyl peak, consistent with a methyl ketone moiety, and a proton singlet at unusually low field (15.1 ppm).