Studies of phthalazine-5,8-quinone, A ring contraction, and some novel and potentially useful fluorescent phthalimides

Abstract

Phthalazine-5,8-quinone 3 has been obtained and some derivatives prepared. Treatment of 5,8-dimethoxy 14 and 5-hydroxy-8-methoxy-2,3-dihydrophthalazin-1,4-dione 16 with ceric ammonium nitrate produces an efficient ring contraction reaction to yield the highly fluorescent 3,6-dimethoxyphthalimide 18 and N-amino-3-hydroxy-6-methoxyphthalimide 19, respectively. The phthalimide 18 has been converted into potentially useful fluorescent labels for use in amine and peptide chemistry and investigations of peptidase activity, while 19 has yielded a potentially useful thiol probe 29.