Access to N-Hydroxyisoindolinones by Superacid-Induced Reactons of N-Hydroxyphthalimide and their Catalytic Activity
Alexander M Genaev1, George E Salnikov1, Konstantin Yu Koltunov2
1N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Pr. Akademika Lavrentieva 9, Novosibirsk 630090, Russia.
Abstract:
N-Hydroxyphthalimide (NHPI) is widely used as a versatile N-oxyl catalyst. Herein, we disclose that this compound rearranges smoothly in superacids such as CF3SO3H (triflic acid, TfOH) or FSO3H-SbF5 with ring expansion to give 1H-benzo[d][1,2]oxazine-1,4(3H)-dione. However, when condensed with di-p-tolyl ether in TfOH or underwent ionic hydrogenation with cyclohexane in the presence of aluminum chloride, NHPI retains its skeleton, yielding 2-hydroxy-2',7'-dimethylspiro[isoindoline-1,9'-xanthen]-3-one and N-hydroxyisoindolinone, respectively. The catalytic properties of the obtained compounds were tested in the oxidation of fluorene to fluorenone with sodium chlorite, where the superior catalytic activity of N-hydroxyisoindolinone was demonstrated compared to that of both the starting NHPI and the resulting spiro derivative.
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