[Synthesis of 2-aminoisoindolin-1-ones with or without 6-substituents]

The synthesis of 5- and 6-chloro, 5- and 6-methoxy, 5,6-dimethoxy, 6-amino and 6-nitro-2-aminoisoindolin-1-ones (III b...h), starting from the substituted phthalides (Vb...g), are reported. Chloro and methoxy-derivatives (III b...f) have been prepared by reduction of phthalazin-1-(2H)-ones (Ib...f) with zinc and acids under controlled conditions to afford the 3,4-dihydrocompounds (II), that have been rearranged to (III b...f) with hydrazine hydrate or hydrochloric acid (Scheme 3). The synthesis of 6-nitro and 6-amino-derivatives (III g,h) have been respectively accomplished by hydrolysis and hydrogenolysis of 6-nitro-2-benzylidenaminoisoindolin-1-one (IV g), prepared by chlorination and ring closure with sodium carbonate of benzylidenhydrazide of 5-nitro-2-hydroxymethyl-benzoic acid (Scheme 2).