Convenient synthesis of pyrrolo[3,4-g]indazole

The synthesis of a novel class of tetrahydropyrrolo[3,4-g]indazoles is reported, by annelation of the pyrazole ring on the isoindole moiety by means of 5-hydroxymethylene tetrahydroisoindole-4-ones key intermediates, with good regioselectivity. Dihydroderivatives were also obtained by oxidation with DDQ of the corresponding tetrahydropyrrolo[3,4-g]indazoles. The growth inhibitory effect was evaluated at the National Cancer Institute of Bethesda and some derivatives showed modest activity.