Reactions of 1-aryl- and 2,3-diaryl- 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7- tetra- hydroindazoles with N-ethyl- and N-phenyl-substituted maleimides

[3+2] Cyclocondensation reactions of a series of 1,3- and 2,3-disubstituted 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles with N-ethyl- and N-phenyl-substituted maleimides have been used to obtain the corresponding 6,6-dimethyl-4,4',6'-trioxo-4,5,6,7-3',3'a,4',5',6',6'a-decahydrospiro- [indazole-5,3'-pyrrolo[3,4-c]pyrazoles]. On boiling these compounds in toluene nitrogen is split off and they are converted into 6',6'-dimethyl-2,4,4'-trioxo- 4',5',6',7'-tetrahydro-1'H-spiro[3-azabicyclo-(3.1.0)hexane-6,5'-indazoles].