5-Diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles in [3+2] cycloaddition reactions

The [3+2] cycloaddition reactions of a series of 1,3-substituted 5-diazo-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazoles with maleic anhydride and dimethyl acetylenedicarboxylate gave 1′,3′-substituted 3-spiro[4,6-dioxo-4,6,3a,6a-tetrahydro-3H-furo[3,4-c]pyrazole] -5′-[6′,6′-dimethyl-4′-oxo-4′,5′,6′, 7′-tetrahydroindazoles] and 1′,3′-substituted 3-spiro[4,5-di(methoxycarbonyl)-3H-pyrazole]-5′-[6′, 6′-dimethyl-4′-oxo-4′,5′,6′,7′- tetrahydroindazoles] respectively. When heated the former eliminate nitrogen and are transformed into 1′,3′-substituted 6-spiro[2,4-dioxo-3- oxabicyclo[3.1.0]hexane]-5′-[6′,6′-dimethyl-4′-oxo- 4′,5′,6′,7′-tetrahydroindazoles]. © 2007 Springer Science+Business Media, Inc.