ISOTHIAZOLES .3. CYCLOADDITIONS OF DIAZOALKANES TO 3-DIALKYLAMINOISOTHIAZOLE 1,1-DIOXIDES - COMPETITIVE RING-CLEAVAGE IN 3A,4-DIHYDRO-6AH-PYRAZOLO[3,4-D]ISOTHIAZOLE 1.1-DIOXIDES - FORMATION OF 2-THIA-3-AZABICYCLO[3.1.0]HEX-3-ENE 2,2-DIOXIDES AND/OR PYRAZOLES

3-Dialkylaminoisothiazole 1,1-dioxides 1 readily undergo cycloadditions with diazoalkanes 2. The reaction is characterized by high site- and regio-selectivity. Cycloadducts 3 and 4 were found to undergo straightforward thermolysis reactions at elevated temperature through two different paths characterized respectively by loss of nitrogen or sulfur dioxide and diethylcyanamide. The different transformations affording pyrazoles 6 and derivatives of the new heterocycle 2-thia-3-azabicyclo[3.1.0]hex-3-ene 2,2-dioxide 5 are discussed.