| Abstract
| - Heating dipolarophiles with 4-alkyl-3-hydroxy-2H-pyrazolo[4,3-c]isoquinolinium hydroxide inner salts results in [3 + 2] cycloaddition across positions 3a and 5 ofthe aromatic system to give the [3 + 2] cycloadducts in goodyield. When the 4-alkyl substituent is a 2-acetate ester andthe methylene group can be deprotonated, a second mode of[3 + 2] cycloaddition becomes available for the resultinganion (across the side chain methine group and position 5of the aromatic system) and occurs under basic conditions,allowing either of two modes of [3 + 2] cycloaddition to beselected by appropriate choice of reaction conditions.
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