ChemInform Abstract: Type-Two Intramolecular Diels—Alder Reactions of Pyrazolo-o-quinodimethanes.
Abstract
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ChemInform Abstract
Thermolysis of the pyrazolosulfolenes (V) and (IX) leads to the corresponding o-quinodimethanes which spontaneously undergo type-two intramolecular Diels—Alder reaction to afford two- and three-atom bridged tricyclic pyrazoles which are otherwise difficult to prepare. Depending on the N-substitution position the temperature required for extrusion of SO2 and the regioselectivity of cyclization are influenced substantially.
