Organic Letters · 2019 · 14 citations · 30 references
Natural SciencesChemistryMedicinal ChemistryDrug DiscoveryOrganic ChemistrySynthetic Medicinal ChemistryHeterocycle SynthesisHeterocyclic ChemistryHeterocyclic CompoundsMacrocycle SynthesisOrganic SynthesisRetrosynthetic Analysis1, 3-Dipolar CycloadditionAromatic Ring ContractionFused Heterocycle SynthesisPyrazole ChemistryPyrazole SynthesisRing-forming ReactionsSpiroheterocycle SynthesisSpiropyran Compounds
The formation of fused pyrazoles via intramolecular 1,3-dipolar cycloadditions of diazo intermediates with pendant alkynes is described. A subsequent thermal [1s, 5s] sigmatropic shift of these pyrazole systems resulted in a ring contraction, forming spirocyclic pyrazoles. The limitations of this rearrangement were explored by changing the substituents on the nonmigrating aromatic ring and by using substrates lacking an aromatic linkage to the propargyl group.
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