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Schlagwörter:
electrocyclic reactions; enantioselective organocatalysis; heterocycles; diastereoselectivity; 2-pyrazolines
Zusammenfassung:
The chiral phosphoric acid catalyzed asymmetric electrocyclization of α,β-unsaturated hydrazones has been studied. This reaction is one of the first catalytic asymmetric 6π-electrocyclizations reported, and enables the synthesis of 2-pyrazolines in high yields and enantiomeric ratios. The obtained products are not only interesting because of their pharmaceutical properties, but can be manipulated in highly diastereoselective fashion, as shown for alkylation reactions. Thus, the combination of catalytic asymmetric 6π-electrocyclization followed by diastereoselective alkylation can provide interesting synthetic building blocks in optically active form.
