Divergent Synthesis of 6- or 7-Aza-Indazoles via Intramolecular Diels-Alder Cascade of Pyrazines
Nicolas Brach1, Lucas Popek1, Mathieu Truong1
1Université de Haute-Alsace, Université de Strasbourg, CNRS, LIMA, UMR 7042, 68000 Mulhouse, France.
Abstract:
Pyrazines are reactive 4π partners in intermolecular Diels-Alder cycloaddition with exceptionally activated dienophiles or in an intermolecular version at elevated temperatures. Herein, it is shown that an intramolecular cascade could occur even at room temperature, delivering a collection of 6- or 7-aza-indazoles. An interesting substituent effect of the cycloaddition precursor on the product distribution was uncovered, and in situ NMR studies were conducted to gain insights into this unexpected selectivity.
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