Indazole heterocycles are important molecules in medicinal chemistry and methods to functionalise them are widely sought after. Direct metalation of indazoles at their 3 position is often problematic as this can quite easily lead to ring opening and formation of an aminonitrile product. Knochel overcame this problem by using a zinc reagent to form a bis-indazoylzinc compound.
The bis-indazoylzinc compound reacts with a wide range of electrophiles and can also undergo arylation in a Negishi cross-coupling reaction. In general, such reactions are not possible using normal metalation reagents. Future work will concentrate on the synthesis of biologically active molecules using this methodology.