A novel copper-catalyzed, hydrazine-free synthesis of N-1 unsubstituted 1H-indazoles using stable guanylhydrazone salts as substrates
A CuI-catalyzed, hydrazine-free transformation of 2-(2-bromoarylidene)guanylhydrazone hydrochlorides using Cs2CO3 as a base and DMEDA as a ligand at 120 °C for 5 h delivers substituted 1H-indazoles with yields up to 75%. The C,N double bond configuration of the substrates was determined by NMR experiments and quantum chemical calculations. The reaction mechanism was studied using quantum chemical calculations.