Extending the scope of the aza-Fischer synthesis of 4- and 6-azaindoles
Fischer indole cyclization has recently been described as an efficient approach to the synthesis of azaindoles bearing electron-donating groups. We now show that this cascade reaction can be very efficient for the formation of a wider range of 4- and 6-azaindoles by using microwave irradiation. Fischer indole cyclization starting from aminopyridines is a very efficient cascade sequence leading to 4- and 6-azaindoles. The scope of the substituents on the pyridine ring was extended to include halogens and to weakly electron-donating substituents by using microwave irradiation. Copyright