Pd-Catalyzed Heteroannulation Route to Substituted 5-Azaindoles

Significance

Reported is a general and efficient procedure for the synthesis of 2,3-diaryl-substituted 5-azaindoles. The reaction was extensively optimized in terms of base, Pd source and additive. Interestingly, the use of potassium carbonate failed to give product, whereas sodium carbonate was the base of choice. The latter is usually inefficient for the analogous indole syntheses. NMs, NTs and unsubstituted aminopyridines were reported to be completely unreactive substrates. Study of substrate scope was quite limited in terms of both acetylenic and pyridine counterparts. Three unsymmetrical acetylenes were tested and led to 1:1 mixtures of both regioisomeric products.