SingaCycle(TM)-A1-Catalyzed Successive Suzuki-Miyaura and Buchwald Couplings for the Synthesis of Various New Pyridine Analogues

A new diversified, rapid and easily accessible, N-heterocyclic carbene based palladacycle, SingaCycle(TM)-A1 exploited for the cross coupling reactions on heterocyclic amines. This Pd-NHC catalyst is considered to be merely stable and takes part in dynamic conversion of various organic functionalities. Herein, we report its first time use in the synthesis of C- and N- diaryl/ heteroaryl pyridine analogues from the less active parent 5-bromopyridine-2-amine via sequential Suzuki-Miyaura and Buchwald couplings. Surprisingly, both the coupling reactions proceed very smoothly and efficiently under mild reaction conditions in green solvent system (ethanol:water) at a faster rate. Moreover 1 mol% of the catalyst is sufficient to proceed the reactions and obtain comparatively better results.