Sonochemical‑synthesis of imidazo[1,2‑a]pyridines via Groebke–Blackburn–Bienaymé reaction catalyzed by TSOH

The development of environmentally friendly and efficient synthetic processes that minimize the use and generation of hazardous substances is one of the main goals of green chemistry. One powerful strategy to achieve this goal involves the use of versatile a convergent, synthetic tools with high atom economy and operational simplicity, such as Isocyanide-Based Multicomponent Reactions (IMCRs).

IMCRs have attracted significant interest in both academic and industry fields due to their efficiency synthesized target molecules in one-pot process. Reducing the number of steps, minimizing waste generated during the purification of intermediates. On the other hand, ultrasound irradiation (USI) in chemistry change reactivity, improve yields and selectivity, reduce reaction times, energy consumption and waste production, use of water as solvent instead of organic solvents, activation of catalysts, etc. The synthesis of Imidazo[1,2-α]pyridines (IMPs), via IMCR has several advantages over multistep and or conventional synthetic strategies. The Groebke-Blackburn-Bienaymé reaction (GBB) is the method of choice for synthesizing IMPs. The synthesis of IMPs with fluorescent properties; as emerging as a research field focus in the development of novel greener strategies. To date the GBB synthesis of IMPs using cheap catalysts such as p-toluenesulfonic acid (TsOH) assisted by USI is practically unreported. In the present work, we describe the TsOH-catalyzed GBB reaction by USI for the synthesis of a library of IMP analogs.