A metal‐free sequential one‐pot three‐component protocol is described for the synthesis of C3‐functionalized imidazo[1,2‐a]pyridines. A successive construction of imidazo[1,2‐a]pyridine followed by iodine‐catalysed sulfenylation has been achieved in a one‐pot operation from readily available α‐bromomethyl ketones, 2‐aminopyridines and thiosulfonates. An immense array of 3‐sulfenylimidazo[1,2‐a]pyridines were obtained in good to high yields. Also, the method extended for the synthesis of C3‐halogenated imidazo[1,2‐a]pyridines using sodium halides in the presence of K2S2O8. Notably, the reaction between α‐bromomethyl ketones and 2‐aminopyridines in the presence of K2S2O8 to yield 3‐bromo‐2‐aryl‐imidazo[1,2‐a]pyridines, thus implies α‐bromomethyl ketones also served as brominating agent. Overall, the present sequential one‐pot protocol is straightforward, operationally simple, tolerates a broad range of functional groups, and is reliable for gram‐scale experiments.
A highly efficient and eco-friendly method has been developed for the synthesis of allyl sulfones using Morita-Baylis-Hillman (MBH) adducts and thiosulfonates under mild conditions. The Cs2CO3-promoted radical sulfonylation provided a series of allyl sulfones in good to high yields with high stereoselectivities. A wide variety of MBH bromides/acetates as well as thiosulfonates were tolerated and reliable in scale-up synthesis. A plausible mechanism was also proposed to rationalize the radical sulfonylation of the experimental outcome and control experiments.
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