Nitrosylation Of Imidazo[1,2-a]pyridines In Metal Free System

This thesis systematically studied selective nitrosylation of imidazo[1,2-a]-pyridine in the absence of metal catalyst. Under the optimized conditions, a broad rang of imidazo[1,2-a]pyridine derivatives proceeded smoothly to afford the corresponding nitrosylated products using tert-butyl nitrite(TBN) as the NO resource Also, the plausible reaction mechanism has been proposed. The main results were as follows:1. Synthesis of the imidazo[1,2-a]pyridine derivatives.Imidazo[1,2-a]pyridine derivatives were synthesized via employing of2-aminopyridine and acetophenones as starting materials, copper acetate and zinc iodide as catalyst, and 1,10-phenanthroline as ligand using ortho-dichloro- benzene as the solvent.2. Nitrosylation of imidazo[1,2-a]pyridines in metal free system.2-phenylimidazo[1,2-a]pyridine and TBN was used as the model subustrates to optimize the nitrosylation reaction conditions. In a 10 m L vial were combined the requisite 2-phenylimidazo[1,2-a]pyridine derivatives(1.0 eq), TBN(2.0 eq) in DCE(1 m L). The reaction vial was sealed and heated to 90 °C for 30 min. After cooling to room temperature, the product was isolated to afford the desired product in 99% yield.Afterwards, various nitrosylation of imidazo[1,2-a]pyridine compounds were carried out under the same conditions, and the yield varied from 82% to 99%. The current protocol was operationally simple with a widely substrate tolerance and high efficiency(Scheme 1). A radical or electrophilic addition pathway was proposed in the mechanism studies.