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Synthesis of new pyrrole derivatives from npropargylic β-enaminones

2020
Kanova, Nilay
Heterocyclic compounds are a momentous area of synthetic organic chemistry because of their existence in bioactive molecules. Pyrroles, which are one of the most important classes of heterocyclic compounds, have great importance in pharmaceutical chemistry due to their biological activities. Having these characteristics makes them drawn attention of most chemists to develop new methodologies for the synthesis of pyrroles. Recently, the cyclization of Npropargylic β-enaminones has been used for the synthesis of heterocyclic compounds, especially pyrroles. In this study, we have investigated the synthesis of new 2-acetylpyrrole derivatives which may have potential biological activities. Various pyrrole derivatives have been synthesized with two unprecedented way which are synthesis method from 1,4- oxazepines and one-pot two-step synthesis method from N-propargylic βenaminones. Firstly, α,β-alkynic ketone derivatives have been synthesized via Sonogashira coupling reaction between benzoyl chlorides and terminal alkynes. After synthesizing α,β-alkynic ketone derivatives, N-propargylic β-enaminone derivatives vi have been synthesized by the conjugate addition between propargylamine and the corresponding α,β-alkynic ketones. Secondly, the cyclization of N-propargylic β-enaminones have been carried out for the synthesis of 2-methylene-2,3-dihydro-1,4-oxazepines. A number of 2- methylene-2,3-dihydro-1,4-oxazepine derivatives have been synthesized in the presence of ZnCl2. Lastly, we have investigated the synthesis of 2-acetylpyrroles by using 1,4- oxazepines and N-propargylic β-enaminones as starting materials. We have achieved that the synthesis of the mentioned pyrroles via two original synthesis procedures. In the light of these two methods, 19 novel pyrrole derivatives have been synthesized.