Five-membered ring systems pyrroles synthesis

Five-membered ring heterocyclic compoxmds containing nitrogen are one of the most common heterocycles. In fact, the synthesis of a great variety of that such as pyrrole, pyrazole, imidazole, triazole, tetrazole, lactams, and imides involving porous catalytic systems have been investigated. 

The ring synthesis of five-membered heterocycles has been extensively investigated, and many and subtle methods have been devised. Each of these three heterocyclic systems can be prepared from 1,4-dicarbonyl-compounds, for furans by acid-catalysed cyclising dehydration, and for pyrroles and thiophenes by interaction with ammonia or a primary amine, or a source of sulfur, respectively. 

Five-membered heterocycles Most papers dealing with the synthesis of cyclic compounds with 10 report on the formation of six-membered or condensed heterocyclic systems. Nevertheless, a number of new five-membered heterocyclic derivatives have been described. So furane, thiophene and pyrrole derivatives were prepared by ring enlargement when oxiranes, thiirane and A -tosylhydrazide, respectively, were reacted with 10 at -10 Various other ways to prepare pyrrole derivatives include cyclization of amino... 

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