Electrocyclizations five-member heterocyclic synthesis

E. Synthesis of Perfluoroalkyl-substituted Five-Membered Heterocycles via 1, 5-Electrocyclization Reactions... 

There is a type of electrocyclic process that is of considerable value for heterocyclic ring synthesis 1,3-dipolar cycloadditions producing five-membered heterocycles. 

The generation and reactivity of conjugated azomethine ylides has been reviewed.148 1,3-Dipolar cycloaddition and 1,5- and 1,7-electrocyclizations have been described as powerful strategies for the synthesis of monocyclic and annulated five- and seven-membered nitrogen heterocyclic compounds. 

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