Sequential Construction of Complex Pyrrole-Pyrrole or Pyrrole-Pyrazole Systems from 1,2-Diaza-1,3-butadienes

The treatment of cyanoacetic acid hydrazide or ethyl 3-hydrazino-3-oxopropionate with methyl 2-chloroacetoacetate leads to the corresponding hydrazone derivatives. In the presence of sodium carbonate, these compounds react at room temperature with acetoacetanilide or 2,4-pentanedione to give the relevant 1-aminopyrrole rings. In the presence of sodium methoxide, the activated methylene group present on the 1-amino side chain of these heterocycles attacks at room temperature 1,2-diaza-1,3-butadienes affording the respective hydrazonic 1,4-adducts. Under basic conditions, these adducts surprisingly cyclise at room temperature in different way providing pyrrole-pyrrole or pyrrole-pyrazole systems depending on the starting cyano or ethylcarboxylate group, respectively.

hydrazones - 1,2-diazal - 3-butadienes - cyclization - pyrroles - pyrazoles