Organic Letters 2008-05-15

Flexible protocol for the chemo- and regioselective building of pyrroles and pyrazoles by reactions of Danishefsky's dienes with 1,2-diaza-1,3-butadienes.

Orazio A Attanasi, Gianfranco Favi, Paolino Filippone, Gianluca Giorgi, Fabio Mantellini, Giada Moscatelli, Domenico Spinelli

Index: Org. Lett. 10(10) , 1983-6, (2008)

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Abstract

The versatility of the Mukaiyama-Michael-type addition/heterocyclization of Danishefsky's diene with 1,2-diaza-1,3-butadienes was applied to the synthesis of both 4 H-1-aminopyrroles and 4,5 H-pyrazoles. Thus, the same reagents furnished different types of highly functionalized azaheterocycles essentially depending on their structure: as a matter of fact, R1 = COOR or CONR 2 differently affects the acidity of the proton at the adjacent carbon. An unexpected formation of 5 H-1-aminopyrroles from the reactions carried out in water was also observed.