Iron(III) Salt‐Catalyzed Nazarov Cyclization/Michael Addition of Pyrrole Derivatives

The Nazarov cyclization of two types of pyrrole derivatives was effectively catalyzed by 5 mol% alumina‐supported iron(III) perchlorate [Fe(ClO 4 ) 3 ⋅Al 2 O 3 ] which provided the desired cyclization with high trans selectivity in good to excellent yield. The cyclized product was next reacted with a vinyl ketone in the presence of the same iron salt to afford the corresponding Michael product. A sequential type Nazarov/Michael reaction of pyrrole derivatives has also been accomplished; the synthetic route to 4,5‐dihydrocyclopenta[ b ]pyrrol‐6(1  H )‐one derivative 5 or 5,6‐dihydrocyclopenta[ b ]pyrrol‐4(1  H )‐one derivative 6 has thus been established using a very economical iron catalyst.