A three-component condensation of aldehydes, amines, and nitroalkanes in the presence of catalytic amounts of SmCl3 as Lewis acid leads to the formation of highly substituted pyrroles of type 29 (Scheme 17) . The reaction is considered to involve the coupling of a,p-unsaturated imines, which are provided by the Sm-catalyzed aldol-type condensation of imines generated from amines and aldehydes, with nitroalkanes. The yield was highly dependent on the nature of the different building blocks, and the products had to be purified by chromatography. Thus, the reaction may be of less importance for the routine synthesis of pyrrole libraries.
Scheme 17 29
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