New Scope and Limitations in the Knorr–Paal Synthesis of Pyrroles

Newly-found steric limits for the Knorr–Paal reaction in the case of 2-methyl-1,2-propanediamine and acetonylacetone make it possible for the process to occur with only one amino group, giving aminopyrrole 2, and with aziridines, due to dimerization under the conditions of the reaction, giving 1-((β-aziridinoalkyl)pyrroles 4a,b.