The Knorr Synthesis of Pyrroles

Pyrrole Knorr was synthesized to prepare a mixture of ethyl acetoacetate 1 (7.52 g, 5 mL) in glacial acetic acid (18 mL) and cooled to 5 ° C. with stirring. Sodium nitrate solution (2.1 g in 5 mL deionized water) was added at a rate such that the reaction temperature did not exceed 7 ° C. After the addition was complete, the mixture was cooled and stirred for 10 minutes and then allowed to warm to room temperature. Zinc powder (4.0 g) was added little by little to the reaction mixture, and after gentle refluxing, the reaction mixture was heated under reflux for 1 hour.

Synthesis of pyrrole 2,4-diethoxycarbonyl-3,5-dimethylpyrrole by double condensation reaction using α-amino ketone acetoacetamidoacetate. When the product was analyzed by 1 H NMR, 13 C NMR, mass spectrum and IR spectrum, a positive result was obtained. Introduction Because of its heteroaromatic character, pyrrole has always been a very interesting molecule. A lone pair of electrons on nitrogen is delocalized within the ionic ring, resulting in an electron rich heterocycle.

Pyrrole Knorr was synthesized to prepare a mixture of ethyl acetoacetate 1 (7.52 g, 7.5 mL) in glacial acetic acid (18 mL) and cooled to 5 ° C. with stirring. Sodium nitrate solution (2.1 g in 5 mL deionized water) was added at a rate such that the reaction temperature did not exceed 7 ° C. After the addition was complete, the mixture was cooled and stirred for 10 minutes and then allowed to warm to room temperature. Zinc powder (4.0 g) was added little by little to the reaction mixture, and after gentle refluxing, the reaction mixture was heated under reflux for 1 hour.

Under different conditions, the reaction of propargyl alcohol with a terminal alkyne results in the selective formation of 1,4-diyne and polysubstituted furan / pyrrole. Water is the only by-product of the atomic economy, selective synthesis of 1,4-diyne and pyrrole, and the synthesis of furans is totally atomic. Herrmann-Beller cyclododecane catalyzes the highly diastereoselective addition of terminal alkynes to asymmetric gem-disubstituted cyclopropenes to obtain good to very good yields of alkynylcyclopropanes. It is considered that stereoscopic region discrimination when bulky alkynylpalladium species approaches is a cause of diastereoselective control of addition reaction.