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[1] [2] Pyrroles are found in a variety of natural products with biological activity, so the synthesis of substituted pyrroles has important applications in medicinal chemistry. [3] [4] Alternative methods for synthesizing pyrroles exist, such as the Knorr Pyrrole Synthesis and Paal-Knorr Synthesis. The Hantzsch pyrrole synthesis
The Knorr pyrrole synthesis is a widely used chemical reaction that synthesizes substituted pyrroles (3). [ 1 ] [ 2 ] [ 3 ] The method involves the reaction of an α- amino - ketone (1) and a compound containing an electron-withdrawing group (e.g. an ester as shown) α to a carbonyl group (2) .
The Knorr pyrrole synthesis involves the reaction of an α-amino ketone or an α-amino-β-ketoester with an activated methylene compound. [15] [16] [17] The method involves the reaction of an α-amino ketone (1) and a compound containing a methylene group α to (bonded to the next carbon to) a carbonyl group (2). [18] The Knorr pyrrole synthesis
The pyrrole synthesis requires a primary amine under similar conditions, or ammonia (or ammonia precursors) can be used. Synthesis of a thiophene requires a sulfurizing agent which is typically a sufficient dehydrator, such as phosphorus pentasulfide , Lawesson's reagent , or hydrogen sulfide .
2-mesityl-3-methylpyrrole was synthesized in 2004 via the Trofimov reaction. The reaction of the ketoxime with acetylene yielded a mixture of products with the primary one being the N-H pyrrole. Small amounts of the N-vinyl product were also observed as well as O-vinylketoxime. The N-vinyl product was then used in the synthesis of a new BODIPY. [5]
[3] [4] This has inspired the work of his student Paul Rothemund to develop a simple one pot synthesis of porphyrins. In 1935, Paul Rothemund reported the formation of porphyrin, from a simple reaction of pyrrole with gaseous acetaldehyde or formaldehyde in methanol followed by treatment with various concentrations of hydrochloric acid. [5]
The Barton–Zard reaction is a route to pyrrole derivatives via the reaction of a nitroalkene with an α-isocyanide under basic conditions. [1] It is named after Derek Barton and Samir Zard who first reported it in 1985.
The Hantzsch pyridine synthesis, [1] a multi-component organic reaction, is named after him, as is the Hantzsch pyrrole synthesis and the Hantzsch thiazole synthesis. [ 2 ] His surname is correctly pronounced /Haːntʃ/ (rhymes with cattle ranch).