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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
In organic chemistry, the Bohlmann–Rahtz pyridine synthesis is a reaction that generates substituted pyridines in two steps, first a condensation reaction between an enamine and an ethynylketone to form an aminodiene intermediate, which after heat-induced E/Z isomerization undergoes a cyclodehydration to yield 2,3,6-trisubstituted pyridines.
Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole. Pyrrole contains a lone pair that is part of the pi-conjugated system, so it is not available to deprotonate an acidic proton. [1] The basic aromatic rings purines and pyrimidines are nucleobases found in DNA and RNA.
The Boger pyridine synthesis is a cycloaddition approach to the formation of pyridines named after its inventor Dale L. Boger, who first reported it in 1981. [1] The reaction is a form of inverse-electron demand Diels-Alder reaction in which an enamine reacts with a 1,2,4- triazine to form the pyridine nucleus.
Kröhnke condensation of enamino nitrile 20 with enone 21 yielded fused pyridine 22. Figure 5. The mechanism of this Kröhnke-type reaction likely proceeds via a vinylogous cyanamide 23 which undergoes elimination of hydrocyanic acid, deprotonation to form enamine 24 and cyclization to form intermediate 25, which is then dehydrated to form the ...
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). [4] The Knorr pyrrole synthesis
The mechanism for the synthesis of the pyrrole was investigated by V. Amarnath et al. in 1991. [4] His work suggests that the protonated carbonyl is attacked by the amine to form the hemiaminal. The amine attacks the other carbonyl to form a 2,5-dihydroxytetrahydropyrrole derivative which undergoes dehydration to give the corresponding ...
[1] [2] The initial reaction product is a dihydropyridine which can be oxidized in a subsequent step to a pyridine. [3] The driving force for this second reaction step is aromatization. This reaction was reported in 1881 by Arthur Rudolf Hantzsch. A 1,4-dihydropyridine dicarboxylate is also called a 1,4-DHP compound or a Hantzsch ester.