AI Article Synopsis
- The study utilized isoxazolo[3,4-b]pyridin-3(1H)-one and isoxazolo[3,4-b]quinolin-3(1H)-one as advanced reagents to create previously unattainable Paal-Knorr intermediates in Trofimov pyrrole synthesis.
- The intermediates were obtained by reacting isoxazolones with excess ethyl propiolate under basic conditions, and their structures were confirmed using various spectroscopic techniques and single crystal X-ray analysis.
- Quantum chemical calculations indicated that the transformation from N,O-divinyl hydroxylamines to imino-aldehydes occurs through a stable chairlike transition state and is energetically favorable.
Article Abstract
We have used isoxazolo[3,4-b]pyridin-3(1H)-one and isoxazolo[3,4-b]quinolin-3(1H)-one as "masked" heterocyclic hydroxylamines to generate Paal-Knorr intermediates of the Trofimov pyrrole synthesis. The previously inaccessible intermediates, trapped by ethyl propiolate, were obtained by reacting corresponding isoxazolones with 4-fold excess of ethyl propiolate under basic conditions at ambient temperature, and characterized by means of IR and NMR spectroscopic data as well as by single crystal X-ray analysis. Quantum chemical calculations of a [3,3]sigmatropic rearrangement of the N,O-divinyl hydroxylamines to corresponding imino-aldehydes (Paal-Knorr intermediates) revealed that this reaction proceeds via chairlike transition state and is exothermic.
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| http://dx.doi.org/10.1021/acs.joc.7b01851 | DOI Listing |
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