Abstract
The 1,3-dipolar cycloadditions of diazomethane and diazoethane with methyl 3-(diethylamino)propiolate were investigated experimentally and computationally by employing density functional theory (DFT). The experiments provided methyl 3-(diethylamino)-pyrazole-4-carboxylates as the only isolated regioisomers. The constitution of these cycloadducts was secured by independent synthesis and decarboxylation to 3-(diethylamino)pyrazoles. The calculations fully support the experimental findings. For the preferred pathway of the diazomethane cycloaddition with the alkyne, a kinetic preference of 9.6 kJmol(-1) was calculated in Et2O solution. The computational analysis was extended to other alkynes, for instance to heteroatom-substituted alkynes such as ethoxyethyne and (ethylthio)ethyne. Again, the calculations nicely explain the switch in regioselectivity of the 1,3-dipolar cycloadditions of diazomethane with these two alkynes, which has been reported earlier by the group of Arens.
Item Type: | Journal article |
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Faculties: | Chemistry and Pharmacy > Department of Chemistry |
Subjects: | 500 Science > 540 Chemistry |
ISSN: | 1434-193X |
Language: | English |
Item ID: | 67449 |
Date Deposited: | 19. Jul 2019, 12:22 |
Last Modified: | 04. Nov 2020, 13:49 |