Regioselective 1,3-Dipolar Cycloadditions of Diazoalkanes with Heteroatom-Substituted Alkynes: Theory and Experiment

Breugst, Martin; Huisgen, Rolf and Reissig, Hans-Ulrich (2018): Regioselective 1,3-Dipolar Cycloadditions of Diazoalkanes with Heteroatom-Substituted Alkynes: Theory and Experiment. In: European Journal of Organic Chemistry, No. 20-21: pp. 2477-2485

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
• Faculties: Chemistry and Pharmacy > Department of Chemistry
• Subjects: 500 Science > 540 Chemistry
• ISSN: 1434-193X
• Language: English