期刊
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
卷 2018, 期 20-21, 页码 2477-2485出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/ejoc.201800100
关键词
Cycloaddition; Density functional calculations; Diazo compounds; Reaction mechanisms; Regioselectivity
资金
- Deutsche Forschungsgemeinschaft
- Fonds der Chemischen Industrie
- University of Cologne
- DFG
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.
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