Synthesis of meso-Alkyl-Substituted Norcorrole-NiII Complexes and Conversion to 5-Oxaporphyrins(2.0.1.0).
The synthesis of antiaromatic NiII -norcorroles having primary, secondary, and tertiary alkyl groups at the reactive meso-positions was attempted. Reductive coupling of a NiII -dipyrrin precursor provided NiII -meso-dihexylnorcorrole, which underwent substantial degradation on silica gel. Introduction of tert-butyl groups was unsuccessful due to the difficult preparation of the corresponding dipyrrin precursor. Meanwhile, NiII -norcorroles with isopropyl and cyclohexyl groups were isolated as stable molecules under ambient conditions. Furthermore, we found that oxidation of NiII -meso-dialkylnorcorroles with hydrogen peroxide in the presence of sodium carbonate gave NiII -5-oxaporphyrins(2.0.1.0). In contrast, oxidation of NiII -meso-dimesitylnorcorrole under the same reaction conditions gave 10-oxaporphyrin(1.1.1.0). The contrasting reactivity can be attributed to the steric congestion around the meso-positions.
['Liu|Si-Yu|SY|', 'Tanaka|Hiroko|H|', 'Nozawa|Ryo|R|', 'Fukui|Norihito|N|http://orcid.org/0000-0002-0466-0116', 'Shinokubo|Hiroshi|H|http://orcid.org/0000-0002-5321-2205']
antiaromaticity alkyl groups reactivity norcorroles porphyrinoids