Towards the functionalization of the methine carbon of a sterically hindered tris(pyrazolyl)methane: is a radical pathway envisageable? Synthesis and structure of tetrakis(3,5-dimethylpyrazolyl)methane

Iodine oxidation, at −80 °C, of the carbanion in [{−C(pzMe2)3}Li+(THF)] (1) (with pzMe2=3,5-dimethylpyrazolyl) yields the C-centred radical in [{C(pzMe2)3}Li(THF)]+ (1+), which, upon warming to room temperature, produces the unprecedented tetrakis(3,5-dimethylpyrazolyl)methane C(pzMe2)4 (3), the X-ray structure of which revealing intramolecular C–H⋯π interactions between each 5-Me group and an adjacent pyrazolyl ring. Oxidation of the radical by O2 appears to lead to the novel ether (pzMe2)3C–O–C(pzMe2)3 (2).

Graphical abstractIodine oxidation, at −80 °C, of the stable carbanion −C(pzMe2)3 yields the green C-centred radical C(pzMe2)3 which, upon warming to room temperature, yields the unprecedented tetrakis(3,5-dimethylpyrazolyl)methane, C(pzMe2)4, which is stabilized by intramolecular C–H⋯π interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide