Treatment of nonaromatic N-fused pentaphyrin with trichloromethylsilane in the presence of a base afforded doubly N-fused pentaphyrin and its silicon complex. Addition of fluoride ion to the silicon complex led to the formation of its fluorosilicate as an unprecedented monoanionic six-coordinated SiIVcomplex of porphyrinoid. Treatment of the fluorosilicate with acid led to the recovery of the silicon complex. The doubly N-fused pentaphyrin, the silicon complex, and the fluorosilicate were all characterized as distinct Möbius aromatic molecules by spectroscopic measurements and X-ray crystallographic analyses. Importantly, the second N-fusion reaction, Si-incorporation and fluoride addition to the Si-atom enhanced the aromaticity of doubly N-fused pentaphyrins in this order. Tamao–Fleming oxidation of the silicon complex gave β-keto doubly N-fused pentaphyrin and triply fused pentaphyrin, which were nonaromatic and Hückel anti-aromatic, respectively.
Bibliographical noteFunding Information:
The work at Kyoto was supported by JSPS KAKENHI Grant Numbers (26810021, 25220802 and 25620031). The research at Yonsei University was supported by the Global Research Laboratory (GRL) Program (2013K1A1A2A02050183) of the Ministry of Education, Science and Technology (MEST) of Korea. S.I. acknowledges a JSPS Fellowship for Young Scientists. We thank Prof. K. Maruoka and Mr. H. Maruyama of Kyoto University for IR measurements.
All Science Journal Classification (ASJC) codes
- Organic Chemistry