by Hirokazu Miyoshi, Shunpei Nobusue, Akihiro Shimizu, Ichiro Hisaki, Mikiji Miyata and Yoshito Tobe*
Synthesis of 13,14-dimesitylbenz[c]indeno[2,1-a]fluorene, a 2,3-naphthoquinodimethane derivative isolated for the first time, was achieved. The X-ray crystallographic structure and spectroscopic and electrochemical properties of this compound indicate substantial singlet biradical character which is higher than that of 11,12-dimesityindeno[2,1-a]fluorene, in accord with the quantum chemical study. Cycloadditions with oxygen and dichlorodicyano-p-benzoquinone took place at the inner naphthalene carbons rather than the most reactive exocyclic carbons because of effective steric protection by the mesityl groups at the latter positions. [4+2] cyclodimerization also took place at the inner naphthalene position as a 4π component and the outer naphthalene ring as a 2π component.
Chemical Science
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