1. Photochemical Intramolecular C-H Addition of Dimesityl(hetero)arylboranes through a [1,6]-Sigmatropic Rearrangement
- Author
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Shuhei Itoyama, Yasunori Matsui, Yutaro Kuramoto, Yoshihito Shiota, Kazunari Yoshizawa, Shigehiro Yamaguchi, Hiroshi Ikeda, Aiko Fukazawa, Naoki Ando, and Tomokatsu Kushida
- Subjects
chemistry.chemical_classification ,Pericyclic reaction ,Double bond ,010405 organic chemistry ,Aryl ,General Medicine ,General Chemistry ,Sigmatropic reaction ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Absorption band ,Intramolecular force ,Flash photolysis ,Cope rearrangement - Abstract
A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C-H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C-C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted π-conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (λ=370-400 nm).
- Published
- 2017