Synthesis of Bridged Indigos and Their Thermoisomerization and Photoisomerization Behaviors.

Junya Kanda, Naoki Egami, Takahiro Sasamori, Ayumi Imayoshi, Takashi Hosoya, Kazunori Tsubaki

The Journal of organic chemistry 2021 Dec 17

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Bridged indigos were synthesized by bridging the two nitrogen atoms in the indigo structure with a carbon chain, and their properties were carefully examined. These bridged indigos have intrinsic planar chirality, and the enantiomers were separated using chiral high-performance liquid chromatography. When the chiral bridged indigos were subjected to thermo- and photoisomerization, the corresponding (Z)-indigo was not observed at all, and racemization was observed. This phenomenon is caused by the low activation energy of inversion due to the 1.5 bond order of the double bond of the indigo skeleton and the large energy difference between the ground states of (E)-indigo and (Z)-indigo.

Citation

Junya Kanda, Naoki Egami, Takahiro Sasamori, Ayumi Imayoshi, Takashi Hosoya, Kazunori Tsubaki. Synthesis of Bridged Indigos and Their Thermoisomerization and Photoisomerization Behaviors. The Journal of organic chemistry. 2021 Dec 17;86(24):17620-17628