Synthetic Strategy for Tetraphenyl‐Substituted All‐E‐Carotenoids with Improved Molecular Properties

The synthetic method of tetraphenyl‐substituted all‐E‐carotenes 1 with improved properties of antioxidant and molecular electronic conductance was developed through the formation of tetraphenyl‐substituted all‐E‐apocarotenedial 4. The synthesis highlighted the preparation of novel subunits containin...

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Bibliographic Details
Published in:	European journal of organic chemistry Vol. 2020; no. 11; pp. 1769 - 1777
Main Authors:	Lim, Boram, Jung, Hyunuk, Yoo, Hyebin, Park, Myeongnam, Yang, Huijeong, Chung, Wook‐Jin, Koo, Sangho
Format:	Journal Article
Language:	English
Published:	Weinheim Wiley Subscription Services, Inc 22-03-2020
Subjects:	Antioxidants Carotenoids Conducting materials Conjugation Coupling (molecular) Molecular properties Olefination Recrystallization Resistance Selectivity Silicon dioxide Substitutes Synthesis design Total synthesis
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Summary:	The synthetic method of tetraphenyl‐substituted all‐E‐carotenes 1 with improved properties of antioxidant and molecular electronic conductance was developed through the formation of tetraphenyl‐substituted all‐E‐apocarotenedial 4. The synthesis highlighted the preparation of novel subunits containing phenyl substituent(s) with E‐configuration starting from the key (E)‐4‐chloro‐2‐phenylbut‐2‐enal (10), utilizing conjugation effect with formyl group or easy recrystallization of sulfone compounds. Sulfone‐mediated coupling methods of Julia and modified Julia–Kocienski olefinations utilizing the subunits were demonstrated to produce tetraphenyl‐substituted apocarotenedials 4. The major all‐E‐forms (73–85 % selectivity) were easily purified by SiO2 chromatography and trituration with Et2O due to the presence of the polar formyl groups. The olefination of all‐E‐apocarotenedials 4 and Wittig salt 5 provided all‐E‐9,9',13,13'‐tetraphenylcarotenes 1. Tetraphenyl‐substituted carotenoids with improved antioxidant and electronic conducting properties than natural carotenoids were synthesized through the formation of all‐E‐apocarotenedials (4), which were prepared by the sulfone‐mediated olefinations of the novel building blocks 7 and 3, or 8 and 9 with E‐configurations. (E)‐4‐Chloro‐2‐phenylbut‐2‐enal (10) was the key material for the syntheses.
ISSN:	1434-193X 1099-0690
DOI:	10.1002/ejoc.202000130