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Bromoacetate Olefination Protocol for Norbixin and Julia–Kocienski Olefination for Its Ester Syntheses

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journal contribution
posted on 07.06.2019, 18:54 by Dahye Kim, Mohammad Shariful Alam, Wook-Jin Chung, Sangho Koo
A new olefination protocol utilizing ethyl bromoacetate was highlighted, in which magnesium enolate of the ester coupled with C20 dialdehyde 6, and double eliminations of the protected hydroxyl groups and bromine atoms of the coupling bromohydrin product, efficiently produced norbixin 1 after concomitant hydrolysis of the ester. A new (C7 + C10 + C7) disconnection approach was demonstrated for the synthesis of norbixin ethyl ester 2 by the Julia–Kocienski olefination of novel C7 benzothiazolyl-sulfone 11 and C10 2,7-dimethyl-2,4,6-octatrienedial (12).