- Claisen Rearrangement of meta-Substituted Allyl Phenyl Ethers
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Electron-releasing substituents at the 3-position of allyl phenyl ethers favour Claisen rearangement of the allyl group to the 6-position, whereas electron-acceptors favour migration to the 2-position. 2-Acylhydroquinone 4-allyl ethers yield, predominantly, the 3-allyl isomers, probably because internal hydrogen bonding confers naphthalenoid character on the aryl residue.
- Bruce, J. Malcolm,Roshan-Ali, Yusuf
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p. 2677 - 2679
(2007/10/02)
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- Allylation of Quinones with Allyltin Reagents
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Lewis acid (BF3) catalyzed allylation of quinones with allyl- (2a), 2-methyl-2-propenyl- (2b), trans-2-butenyl- (2c,d), 3-methyl-2-butenyl- (2e,f), and trans-cinnamyltrialkyltin (2g) gives the corresponding allylhydroquinones with high regioselectivity.Vitamin K2(5) (7) and coenzyme Q1 (9) were prepared in yields of 78 and 75percent, respectively.These reactions appear to proceed through allylquinol intermediates which undergo rearrangement under the influence of BF3.The success of this synthesis of vitamin K2(5) and coenzyme Q1 depends on the fact that the reaction of 3-methyl-2-butenyltin with quinones occurs at the α carbon of the allylic system.
- Naruta, Yoshinori
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p. 3774 - 3783
(2007/10/02)
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