The reactivity, as electrogenerated bases, of chiral and achiral phenazine radical-anions, including application in asymmetric deprotonation

Radical-anions, electrochemically generated in aprotic solvent from C-2 symmetric homochiral phenazine derivatives, act as chiral electrogenerated bases (EGBs) in the desymmetrisation by selective deprotonation of a prochiral epoxide (3,4-epoxy-2,3,4,5-tetrahydrothiophene-1,1-dioxide); the anion pro...

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Bibliographic Details
Published inOrganic & biomolecular chemistry Vol. 3; no. 15; pp. 2842 - 2847
Main Authors Alonso, AM, Horcajada, R, Motevalli, M, Utley, JHP, Wyatt, PB
Format Journal Article
LanguageEnglish
Published CAMBRIDGE Royal Soc Chemistry 07.08.2005
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
LITHIUM AMIDE BASES
MECHANISMS
KINETICS
PROTONATION
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Summary:Radical-anions, electrochemically generated in aprotic solvent from C-2 symmetric homochiral phenazine derivatives, act as chiral electrogenerated bases (EGBs) in the desymmetrisation by selective deprotonation of a prochiral epoxide (3,4-epoxy-2,3,4,5-tetrahydrothiophene-1,1-dioxide); the anion produced is trapped by mesitoic anhydride. The phenazines may be recovered in high yield by air oxidation. Enantiomeric excesses are modest (8-34%) but this is to our knowledge the first demonstration of such stereoselective electrochemically-initiated deprotonation. The reactivity of phenazine radical-anions as EGBs has also been explored by measurements of the rates of proton transfer; the prochiral epoxide was found to have a kinetic acidity similar to that of the methyltriphenylphosphonium cation.
ISSN:1477-0520
1477-0539
DOI:10.1039/b506309d