Reactions of both diastereomers of 1,2-bis(4-methoxyphenyl)cyclohexane-1,2-diol (1 d) with tris(2,4-dibromo-phenyl)aminium hexachloroantimonate as the oxidant in dichloromethane have been investigated to get evidence on the possibility that a pinacol rearrangement may be oxidatively activated rather than acid-catalyzed. Relevant to this, we found that in the presence of an excess (4 eq) of oxidant, cis-1 d afforded the rearrangement product 2,2-bis(4-methoxyphenyl)cyclohexanone in large amounts, while trans-1 d gave exclusively the oxidative cleavage product 1,6-bis(4-methoxyphenyl)hexane-1,6-dione. Stereospecific implications explaining the reactivity difference between the two diastereomeric radical cation intermediates, cis- and trans-1 d⋅+, are discussed.
Insights into Pinacol Rearrangement: Oxidative versus Acid-Catalyzed Mechanism
Monopoli A.
;Casiello M.;D'Accolti L.;Nacci A.
2021-01-01
Abstract
Reactions of both diastereomers of 1,2-bis(4-methoxyphenyl)cyclohexane-1,2-diol (1 d) with tris(2,4-dibromo-phenyl)aminium hexachloroantimonate as the oxidant in dichloromethane have been investigated to get evidence on the possibility that a pinacol rearrangement may be oxidatively activated rather than acid-catalyzed. Relevant to this, we found that in the presence of an excess (4 eq) of oxidant, cis-1 d afforded the rearrangement product 2,2-bis(4-methoxyphenyl)cyclohexanone in large amounts, while trans-1 d gave exclusively the oxidative cleavage product 1,6-bis(4-methoxyphenyl)hexane-1,6-dione. Stereospecific implications explaining the reactivity difference between the two diastereomeric radical cation intermediates, cis- and trans-1 d⋅+, are discussed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
