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The First Anionic Thia‐Fries Rearrangements at Ferrocene: Ready Access to Trifluoromethylsulfonyl‐Substituted Hydroxyferrocenes and an Extremely High Interannular Stereoinduction between Cyclopentadienyl Ligands
Author(s) -
Werner Georg,
Lehmann Christian W.,
Butenschön Holger
Publication year - 2010
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201000068
Subject(s) - chemistry , cyclopentadienyl complex , ferrocene , trifluoromethanesulfonate , steric effects , fries rearrangement , yield (engineering) , ring (chemistry) , medicinal chemistry , stereochemistry , photochemistry , catalysis , organic chemistry , electrochemistry , materials science , electrode , metallurgy
Attempts originally directed towards the generation of ferrocyne (1,2‐dehydroferrocene, 4 ) and ferrocenediyne (1,2,1′,2′‐tetradehydroferrocene, 5 ) by triflate elimination from the respective ferrocenyl triflates led to the discovery of the first anionic thia‐Fries rearrangements at a five‐membered ring. These reactions take place with remarkable efficiency under very mild reaction conditions and yield the respective trifluoromethylsulfonyl‐substituted ferrocenols. Most remarkably, the reaction starting from 1,1′‐ferrocenediyl ditriflate ( 9 ) adopts an extremely high interannular stereoinduction in that exclusively the meso rearrangement product, meso ‐2,2′‐bis(trifluoromethylsulfonyl)‐1,1′‐ferrocenediol ( 16 ), is formed, the corresponding racemic product 17 is not observed. It is shown that the second anionic thia‐Fries rearrangement proceeds at a much larger rate than the first one. The stereochemistry and the high rate of this reaction are explained on the basis of electronic as well as steric considerations. The redox behavior of some of the unprecedented ferrocene derivatives has been characterized by cyclovoltammetry.