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Divergent Reactivity of Alkyl Aryl Sulfones with Bases: Selective Functionalization of ortho ‐Aryl and α‐Alkyl Units Enabled by a Unique Carbanion Transmetalation
Author(s) -
Řehová Lucie,
Císařová Ivana,
Jahn Ullrich
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201301553
Subject(s) - transmetalation , carbanion , metalation , chemistry , regioselectivity , alkyl , aryl , reactivity (psychology) , sulfonyl , medicinal chemistry , stereochemistry , organic chemistry , catalysis , medicine , alternative medicine , pathology
The electron‐accepting sulfonyl group exhibits a strong acidifying influence on neighboring α‐H atoms. The Julia and related olefinations are based on this effect. Here a surprising reversal in the metalation selectivity of branched alkyl aryl sulfones is described. Such sulfones were found to initially undergo directed ortho ‐metalation with good regioselectivity, despite having a more acidic α‐H atom. The structure of the alkyl unit profoundly, but predictably, influences the regioselectivity of the attack of the base. In β‐ and γ‐branched ortho ‐(alkylsulfonyl)aryllithiums a transmetalation to the α‐carbanion proceeds only upon warming. Correspondingly generated ortho ‐ or α‐carbanions were then selectively applied thus permitting access to synthetically interesting compound classes.