Nitrobenzyl aryl sulfones

The few examples indicate that sulfone-stabilized carbanions should react normally with electrophilic animating reagents (Eqs. 145158 and 146465) with the caveat that free a-amino sulfones are unstable.158,465 The (3,y-unsaturated sulfone 74 is animated at the y-position (Eq. 147),250 presumably by an ene reaction. The preparation of a-tosyl azides from nitronates was shown above in Eq. 144. The scope of this reaction does not seem to have been determined. Reaction of the anions of nitrobenzyl aryl sulfones with l-oxa-2-azaspiro[2.5]octane (13a) gives nitrobenzaldehydes by cleavage of the initially formed amination products.466 Similarly, reaction of the lithium salt of benzyl phenyl sulfone with phenyl azide gives benzilydeneaniline and phenyl sulfinate.467 No reports on animations of sulfoxide-stabilized carbanions were found. 

Introduction of arylsulfonylmethyl substituents into nitroheteroaromatic rings is of great practical value because these sulfones are versatile intermediates in organic synthesis. Nitrobenzyl aryl sulfones and their heterocyclic analogues can easily be transformed into the corresponding ethenyl derivatives by a simple alkylation with simultaneous elimination of arylsulfinate anion [125]. Diethyl methylenemalonate substituent can be introduced in the positimi 4- of 5-nitroimidazole via the VNS reaction of 5-nitroimidazole with the carbanion of chloromethyl phenyl sulfone [112, 124], followed by condensation of the obtained 4-(phenylsulfonyl)methyl derivative with diethyl bromomalonate or diethyl ketomalonate (Scheme 33) [126]. 

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