Bromomalonate carbanion

The additions of bromomalonate carbanions to chiral a-acylvinyl sulfoxides provide optically active dialkyl cyclopropanecarboxylates in up to 84% ee107. 

A reaction fulfilling this requirement is the Bingel addition [130], a methano-fullerene synthesis in which the attack of 2-bromomalonate carbanions on the fullerene is followed by intramolecular halide displacement. In the mono-func-tionalization of C7o,it shows a high preference for the C(l)-C(2) bond [54,130]. This can be rationalized by the preference of the -hybridized carbanionic cen-... 

The structurally related optically active a-acyl vinyl p-tolyl sulfoxide 269 underwent asymmetric cyclopropanation. Michael addition of the carbanion of bromomalonate to 269 and the subsequent intramolecular alkylation yielded the corresponding optically active a-acyl-cyclopropane 271, with a high degree of diastereoselectivity (Scheme 70).142 It was proposed that the stereochemical outcome of the reaction can be rationalized by transition state 270, in which there is chelation of the oxygen atom of the carbonyl and sulfinyl groups to the metal cation. 

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]. 

Reaction of the aziridine (15) with the carbanion of bromomalonate at room temperature or the carbanion of bromomalononitrile leads to azetidines in high yield (Scheme 43). ... 

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