Scope and Limitation of VNS

SCHEME 11.25 General scheme of the VNS reaction with carbanions. 

For mechanistic studies presented in Section 11.4.2, carbanions of chloromethyl aryl sulfones were chosen, because they are relatively stable and at temperatures below -20°C they can be generated in advance and used without decomposition [32, 35, 40, 41]. Because of their stability, these carbanions were also used in most of exploratory studies. Carbanions of a-chloronitriles and esters of a-chlorocarboxylic acids are rather unstable nevertheless, they enter efficiently VNS reaction 

SCHEME 11.28 VNS reaction in 5-nitroquinoUne used for nucleophilic formylation [50]. 

SCHEME 11.29 VNS reaction in 5-nitroisoquinoline used for nucleophilic methylation [51]. 

SCHEME 11.31 VNS reaction of carbanion of dimethyl chloromalonate with nitrothiazole [53] 

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