Vicarious nucleophilic substitution of hydrogen (VNS) in 1,4-naphthoquinone derivatives—competition between VNS and vinylic nucleophilic substitution (SNV)

Carbanions of dimethyl chloromalonate, ethyl 2-chloroacetoacetate and dimethyl malonate react with naphthoquinone derivatives mainly via vicarious nucleophilic substitution or oxidative nucleophilic substitution of hydrogen processes. These reactions in 2-halo substituted naphthoquinones are generally faster processes than vinylic nucleophilic substitution of halogen (SNV). Introduction of one Cl substituent into position 2- of 1,4-naphthoquinone increases substantially its electrophilic activity resulting in much faster addition of the carbanion in the position occupied by hydrogen. On the other hand addition of the carbanions to 2,3-dichloro-1,4-naphthoquinone proceeds slower than to 1,4-naphthoquinone.