Deprotonative metalation salt-activated compounds

Excellent nucleophiles in palladium(0)-eatalyzed allylic alkylations are soft carbanions, i.e.. metal salts of C — H acids with a pKa in the range of 10-20. These are activated methylene compounds which are substituted with at least two geminal electron-withdrawing groups [CO.R, S02R, — CN, —NC. COR, N02, (C6H5)2C = N]. As an exception, deprotonated simple nitroalkanes are sometimes also effective as nucleophiles. 

Morken and Lavastre used the formation of a colored side product to identify catalysts for the allylation of /i-dicarbonyl compounds [8]. The researchers employed 1-naphthyl allyl carbonate 5 as an allyl source and the diazonium salt of fast red as an indicator. Formation of the active 7z>allyl complex furnishes C02 and 1-naphthoxide which deprotonates the 1,3-dicarbonyl compounds which can, in turn, react with the 71-allyl metal complex. 1-Naphthol is the only species in the reaction mixture that can react with the diazonium salt 6 to generate the bright red azo dye fast red. Thus the red color is indicative of successful formation of the active re-allyl complex (Figure 5.4.3). 

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