Zinc reagents nitrone additions

Nucleophilic addition of zinc-containing reagents to nitrones 398... 

Nitrones have a more reactive C=N bond toward nucleophilic addition compared to imines. In spite of this fact, there have been only a limited number of studies on the nucleophilic addition reactions of nitrones, particularly organometallic reagents.352-355 During the last decade, research related to reactions of nitrones with zinc-containing reagents was essentially focused on (i) dialkylzinc-assisted alkynylations356-358 and vinylations359 of nitrones, (ii) catalytic asymmetric nucleophilic additions to the C=N bond,360-364 and (iii) nitrone allylations by allylzinc halides.365,366... 

In general, copper-zinc compounds, unlike organolithium-derived organocopper reagents, undergo clean addition reactions to nitroolefins. After Michael addition, the resulting zinc nitronates can be oxidatively converted into polyfunctional ketones, such as 117 (Scheme 2.45) [96]. 

Addition reaction of zinc-copper reagents to nitro olefins is a versatile method for preparing polyfunctional nitroalkanes.20 A direct ozonolysis of the intermediate zinc nitronate furnishes the corresponding ketone (Nef-reaction).20... 

A zinc-silver couple has been reported to be an improved reagent for the reductive addition of allylic bromides to nitriles. l-Trimethylsilyl-2-methyl-cyclopropane is a convenient regio- and stereospecific precursor of unsaturated ketones [equation (37)]. The reaction of allylsilanes with a-nitro-olefins has been found to proceed smoothly in the presence of aluminium trichloride [equation (38)]. The unstable nitronic acid product may be converted readily into the unsaturated ketone by the Nef reaction. 

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