Aldol-type reactions Nickel carbonyl

A nickel hydride complex, NiHCl(diphenylphosphinoethane), catalyses the tandem isomerization-aldolization reaction of allylic alcohols with aldehydes.156 The atom- (g) efficient process proceeds at or below ambient temperature with low catalyst loading, and works well even for bulky aldehydes. Magnesium bromide acts as a co-catalyst, and mechanistic investigations suggest that a free enol is formed, which then adds to the aldehyde in a hydroxyl-carbonyl-ene -type reaction. 

Synthesis ofp-epoxy ketones.20-21 Nickel carbonyl reacts with an a-bromo ketone (DMF, argon, 30°, 5 hrs.) to give a/3-epoxy ketone, for example (2). Yields are in the range 50-80%. The reaction is considered to proceed via an aldol-type condensation between the ketone and the nickel enolate followed by elimination of NiBr2. 

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