Ketones organomagnesium amide reactions

Addition of organolithium or organomagnesium reagents to N-methoxy- N-methyl amides gives a tetrahedral intermediate that is stabilized by chelation of the magnesium atom by the two oxygen atoms. This intermediate collapses, to give a ketone, only when acid is added at the end of the reaction. 

In contrast with conjugated ketones and esters, the reaction between conjugated amides and all types of RMgX proceeds through a 1,4-addition [1-4], particularly with the allylic [21,22] and allenylic [6] organomagnesium derivatives [Eq. (7)] ... 

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