Acetates organomagnesiums

Uncatalyzed addition reactions of Grignard reagents with nonconjugated alkenes and aUcynes are of limited use in synthesis. However, carbon-carbon double bonds substituted by a leaving group, such as an acetate, are susceptible to be displaced by organomagnesium compounds presumably by an addition-elimination pathway. A few examples have been reported (equation 64). 

Imines 223 derived from glyoxal acetals react with various organomagnesium compounds with high diastereoselectivity (equation 152) . The 1,2-aminoalcohols 224 can be converted into the protected enantiopure aminoaldehydes 225. For these reactions toluene was found to be a superior solvent. 

Dioxopyrrolizidine was widely used by Micheel et al33,118 as starting compound in the syntheses of some pyrrolizidine derivatives. Its reaction with phosphorus pentasulfide gave rise to pyrrolizidine-3,5-dithione, and it was converted via a Reformatsky reaction into ethyl 3-oxo-5-hydroxypyrrolizidine-5-acetate (165) and ethyl 3-oxo-pyrrolizylidene-5-acetate (166). Condensation with organomagnesium... 

Under mild conditions, acetals are sufficiently unreactive towards organomagnesium compounds to serve as protected carbonyl compounds. Under more vigorous conditions, however, displacement of one alkoxy group occurs ... 

Catalysed reactions of organomagnesium compounds with allylic acetates are potentially useful in synthesis, but lack of regioselectivity may be a problem ... 

Here, mixed cuprates prepared from organolithium or organomagnesium compounds serve as a carbanion, while derivatives like alkyl halides, alkyl sulfonates, or alkyl acetates are suitable equivalents for the carbocationic counterpart (Scheme 2.34). 

Electrolysis of organomagnesium chlorides in ethereal solution using a sacrificial black phosphorus anode, is reported to yield tertiary phosphines A tertiary phosphine oxide, tris (hydroxymethyl) phosphine oxide is produced in 64% yield (60% with respect to current) in the electrolysis of white phosphorus in a solution containing acetic acid, HCl, (CH3CO2)2Zn, (to improve the conductivity) and formalin and using a lead cathode. Tris (ct-hydroxyethyl) phosphine oxide was similarly obtained in 42% yield ... 

In acyclic systems, reductions of the ketone group of 1.155 (Y = COR) give poor selectivities. Reactions of o-substituted aldehydes 1.155 (Y = CHO) with organomagnesium reagents, perfluoroalkyllithiums or nitromethane [540] or chloracetophenone [540, 544] anions are very selective. Such is also the case for their reactions with functionalized isonitriles [540], silyl enolethers or thioketene acetals in the presence of Lewis acids [545, 546], or in B aylis-Hillmann reactions [547],... 

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