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20.5.15.1.1.7.2 Variation 2: Using a Reformatsky Reagent and a Nitrile

DOI: 10.1055/sos-SD-020-01264

Beignet, J.Science of Synthesis, (2007201352.

The addition of a Reformatsky reagent to a nitrile, known as the Blaise reaction, produces β-oxo esters in good yields when the product is mono- or disubstituted at the α-position.[‌24‌] The reaction can be carried out with modest efficiency using ethyl bromoacetate as a starting material, which when gradually added to a mixture containing a nitrile, zinc, and mercury(II) chloride in refluxing benzene generates an organometallic nucleophile. This nucleophile reacts immediately with the nitrile (always present in excess to avoid self-condensation). In the workup procedure, hydrolysis of the iminometallic intermediate 37 that is formed then produces aliphatic 3-oxo esters 38 in moderate yields (Scheme 16). The efficiency of the Blaise reaction is partially limited by the occasional formation of nitrogen-containing impurities; for example, the zinc intermediate 37 may undergo partial hydrolysis to the moderately stable enamine 39, or it can react further acting as a nucleophile with the nitrile.

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