Selective introduction of a trifluoroacetyl group onto 4-vinylpyridines through magnesium-promoted reduction

Magnesium-promoted reductive coupling of 4-vinylpyridines and ethyl trifluoroacetate in the presence of chlorotrimethylsilane in N-methyl-2-pyrrolidone resulted in selective formation of the trifluoroacetylated compounds at the β-olefinic carbon of the pyridine ring, the electron deficient carbon in good yields. In particular, 4-vinylpyridine with an aromatic ring at the β-olefinic position of the pyridine ring gave higher yield of the trifluoroacetylated compound. The nitrogen atom of the pyridine ring may play an important role in the regioselectivity of the product.

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