The Value of a Nickel

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Science  30 Sep 2005:
Vol. 309, Issue 5744, pp. 2139
DOI: 10.1126/science.309.5744.2139b

Ethylene and other terminal olefins are produced inexpensively and in large quantities from petroleum and can be used directly as electrophiles in reactions for making pricey chemicals. However, to use olefins as nucleophiles, it's generally necessary to transform them into air-sensitive lithium or magnesium organometallics.

Ng and Jamison have developed a homogeneous nickel catalyst for the direct addition of terminal olefins to aldehyde electrophiles, which leads to synthetically useful allylic alcohols without the need for metallation. The key to the catalyst is a hindered arylphosphine ligand. High yields are obtained at room temperature for the addition of ethylene to aromatic or tertiary alkyl aldehydes, coupled with silylation of the resulting alcohol by triethylsilyl triflate and quenching of the triflic acid byproduct by an amine base. The reaction also works for alkyl-substituted olefins, albeit with a drop in yield, and regioselectively affords the geminal addition product. The authors speculate that the mechanism involves a five-membered Ni-metallacycle intermediate. — JSY

J. Am. Chem. Soc. 10.1021/ja055363j (2005).

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