Takai

A valuable feature of the Nin/Crn-mediated Nozaki-Takai-Hiyama-Kishi coupling of vinyl iodides and aldehydes is that the stereochemistry of the vinyl iodide partner is reflected in the allylic alcohol coupling product, at least when disubstituted or trans tri-substituted vinyl iodides are employed.68 It is, therefore, imperative that the trans vinyl iodide stereochemistry in 159 be rigorously defined. Of the various ways in which this objective could be achieved, a regioselective syn addition of the Zr-H bond of Schwartz s reagent (Cp2ZrHCl) to the alkyne function in 165, followed by exposure of the resulting vinylzirconium species to iodine, seemed to constitute a distinctly direct solution to this important problem. Alkyne 165 could conceivably be derived in short order from compound 166, the projected product of an asymmetric crotylboration of achiral aldehyde 168. 

In 1983, Nozaki, Takai, Hiyama, and their coworkers disclosed that vinyl and aryl iodides or bromides are reduced with chromium(n) chloride, and that the resulting organochromium(in) species react smoothly with a host of aldehydes to give allylic or benzylic alcohols in excellent yields.6 As shown in Scheme 1, the chromium(n) chloride-mediated carbonyl addition can be conducted efficiently at... 

Scheme 1. The chromium(n) chloride-mediated carbonyl addition process of Nozaki, Takai, and Hiyama.

For examples of this coupling reaction involving enol triflates derived from ketones, see Takai, K. Taga-shira, M. Kuroda, T. Oshima, K. Utimoto, K. Nozaki, H. J. Am. Chem. Soc. 1986, 108, 6048. 

Nozaki-Takai-Hiyama-Kishi coupling Ni(n)/Cr(n)-mediated 603, 605 f, 620 f. 

Takai K, Hotta Y, Oshima K, Nozaki H (1978) Tetrahedron Lett 2417... 

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