Hydrozirconation review

In deciding on the material to be covered in this chapter, limitations had to be set. The first section will present the synthesis of various zirconocene hydrides. The focus of the subsequent sections is to present a general synopsis of the different aspects of the hydrozirconation reactions using 1 not only on carbon-carbon multiple bonds but also on heteropolar multiple bonds. Those aspects of hydrozirconation that were covered in previous reviews [1-5, 27] and in the excellent chapter by Labinger in Comprehensive Organic Synthesis [28] are summarized or briefly mentioned here. For other aspects of organozirconium chemistry not covered by the above-mentioned reviews, the reader is referred to a number of monographs and reviews [29, 30]. 

Hydrozirconation. Detailed information about hydrozirconation can be found in a review paper by Wipf and Jahn.631... 

Schwartz hydrozirconation works on both alkenes and alkynes even at room temperature. It works significantly better in ether solvents than hydrocarbon solvents. In addition, the reaction intermediate can be transmetallated into other organometallics that can be used in palladium-catalyzed reactions or trapped with electrophiles. Review Schwartz, J. Labinger, J. A. Angew. Chem. Int. Ed. 1976,15, 333-340. 

Instead of the commercially available CpZrHCl, this reagent can be prepared in situ from Cp2ZrCl2 and lithium triethylborohydride. The reaction mixture hydrozirconates terminal acetylenes without affecting e.g. an ester or trimethylsilyl functionality in the alkyne. An application of the Schwartz reagent in natural product synthesis is the hydrozirconation of the terminal triple bond of Me3SiC=C(CH2)4C=CH. A review on hydrozirconation has been published . ... 

Hydrozirconation, This process has been reviewed (77 references). xfi-Unsaturoted aldehydes. This zirconium hydride reacts with 1,3-dienes via 1,2-addition to the less hindered double bond to give homoallylic complexes. These complexes insert carbon monoxide readily to form unsaturated aldehydes. Examples ... 

There is much important material in reviews of methods for the synthesis of hydrocarbon bridged transition metal complexes without metal-metal bonds, hydrozirconation-isomerisation, the complexation of a-bonds by transition metals, the chemistry of carborane metal complexes incorporating d- and f-block elements, and transition metals in organic synthesis covering the year 1991.20... 

Mechanistic aspects of olefin insertion reactions in catalytic systems have been reviewed. A second review concerned with hydrozirconation of olefins and acetylenes contains sections of interest to readers of this Chapter. ... 

An improved procedure for the synthesis of alkyl iodides from organoboranes (and thus ultimately from alkenes), involving the use of iodine and sodium meth-oxide, has been shown to entail inversion at the C-B bond, and is employed in a new route to optically active iodides from alkenes e.g. Scheme 30). A similar sequence for conversion of alkenes to primary halides via hydrozirconation (Scheme 31) has been reviewed. Zr also catalyses addition of lithium aluminium hydride to alkenes under mild conditions, and the alanes so formed can likewise be converted into alkyl halides (Scheme 32). 

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