Allyl ethers, hydroalumination

Hydroalumination of allylic alcohols or ethers. llydroalumination of these substrates under usual conditions (9. 276) proceeds poorly because of deoxygenation associated with titanium catalysts.3 The desired reaction, however, can be effected in 50 80" yield with ZrC l4 in the case of alcohols and Cp.ZrCL in the case of cllieis (equations 1 and II). 

Trifluoromethyl)allyltrimethylsilane results frwith aldehydes and ketones gives trifluoromethyl-ated alcohols and silyl ethers. Synthesis of allyl and allenyl-silanes is stereospecific from hydroalumination or hydroboration of... 

Silicon.—Alkenyl, Vinyl-, and Allyl-silanes. Hydroboration of alkynylsilanes proceeds stereospecifically, subsequent carbodeboronation leading to stereochemically defined vinylsilanes (Scheme 26). A similar route using hydroalumination can also be employed, but the stereochemistry is dependent upon the conditions of the hydroalumination step (product of cw-hydroalumination in ether-hexane, transin hexane alone). ... 

In addition to the high regio- and stereospecificity, the catalytic hydroalu-mination has one more advantage over the thermal version of this reaction, namely, there appears the possibility to hydroaluminate at least some functionally substituted olefins, for example, allyl alcohols and ethers (Scheme 5). 

The hydroalumination of terminal alkenes and dienes using BujAl as aluminum source can also be catalyzed by late transition metal complexes such as (PPh3)2PdCl2 [38]. The reactions are carried out at room temperature, the use of dichloromethane as a solvent is crucial because it probably regenerates the catalytically active Pd(II) species by reoxidizing Pd(0) complexes formed in side reactions. Internal C=C bonds are not hydroaluminated under these conditions. Functional groups such as Cl, Br, and PhS in a position remote to the terminal C=C bond are tolerated, however, certain substrates such as 4-bromo-l-butene, 11-iodo-l-undecene, allyl phenyl ether, allyl benzyl ether, and (3 )-l,3-decadiene did not provide the desired hydroa-... 

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