Non-allylic Unsaturated Alcohols

Non-allylic Unsaturated Alcohols. Two reports have described the formation of yS-unsaturated alcohols (homoallylic) from the reaction of allyl silanes and aldehydes or ketones under the influence of a Lewis acid (TiCI or AICI3 ). 

Long-chain alkyneols (33) can be isomerized to the corresponding terminal alkynes (34) with potassium hydride ],3-diaminopropane. It is presumed that the carbanionic intermediates migrate away from the alkoxide site on electrostatic grounds. 

4-Alkoxy-2-butyne-l-ols provide a route to allenyl alcohols by reaction with alkyl lithiums (equation 5). 

Conversion of alcohols to hydrocarbons by generation of carbenium ions, using protic acid, and then transfer of hydrogen from an organosilane to the cation, is unsatisfactory if either the carbenium ion is formed only in low concentrations or if it tends to rearrange or eliminate. These problems are somewhat alleviated by use of BF3 in dichloromethane as the acid e.g. (35) can be converted into (36) without elimination, and simple secondary alcohols are reduced. The hydride 

The alcohol group can be replaced by various nucleophilic entities (such as cyanide, azide, halide, etc.) by reaction with triphenylphosphine, diethyl azodicar boxylate, and either the conjugate acid (HX) or an organic derivative (R X) of the nucleophilic residue (equation 6). The reactions are found to proceed with inversion at the alcohol carbon, and mechanisms for these conversions have been discussed. 

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Trufy exceptional only in non-allylic unsaturated alcohols. Only with naphthols and phenanthrols. 

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