Selective Reductions. 27. Reactions of Alkyl Halides with Representative Complex Metal Hydrides and Metal Hydrides. Comparison of Various Hydride Reducing Agents

Article abstract of DOI:10.1021/jo01293a018

The approximate rates and products of the reaction of alkyl halides with representative metal hydrides and complex metal hydrides were examined in order to identify the most promising hydride reducing agents for the hydrogenolysis of alkyl halides.Among the various reagents tested, both lithium triethylborohydride and lithium aluminum hydride exhibit exceptional utility for the dehydrohalogenation reaction.Of the two most promising reagents, lithium triethylborohydride exhibits far greater hydride-transfer ability than does lithium aluminum hydride.Lithium trimethoxyaluminohydride, lithium tri-tert-butoxyaluminohydride, sodium borohydride, and lithium borohydride all react with primary alkyl iodides and bromides at a moderate rate; they are essentially inert toward alkyl chlorides.The reaction of alkyl halides with alane is quite slow; borane and dialkylboranes are essentially inert toward alkyl halides.Thus the study has defined those reagents which are most effective for hydrodehalogenation, as well as those reagents which can be utilized for reduction of functional groups with minimum attack on halogen substituents.