REACTION OF SODIUM TRIS(DIETHYLAMINO)ALUMINUM HYDRIDE WITH SELECTED ORGANIC-COMPOUNDS CONTAINING REPRESENTATIVE FUNCTIONAL-GROUPS

The approximate rates and stoichiometry of the reaction of excess sodi um tris(diethylamino)aluminum hydride (STDEA) with selected organic co mpounds containing representative functional groups under standardized conditions (tetrahydrofuran, 0 degrees C) were studied in order to ch aracterize the reducing characteristics of the reagent for selective r eductions. The reducing ability of STDEA was also compared with those of the parent sodium aluminum hydride (SAH) and lithium tris(diethylam ino)aluminum hydride (LTDEA). The reagent appears to be milder than LT DEA. Nevertheless, the reducing action of STDEA is very similar to tha t observed previously for LTDEA, as is the case of the corresponding p arent sodium and lithium aluminum hydrides. STDEA shows a unique reduc ing characteristics. Thus, benzyl alcohol, phenol and 1-hexanol evolve d hydrogen slowly, whereas 5-hexanol and 3-ethyl-3-pentanol, secondary and tertiary alcohols, were essentially inert to STDEA. Primary amine , such as n-hexylamine, evolved only 1 equivalent of hydrogen slowly. On the other hand, thiols examined were absolutely stable. STDEA reduc ed aldehydes and ketones rapidly to the corresponding alcohols. The st ereoselectivity in the reduction of cyclic ketones by STDEA was simila r to that by LTDEA. Quinones, such as p-benzoquinone and anthraquinone , were reduced to the corresponding 1,4-dihydroxycyclohexadienes witho ut evolution of hydrogen. Carboxylic acids and anhydrides were reduced very slowly, whereas acid chlorides were reduced to the corresponding alcohols readily. Esters and epoxides were also reduced readily. Prim ary carboxamides consumed hydrides for reduction slowly with concurren t hydrogen evolution, but tertiary amides were readily reduced to the corresponding tertiary amines. The rate Df reduction of aromatic nitri les was much faster than that of aliphatic nitriles. Nitrogen compound s examined were also reduced slowly. Finally, disulfide, sulfoxide, su lfone, and cyclohexyl tosylate were readily reduced without evolution of hydrogen. In addition to that, the reagent appears to be an excelle nt partial reducing agent: llike LTDEA, STDEA converted ester and prim ary carboxamides to the corresponding aldehydes in good yields. Furthe rmore, the reagent reduced aromatic nitriles to the corresponding aldo hydes chemoselectively in the presence of aliphatic nitriles. Conseque ntly, STDEA can replace LTDEA effectively, with a higher selectivity, in most organic reductions.