Aluminumoxyhydride:  Improved Synthesis and Application as a Selective Reducing Agent

Abstract

Aluminumoxyhydride (HAlO) has been obtained by the reaction of aluminum hydride with the siloxane (Me2HSi)2O or the stannoxane (Bu3Sn)2O as an amorphous colorless insoluble powder. The highest-purity product resulted from the reaction of H3Al.NMe3 with (Me2HSi)2O. However, HAlO suspensions in tetrahydrofuran (THF) of sufficient quality for synthetic applications can be prepared from commercially available reagents with only minor precautions. A LiAlH4 solution in THF was treated successively with Me3SiCl and (Me2HSi)2O, followed by heating at 60 degrees C for 20 h. The resulting suspensions are 0.4-0.5 M in active hydride content and selectively reduce aldehydes and ketones to the respective alcohols in the presence of any other common nonprotic functional group.

A Direct Stereoselective Preparation of a Fish Pheromone and Application of the Zinc Porphyrin Tweezer Chiroptical Protocol in Its Stereochemical Assignment

“…We aimed to accomplish an equaly stereoselective preparation of the pheromone C20 epimer, and provide a rationale for the stereoselectivity. Although it was evident that aluminumoxyhydride (HAlO) was capable of exhibiting selectivity towards reducing ketones, the presence of the 17‐OH guided such reduction to the C20 over the C3 ketone which was reduced preferentially in the case of progesterone . The HAlO reduction of chlorocortexolone, shown in Scheme , generated the diastereomer of the chloroalcohol that was obtained by NaBH 4 reduction.…”

“…Although it was evident that aluminumoxyhydride (HAlO) was capable of exhibiting selectivity towards reducing ketones, the presence of the 17-OH guided such reduction to the C20 over the C3 ketone which was reduced preferentially in the case of progesterone. 25 The HAlO reduction of chlorocortexolone, shown in Scheme 4, generated the diastereomer of the chloroalcohol that was obtained by NaBH 4 reduction. Further reductive dechlorination was achieved using Ti 3+ on (20S)-3 to afford the C20 epimer (i.e., 20a) of the pheromone, (20S)-1 (three steps from cortexolone, overall 47% yield).…”

Boron, aluminium, gallium, indium and thallium

“…109 The term 'Al 3+ (aq) ' is known to most chemists as an abstraction in most aqueous circumstances, and last year the existence of Al(OH) 3À 6(aq) , as written, was also called into question. 110 The synthesis and applications of the enigmatic 'HAlO' as a mild organic reducing reagent were revisited, 111 and a powder diffraction analysis of CaAlH 5 showed 6-coordination of Al and 9coordination of Ca by H. 112 Inelastic neutron scattering studies during regeneration of Ti-doped NaAlH 4 used as a depleted hydrogen storage material show traces of the volatile higher alanes (AlH 3 ) n (n = 1-4). This is interesting for theoretical reasons, but bodes ill for NaAlH 4 in this application.…”

Lewis base adducts of diisobutylaluminum azide: synthesis and thermal stability

“…There also has been interest in the synthesis of aluminum nitride nanoparticles under mild conditions from molecular precursors, and aluminum azides were among the materials investigated [7,8]. As part of our activities in the development of precursors for the synthesis of nitride [9], oxynitride [10] and oxide [11] materials using routine bench top chemistry, we were interested in the potential of Lewis base adducts of iBu 2 AlN 3 as such a precursor. We hypothesized that the combination of a Lewis base with the known facile β-butene elimination of butylalanes [12] and the lability of the azide substituent could lead to well-defined intermediates such as (L·AlN) n .…”