[56252-56-3] · C23H41AlO · Diisobutylaluminum 2,6-Di-t-butyl-4-methylphenoxide · (MW 360.62)
Solubility: sol toluene, CH2Cl2, hexane.
Form Supplied in: prepared from commercially available reagents and used in situ.
Handling, Storage, and Precautions: the dry solid and solutions are highly flammable; use in a fume hood and protect from oxygen and moisture; solution is stable at 0 °C for several weeks.
One of the most crucial problems in prostaglandin syntheses is the stereoselective reduction of the C15 keto group to the desired (15S)-alcohol. The title compound has been devised as the key reagent for a simple and practical solution to this problem.1 Thus a prostaglandin intermediate is reduced to dihydroxylactone with 92% stereoselectivity (eq 1). In marked contrast, the acetate of the prostaglandin intermediate is reduced without any stereoselectivity, thereby implying the importance of the coordination of the bulky aluminum reagent with the 11-hydroxy group. This reagent has been successfully used for stereoselective reduction of several other prostaglandin intermediates.3
This reducing agent has also been used to reduce an oxodienelactone to a dienol as a key step in the synthesis of the lichen macrolide (+)-aspicilin (eq 2).4 Dihydroxylation of the dienol with Osmium Tetroxide and pyridine followed by Hydrogen Sulfide reduction gave the macrolide in 40% yield.
Reduction of b-keto esters of the chiral a-naphthylborneol is stereoselective because one face of the carbonyl group is blocked by the naphthyl group (eq 3).5
The regioselective reduction of methylenecycloalkane oxides has been studied with a variety of reducing agents. Among these, the title reducing agent and its analogs (diisobutylaluminum 2,4,6-tri-t-butylphenoxide and diisobutylaluminum 4-bromo-2,6-di-t-butylphenoxide) were found to be most satisfactory, giving the desired less-substituted alcohols with good selectivity (eqs 4-6).6
The hydroalumination of alkenes with diisobutylaluminum 2,6-di-t-butyl-4-methylphenoxide is carried out in the presence of Dichlorobis(cyclopentadienyl)zirconium and Diisobutylaluminum Hydride as catalysts.7
The combination of Lithium and diisobutylaluminum 2,6-di-t-butyl-4-methylphenoxide was found to be effective as an initiator for several types of polymerization of methyl methacrylate at elevated temperature.8
Keiji Maruoka & Hisashi Yamamoto
Nagoya University, Japan