Diisobutylaluminum phenoxide

ALDOL CONDENSATION Cesium fluoride. Dialkylboron trifluoromethane-sulfonates. Dichlorobis(cyclopentadi-enyl)zirconium. Diisobutylaluminum phenoxide. 2,5-Dimethylphenylpropi-onate. DimetIiyl(phenyllhio)aIuminum. Lithium iodide. Triethylborane. Tri-methylsilyl trifluoromethanesulfonate. Triphenyltin chloride. TrisCdiethyI-amino)sulfonium difluorotrimethyl-siliconate. 

Diisobutylaluminum phenoxide, [(CH3)2CHCH2]2A10C6Hs (1). Mol. wt. 234.30. The reagent is prepared in situ from diisobutylaluminum hydride and phenol inTHF. 

Diisobutylaluminum hydride, 149 Diisobutylaluminum phenoxide, 150 Diisopropylethylamine, 151 Diketene-Iodotrimethylsilane, 151... 

Tsuji and coworkers have developed diisobutylaluminum phenoxide-pyridine as an effective aldol condensation catalyst and applied it to the macrocyclization of 2,15-hexadecanedione (equation 132). Addition of the diketone at high dilution to a solution of the catalyst in hexane provides a mixture of cis and trans isomers of the and A enones. Catalytic hydrogenation of the mixture affords ( )-muscone. The authors explain the regioselectivity of the process by assuming that the aluminum phenoxide functions as a Lewis acid, coordinating to the carbonyl group. Pyridine functions as a base to remove a proton from the less hindered methyl group. 

Particularly high sclcctivities are obtained with diisobutylaluminum 2,6-di-/m-buty 1-4-methyl phenoxide (16, see Table 1, p4101). Thus, the prostaglandin PGE2 methyl ester is reduced to the 8,9-cis-prostaglandin PGF2a methyl ester in 95% yield and 100% ee132. 

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