Methylaluminum Bis(2,4,6-tri-t-butylphenoxide)

[65260-46-0]  · C37H61AlO2  · Methylaluminum Bis(2,4,6-tri-t-butylphenoxide)  · (MW 564.96)

(designer Lewis acid for amphiphilic alkylation,1 conjugate addition,2,3 and polymerization4)

Alternate Name: MAT.

Solubility: sol CH2Cl2, toluene.

Form Supplied in: prepared from commercially available reagents.

Preparative Method: prepared by reaction of a 1-2 M hexane solution of Trimethylaluminum with 2 equiv of 2,4,6-tri-t-butylphenol in CH2Cl2 at rt for 1 h.1

Handling, Storage, and Precautions: the dry solid and solutions are highly flammable and must be handled in the absence of oxygen and moisture. The solution should be used as prepared for best results. Use in a fume hood.

Amphiphilic Alkylation.

The exceptionally bulky, oxygenophilic organoaluminum reagent MAT, like Methylaluminum Bis(2,6-di-t-butyl-4-methylphenoxide) (MAD), has been used for stereoselective activation of carbonyl groups. In combination with Grignard reagents or organolithium reagents, amphiphilic alkylation of substituted cyclohexanones affords equatorial alcohols almost exclusively. The equatorial selectivity is generally superior to that observed with MAD/RMgX or MAD/RLi systems (eqs 1 and 2).1

This approach is useful in the stereoselective alkylation of steroidal ketones. Thus the amphiphilic alkylation of cholestan-3-one with MAT/MeLi gives 3a-methylcholestan-3b-ol (equatorial alcohol) almost exclusively with only trace amounts of 3b-methylcholestan-3a-ol (axial alcohol) (eq 3).1

A similar trend is observed in the amphiphilic alkylation of a-substituted aldehydes with MAT/RMgX, giving anti-alcohols preferentially (eq 4).

Conjugate Addition.

The MAT/RLi system can also be used for conjugate addition of organolithiums to a,b-unsaturated ketones. MAT gives comparable results to MAD in 1,4-selectivity (eq 5).2 However, the conjugate reduction of a,b-unsaturated ketones with MAT/Lithium n-Butyl(diisobutyl)aluminum Hydride gives generally less satisfactory results (eq 6).3


The addition polymerization of methyl methacrylate (MMA) via an enolate complex of aluminum tetraphenylporphyrin as the nucleophilic growing species has been effected in the presence of MAT and the related Lewis acid MAD.4

1. (a) Maruoka, K.; Itoh, T.; Yamamoto, H. JACS 1985, 107, 4573. (b) Maruoka, K.; Itoh, T.; Sakurai, M.; Nonoshita, K.; Yamamoto, H. JACS 1988, 110, 3588.
2. Maruoka, K.; Nonoshita, K.; Yamamoto, H. TL 1987, 28, 5723.
3. Nonoshita, K.; Maruoka, K.; Yamamoto, H. BCJ 1988, 61, 2241.
4. Kuroki, M.; Watanabe, T.; Aida, T.; Inoue, S. JACS 1991, 113, 5903.

Keiji Maruoka & Hisashi Yamamoto

Nagoya University, Japan

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