[86014-18-8]  · C12H21AlSi  · Diethyl[dimethyl(phenyl)silyl]aluminum  · (MW 220.36)

(can silylaluminate terminal alkynes;1 can cross couple with alkenyl, allyl, and aryl phosphates;3 can deoxygenate epoxides5)

Physical Data: see Diethylaluminum Chloride and Dimethylphenylsilyllithium.

Solubility: commonly prepared and used in THF-hexane.

Preparative Method: prepared in situ by adding PhMe2SiLi in THF to a hexane solution of Et2AlCl at 0 °C.1

Handling, Storage, and Precautions: see Diethylaluminum Chloride and Dimethylphenylsilyllithium.

Silylalumination of Alkynes and Alkenes.

The reagent adds to 1-alkynes in a regio- and stereoselective (cis addition) manner. Transition metal catalysts alter the regioselectivity (eq 1).1

In addition reactions with allenes, PhMe2SiAlEt2 gives, albeit in low yield, allylsilanes as the major product, while contrasting regioselectivity is observed in the Cu-catalyzed silylmagnesiation by a related silylmagnesium reagent, PhMe2SiMgMe (eq 2).2

Coupling with Allylic and Enol Phosphates.

The reagent converts allylic phosphates into allylsilanes (eq 3).3 Reaction with (2-vinyl-1,1-cyclopropanedicarboxylate gives the 1,7-homoconjugate addition product (eq 4).4 In the presence of a Pd catalyst, PhMe2SiAlEt2 converts enol phosphates into vinylsilanes (eq 5).3 Higher yields are usually obtained with PhMe2SiMgMe.

Deoxygenation of Epoxides.

The reagent deoxygenates epoxides in a stereospecific manner, although the reaction is limited to aryl-substituted epoxides (eq 6). A related reagent, [n-Bu3SnAlMe3]-Li+, has broader applicability.5

1. Hayami, H.; Sato, M.; Kanemoto, S.; Morizawa, Y.; Oshima, K.; Nozaki, H. JACS 1983, 105, 4491.
2. Morizawa, Y.; Oda, H.; Oshima, K.; Nozaki, H. TL 1984, 25, 1163.
3. Okuda, Y.; Sato, M.; Oshima, K.; Nozaki, H. TL 1983, 24, 2015.
4. Fugami, K.; Oshima, K.; Utimoto, K.; Nozaki, H. BCJ 1987, 60, 2509.
5. Matsubara, S.; Nonaka, T.; Okuda, Y.; Kanemoto, S.; Oshima, K.; Nozaki, H. BCJ 1985, 58, 1480.

Keisuke Suzuki & Tetsuya Nagasawa

Keio University, Yokohama, Japan

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