[92074-24-3]  · C16H37AlSn  · Diethyl(tributylstannyl)aluminum  · (MW 375.15)

(in the presence of Pd(PPh3)4 or CuCN catalyst, is a reagent for synthesis of allylstannanes or vinylstannanes from allylic acetates or alkynes; mediates Reformatsky reactions)

Physical Data: see entries for Diethylaluminum Chloride and Tri-n-butylstannyllithium.

Solubility: sol THF.

Preparative Methods: Et2AlCl (hexane, toluene, or THF solution, 1.0 equiv) is added to n-Bu3SnLi1 (1.0 equiv) derived from n-Butyllithium (3.0 equiv) and anhydrous Tin(II) Chloride (1.0 equiv) in THF at 0 °C. The mixture is stirred for 20 min at 0 °C and the reagent is used directly for further reactions.

Synthesis of Allylstannanes.

Addition of the reagent (1) to allylic acetates or allylic phosphates in the presence of Tetrakis(triphenylphosphine)palladium(0) catalyst affords allylstannanes (eqs 1-3).2,3 The reagent reacts with the less substituted carbon of allylic substrates to form allylstannanes with inversion of configuration. Reaction of the crude products, generated from allylic acetates and (1), with aldehydes catalyzed by Boron Trifluoride Etherate provides homoallylic alcohols.3 The allylic phosphate protocol does not require the extra Lewis acid since the aluminum phosphate serves as a Lewis acid. Alternatively, the presence of an equimolar amount of aldehyde in the reaction system results in the direct formation of homoallylic alcohols (eq 4).2 n-Bu3SnAlEt2 and a Pd0 complex catalyze the intramolecular reductive coupling of allyl acetates with vinyl and aryl bromides (eq 5).4

Stannylalumination of Alkynes.

Reaction of 1-alkynes with (1) in the presence of Copper(I) Cyanide catalyst provides a mixture of (E)-1-tributylstannyl-1-alkenes and their regioisomers in good yield (eq 6).5 The intermediate adducts undergo electrophilic substitution reactions to provide alkenylstannanes. The kinetically favored regioisomer is the 1-stannylalkene, whereas the thermodynamically favored regioisomer is the 2-stannyl derivative.1d,6 This reaction has been applied to functionalized alkynes,7a enynes,7b and allenes.8 Stannylalumination of propargyl or homopropargyl acetals affords vinylstannanes (eq 7).7a Reaction of 5-hydroxy-1,2-pentadiene with (1) gives 5-hydroxy-2-tributylstannyl-1-pentene in the presence of a Co catalyst (eq 8).8

Reformatsky-Type Reaction.9

Treatment of a-bromo carbonyl compounds with the reagent affords aluminum enolates which react with ketones or aldehydes to give b-hydroxy carbonyl compounds in good yields (eq 9). Yields are generally improved by addition of catalytic amounts of Pd(PPh3)4. Treatment of a mixture of 2-bromo-2-methylcyclohexanone and benzaldehyde with the reagent provides the expected b-hydroxy ketone (eq 10). Reaction of methyl g-bromocrotonate gives a-adducts exclusively (eq 11). Bu3PbAlEt2 can be used in the same way.9

1. (a) Tamborski, C.; Ford, F. E.; Soloski, E. J. JOC 1963, 28, 237. (b) Still, W. C. JACS 1977, 99, 4836; JACS 1978, 100, 1481. (c) Kitching, W.; Olszowy, H. A.; Harvey, K. JOC 1982, 47, 1893. (d) Sharma, S.; Oehlschlager, A. C. JOC 1989, 54, 5064.
2. Matsubara, S.; Wakamatsu, K.; Morizawa, Y.; Tsuboniwa, N.; Oshima, K.; Nozaki, H. BCJ 1985, 58, 1196.
3. Trost, B. M.; Herndon, J. W. JACS 1984, 106, 6835.
4. Trost, B. M.; Walchli, R. JACS 1987, 109, 3487.
5. (a) Hibino, J.; Matsubara, S.; Morizawa, Y.; Oshima, K.; Nozaki, H. TL 1984, 25, 2151. (b) Matsubara, S.; Hibino, J.; Morizawa, Y.; Oshima, K.; Nozaki, H. JOM 1985, 285, 163.
6. Sharma, S.; Oehlschlager, A. C. TL 1986, 27, 6161.
7. (a) Beaudet, I.; Parrain, J.-L.; Quintard, J.-P. TL 1991, 32, 6333. (b) Aksela, R.; Oehlschlager, A. C. T 1991, 47, 1163.
8. Singh, S. M.; Oehlshlager [Oehlschlager], A. C. CJC 1991, 69, 1872.
9. (a) Tsuboniwa, N.; Matsubara, S.; Morizawa, Y.; Oshima, K.; Nozaki, H. TL 1984, 25, 2569. (b) Matsubara, S.; Tsuboniwa, N.; Morizawa, Y.; Oshima, K.; Nozaki, H. BCJ 1984, 57, 3242.

Koichiro Oshima

Kyoto University, Japan

Keisuke Suzuki & Tetsuya Nagasawa

Keio University, Yokohama, Japan

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