Org. Synth. 1990, 68, 104
DOI: 10.15227/orgsyn.068.0104
ALLYLTRIBUTYLTIN
[Stannane, tributyl-2-propenyl-]
Submitted by Noreen G. Halligan and Larry C. Blaszczak
1.
Checked by Christophe M. G. Philippo and Leo A. Paquette.
1. Procedure
Magnesium turnings (72.6 g, 3 g-atom) and 1000 mL of anhydrous ethyl ether are placed under argon in a dry, 3-L, three-necked flask equipped with a mechanical stirrer, a 500-mL pressure-equalizing dropping funnel, a Claisen adapter, a thermometer, an ice–water-cooled condenser, and an argon inlet. The dropping funnel is charged with allyl bromide (158 mL, 1.8 mol) (Note 1) in 150 mL of anhydrous ether. Stirring is initiated and a 10–12-mL portion of the allyl bromide solution is run into the reaction flask. The resulting mixture is treated with a few crystals of iodine, whereupon a rise in temperature and clouding of the reaction mixture occurs, indicating that the reaction has begun (Note 2). The remainder of the allyl bromide solution is added dropwise with continued stirring at such a rate as to maintain a gentle reflux. The addition requires approximately 1.5 hr. The mixture is then refluxed for an additional 1.5 hr.
While the Grignard solution is being refluxed, the dropping funnel is charged with bis(tributyltin) oxide (371 g, 0.62 mol) (Note 1) in 150 mL of anhydrous ether. After the reflux, heating is stopped and the bis(tributyltin) oxide solution is added at such a rate as to maintain a reaction temperature of 36–38°C. The addition requires approximately 1 hr. After the addition is complete, the reaction mixture is refluxed for 1.5 hr and then stirred overnight at room temperature.
The reaction mixture is cooled in a
water–ice bath, and a saturated aqueous
ammonium chloride solution is added at such a rate as to maintain the temperature below 35°C.
Ammonium chloride solution is added in portions until addition produces no further exothermic reaction
(Note 3). The supernatant solution is decanted through glass wool onto 400 g of ice in a
4-L separatory funnel. The residual solids are washed with three portions of
hexane, approximately 1000 mL total, and the washes are decanted into the separatory funnel. After the phases are separated, the aqueous phase is washed with an additional
500-mL portion of hexane. The combined organic extracts are washed with
500 mL of saturated ammonium chloride, and then with
500 mL of brine. The organic layer is dried over anhydrous
magnesium sulfate and filtered. Most of the solvent is removed by a
rotary evaporator and the residual oil is distilled at reduced pressure using an
ice–water-cooled fraction cutting head. After a small forerun, approximately
390–392 g (
94% of theory) is collected as a colorless oil, bp
116°C at 1.6 mm (lit. 155°C at 17 mm).
2
2. Notes
1.
Allyl bromide and bis(tributyltin) oxide were obtained from Aldrich Chemical Company, Inc.2.
Initiation of the reaction required about 1 min of sonication in an ordinary laboratory cleaner.
3.
Approximately
190 mL of saturated aqueous ammonium chloride is required.
3. Discussion
Within the last decade, organotin chemistry has become a major source of new and highly selective reagents for effecting carbon–carbon bond formation. Transmetalation, nucleophilic substitution, stereoselective carbonyl addition, and transition-metal- or radical-mediated substitution reactions have all been accomplished using allyltributyltin. Because of the broad range of selective reactivities under which the synthetically versatile allyl group may be transferred to a highly functionalized substrate, allyltin compounds have secured a position on the modern chemist's list of indispensable reagents.
Transmetalation of
allyltributyltin with organolithium species
3 has been used for the generation of
allyllithium solutions free of the coupling by-products that often result from reduction of allylic halides with
lithium metal. These solutions may then be used directly for the preparation of Gilman reagents and other reactive modifications of the parent
allyllithium.
The use of
allyltributyltin in combination with a Lewis acid has been used to effect both nucleophilic substitution
4 and stereoselective carbonyl addition
5 reactions. These reactions occur with a high degree of selectivity because of the reagent's nucleophilic, completely nonbasic character in the presence of a sufficiently reactive carbon electrophile.
Allyltin reagents appear to be more useful than the corresponding allylsilanes for these purposes.
By far the most generally useful synthetic application of
allyltributyltin is in the complementary set of transition-metal- and radical-mediated substitution reactions. When the halide substrates are benzylic, allylic, aromatic, or acyl, transition-metal catalysis
6 is usually the method of choice for allyl transfer from
tin to
carbon. When the halide (or halide equivalent) substrate is aliphatic or alicyclic, radical chain conditions
7 are appropriate, as β-hydrogen elimination is generally not a problem in these cases.
Allyltriorganotin compounds have been prepared by the reaction of allyl Grignard
8 or
allyllithium reagents with triorganotin halides as well as by the procedure described. This procedure is an adaptation of that used by Rosenberg
9 for the preparation of vinyltrialkyltin compounds. Allyltriorganotin compounds in which the allyl group bears complex substituents can be prepared by desulfurization of allylic sulfides, sulfoxides, or sulfones with triorganotin hydrides.
10This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
brine
ether,
ethyl ether (60-29-7)
ammonium chloride (12125-02-9)
magnesium turnings (7439-95-4)
Allyl bromide (106-95-6)
tin (7440-31-5)
iodine (7553-56-2)
carbon (7782-42-5)
lithium (7439-93-2)
magnesium sulfate (7487-88-9)
hexane (110-54-3)
allyltin
Allyllithium
Allyltributyltin,
Stannane, tributyl-2-propenyl- (24850-33-7)
bis(tributyltin) oxide (56-35-9)
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