[1983-10-4]  · C12H27FSn  · Tri-n-butylfluorostannane  · (MW 309.10)

(selective silyl/stannyl exchange of enol silyl ethers;1 fluoride source2)

Alternate Name: fluorotributyltin.

Form Supplied in: white solid; commercially available. Drying: this chemical seems not to be hygroscopic. Drying may be done in vacuo (ca. 0.1 mmHg) for 6 h at 100 °C (bath temperature).1,2

Handling, Storage, and Precautions: this reagent is toxic (acute oral LD50 (rats): 200 mg kg-1)3 and should be handled with care. Use in a fume hood.

Arylation, Alkenylation, and Aldol Reactions of Enol Silyl Ethers via Tin Enolates and/or a-Stannyl Ketones.

This reagent reacts with enol silyl ethers of methyl ketones to generate tin enolates and/or a-stannyl ketones in the presence of a palladium catalyst (eq 1).1 The palladium may work as a mild Lewis acid to activate the enol silyl ether. The resulting stannyl enolate derivatives can be trapped in situ with aryl or alkenyl bromides in the presence of the palladium catalyst to give a-aryl or a-alkenyl ketones in a regioselective manner, as shown in eqs 2 and 3.1,4 The reaction with aldehydes affords aldols (eq 4).5 The latter example demonstrates site selectivity for silyl/stannyl exchange at the less hindered silyl enol ether.

Selective Desilylation of Bis-silyl Enol Ethers.

As described above, the silyl/stannyl exchange with Bu3SnF/Pd catalyst is greatly influenced by the steric hindrance around the enol silyl ether moiety. Thus the highly selective desilylation of bis-silyl enol ether derivatives of diketones is also possible, (probably via intermediacy of a tin derivative) (eqs 5 and 6).6,7 This method for the differentiation of two ketone groups should complement existing methods for selective monosilylation of diketones.

Additive to Facilitate Reactions.

Some other uses of Bu3SnF (and also Me3SnF or Ph3SnF) to promote reactions have been documented and are illustrated in eqs 7 and 8.2,8,9 In the latter case, it is proposed that Bu3SnF serves as a mild source of fluoride ion.

1. Kuwajima, I.; Urabe, H. JACS 1982, 104, 6831.
2. Kobayashi, S.; Uchiro, H.; Fujishita, Y.; Shiina, I.; Mukaiyama, T. JACS 1991, 113, 4247.
3. Sheldon, A. W. J. Paint Technol. 1975, 47 (600), 54.
4. Urabe, H. Dissertation, Tokyo Institute of Technology, 1985.
5. Urabe, H.; Kuwajima, I. TL 1983, 24, 5001.
6. Urabe, H.; Takano, Y.; Kuwajima, I. JACS 1983, 105, 5703.
7. Paquette, L. A.; Wiedeman, P. E.; Bulman-Page, P. C. TL 1985, 26, 1611.
8. Mori, I.; Oshima, K.; Nozaki, H. TL 1984, 25, 4683.
9. Mukaiyama, T.; Shiina, I.; Kobayashi, S. CL 1991, 1901, and references cited therein.

Hirokazu Urabe

Tokyo Institute of Technology, Yokohama, Japan

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