[17314-40-8]  · C8H18Sn  · Trimethyl(3-methyl-2-butenyl)stannane  · (MW 232.97)

(g-regioselective prenylation of aldehydes and ketones; a-regioselective prenylation of quinones; palladium-catalyzed regioselective coupling with electrophiles)

Alternate Name: prenyl trimethylstannane.

Physical Data: bp 56-57 °C/15 mmHg.

Solubility: sol most organic solvents.

Preparative Methods: by the reaction of Trimethylstannyllithium with 3-methyl-2-butenyl bromide.1 Alternatively, it is prepared from 3-methyl-2-butenylmagnesium bromide and Chlorotrimethylstannane.2

Handling, Storage, and Precautions: is air- and moisture-stable. However, it should be kept under N2 in a refrigerator for prolonged storage.

Prenylation of Aldehydes and Ketones.

Prenyltrimethylstannane reacts with aldehydes and ketones in the presence of Boron Trifluoride Etherate at low temperatures to give the corresponding homoallyl alcohols in high yield (eq 1).3 The BF3.OEt2-mediated reaction of the prenyltin reagent with acenaphthenequinone affords the g-adduct exclusively (eq 2), whereas the photochemical reaction in MeCN produces a 68:32 mixture of the a- and g-adducts in 87% yield.4 An a-regioselective prenylation occurs in the photochemical reaction of benzil with the prenyltin reagent (eq 3).4

Prenylation of Quinones.

Lewis acid (BF3) mediated allylation of a,b-unsaturated ketones with allylstannanes affords only 1,4-addition products.3 However, the BF3.OEt2-mediated reaction of o-quinones, such as 9,10-phenanthrenequinone and acenaphthenequinone, with allylstannanes gives exclusively 1,2-addition products (quinols) (eq 2). Similarly, p-quinones, such as 2,6-dimethoxybenzoquinone and 2-methoxy-1,4-naphthoquinone, afford only 1,2-adducts (quinols).1 On the other hand, the allylation of simple benzoquinone with allyltrialkylstannane produces allylhydroquinone (1,4-adduct) in high yield, which is converted to allylbenzoquinone upon oxidation with Silver(I) Oxide or Iron(III) Chloride.1 The reaction of benzoquinone with 3-methyl-2-butenyltributylstannane gives the a-1,4 adduct (eq 4).1 Similarly, a-1,4-addition products are obtained from 2,3-dimethyl-, 2,5-dimethyl-, 2,6-dimethyl, and trimethylbenzoquinone, 2-methyl-1,4-naphthoquinone, and 2,3-dimethoxy-5-methylbenzoquinone. 2-Acetyl-1,4-naphthoquinone, in which the C-3 position is sterically crowded, gives a 70:30 mixture of g-1,4 and a-1,4 adducts in 80% yield upon treatment with the title reagent.5

Substitution with Allylic Substrates and Vinyl Epoxides.

The allylic-allylic coupling of trimethyl(3-methyl-2-butenyl)stannane with allylic acetates promoted by bis(diethylaluminum) sulfate affords, in general, a mixture of the g-a and g-g products (eq 5).2 It should be noted that the coupling takes place at the g-position of the tin reagent. The coupling with allylic ethers and halides results in lower yields. The coupling between allylic stannanes and allylic halides takes place at rt in CH2Cl2 at high pressures (~10 kbar) to give head-to-tail coupling products (g-a adducts), with allylic rearrangement of the tin reagents, in high yields.6 The BF3.OEt2-mediated reaction of the tin reagent with vinyl epoxides normally gives 1,2-addition products, with 1,3-allylic rearrangement of the allylstannane, in high yields (eq 6).7

Palladium-Catalyzed Coupling.

The palladium-catalyzed coupling reaction of organotin reagents with organic electrophiles, such as acid halides, allylic halides, aromatic and benzylic halides, vinyl iodides and triflates, and a-halo esters, takes place under mild conditions in high yields.8 A wide variety of organic halides and organotin compounds can be coupled either directly or in the presence of carbon monoxide (to yield a ketone R1COR2). Moreover, a wide variety of functional groups (e.g. CO2R, CN, OH, and even CHO) are tolerated on either reaction partner. In addition, the coupling of allylic components (i.e. allylstannane or allyl halide) is regioselective and occurs stereospecifically with inversion of configuration at sp3 carbon centers bound to tin and/or halogen. Usually retention of configuration of the double bond is observed, regardless of which reactant contains the double bond. The palladium-catalyzed direct coupling of prenyltributyltin with allyl bromide occurs with preferential allylic rearrangement of the tin reagent (eq 7).9 However, no allylic rearrangement takes place in coupling reactions of the prenyl bromide partner (eq 8). In contrast to direct coupling, carbonylative coupling occurs without allylic rearrangement of the allylic tins and allylic halides, and CO insertion takes place exclusively at the least hindered site (eq 9).10

1. Naruta, Y. JACS 1980, 102, 3774.
2. Hosomi, A.; Imai, T.; Endo, M.; Sakurai, H. JOM 1985, 285, 95.
3. (a) Hosomi, A.; Iguchi, H.; Endo, M.; Sakurai, H. CL 1979, 977. (b) Naruta, Y.; Ushida, S.; Maruyama, K. CL 1979, 919.
4. Takuwa, A.; Nishigaichi, Y.; Yamashita, K.; Iwamoto, H. CL 1990, 639.
5. Uno, H. JOC 1986, 51, 350.
6. Yamamoto, Y.; Maruyama, K.; Matsumoto, K. CC 1984, 548.
7. Naruta, Y.; Maruyama, K. CL 1987, 963.
8. Stille, J. K. AG(E) 1986, 25, 508.
9. (a) Kosugi, M.; Migita, T. J. Syn. Org. Chem. Jpn. 1980, 38, 1142. (b) Godschalx, J. P.; Stille, J. K. TL 1980, 21, 2599.
10. Merrifield, J. H.; Godschalx, J. P.; Stille, J. K. OM 1984, 3, 1108.

Yoshinori Yamamoto

Tohoku University, Sendai, Japan

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