Allyl Iodide

[556-56-9]  · C3H5I  · Allyl Iodide  · (MW 167.99)

(allylating agent which attacks C, O, N, S, Se, Te nucleophiles; organometallic derivatives provide homoallyl alcohols; expected electrophilic addition reactions)

Physical Data: mp -99.3 °C; bp 103.1 °C; d 1.848 g cm-3.

Solubility: miscible with organic liquids.

Form Supplied in: yellow liquid, discoloring on heating, standing, and exposure to air.

Purification: wash with aq Na2SO3 to remove iodine, dry (MgSO4), and distil under reduced pressure (~20 mmHg).1 Protect from light.

Handling, Storage, and Precautions: store in a light-tight vessel at 0 °C. Volatile, flammable, toxic, irritant alkylating agent. Light sensitive.

Allyl iodide (RI) is usually prepared by ion exchange (NaI-Me2CO) of allyl chloride or from allyl alcohol using reagents such as Diphosphorus Tetraiodide.2 The weak C-I bond facilitates both heterolytic and homolytic displacement reactions (eq 1). Thus Barbier-Grignard type processes may also be achieved using Sb,3 Ga,4 In,5 Bi,6,7 or BiCl3-metal combinations.7 Cerium powder with allyl iodide provides organocerium species which with ketones give a mixture of secondary alcohol, pinacol dimerization product, and Barbier-Grignard product. With aldehydes the major product is the pinacol product.8 In contrast, allyl iodide with Al and Ce/Hg in THF at 0 °C under N2 for 5 h gives excellent yields of the tertiary alcohol with a range of ketones.9 Other such reductive allylation methods use CrCl3 + 0.5 mol LiAlH4, which seems to provide CrII which with RI or RBr in THF gives allyl CrII species. These may lead to biallyl formation or to the Barbier-Grignard reaction with ketones and aldehydes, but not with nitriles or carboxylates (eq 2).

Allyl chloride behaves similarly, but in DMF and not THF.10 Samarium(II) Iodide (THF, N2, rt) encourages the reaction of aldehydes with RI to give secondary alcohols (eq 3);11 so also does SnII, both as the carboxylate12 and as the halide,12,13 especially the fluoride.13 Acyl chlorides similarly react with RI in the presence of SmI2.14 The reduction may also be brought about electrochemically; RI (and other allyl halides) provides Me2C(R)OH with Me2CO (0.5 M Bu4NClO4 in HMPA)15a and adds across &cvbond;C=C&dvbond; in diethyl fumarate (Et4N+C7H7SO3- in DMF) to give the 2-allylsuccinate system (eq 4).15b

The analogous photochemical addition of RI to benzaldehydes is promoted by lanthanum iodides.16

Carbanions (e.g. (1), generated from NaH in DMF) allylate without rearrangement (eq 5),17 while Na salts of penta-2,4-dione enolates allylate exclusively at C-3 (DMSO, RI)18 and lithio derivatives of silylated acrylate esters (MeLi) show similar specificity of allylation.19 The stereoselective attack of chiral malonic half-esters,20 dimethyl tartrate stannylene acetal,21 chiral imide enolates,22 and chiral nitro keto imines23 proceeds well and with high diastereoselectivity. Simple exchange reactions provide radiolabeled products; Ag18F and Ag83Br react with RI in the gas phase to provide high-level R18F and R83Br.24 Iodolactams also undergo stereospecific N-allylation.25 Diphenyl Diselenide provides PhSeR in the presence of SmI2.26

Related Reagents.

Allyl Bromide; Allyl Chloride.

1. Sibbert, D. J.; Noyes, R. M. JACS 1953, 75, 761.
2. Lasne, M. C.; Cairon, P.; Villemin, D. SC 1990, 20, 41.
3. Butsugan, Y.; Ito, H.; Araki, S. TL 1987, 28, 3707.
4. Araki, S.; Ito, H.; Butsugan, Y. Appl. Organomet. Chem. 1988, 2, 475 (CA 1989, 110, 172 338x).
5. Araki, S.; Ito, H.; Butsugan, Y. JOC 1988, 53, 1831.
6. Wada, M.; Ohki, H.; Akiba, S. TL 1986, 27, 4771.
7. Wada, M.; Ohki, H.; Akiba, S. BCJ 1990, 63, 1738.
8. Fukuzawa, S.; Fujinami, T.; Sakai, S. JOM 1986, 299, 179.
9. Imamoto, T.; Hatanaka, Y.; Tawarayama, Y.; Yokoyamo, M. TL 1981, 22, 4987.
10. Hiyama, T.; Okude, Y.; Kimura, K.; Nozaki, H. BCJ 1982, 55, 561.
11. Souppe, J.; Namy., J. L.; Kagan, H. B. TL 1982, 23, 3497.
12. Mitsui Petrochemical Industries, Ltd., Jpn. Patent 57 102 828, 1982 (CA 1982, 97, 162 350u).
13. Borch, R. F.; Canute, G. W. JMC 1991, 34, 3044.
14. Araki, S.; Hatano, M.; Ito, H.; Butsugan, Y. Appl. Organomet. Chem. 1988, 2, 79 (CA 1988 109, 109 822q).
15. (a) Satoh, S.; Suginome, H.; Tokuda, M. BCJ 1983, 56, 1791. (b) Satoh, S.; Suginome, H.; Tokuda, M. BCJ 1981, 54, 3456.
16. Kondo, T.; Akazome, M.; Watanabe, Y. CC 1991, 757.
17. Chou, T.-S.; Tso, H.-H.; Chang, L.-J. JCS(P1) 1985, 515.
18. Fischer, G. W. JPR 1985, 327, 983.
19. Piers, E.; Skerlj, R. T. JOC 1987, 52, 4421.
20. (a) Ihara, M.; Takahashi, M.; Niitsuma, H.; Taniguchi, N.; Yasui, K; Fukumoto, K. JOC 1989, 54, 5413 (b) Ihara, M.; Takahashi, M.; Taniguchi, N.; Yasui, K.; Niitsuma, H.; Fukumoto, K. JCS(P1) 1991, 525.
21. Nagashima, N.; Ohno, M. CL 1987, 141.
22. Evans, D. A.; Ennis, M. D.; Mathre, D. J. JACS 1982, 104, 1737.
23. Denmark, S. E.; Ares, J. J. JACS 1988, 110, 4432.
24. (a) Yagi, M.; Murano, Y.; Izawa, G. Int. J. Appl. Radiat. Isot. 1982, 33, 1335. (b) Murano, M.; Izawa, K.; Yagi, M. Kakuriken Kenkyu Hokoku (Tohoku Daigaku) 1982, 15, 114 (CA 1983, 98, 34 183a).
25. Knapp. S.; Gibson, F. S.; Choe, Y. N. TL 1990, 31, 5397.
26. Fukuzawa, S.; Niimoto, Y.; Fujinami, T.; Sakai, S. HC 1990, 1, 491.

Roger Bolton

University of Surrey, Guildford, UK

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