Crotyltrichlorosilane1

(Z)

[49749-84-0]  · C4H7Cl3Si  · Crotyltrichlorosilane  · (MW 189.54) (E)

[52885-13-9]

(regio- and stereospecific crotylation of aldehydes through pentacoordinate silicate intermediates2)

Physical Data: bp (Z) 140-142 °C, (E) 142-144 °C.

Solubility: sol hydrocarbons, halogenated hydrocarbons, and ethers. Protic solvents, especially alcohols, should not be used due to chemical reactivity.

Analysis of Reagent Purity: 1H NMR.

Preparative Methods: the reaction of isomerically pure (E) Crotyl Chloride and Trichlorosilane in the presence of Copper(I) Chloride and Triethylamine in ether at rt produces (E)-crotyltrichlorosilane in 76% yield with isomeric purity higher than 99%.3 Purification of (E)-crotyl alcohol4 is critical for preparation of the isomerically pure compound.2 The Tetrakis(triphenylphosphine)palladium(0)-catalyzed hydrosilation of 1,3-Butadiene5 with trichlorosilane at -78 °C gives (Z)-crotyltrichlorosilane in 84% yield with isomeric purity of 99.1%.2 The reaction temperature is of key importance for the preparation of stereohomogeneous crotyltrichlorosilane. Higher temperatures give unsatisfactory results.2

Purification: by distillation.

Handling, Storage, and Precautions: the reagents can be stored in a glass bottle but should be rigorously protected from moisture. The reagents should be handled in a well-ventilated hood and contact with the skin and eyes should be avoided.

Allylation Through Pentacoordinate Silicate Intermediates.

The reaction of crotyltrichlorosilane with dihydroxy compounds such as catechol gives pentacoordinate crotylsilicon bis(catecholate). The catecholate, isolated and purified, reacts with benzaldehyde without activators to afford homoallyl alcohols with complete regioselectivity. The reaction can be performed without isolation of the intermediate catecholate (eq 1).2,6

Friedel-Crafts Reaction.

Like other allyltrichlorosilanes, crotyltrichlorosilane undergoes Friedel-Crafts reaction with benzene.7 The reaction of crotyltrichlorosilane with benzene in the presence of Aluminum Chloride gives a mixture of two positional isomers, (2- and (3-phenylbutyl)trichlorosilane (eq 2). The former is the initial product, but thermally isomerizes to the latter. The equilibrium mixture of the 2-phenyl and 3-phenyl isomers is 9:91.

Conversion to Crotyltrifluorosilane.

Crotyltrichlorosilanes are readily converted to the corresponding crotyltrifluorosilanes, which are useful for regio- and stereospecific crotylation.2

Related Reagents.

B-Allyldiisocaranylborane; B-Crotyldiisopinocampheylborane; Crotyldimethoxyborane; Crotyltrifluorosilane; Diisopropyl 2-Allyl-1,3,2-dioxaborolane-4,5-dicarboxylate; Triethylammonium Bis(catecholato)allylsiliconate.


1. (a) Sakurai, H. SL 1989, 1. (b) Sakurai, H. Selectivities in Lewis Acid Promoted Reactions, Schinzer, D., Ed.; NATO ASI Series, 1988; Chapter 11. (c) Sakurai, H. Chemistry and Technology of Silicon and Tin; Kumar Das, V. G.; Weng, N. S.; Gielen, M., Eds.; Oxford: OUP, 1992; Chapter 3.
2. Kira, M.; Sato, K.; Sakurai, H. JACS 1988, 110, 4599.
3. (a) Furuya, N.; Sukawa, T. JOM 1975, 96, C1. (b) Kira, M.; Hino, T.; Sakurai, H. TL 1989, 30, 1099.
4. Young, W. G.; Andrews, L. I. JACS 1944, 66, 421.
5. Tsuji, J.; Hara, M.; Ohno, K. T 1974, 30, 2143.
6. Hosomi, A.; Kohra, S.; Ogata, K.; Yanagi, T.; Tominaga, Y. JOC 1990, 455, 2415.
7. Tamao, K.; Yoshida, J.; Akita, M.; Sugihara, Y.; Iwahara, T.; Kumada, M. BCJ 1982, 55, 255.

Hideki Sakurai

Tohoku University, Sendai, Japan



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