Triethylammonium Bis(catecholato)allylsiliconate1

(1; R1 = R2 = H; n = 1)

[114612-18-9]  · C21H29NO4Si  · Triethylammonium Bis(catecholato)allylsiliconate  · (MW 387.60) (2; R1 = R2 = Me; n = 1)

[114571-77-6]  · C23H33NO4Si  · Triethylammonium Bis(catecholato)prenylsiliconate  · (MW 415.66) (E)-(3; R1 = Me, R2 = H; n = 1)

[125715-28-8]  · C22H31NO4Si  · Triethylammonium Bis(catecholato)crotylsiliconate  · (MW 401.63) (Z)-(3; R1 = Me, R2 = H; n = 1)

[125715-32-4] (4; R1 = R2 = H; n = 0)

[123806-99-5]  · C20H27NO4Si  · Triethylammonium Bis(catecholato)vinylsiliconate  · (MW 373.57) (5; R1 = Bu, R2 = H; n = 0)

[123723-08-0]  · C24H35NO4Si  · Triethylammonium Bis(catecholato)(1-hexenyl)siliconate  · (MW 429.69)

(regiospecific and diastereoselective allylation of aldehydes;2 cross-coupling reaction with organic halides and triflates catalyzed by a palladium complex3)

Physical Data: (1) mp 120 °C (dec); (2) mp 94 °C (dec); (3) (E:Z = 90:10), mp 124 °C (dec).

Analysis of Reagent Purity: tetramethylsilane was used as an internal standard for 1H, 13C, and 29Si NMR: (1) 1H NMR (CDCl3) d 1.25 (t, J = 7 Hz, 9H), 1.69 (d, J = 8 Hz, 2H), 3.17 (q, J = 7 Hz, 6H), 4.50-4.76 (m, 2H), 5.52-5.91 (m, 1H), 6.67 (m, 8H), 7.69 (bs, 1H); 13C NMR (CDCl3) d 8.72 (q), 24.60 (t), 46.43 (t), 110.69 (d), 111.56 (t), 118.77 (d), 136.91 (d), 149.48 (s); 29Si NMR (CDCl3) d -78.40. (4) 1H NMR (CDCl3) d 1.24 (t, J = 7 Hz, 9H), 3.17 (q, J = 7 Hz, 6H), 5.59-6.24 (m, 3H), 6.67 (m, 8H), 7.48 (bs, 1H); 13C NMR (CDCl3) d 8.75 (q), 28.88 (t), 110.77 (d), 118.84 (d), 132.96 (t), 137.78 (d), 149.40 (s); 29Si NMR (CDCl3) d -87.45.

Handling, Storage, and Precautions: these reagents should be stored under an inert atmosphere in a dry box.

Allylation of Aldehydes.

Triethylammonium bis(catecholato)allylsiliconates (1-3) are readily prepared from allyltrimethoxysilanes, two equivalents of Catechol, and Triethylamine.4 Synthetic routes to other pentacoordinate allylsiliconates have been described.5,6 Allylsiliconate (1) reacts with aliphatic and aromatic aldehydes without Lewis acid7 or fluoride ion8 catalysts to give the corresponding homoallyl alcohols in good yield (eq 1). However, these reagents are not effective for the allylation of ketones. The aldehyde allylation occurs even in the presence of the nitro and cyano groups. The reaction of a,b-unsaturated aldehydes proceeds exclusively by 1,2-addition.

The allylation of aldehydes is completely regiospecific and carbon-carbon bond formation occurs at the g-position of the allyl group of prenyl- (2) and crotylsiliconate (3). In addition, high anti diastereoselectivity is observed in the reaction of (3) (Table 1).

Allylsiliconates can be generated in situ from trimethoxyallylsilane in the presence of aldehydes (eq 2). Enantioselective allylation of an aldehyde by optically active allyltriethoxysilanes, catechol, and triethylamine reveals that the reaction mechanism involves a cyclic transition state (eq 3), in sharp contrast to the results for the tetracoordinate allylsilane in which the acyclic SE pathway has been demonstrated.9

Cross-Coupling Reactions.

Triethylammonium bis(catecholato)vinylsiliconate (4), derived from vinyltrimethoxysilane, undergoes palladium-catalyzed cross-coupling reactions with aryl halides or triflates (eq 4). Tetrakis(triphenylphosphine)palladium(0), Bis(benzonitrile)dichloropalladium(II), and Bis(allyl)di-m-chlorodipalladium are effective catalysts for this reaction, but Triethyl Phosphite or Lithium Chloride additives are required. The reaction with (E)-1-halo-1-alkenes proceeds with retention of stereochemistry to provide 1,3-dienes (eq 5).

(E)-1-Hexenylsiliconate (5) can be used for the reaction with aryl halides and triflates, although the products are not 1,2-disubstituted ethylenes, normal coupling products, but 1,1-disubstituted ethylenes (eq 6).10


1. Hosomi, A. In Reviews on Heteroatom Chemistry; Oae, S., Ed.; MYU: Tokyo, 1992; Vol. 7, pp 214-228.
2. (a) Hosomi, A.; Kohra, S.; Tominaga, Y. CPB 1987, 35, 2155. (b) Hosomi, A.; Kohra, S.; Tominaga, Y. CC 1987, 1517. (c) Hosomi, A.; Kohra, S.; Ogata, K.; Yanagi, T.; Tominaga, Y. JOC 1990, 55, 2415. (d) Hayashi, T.; Matsumoto, Y.; Kiyoi, T.; Ito, Y.; Kohra, S.; Tominaga, Y.; Hosomi, A. TL 1988, 29, 5667.
3. Hosomi, A.; Kohra, S.; Tominaga, Y. CPB 1988, 36, 4622.
4. Frye, C. L. JACS 1964, 86, 3170.
5. Cerveau, G.; Chuit, C.; Corriu, R. J. P.; Reye, C. JOM 1987, 328, C17.
6. Kira, M.; Sato, K.; Sakurai, H. JACS 1988, 110, 4599.
7. Hosomi, A.; Sakurai, H. TL 1976, 1295.
8. (a) Hosomi, A.; Shirahata, A.; Sakurai, H. TL 1978, 3043. (b) Sarkar, T. K.; Andersen, N. H. TL 1978, 3513.
9. Hayashi, T.; Konishi, M.; Ito, H.; Kumada, M. JACS 1982, 104, 4962.
10. Hatanaka, Y.; Hiyama, T. SL 1991, 845.

Akira Hosomi & Katsukiyo Miura

University of Tsukuba, Japan



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