Organic Syntheses, CV 8, 501
Submitted by Rick L. Danheiser, David M. Fink, Kazuo Okano, Yeun-Min Tsai, and Steven W. Szczepanski
1.
Checked by Masahiko Hayashi and Ryoji Noyori.
1. Procedure
A.
(1-Hydroxy-2-propenyl)trimethylsilane. A
2-L, three-necked, round-bottomed flask is equipped with a
magnetic stirring bar,
two pressure-equalizing dropping funnels (250 and 500 mL), and a
Claisen adapter fitted with an
argon inlet adapter and a
rubber septum (Note
1). The flask is charged with
20.0 g (0.344 mol) of allyl alcohol (Note
2), and
400 mL of dry tetrahydrofuran (Note
3), and then cooled below −75°C with a
dry ice–acetone bath and maintained at that temperature while
157 mL (0.363 mol) of a 2.31 M solution of n-butyllithium in hexane (Note
4) is added dropwise over 1 hr. After 50 min, a solution of
39.3 g (0.362 mol) of chlorotrimethylsilane (Note
5) in
25 mL of tetrahydrofuran is added dropwise via syringe over 30 min, and the resulting colorless reaction mixture is stirred for 1 hr further, and then treated dropwise over 1.5 hr with
258 mL (0.415 mol) of a 1.61 M solution of tert-butyllithium in pentane (Note
4). After 2 hr of further stirring at −75°C the cold bath is removed, and
100 mL of saturated ammonium chloride solution is added in one portion to the yellow reaction mixture. The resulting solution is stirred for 5 min and then diluted with 50 mL of water and
300 mL of pentane. The organic phase is separated and washed successively with three 100-mL portions of water and two
100-mL portions of saturated sodium chloride solution, dried over anhydrous
sodium sulfate, filtered, and concentrated by carefully distilling off the solvents at atmospheric pressure through a
10-cm Vigreux column. The residual pale yellow liquid is transferred to a
100-mL round-bottomed flask, and the remaining volatile impurities are removed by distillation at 15 mm through a
4-cm column packed with glass helices (Note
6), leaving
35.1–39.7 g of
(1-hydroxy-2-propenyl)trimethylsilane as a pale-yellow liquid (Note
7) and (Note
8) used in the next step without further purification.
B.
(1-Oxo-2-propenyl)trimethylsilane. A 2-L, three-necked, round-bottomed flask is equipped with a
mechanical stirrer and two 250-mL pressure-equalizing dropping funnels, one of which is fitted with an argon inlet adapter (Note
1). The flask is charged with
41.71 g (0.329 mol) of oxalyl chloride (Note
9) and
500 mL of dichloromethane (Note
10), and cooled below −75°C with a dry ice–acetone bath and maintained at that temperature while a solution of
55.82 g (0.715 mol) of dimethyl sulfoxide (Note
11) in
60 mL of dichloromethane is added dropwise over 1 hr. After 1 hr, a solution of the crude
(1-hydroxy-2-propenyl)trimethylsilane in
100 mL of dichloromethane is added dropwise over 1.25 hr to the colorless reaction mixture, which is stirred at −75°C for 1 hr further, and then treated dropwise over 30 min with
150.38 g (1.486 mol) of triethylamine (Note
12). After 1 hr, the cold bath is removed and the reaction mixture is poured into 200 mL of water. The organic phase is separated and washed successively with five
100-mL portions of 10% hydrochloric acid, three 100-mL portions of water, and two
100-mL portions of saturated sodium chloride solution, dried over anhydrous
sodium sulfate, filtered, and concentrated by carefully distilling off the solvents at atmospheric pressure through a 10-cm Vigreux column. The residual yellow oil is transferred to a
250-mL, round-bottomed flask containing
0.050 g of
3-tert-butyl-4-hydroxy-5-methylphenyl sulfide (Note
13) and distilled through a 4-cm column packed with glass helices to afford
27.8–30.0 g (
63–68% overall yield based on
allyl alcohol) of
(1-oxo-2-propenyl)trimethylsilane as a brilliant-yellow oil, bp
47–50°C (30 mm) (Note
14) and (Note
15).
2. Notes
1. The glass components of the apparatus are dried overnight in a 120°C oven, and then assembled and maintained under an atmosphere of
argon during the course of the reaction.
3.
Tetrahydrofuran was distilled from
sodium benzophenone ketyl immediately before use.
4.
n-Butyllithium was purchased from Aldrich Chemical Company, Inc. or Mitsuwa Pure Chemicals,
tert-Butyllithium was obtained from Aldrich Chemical Company, Inc. These were titrated using the method of Watson and Eastham
2 submitters) or Lipton
3 (checkers).
6. The heating bath temperature was not permitted to exceed 70°C during the course of the distillation.
7. The purity of this material was determined to be 95% by gas-chromatographic analysis (10% OV-101 on 100–120-mesh Chromosorb W, 6 ft × 1/8 in., program: 50°C for 2 min and then 50–250°C at 32°C/min).
8. The product exhibits the following spectral properties: IR (film) cm
−1: 3420, 2955, 2895, 2820, 1625, 1410, 1245, 1140, 1095, 990, 900, 840;
13C NMR (67.9 MHz, CDCl
3) δ: −4.4, 68.9, 109.4, 139.9;
1H NMR (250 MHz, CDCl
3) δ: 0.05 (s, 9 H), 2.86 (br s, 1 H), 3.88 (m, 1 H), 4.86 (ddd, 1 H,
J = 2, 2, 11), 4.98 (ddd, 1 H,
J = 2, 2, 17), 5.89 (ddd, 1 H,
J = 5.5, 11, 17); HRMS
m/e calcd. for C
6H
14OSi (M
+): 130.0814, Found: 130.0810.
9.
Oxalyl chloride purchased from Aldrich Chemical Company, Inc. was fractionally distilled under
argon before use.
14. The purity of this material was determined to be >97% by gas-chromatographic analysis (10% OV-101 on 100–120-mesh Chromosorb W, 6 ft × 1/8 in., program: 50°C for 2 min and then 50–250°C at 32°C/min).
15. The product exhibits the following spectral properties: IR (film) cm
−1: 2960, 2900, 1635, 1600, 1590, 1415, 1390, 1255, 1185, 985, 960, and 845;
13C NMR (67.9 MHz, CDCl
3) δ: −2.2, 128.5, 141.3, 237.9;
1H NMR (250 MHz, CDCl
3) δ: 0.23 (s, 9 H), 5.94 (dd, 1 H,
J = 1, 11), 6.13 (dd, 1 H,
J = 1, 18), 6.38 (dd, 1 H,
J = 11, 18).
3. Discussion
α,β-Unsaturated acylsilanes serve as valuable building blocks for the synthesis of a variety of complex organic compounds. These α,β-unsaturated carbonyl derivatives participate in a number of carbon–carbon bond forming processes including organocuprate conjugate additions,
4 TiCl
4-mediated conjugate allylations,
13 Diels–Alder reactions,
4 1,3-dipolar cycloadditions,
14 and the [3+2] annulation method recently developed in our laboratory.
14 The utility of these reactions is enhanced by the fact that the product acylsilanes are subject to a variety of useful further transformations,
15 16 including, for example, Brook reactions,
4,17 18 oxidation to carboxylic acids,
19 20 and fluoride-promoted conversion to ketones and aldehydes.
20,21 22 23 24 The present procedure provides a practical method for the preparation of multigram quantities of the simplest α,β-unsaturated acylsilane.
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