Org. Synth. 1998, 75, 124
DOI: 10.15227/orgsyn.075.0124
EFFICIENT SYNTHESIS OF BROMIDES FROM CARBOXYLIC ACIDS CONTAINING A SENSITIVE FUNCTIONAL GROUP: DEC-9-ENYL BROMIDE FROM 10-UNDECENOIC ACID
[
1-Decene, 10-bromo-
]
Submitted by Derek H. R. Barton
1
, John MacKinnon, Roland N. Perchet, and Chi-Lam (Ivan) Tse.
Checked by Jessica E. Reed and Robert K. Boeckman, Jr..
1. Procedure
Caution! Barton esters are light sensitive; therefore all procedures should be carried out in the absence of light.
N-(10-Undecenoyloxy)pyridine-2-thione
(3)
. To an oven-dried, one-necked, 250-mL, round-bottomed flask equipped with a nitrogen inlet with gas bubbler, a magnetic stirrer, and a dropping funnel are added
3.61 g (28.4 mmol) of N-hydroxythiopyridone
(2)
(Note 1),
6.20 g (30.0 mmol) of dicyclohexylcarbodiimide
(Note 2), and
40 mL of methylene chloride
(Note 3). The resulting homogeneous solution is cooled to 0°C and
4.99 g (27.1 mmol) of 10-undecenoic acid
(1)
is added dropwise (Note 4). Following the addition of the undecenoic acid, the ice bath is removed and the reaction mixture is allowed to warm to room temperature and stirred for a further 8 hr. The bright yellow suspension that results is filtered through a bed of silica gel (Note 5). The solvent is removed under reduced pressure to give 8.06 g of the crude Barton ester (3)
(Note 6) and (Note 7).
Dec-9-enyl bromide
(4). To an oven-dried, one-necked, 250-mL, round-bottomed flask equipped with a nitrogen inlet with gas bubbler, magnetic stirrer and a
condenser are added
8.06 g (27.1 mmol) of the Barton ester
(3)
,
100 mL of methylene chloride
(Note 3), and
3 mL (30.0 mmol) of bromotrichloromethane
(Note 8). The reaction mixture is photolyzed with a
250W tungsten lamp under reflux for 30 min
(Note 9). The color of the reaction mixture changes from bright yellow to pale yellow. The reaction mixture is cooled to room temperature and the solvent is removed under reduced pressure. The crude product is purified by flash column chromatography (
hexanes) until all the bromide
4
(Note 10) is eluted, affording
5.81 g of
dec-9-enyl bromide
(
98%)
(Note 11).
2. Notes
1.
N-Hydroxythiopyridone is purchased from the Olin Corp. as an aqueous 40% solution of sodium 2-pyridinethiol-1-oxide (sodium omadine).
Sodium omadine (1 L) is diluted with water (H
2O, 600 mL) and the solution cooled to 0°C.
Hydrochloric acid (350 mL) is added dropwise over a 20-min interval with continuous stirring and cooling for a further 20 min. The resulting suspension containing
N-hydroxythiopyridone is filtered and the solid is washed with H
2O (2 L). The
N-hydroxythiopyridone is dried over
sodium hydroxide or potassium hydroxide
under reduced pressure and recrystallized from
ethanol (250-300 mL). The product is finally dried over
phosphorus pentoxide
and stored at all times in a refrigerator. The checkers employed
N-hydroxythiopyridone obtained from Aldrich Chemical Company, Inc.
2.
Dicyclohexylcarbodiimide was purchased from the Aldrich Chemical Company, Inc.
, and used directly.
3.
Dichloromethane is distilled from
calcium hydride
under
argon immediately prior to use.
4.
10-Undecenoic acid was purchased from the Aldrich Chemical Company, Inc.
, and used after distillation under reduced pressure (bp
87°C / 2 mm Hg).
5.
Using a
medium size filter funnel, add enough silica gel to the depth of about 1.5" covered with sand. Prewash the silica gel with
methylene chloride (CH
2Cl
2) under suction, discarding the filtrate. Add the reaction mixture and flush with CH
2Cl
2.
Dicyclohexylurea
remains at the top of the silica gel bed.
6.
Spectral data for
3 are as follows:
1H NMR (300 MHz, CDCl
3) δ: 1.22-1.45 (m, 10 H), 1.75-1.85 (m, 2 H), 1.99-2.06 (ddd, 2 H, J = 7.2, 6.9, 6.6), 2.70 (t, 2 H, J = 7.5) 4.89-5.02 (m, 2 H), 5.75-5.84 (m, 1 H), 6.62 (ddd, 1 H, J = 7.0, 6.5, 1.6), 7.19 (ddd, 1 H, J = 8.8, 7.0, 1.3), 7.53 (dd, 1 H, J = 6.5, 1.3), 7.68 (dd, 1 H, J = 8.8, 1.6)
;
13C NMR (100 MHz, CDCl
3) δ: 24.21, 28.78, 28.86, 28.93, 28.99, 29.13, 31.50, 33.68, 112.46, 114.10, 133.42, 137.36, 137.57, 139.07, 168.99, 175.86
; IR (film) cm
−1: 3074, 1807, 1639, 1608, 1525, 1447, 1410, 1283
.
7.
The purity is estimated to be 98% by NMR. Crude material is obtained with a mass balance in excess of theoretical. Minor impurities can be detected by
13C NMR having signals at δ: 24.61, 25.36, and 34.84 which may be due to the presence of a small amount of internal olefin in the
10-undecenoic acid.
8.
Bromotrichloromethane was purchased from Aldrich Chemical Company, Inc.
, and used as received.
9.
The 250W tungsten lamp generates a sufficient amount of heat to reflux the solution. The submitters used a
300W lamp. No other external source is required. The checkers observed the reaction to be complete in less than 30 min, although irradiation was carried out for the specified amount of time.
10.
Spectral data for
4 are as follows:
1H NMR (300 MHz, CDCl
3) δ: 1.32-1.46 (m, 10 H), 1.82-1.91 (m, 2 H), 1.96-2.09 (m, 2 H), 3.41 (t, 2 H, J = 6.8), 4.93-5.04 (m, 2 H), 5.81 (m, 1H)
;
13C NMR (75 MHz, CDCl
3) δ: 28.15, 28.71, 28.86, 28.99, 29.27, 32.82, 33.75, 33.82, 114.16, 138.99
; IR (film) cm
−1: 3075, 1640, 1463, 1438, 993, 791
. The purity is estimated to be >98% by NMR.
11.
This procedure is also suitable for large scale preparation.
Handling and Disposal of Hazardous Chemicals
The procedures in this article are intended for use only by persons with prior training in experimental organic chemistry. All hazardous materials should be handled using the standard procedures for work with chemicals described in references such as "Prudent Practices in the Laboratory" (The National Academies Press, Washington, D.C., 2011 www.nap.edu). All chemical waste should be disposed of in accordance with local regulations. For general guidelines for the management of chemical waste, see Chapter 8 of Prudent Practices.
These procedures must be conducted at one's own risk. Organic Syntheses, Inc., its Editors, and its Board of Directors do not warrant or guarantee the safety of individuals using these procedures and hereby disclaim any liability for any injuries or damages claimed to have resulted from or related in any way to the procedures herein.
3. Discussion
The procedure described here allows for a convenient and efficient preparation in very high yields of large quantities of bromides from carboxylic acids containing an olefinic functionality. The Hunsdiecker reaction is traditionally accomplished by treating anhydrous silver carboxylates with
bromine
or
iodine
.
2 Heavy metal salts such as
mercury,
3
lead,
4 and
thallium
5 have also been used successfully as well as
tert-butyl hypoiodite
.
6 The major disadvantages associated with the above methods, such as use of heavy metal salts and non-tolerance towards olefins, has led to the development of a more versatile method using O-acyl thiohydroxamates.
7,8 The O-acyl thiohydroxamates are neither strongly oxidizing nor strongly electrophilic species and have therefore a greater potential within organic synthesis.
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Dec-9-enyl bromide:
1-Decene, 10-bromo- (10); (62871-09-4)
Undecenoic acid:
10-Undecenoic acid (8,9); (112-38-9)
N-(10-Undecenoyloxy)pyridine-2-thione:
2(1H)-Pyridinethione, 1-[(1-oxo-10-undecenyl)oxy]- (12); (114050-28-1)
N-Hydroxythiopyridone:
2(1H)-Pyridinethione, 1-hydroxy- (8,9); (1121-30-8)
Dicyclohexylcarbodiimide: HIGHLY TOXIC.
Carbodiimide, dicyclohexyl- (8);
Cyclohexanamine, N,N'-methanetetraylbis- (9); (538-75-0)
Bromotrichloromethane:
Methane, bromotrichloro (8,9); (75-62-7)
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