Org. Synth. 1986, 64, 50
DOI: 10.15227/orgsyn.064.0050
CYCLOBUTENE
Submitted by J. Salaün and A. Fadel
1.
Checked by Lawrence R. McGee and Bruce E. Smart.
1. Procedure
A. Cyclobutanol. A 1-L, three-necked, round-bottomed flask equipped with a reflux condenser and a magnetic stirring bar is charged with 600 mL of water, 57.5 mL (ca. 0.68 mol) of concentrated hydrochloric acid, and 57.7 g (0.80 mol) of cyclopropylcarbinol (Note 1). The reaction mixture is stirred and refluxed for 3 hr. Cyclobutanol is only partially soluble in water and soon separates. The reaction mixture is allowed to cool to room temperature, and the flask is then immersed in an ice bath. To the cold, stirred mixture is added 24 g (0.6 mol) of sodium hydroxide pellets, followed by 6.7 g (0.08 mol) of sodium bicarbonate to complete the neutralization. The mixture is saturated with sodium chloride and extracted for 30 hr with diethyl ether using a liquid–liquid continuous extraction apparatus. The ethereal extract is dried over anhydrous sodium sulfate and the drying agent is removed by filtration. The bulk of the solvent is distilled from the filtrate to give 55.0 g of residual liquid containing 88% cyclobutanol and 12% 3-buten-1-ol by gas chromatography (Note 2). The crude product is carefully distilled through spinning band columns to give 32.8 g (57%) of cyclobutanol, bp 122–124°C. Gas chromatographic analysis of the product shows it to be 95% pure (Note 2),(Note 3),(Note 4).
B. Cyclobutyl tosylate. A 500-mL, three-necked, round-bottomed flask fitted with a stirrer and a theromometer is charged with 200 mL of pyridine (Note 5) and 32.3 g (0.448 mol) of cyclobutanol. The solution is stirred and chilled to 0°C, and then 89.8 g (0.471 mol) of p-toluenesulfonyl chloride (Note 6) is added in portions over a 20-min period. The reaction mixture is allowed to warm to room temperature and is stirred for 16 hr. The mixture is recooled to 0°C, and poured into 260 mL of concentrated hydrochloric acid in 800 mL of ice water. The mixture is extracted with three 300-mL portions of ether and the combined ethereal extracts are dried over anhydrous magnesium sulfate. The drying agent is removed by filtration and the filtrate is concentrated on a rotary evaporator. The residue is held under high vacuum (0.03 mm) at room temperature for 3 hr to give 93.3 g (92%) of cyclobutyl tosylate as a pale-yellow oil (Note 7).
C.
Cyclobutene. A
500-mL, two-necked, round-bottomed flask is fitted with a
100-mL dropping funnel equipped with an
argon-inlet tube, a magnetic stirring bar, and a
water-cooled condenser. The outlet of the condenser is attached to an
all-glass transfer manifold.
Two weighed traps fitted with
gastight stopcocks and immersed in dry
ice–acetone baths are attached to the manifold. A
calcium chloride drying tube is attached to the exit of the second trap. While the system is continuously purged with a slow stream of
argon, the flask is charged with
33.6 g (0.30 mol) of potassium tert-butoxide and
120 mL of anhydrous dimethyl sulfoxide (Note 8), and a solution of
25.6 g (0.113 mol) of cyclobutyl tosylate in
30 mL of anhydrous dimethyl sulfoxide is placed in the dropping funnel. The
potassium tert-butoxide suspension is stirred vigorously and heated to 70°C. The
cyclobutyl tosylate solution is then added dropwise over a 10-min period
(Note 9). After the addition is completed, the reaction mixture is stirred at 70°C for an additional 2 hr. The manifold system is closed off from the reaction vessel and the material collected in the first trap is slowly warmed. The product distills at ca. 2°C into the second
dry-ice-cooled trap to give
4.3–5.1 g (
70–84%) of
cyclobutene [lit.
2 bp
2°C]
(Note 10),
(Note 11),
(Note 12).
2. Notes
1.
The checkers obtained
cyclopropylcarbinol from the Aldrich Chemical Company, Inc. It can be readily prepared by the reduction of
cyclopropanecarboxylic acid with
lithium aluminum hydride.
32.
A
25-m × 0.3-mm HP Ultra Silicone capillary column at 70°C with 30–psi helium head pressure was used for the chromatographic analysis: retention times of
3-buten-1-ol and
cyclobutanol are 1.19 and 1.35 min, respectively. The submitters used a
3-m × 0.3-cm 20 M carbowax column at 90°C/8 psi hydrogen and reported retention times of 13 and 20 min for
3-buten-1-ol and
cyclobutanol, respectively.
3.
The crude product was first distilled on a 50-cm ×
0.8-cm spinning band column (reflux ratio 10:1) to give
19.6 g of
cyclobutanol, bp
124°C. The forerun fractions, bp
66–123°C (
23.0 g), were combined and redistilled on a 30-cm × 0.8-cm spinning band column (reflux ratio 25:1) to give an additional
13.2 g of
cyclobutanol, bp
122–123°C. The major by-product,
3-buten-1-ol, boils at
112–114°C. Gas chromatographic analysis of the combined product fractions indicates a mixture of 95% cyclobutanol/3-buten-1-ol (99.7%/0.3%) and 5% unidentified compounds.
4.
Cyclobutanol shows the following
1H NMR spectrum (CDCl
3): δ: 1.1–2.4 (m, 6 H), 4.16 (quintet, 1 H,
J = 7.5), 4.54 (s, 1 H, OH).
5.
The
pyridine was distilled from
calcium hydride and stored over
potassium hydroxide.
6.
The
p-toluenesulfonyl chloride was obtained from the Aldrich Chemical Company, Inc., and was recrystallized from
hexane prior to use.
7.
The product is >99% pure by NMR and shows the following spectrum:
1H NMR (CDCl
3) δ: 1.1–2.3 (m, 6 H), 2.47 (s, 3 H), 4.77 (quintet, 1 H,
J = 7.5), 7.32 (d, 2 H,
J = 9.0), 7.79 (d, 2 H,
J = 9.0).
8.
Potassium tert-butoxide was obtained from the Aldrich Chemical Company, Inc. The
dimethyl sulfoxide was distilled from
calcium hydride and stored under
argon.
9.
The reaction mixture turns green, then blue indigo, and finally dark pink during the addition.
10.
The submitters report obtaining
5.2 g of
99.2% pure
cyclobutene. The product obtained by the checkers was pure by NMR spectroscopy and shows the following
1H NMR spectrum (CDCl
3) δ: 2.55 (s, 4 H), 6.00 (s, 2 H).
11.
The
cyclobutene can be converted to
1,2-dibromocyclobutane by distilling
4.3–7.3 g (0.079–0.135 mol) of cyclobutene into
100 mL of pentane chilled to −40°C, followed by adding a solution of
15.5–32.0 g (0.097–0.200 mol) of bromine in
30 mL of pentane. After the usual workup with aqueous
sodium thiosulfate and distillation,
14.3–25.3 g (
84–87.5%) of pure
1,2-dibromocyclobutane, bp
60°C (6 mm), is obtained. It shows the following
1H NMR spectrum (CDCl
3) δ: 1.90–3.03 (m, 4 H), 4.27–4.70 (m, 2 H). The
1,2-dibromocyclobutane can be conveniently converted back to
cyclobutene by debromination with
zinc in
ethanol.
412.
Cyclobutene can be prepared on a larger scale (
25–37 g) simply by scaling up the reactants.
3. Discussion
Cyclobutene has been prepared (1) by pyrolysis of
cyclobutyldimethylamine oxide4,5,6 and
cyclobutyltrimethylammonium hydroxide4,6,7 (50–73% yield), which were prepared in eight steps from malonate esters (
2.0–2.1% overall yield of
cyclobutene contaminated with
1,3-butadiene), (2) by pyrolysis of the products of cycloaddition of
dimethyl acetylenedicarboxylate with
cyclooctatriene8,9,10 (
30–32% overall yield) or with
cyclooctatetraene11,12,13 (
34–39% overall yield), (3) by photolysis of
butadiene leading to
cyclobutene (
30% yield) and
bicyclo[1.1.0]butane (
5% yield),
14,15 (4) by oxidation of
cyclobutylcarboxylic acid16 with
lead tetraacetate17 (
67% yield) (
11.8% overall yield), (5) by fragmentation of
1,2-cyclobutyl thiocarbonate with
trialkyl phosphite18 (
68% yield based on
cis-1,2-dihydroxycyclobutane), (6) by ring expansion of
cyclopropylcarbene19 (7) from
cyclobutylidene20 21 and (8) by base-induced ring expansion of
cyclopropylmethyl tosylate with
potassium tert-butoxide in
dimethyl sulfoxide leading to a 1 : 1 mixture of
cyclobutene and
methylenecyclopropane.
22 None of these methods appears to be practical.
The present procedure offers in good yields a simple and ready preparation of pure
cyclobutene from the easily available
cyclopropylcarbinol. The product is free of the impurities (e.g.,
1,3-butadiene,
bicyclobutane,
methylenecyclopropane) usually obtained with the various methods so far reported. The procedure described for the synthesis of
cyclobutanol is patterned after the acid-catalyzed rearrangement of
cyclopropylcarbinol reported by Roberts
23 and Rocek.
24
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
1,2-cyclobutyl thiocarbonate
ethanol (64-17-5)
hydrochloric acid (7647-01-0)
ether,
diethyl ether (60-29-7)
sodium hydroxide (1310-73-2)
sodium bicarbonate (144-55-8)
sodium chloride (7647-14-5)
bromine (7726-95-6)
sodium sulfate (7757-82-6)
sodium thiosulfate (7772-98-7)
pyridine (110-86-1)
potassium hydroxide (1310-58-3)
zinc (7440-66-6)
Pentane (109-66-0)
magnesium sulfate (7487-88-9)
1,3-Butadiene,
butadiene (106-99-0)
lithium aluminum hydride (16853-85-3)
cyclobutylcarboxylic acid (3721-95-7)
Cyclopropanecarboxylic acid (1759-53-1)
hexane (110-54-3)
dimethyl sulfoxide (67-68-5)
argon (7440-37-1)
Dimethyl acetylenedicarboxylate (762-42-5)
calcium hydride (7789-78-8)
cyclobutene (822-35-5)
cyclopropylcarbinol (2516-33-8)
3-buten-1-ol (627-27-0)
Cyclobutanol (2919-23-5)
Bicyclo[1.1.0]butane (157-33-5)
bicyclobutane
p-Toluenesulfonyl chloride (98-59-9)
Methylenecyclopropane (6142-73-0)
Cyclobutyl tosylate (10437-85-1)
1,2-dibromocyclobutane (89033-70-5)
cyclobutyldimethylamine oxide
cyclobutyltrimethylammonium hydroxide
cyclooctatriene (1871-52-9)
cyclooctatetraene
cyclopropylcarbene (19527-12-9)
cyclobutylidene
cyclopropylmethyl tosylate
potassium tert-butoxide (865-47-4)
cis-1,2-dihydroxycyclobutane (35358-33-9)
lead tetraacetate (546-67-8)
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