Org. Synth. 1969, 49, 16
DOI: 10.15227/orgsyn.049.0016
p-CHLOROPHENOXYMETHYL CHLORIDE
[Anisole, p-a-dichloro-]
Submitted by H. Gross and W. Bürger
1.
Checked by J. Longanbach and K. B. Wiberg.
1. Procedure
This preparation must be carried out in efficient hood.
A 250-ml. round-bottomed flask with a side arm is equipped with a distillation head and condenser. The receiving flask is attached to the condenser with an adapter, and the exit from the flask goes to a bubble counter containing high-boiling petroleum ether. A thermometer is inserted in the side arm of the distillation flask, and it reaches to the bottom. With exclusion of moisture, 147 g. (0.704 mole) of phosphorus pentachloride and 100 g. (0.704 mole) of p-chloroanisole are added to the flask. The flask is heated in an oil bath; the reaction begins when the inside temperature reaches 120° and occurs rapidly at 140°. The temperature is raised to 160° over a period of 2 hours, thereby distilling the phosphorus trichloride (Note 1). After the gas evolution subsides, the reaction mixture is heated to 175° for a short time. About 73–75 g. of phosphorus trichloride is collected.
The residue is distilled through a 30-cm. column packed with glass beads giving 10 g. of a fraction, b.p. 85–105° (10 mm.), containing mainly p-chloroanisole, and 85–99 g. (68–80%) of p-chlorophenoxymethyl chloride, b.p. 105–108° (10 mm.), n23D = 1.5496, m.p. 28–29° (Note 2), (Note 3). The n.m.r. spectrum [CCl4, (CH3)4Si reference] had bands at δ 5.6 (s, 2H) and 6.6–7.3 p.p.m.
2. Notes
1.
Some
phosphorus pentachloride may solidify in the upper part of the condenser. This may be removed by rotating the condenser.
2.
The literature values are b.p.
120–124 (18 mm.), m.p.
29–30°.
23.
Gas chromatography analysis using a silicone gum column indicated the product to be 97% pure.
3. Discussion
Aryloxymethyl chlorides may be prepared by the reaction of sodium aryloxymethanesulfonates with
phosphorus pentachloride.
2,3 The chlorination of
anisole does not, as previously reported,
4 give
phenoxymethyl chloride, but rather a mixture of
p- and
o-chloroanisoles.
5 Similarly,
anisole and other unsubstituted methyl aryl ethers undergo ring chlorination with
phosphorus pentachloride and
chlorine,
6 whereas ring-chlorinated anisoles, such as
p-chloroanisole, undergo chlorination at the methyl group with
chlorine at 190–195° in the presence of a catalytic amount of
phosphorus pentachloride.
6 Ring-nitrated aryloxymethyl chlorides may be obtained by the aluminum chloride-catalyzed decarbonylation of the corresponding aryloxyacetyl chlorides.
7,8The present method is simple, proceeds easily and in good yield to give a single product. It is applicable to other cases, such as the preparation of 2,4-dichlorophenoxymethyl chloride (89–92%). The chlorination of p-chloroanisole with chlorine and phosphorus pentachloride gives considerable amounts of p-chlorophenoxydichloromethane which is difficult to separate from the desired compound by distillation.
The reaction of chloromethyl aryl ethers with nucleophilic reagents has been described by Barber
et al.2 Thus, by reaction with
thiourea,
potassium thiocyanate, or
sodium cyanide, there are obtained aryloxyalkylisothiouronium salts, aryloxyalkyl thiocyanates, and aryloxyalkylacetonitriles, respectively.
2 With silver sulfonates the sulfonic acid esters of aryloxymethanols may be obtained.
8 The reaction of chloromethyl aryl ethers with
butyllithium leads to an aryloxycarbene which on reaction with olefins gives aryloxycyclopropanes.
3 The ethers react with
triphenylphosphine and a base to give phenoxymethylene ylides which are useful in converting carbonyl compounds to aromatic enol ethers.
9 The reaction of the chloro ethers with trialkylphosphites gives aryloxymethanephosphonates.
10 Most of these reactions have been studied with
phenoxymethyl chloride and the
p-methyl derivative; they also proceed well and in good yield with the readily obtainable
p-chlorophenoxymethyl chloride.
10
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
phosphorus pentachloride (10026-13-8)
sodium cyanide (143-33-9)
Anisole (100-66-3)
chlorine (7782-50-5)
phosphorus trichloride (7719-12-2)
potassium thiocyanate (333-20-0)
thiourea (62-56-6)
butyllithium (109-72-8)
p-chloroanisole (623-12-1)
triphenylphosphine (603-35-0)
phenoxymethyl chloride
2,4-dichlorophenoxymethyl chloride
p-Chlorophenoxymethyl chloride,
Anisole, p-a-dichloro- (21151-56-4)
p-chlorophenoxydichloromethane
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