The reaction of α,α,α-trifluoromethoxybenzene with AlCl3: A high yield preparation of α,α,α-trichloromethoxybenzene

Article abstract of DOI:10.1081/SCC-120002522

α,α,α-Trifluoromethoxybenzene was allowed to react with AlCl₃ in CH₂Cl₂ to afford α,α,α-trichloromethoxybenzene in excellent yield and purity.

Full text of DOI:10.1081/SCC-120002522

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THE REACTION OF α,α,α-
TRIFLUOROMETHOXYBENZENE WITH AlCl3:
A HIGH YIELD PREPARATION OF α,α,α-
TRICHLOROMETHOXYBENZENE
Qiliang Chen a , Jie Xu a & Wei Zhang a
a Dalian Institute of Chemical Physics , Chinese Academy of Sciences , Dalian, 116023,
China
Published online: 16 Aug 2006.
To cite this article: Qiliang Chen , Jie Xu & Wei Zhang (2002) THE REACTION OF α,α,α-TRIFLUOROMETHOXYBENZENE
WITH AlCl3: A HIGH YIELD PREPARATION OF α,α,α-TRICHLOROMETHOXYBENZENE, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:5, 799-801, DOI: 10.1081/
SCC-120002522
To link to this article: http://dx.doi.org/10.1081/SCC-120002522
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SYNTHETIC COMMUNICATIONS, 32(5), 799–801 (2002)
THE REACTION OF a,a,a-
TRIFLUOROMETHOXYBENZENE WITH
AlCl3 : A HIGH YIELD PREPARATION OF
a,a,a-TRICHLOROMETHOXYBENZENE
*
Qiliang Chen, Jie Xu, and Wei Zhang
Dalian Institute of Chemical Physics, Chinese Academy
of Sciences, Dalian 116023, China
ABSTRACT
a,a,a-Trifluoromethoxybenzene was allowed to react with
AlCl3 in CH2Cl2 to afford a,a,a-trichloromethoxybenzene in
excellent yield and purity.
Numerous chemical transformations have demonstrated the unusual
stability of the OCF3 group to strong acids and bases, as well as to strong
oxidizing and reducing conditions.1–2 As far as substitution, the OCF3
group is similar to the halogens such as bromine and chlorine, and clearly
indicates a deactivating effect on the aromatic ring. It was found that the
OCF3 group orients attacking electrophilic reagents to the ortho/para
position. For example, the nitration of a,a,a-trifluoromethoxybenzene
(TFMB) under usual condition with a mixture of nitric and sulfuric acids
gave para/ortho substitution. However, when a,a,a-trifluoromethoxy-
benzene reacted with acetyl chloride using aluminum chloride as a catalyst,
*Corresponding author. E-mail: chenql@mail.dlptt.ln.cn
799
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
800
CHEN, XU, AND ZHANG
besides the expected 4-acetyl-a,a,a-trifluoromethoxybenzene (PATFMB),
the reaction also produced a,a,a-chlorodifluoromethoxybenzene and a,a,a-
dichlorofluoromethoxybenzene respectively.3 In the present work, the
a,a,a-trichloromethoxybenzene (TCMB), which has received extensive
interest in pharmaceutical and agrochemical industry (as pesticides), was
prepared by the reaction of a,a,a-trifluoromethoxybenzene with aluminum
chloride (Scheme 1), the results in this communication were summarized
in Table 1.
Scheme 1.
The data suggested that in the aluminum chloride catalyzed acetyl-
ation of a,a,a-trifluoromethoxybenzene, which took place in CH2Cl2,
CH2CH2Cl2 and CCl4 solvent, respectively, the amount of 4-acetyl-
a,a,a-trifluoromethoxybenzene afforded was low. Instead, a,a,a-trichloro-
methoxybenzene was obtained as the major product. In the control
experiment, the reaction of a,a,a-trifluoromethoxybenzene with aluminum
chloride in CH2Cl2 yielded a,a,a-trichloromethoxybenzene in excellent
yield and purity, producing only 1.8% a,a,a-dichlorofluoromethoxybenzene
Table 1. AlCl3 Catalyzed Acetylation of a,a,a-Trifluoromethoxybenzene with
Acetyl Chloride
Product (%)
Time
(h) PATFMB TCMB DCFMB
Entry Reagent Catalyst
Solvent
CH2Cl2
CH2CH2Cl2
CCl4
CH2Cl2
1
2
3
4
CH3COCl
CH3COCl
CH3COCl
–
AlCl3
AlCl3
AlCl3
AlCl3
2
25
22.5
20
–
75
–
–
2
2
0.5
77.5
80
98.2
–
1.8

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PREPARATION OF TCMB
801
(DCFMB) and no a,a,a-chlorodifluoromethoxybenzene. From these results,
it was, therefore, concluded that the primary reaction is an exchange of
halogen atoms between a,a,a-trifluoromethoxybenzene and aluminum
chloride. This reaction provides a simple and efficient method for the
preparation of a,a,a-trichloromethoxybenzene.
EXPERIMENTAL
Preparation of TCMB. To a cooled (0ꢀC) and stirred solution of
anhyd. AlCl3 (0.15 mol) in CH2Cl2 (15 ml), a,a,a-trifluoromethoxybenzene
(0.049 mol) was added and it was stirred at 0–10ꢀC for 0.5 h, then poured
it into the mixture of ice with HCl, stirred for 5 min, separated the lower
layer, the aqueous solution was extracted with dichloromethane (10 ml  2),
combined organic phase was washed with water, dried over MgSO4 and
filtered. After removed the solvent, distillation of the solution in vacuo
(15 mmHg, 100–103ꢀC) gave the pure a,a,a-trichloromethoxybenzene
(yield: 85%, purity: 98%). Anal. for C7H5Cl3O: Calc. C 39.81%, H 2.37%,
found: C 39.51%, H 2.30%, MS m/z (assignment, %) 216 (C7H537Cl3O, 6),
212 (C7H535Cl237ClO, 21.2), 210 (C7H535Cl3O, 22.7), 179 (C7H537Cl2O, 7.5),
177 (C7H535Cl37ClO, 50), 175 (C7H535Cl2O, 83), 141 (C7H437ClO, 4.5), 139
(C7H435ClO, 15), 117 (C35Cl3, 53), 77 (C6H5, 100). 1H NMR (CCl4): (d ppm)
8.1–8.2 (1H, p, ArH), 7.4–7.6 (2H, o, ArH), 7.2–7.4 (2H, m, ArH).
REFERENCES
1. Sheppard, W.A. J. Org. Chem. 1964, 29(1), 3–11.
2. Yagupolsky, L.M. Dokl. Akad. Nauk. SSSR. 1955, 105(1), 100–102.
3. George, A. Olah; Takehilco Yamato, et al. J. Am. Chem. Soc. 1987, 109,
3708–3713.
Received in Japan December 20, 2000

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