PAPER
Synthesis of 1-Aryl-2,2-dichloroethanones
2847
Melting points were determined on a Kofler hot stage. 1H NMR and
13C NMR spectra were recorded on a Bruker AC-200, Bruker WM-
250, and Bruker AM-300 instruments in CDCl3 solutions. Analyti-
cal TLC: Silufol UV-254, Silpearl as the sorbent, starch as the bind-
er. Column chromatography was performed on silica gel (63–200
mesh, Merck). 1-Arylethanones 1a–c, 1e–k and 1,4-diacetylben-
zene (3) were purchased from Aldrich and Acros. Compound 1d
was synthesized according to a known procedure,24 bp 150–152 °C/
10 mm Hg.
1-(5,6,7,8-Tetrahydronaphthalen-2-yl)ethanone (2d)27
White crystals; mp 41.5–42.5 °C (Lit.27 mp 42–42.5 °C); Rf 0.6 (pe-
troleum ether–EtOAc, 94:6).
1H NMR (200.13 MHz, CDCl3): d = 1.70–1.90 (m,
CH2CH2CH2CH2), 2.70–2.85 (m, 4 H, ArCH2), 6.75 (s, 1 H, CH),
7.17 (d, 1 H, J = 8.5 Hz, ArH), 7.76 (m, 2 H, ArH).
13C NMR (62.9 MHz, CDCl3): d = 22.4, 22.6 (CH2CH2CH2CH2),
29.1, 29.6 (ArCH2), 67.7 (CHCl2), 126.4, 128.6, 129.5, 130.4,
137.9, 145.1 (Ar).
4 H,
The reactions were carried out using 31% HCl (reagent grade) and
a 35% aq solution of H2O2. Petroleum ether (bp 40–60 °C), Et2O,
CHCl3, EtOAc, MeOH, EtOH, i-PrOH, dioxane, AcOH, and ben-
zene (all of reagent grade) were used as solvents without additional
purification.
1-(3-Bromophenyl)-2,2-dichloroethanone (2e)12
Pale yellow oil; Rf 0.2 (petroleum ether–EtOAc, 94:6).
1H NMR (250.13 MHz, CDCl3): d = 6.65 (s, 1 H, CH), 7.40 (m, 1
H, ArH), 7.76 (m, 1 H, ArH), 8.02 (m, 1 H, ArH), 8.19 (m, 1 H,
ArH).
13C NMR (62.9 MHz, CDCl3): d = 67.5 (CHCl2), 123.0 (C–Br),
128.1, 130.3, (CHarom), 132.8 (CC=O), 132.5, 137.3 (CHarom), 184.6
(C=O).
Chlorination of 1-Arylethanones 1a–k and 1,4-Diacetylbenzene
(3); General Procedure
1-Arylethanone 1 (3.17–8.33 mmol) was dissolved in a mixture of
31% aq HCl (20 mL, 0.2 mol) and EtOH (20–25 mL) and the mix-
ture was heated to reflux (91–93 °C). A solution of 35% aq H2O2 in
EtOH (2 mL, 2.7–6.2 mol of H2O2 per mole of ketone 1) was added
with stirring over 1 min. The reaction mixture was refluxed with
stirring for 10–15 min and cooled to r.t. H2O (10 mL) was added and
the mixture was extracted with CHCl3 (4 × 25 mL). The combined
organic extracts were washed with H2O (4 × 10 mL), dried
(MgSO4), and concentrated. Products 2a–e, 2h–k, 4 and 5 were iso-
lated by column chromatography of the crude product. Compounds
2f and 2g were isolated by recrystallization of the crude product
from petroleum ether. Results are given in Table 1. Experiments on
optimizing the conditions for the synthesis of 1-aryl-2,2-dichloro-
ethanones (see Table 2) were carried out using the general proce-
dure and changing reaction temperature, cosolvent, reaction time
and the volume ratio of conc. HCl and cosolvent. The melting points
of 2a–d, 2f, 2g, and 5 were measured after recrystallization from pe-
troleum ether, the melting points of 2h–k were determined after re-
crystallization from a petroleum ether–CHCl3, and the melting point
of 4 was measured after recrystallization from EtOH.
1-(4-Bromophenyl)-2,2-dichloroethanone (2f)6
White crystals; mp 61–62 °C (Lit.6 mp 61.2–62 °C).
1H NMR (200.13 MHz, CDCl3): d = 6.58 (s, 1 H, CH), 7.65 (d, 2 H,
J = 8 Hz, ArH), 7.95 (d, 2 H, J = 8 Hz, ArH).
13C NMR (50.32 MHz, CDCl3): d = 67.7 (CHCl2), 129.8, 130.0 (C–
Br, CC=O), 131.2, 132.2 (CHarom), 185.1 (C=O).
2,2-Dichloro-1-(4-chlorophenyl)ethanone (2g)28
White crystals; mp 58–59 °C (Lit.28 mp 61–62 °C).
1H NMR (250.13 MHz, CDCl3): d = 6.63 (s, 1 H, CH), 7.48 (d, 2 H,
J = 8.8 Hz, ArH), 8.03 (d, 2 H, J = 8.8 Hz, ArH).
13C NMR (62.9 MHz, CDCl3): d = 67.7 (CHCl2), 129.9 (CC=O),
129.2, 131.1 (CHarom), 141.1 (C–Cl), 184.6 (C=O).
2,2-Dichloro-1-(4-nitrophenyl)ethanone (2h)8
Pale yellow crystals; mp 26.8–27.8 °C (Lit.8 mp 27–28 °C); Rf 0.58
(benzene).
1H NMR (300.13 MHz, CDCl3): d = 6.72 (s, 1 H, CH), 8.22–8.39
(m, 4 H, ArH).
2,2-Dichloro-1-phenylethanone (2a)25
White crystals; mp 19–20.5 °C (Lit.25 mp 20–21.5 °C); Rf 0.27 (pe-
troleum ether–EtOAc, 94:6).
1H NMR (200.13 MHz, CDCl3): d = 6.76 (s, 1 H, CH), 7.42–7.72
(m, 3 H, ArH), 8.04–8.16 (m, 2 H, ArH).
13C NMR (50.32 MHz, CDCl3): d = 67.7 (CHCl2), 123.9, 130.9
(CHarom), 135.8 (CC=O), 150.6 (C–NO2), 184.6 (C=O).
13C NMR (50.32 MHz, CDCl3): d = 67.7 (CHCl2), 128.8, 129.6
(CHarom), 131.2 (Carom), 134.5 (CHCHCHC), 185.8 (C=O).
2,2-Dichloro-1-(3-nitrophenyl)ethanone (2i)12
Pale yellow crystals; mp 52.5–54.0 °C (Lit.12 mp 51.5–53.5 °C;
Rf 0.55 (benzene).
1H NMR (200.13 MHz, CDCl3): d = 6.72 (s, 1 H, CH), 7.77 (m, 1
H, ArH), 8.48 (m, 2 H, ArH), 8.92 (s, 1 H, ArH).
2,2-Dichloro-1-(4-methylphenyl)ethanone (2b)6
White crystals; mp 54–55 °C (Lit.6 mp 54.5–55.3 °C).
Rf = 0.35 (TLC, petroleum ether-EtOAc, 94:6).
13C NMR (50.32 MHz, CDCl3): d = 67.6 (CHCl2), 124.5, 128.5,
130.2, (CHarom), 132.3 (CC=O), 135.2 (CHarom), 148.2 (C–NO2),
184.1 (C=O).
1H NMR (200.13 MHz, CDCl3): d = 2.43 (s, 3 H, CH3), 6.72 (s, 1
H, CH), 7.30 (d, 2 H, J = 8 Hz, ArH), 7.97 (d, 2 H, J = 8 Hz, ArH).
13C NMR (50.32 MHz, CDCl3): d = 21.7 (CH3), 67.7 (CHCl2),
128.6 (CC=O), 129.5, 129.7 (CHarom), 145.8 (CCH3), 185.4 (C=O).
2,2-Dichloro-1-(4-iodophenyl)ethanone (2j)29
Slightly yellow crystals; mp 59–60.5 °C (Lit.29 mp 62–63 °C);
Rf 0.33 (petroleum ether–EtOAc, 94:6).
1H NMR (250.13 MHz, CDCl3): d = 6.60 (s, 1 H, CH), 7.8 (d, 2 H,
J = 8.6 Hz, ArH), 7.91 (d, 2 H, J = 8.6 Hz, ArH).
13C NMR (75.47 MHz, CDCl3): d = 67.7 (CHCl2), 103.1 (C–I),
130.4 (CC=O), 131.0 (CHarom), 138.3 (CHarom), 185.5 (C=O).
1-(4-tert-Butylphenyl)-2,2-dichloroethanone (2c)26
White crystals; mp 51.5–52.5 °C (Lit.26 mp 47–49 °C); Rf 0.85 (pe-
troleum ether–EtOAc, 91:9).
1H NMR (250.13 MHz, CDCl3): d = 1.38 (s, 9 H, t-C4H9), 6.72 (s, 1
H, CH), 7.54 (d, 2 H, J = 8.5 Hz, ArH), 8.03 (d, 2 H, J = 8.5 Hz,
ArH).
13C NMR (62.9 MHz CDCl3): d = 31.0 (CH3), 35.4 [C(CH3)3] 67.9
(CHCl2), 126.0 (CHarom), 128.6 (CC=O), 129.8 (CHarom), 158.8
[CC(CH3)3], 185.6 (C=O).
2,2-Dichloro-1-(3-chloro-4-methoxyphenyl)ethanone (2k)5
Light yellow crystals; mp 101.5–102.5 °C (Lit.5 mp 102 °C);
Rf 0.32 (petroleum ether–EtOAc, 94:6).
Synthesis 2004, No. 17, 2845–2848 © Thieme Stuttgart · New York