Triphosgene mediated chlorination of Baylis-Hillman adducts

Article abstract of DOI:10.1007/s12039-012-0243-3

An efficient method for the preparation of allyl chlorides from Baylis-Hillman adducts has been developed using triphosgene/pyridine system. This method is best illustrated by its advantages like operational simplicity, excellent yields, short reaction ti

Full text of DOI:10.1007/s12039-012-0243-3

c
J. Chem. Sci. Vol. 124, No. 2, March 2012, pp. 513–519. ꢀ Indian Academy of Sciences.
Triphosgene mediated chlorination of Baylis–Hillman adducts
NARENDER REDDY THATIKONDA, NAGA SESHA SAI PAVAN KUMAR CHEBOLU,
MAHENDAR BUDDE and JAYATHIRTHA RAO VAIDYA∗
Organic Chemistry Division II, Indian Institute of Chemical Technology, Uppal Road,
Tarnaka, Hyderabad 500 607, India
e-mail: jrao@iict.res.in
MS received 22 August 2011; revised 19 November 2011; accepted 25 November 2011
Abstract. An efficient method for the preparation of allyl chlorides from Baylis–Hillman adducts has been
developed using triphosgene/pyridine system. This method is best illustrated by its advantages like operational
simplicity, excellent yields, short reaction time, simple procedure and stereoselectivity.
Keywords. Baylis–Hillman adducts; triphosgene; chlorination; stereoselectivity; simple procedure.
1. Introduction
interest on the chemical transformations using Baylis–
Hillman chemistry,15 we report here a new and con-
venient method for the chlorination of Baylis–Hillman
adducts to obtain the allyl chlorides in a stereoselective
manner. In this paper, we describe the use of triphos-
gene as an excellent reagent for the easy and mild
conversion of Baylis–Hillman adducts into their allyl
chlorides. The chlorination using triphosgene is fast,
smooth, clean and high yielding.
Baylis–Hillman reaction1 is now a standard C–C
bond formation reaction widely used in synthetic
organic chemistry. The reaction has been exten-
sively studied and various applications are reported
in the literature.2 The derivatives of Baylis–Hillman
adducts, in particular, Baylis–Hillman allyl halides have
been used as valuable intermediates in the prepara-
tion of several heterocyclic compounds and also in
stereo-selective processes.3 Chlorination of Baylis–
Hillman adducts using various reagents/protocols are
reported in the literature viz., HCl/H2SO4,4 FeCl3 or
InCl3,5 PPh3/CCl4,6 PPh3/Cl3CCONH2,7 TCT/DMF,8
(COCl)2/DMF,9 DMF/POCl3,10 NEt3/MsCl,11 and also
using ionic liquid as medium.12 Unfortunately, many
of these suffer from limitations such as harsh reaction
conditions, lack of general applicability, longer reaction
times, and only one report6 is available in the literature
for the conversion of nitrile containing Baylis–Hillman
adducts to their allyl chlorides. Therefore, reinvestiga-
tion of the classical conditions seemed warranted for
developing suitable conditions for the synthesis of allyl
chlorides. Triphosgene [bis(trichloromethyl)carbonate]
is yet another important chlorinating agent has been
found to be an excellent activating agent in sev-
eral organic reactions.13 The efficiency of triphosgene
(white crystalline compound) as a synthetic auxiliary,
as a carbonylating agent, as a chlorinating agent, as
a replacement of POCl3 in the preparation of many
important classes of organic compounds has been inves-
tigated in the last twenty years.14 In continuation of our
2. Experimental
2.1 General
All the chemicals used were of reagent grade obtained
from local suppliers, Aldrich and Fluka. All reactions
were performed in oven-dried glassware under nitro-
gen atmosphere. Analytical thin layer chromatography
(TLC) was performed on silica gel plates and TLC visu-
alization was carried out with UV. Melting points were
determined on a Mettlers-Temp and are uncorrected.
IR Spectra were recorded using a Perkin-Elmer-1600
FT-IR spectrometer; ν in cm−1. 1H and 13C-NMR spec-
trum (CDCl3/DMSO-d6) was recorded with Gemini-
200 and Bruker-Avance-300 instruments; chemical
shifts δ in ppm relative to SiMe4 as an internal standard,
couplings in Hz. HRMS (ESI) data were recorded on a
QSTAR XL High resolution mass spectrometer; in m/z
(rel. %). GC was recorded on GC-17A Gas Chromato-
graph SHIMADZU system (column: Zebron-1 C49045
30 m × 53 mm I.D. × 1.5 μ F. T.), Oven program 50◦C
for 5 min temp. raised 10◦C/min to 280◦C; hold 5 min;
gas flow rate 1 mL/min.
∗For correspondence
513

514
Narender Reddy Thatikonda et al.
2.2 General experimental procedure for the synthesis δ = 166.8, 150.9, 143.8, 129.9, 128.9, 126.9, 126.6,
of allyl chlorides from Baylis–Hillman adducts (1a–v)
126.2, 52.3, 39.3, 34.0, 23.7. IR (Neat): 2961, 1717,
1628, 1509, 1436, 1281 cm−1; MS (ESI): m/z 275
[M+Na]+; HRMS (ESI) calcd. for C14H17ClO2Na:
275.0814; found: 275.0826; GC: Z:E = 96:4.
To a stirred solution of triphosgene (0.93 g, 3.14 mmol)
in dichloromethane (5 mL) at 0◦C, pyridine (1.26 mL,
15.72 mmol) was added drop-wise followed by Baylis–
Hillman adduct (1m) (0.5 g, 3.14 mmol) in DCM
(5 mL) and stirred the reaction at room temperature 2.2e (Z)-Methyl 2-(chloromethyl)-3-(4-methoxyphenyl)
(Monitored by TLC). After completion of the reaction, acrylate (2e): Colourless liquid; Yield 90%; 1H NMR
the reaction mixture was diluted with DCM (10 mL); (300 MHz, CDCl3): δ = 7.77 (s, 1H), 7.54 (d, J =
the organic layer was washed with water (5 mL), sat. 8.3 Hz, 2H), 6.95 (d, J = 9.0 Hz, 2H), 4.47 (s, 2H),
CuSO4 solution (5 mL), dried over Na2SO4 and the sol- 3.86 (s, 3H), 3.84 (s, 3H); IR (Neat): 2960, 2840, 1908,
vent was removed under reduced pressure to get the 1718, 1633, 1599, 1439, 1278 cm−1; MS (EI): m/z 240
desired allyl chloride (2m) as colourless liquid (0.57 g, [M+], 205, 145 (100) 131, 115; GC: Z:E = 95:5.
95%) Rf = 0.8 (20% EtOAc/hexane). Same experi-
mental procedure was adopted for the preparation of
other allyl chlorides.
2.2f (Z)-Methyl 2-(chloromethyl)-3-(4-fluorophenyl)
acrylate (2f): Colourless liquid; Yield 93%; 1H NMR
(300 MHz, CDCl3): δ = 7.78 (s, 1H), 7.56 (t, J =
8.8 Hz, J = 7.8 Hz, 2H), 7.15 (t, J = 8.8 Hz, 2H),
4.40 (s, 2H), 3.80 (s, 3H); IR (Neat): 2952, 1718,
1631, 1490, 1438, 1312, 1281, 1208, 1090 cm−1; MS
(EI): m/z 228 [M+], 193, 133 (100), 115, 107; GC:
Z:E = 98:2.
2.2a (Z)-Methyl 2-(chloromethyl)-3-phenylacrylate (2a):
1
Colourless liquid; Yield 95%; H NMR (300 MHz,
CDCl3): δ = 7.83 (s, 1H), 7.52–7.43 (m, 2H), 7.45–
7.25 (m, 3H), 4.43 (s, 2H), 3.87 (s, 3H); IR (Neat):
2988, 2853, 1750, 1630, 1250, 1170 cm−1; MS (EI):
m/z 210 [M+], 176 (100), 131, 115; GC: Z:E = 97:3.
2.2g (Z)-Methyl 2-(chloromethyl)-3-(2-chlorophenyl)
acrylate (2g): Colourless liquid; Yield 90%; 1H NMR
(300 MHz, CDCl3): δ = 7.92 (s, 1H), 7.69–7.65 (m,
1H), 7.46–7.32 (m, 3H), 4.32 (s, 2H), 3.90 (s, 3H);
IR (Neat): 2982, 1717, 1636, 1469, 1439, 1371, 1288,
1208, 1179 cm−1; MS (EI): m/z 244 [M+], 209, 149
(100), 130, 115; GC: Z:E = 98:2.
2.2b (Z)-Methyl 2-(chloromethyl)-3-(4-chlorophenyl)
acrylate (2b): Colourless liquid; Yield 92%; 1H NMR
(300 MHz, CDCl3): δ = 7.71 (s, 1H), 7.49 (d, J =
8.8 Hz, 2H), 7.42 (d, J = 7.8 Hz, 2H), 4.39 (s, 2H),
3.87 (s, 3H); IR (Neat): 2953, 2849, 1718, 1633, 1599,
1509, 1439, 1278, 1230, 1163 cm−1; MS (EI): m/z 244
[M+], 209, 149 (100), 130, 115; GC: Z:E = 95:5.
2.2h (Z)-Ethyl 2-(chloromethyl)-3-(4-chlorophenyl)
acrylate (2h): Colourless solid; Yield 92%; M.p.:
2.2c (Z)-Methyl 2-(chloromethyl)-3-(4-ethylphenyl)
acrylate (2c): Colourless liquid; Yield 95%; 1H NMR
(300 MHz, CDCl3): δ = 7.80 (s, 1H), 7.40 (d, 2H,
J = 7.9 Hz), 7.26 (d, 2H, J = 7.9 Hz), 4.45 (s, 2H),
3.86 (s, 3H), 2.72 (q, 2H, J = 7.5 Hz), 1.29 (t, 3H,
J = 7.5 Hz); 13C NMR (75 MHz, CDCl3): δ = 166.8,
146.4, 143.9, 131.4, 129.8, 128.8, 128.4, 52.3, 39.3,
28.7, 15.2; IR (Neat): 2965, 1718, 1628, 1509, 1436,
1272 cm−1; MS (ESI): m/z 261 [M+Na]+; HRMS
(ESI) calcd. for C13H15ClO2Na: 261.0658; found:
261.0653; GC: Z:E = 96:4.
1
78–80◦C; H NMR (300 MHz, CDCl3): δ = 7.76 (s,
1H), 7.50 (d, J = 8.30 Hz,2H), 7.47 (d, J = 8.6 Hz,
2H), 4.39 (s, 2H), 4.36 (q, J = 7.1 Hz, 2H), 1.41
(t, J = 7.1 Hz, 3H); IR (KBr): 2924, 2853, 1701,
1624, 1489, 1378, 1263, 1213, 1179 cm−1; MS (EI):
258 [M+], 223, 195, 159 (100), 149, 131, 115; GC:
Z:E = 97:3.
2.2i (Z)-Ethyl 2-(chloromethyl)-3-(4-methoxyphenyl)
acrylate (2i): Colourless liquid; Yield 90%; 1H NMR
(300 MHz, CDCl3): δ = 7.78 (s, 1H), 7.57 (d, J =
8.3 Hz, 2H), 6.94 (d, J = 9.0 Hz, 2H), 4.49 (s, 2H),
4.36 (q, J = 7.1 Hz, 2H), 3.86 (s, 3H), 1.39 (t, J =
7.1 Hz, 3H). IR (Neat): 2966, 2848, 1908, 1708, 1633,
1599, 1439, 1278 cm−1; MS (EI): 254 [M+], 219 (100)
145, 131, 115. GC: Z:E = 98:2.
2.2d (Z)-Methyl 2-(chloromethyl)-3-(4-isopropylphenyl)
acrylate(2d): Colourless liquid; Yield 93%; 1H NMR
(300 MHz, CDCl3): δ = 7.79 (s, 1H), 7.47 (d, J =
7.9 Hz, 2H), 7.28 (s, J = 8.9 Hz, 2H), 4.44 (s, 2H),
3.85 (s, 3H), 2.94 (m, J
=
6.9 Hz, 1H), 1.27
(d, J = 6.9 Hz, 6H); 13C NMR (75 MHz, CDCl3):

Triphosgene mediated chlorination of Baylis-Hillman adducts
515
2.2j (Z)-Ethyl 2-(chloromethyl)-3-(2,4-dichlorophenyl) (s, 2H); IR (KBr): 2963, 2855, 2210, 1891, 1602, 1510,
acrylate (2j): Colourless solid; Yield 90%; M.p.: 74– 1417, 1246, 1169 cm−1; MS (EI): m/z 195 [M+], 160,
1
76◦C; H NMR (300 MHz, CDCl3): δ = 7.82 (s, 1H), 140, 133, 120; GC: Z:E = 10:90.
7.63 (d, J = 7.8 Hz, 2H), 7.40 (s, 1H), 7.36 (d, J =
7.8 Hz, 2H), 4.35 (q, J = 6.8 Hz, 2H), 4.29 (s, 2H),
2.2p
(E)-3-(3-Bromophenyl)-2-(chloromethyl)
1.41 (t, J = 6.8 Hz, 3H); IR (KBr): 2980, 2928, 1717,
1583, 1469, 1375, 1280, 1251, 1178 cm−1; MS (EI):
292 [M+], 257, 247, 229, 193 (100), 149, 113; GC:
Z:E = 98:2.
acrylonitrile (2p): Colourless solid; Yield 85%; M.p.:
76–78◦C; H NMR (300 MHz, CDCl3): δ = 7.82 (d,
1
J = 9.0 Hz, 2H), 7.58–7.55 (m, 1H), 7.36–7.30 (t,
J = 8.3 Hz, 1H), 7.13 (s, 1H), 4.29 (s, 2H); IR (KBr):
2963, 2925, 2214, 1314, 1467, 1268, 1215 cm−1;
MS (EI): m/z 254 [M+], 220, 141 (100) 114; GC:
Z:E = 4:96.
2.2k (Z)-Ethyl
2-(chloromethyl)-3-(4-nitrophenyl)
acrylate (2k): Yellow solid; Yield 93%; M.p.: 77–
1
79◦C; H NMR (300 MHz, CDCl3): δ = 8.33 (d,
J = 9.0 Hz, 2H), 7.83 (s, 1H), 7.72 (d, J = 9.0 Hz,
2H), 4.39 (q, J = 6.7 Hz, 2H), 4.36 (s, 2H), 1.43 (t,
J = 6.7 Hz, 3H); IR (KBr): 2920, 2855, 1595, 1510,
1438, 1344, 1258, 1105 cm−1; MS (EI): 269 [M+], 234,
150, 129, 115, 79 (100); GC: Z:E = 95:5.
2.2q
(E)-2-(Chloromethyl)-3-(3-chlorophenyl)
acrylonitrile (2q): Colourless solid; Yield 88%; M.p.:
75–77◦C; 1H NMR (300 MHz, CDCl3): δ = 7.75–7.73
(m, 1H), 7.66 (s, 1H), 7.41–7.39 (m, 2H), 7.14 (s, 1H),
4.28 (s, 2H); IR (KBr): 2925, 2855, 2212, 1616, 1587,
1486, 1407, 1266, 1090 cm−1; MS (EI): m/z 212 [M+],
176, 160, 140 (100), 133, 125, 113; GC: Z:E = 10:90.
2.2l (Z)-Ethyl 2-(chloromethyl)pent-2-enoate (2l):
1
Colourless liquid; Yield 89%; H NMR (300 MHz,
CDCl3): δ = 6.96 (t, J = 7.7 Hz, 1H), 4.28 (s, 2H),
4.27 (q, J = 7.1 Hz, 2H), 2.40 (q, J = 7.5 Hz, 2H),
1.35 (t, J = 7.1 Hz, 3H), 1.17 (t, J = 7.5 Hz, 3H);
IR (Neat): 2977, 2938, 1779, 1717, 1645, 1460, 1374,
1279, 1181 cm−1; MS (EI): 176 [M+], 157, 141, 133,
113, 99, 57 (100); GC: Z:E = 90:10.
2.2r
(E)-2-(Chloromethyl)-3-(4-chlorophenyl)
acrylonitrile (2r): Colourless solid; Yield 92%; M.p.
73–75◦C; H NMR (300 MHz, CDCl3): δ = 7.73 (d,
1
J = 8.3 Hz, 2H), 7.43 (d, J = 8.3 Hz, 2H), 7.14 (s,
1H), 4.28 (s, 2H); IR (KBr): 2925, 2855, 2212, 1616,
1587, 1486, 1407, 1266, 1090 cm−1; MS (EI): m/z 212
[M+], 176 (100) 140, 113, 99; GC: Z:E = 1:99.
2.2m (E)-2-(Chloromethyl)-3-phenylacrylonitrile (2m):
1
Colourless liquid; Yield 95%; H NMR (300 MHz,
2.2s (E)-3-(4-Bromophenyl)-2-(chloromethyl)
acrylonitrile (2s): Colourless solid; Yield 93%; M.p.:
CDCl3): δ = 7.78–7.75 (m, 2H), 7.44 (t, 3H), 7.18
(s, 1H), 4.29 (s, 2H); IR (Neat): 2955, 2830, 2210,
1602, 1590, 1510, 1439, 1258, 1105 cm−1; MS (EI):
177 [M+], 142, 127, 115 (100), 102; GC: Z:E = 3:97.
1
72–74◦C; H NMR (300 MHz, CDCl3): δ = 7.66 (d,
J = 8.3 Hz, 2H), 7.59 (d, J = 8.3 Hz, 2H), 7.13 (s,
1H), 4.27 (s, 2H); IR (KBr): 2924, 2855, 2211, 1616,
1582, 1481, 1403, 1261, 1071 cm−1; MS (EI): m/z 254
(100) [M+], 220, 140, 114, 100; GC: Z:E = 5:95.
2.2n
(E)-2-(Chloromethyl)-3-(4-ethylphenyl)
1
acrylonitrile (2n): Colourless liquid; Yield 95%; H
NMR (300 MHz, CDCl3): δ = 7.71 (d, J = 8.1 Hz,
2H), 7.26 (d, J = 8.1 Hz, 2H), 7.10 (s, 1H), 4.28 (s,
2H), 2.70 (q, J = 7.5 Hz, 2H), 1.20 (t, J = 7.5 Hz,
3H); 13C NMR (75 MHz, CDCl3): δ = 148.3, 146.7,
129.4, 128.7, 128.5, 117.2, 106.3, 46.2, 28.8, 15.1;
IR (Neat): 2968, 2217, 1607, 1621, 1266 cm−1; MS
(ESI): m/z 228 [M+Na]+. HRMS (ESI) calcd. for
C12H12ClNNa: 228.0555; found: 228.0553; GC:
Z:E = 5:95.
2.2t (E)-2-(Chloromethyl)-3-(4-fluorophenyl)
acrylonitrile (2t): Colourless solid; Yield 96%; M.p.:
1
70–72◦C; H NMR (300 MHz, CDCl3): δ = 7.98
o
2.2o
(E)-2-(Chloromethyl)-3-(3-fluorophenyl)
acrylonitrile (2o): Colourless solid; Yield 88%; M.p.:
72–74◦C; H NMR (300 MHz, CDCl3): δ = 7.58 (d,
1
Scheme 1. Chlorination of Baylis–Hillman adducts.
J = 7.9 Hz, 2H), 7.48–7.41 (m, 3H), 7.16 (s, 1H), 4.29

516
Narender Reddy Thatikonda et al.
1510, 1438, 1344, 1258, 1105 cm−1; MS (EI): m/z 222
[M+], 187, 170, 140 (100), 114; GC: Z:E = 6:94.
Table 1. Comparison study of bases in chlorination of
Baylis–Hillman adducts using triphosgene for the reference
reaction (1m–2m).
Isolated
yield (%)*
S. No
Base
Time
3. Results and discussion
1
2
3
4
5
6
7
Pyridine
DMAP
DBU
DABCO
Piperidine
Diisopropyl Ethyl Amine
Et3N
10 min
15 min
4 h
12 h
12 h
12 h
12 h
95
90
85
20
30
–
The starting material, Baylis–Hillman adducts are syn-
thesized by modifying the reported procedure by treat-
ing various aldehydes with acrylates/acrylonitrile in
presence of 30 mol% DABCO as a catalyst under
solvent-free conditions. In a reference reaction, we have
studied the reaction conditions elaborately like selec-
tion of base, temperature, and solvent system for the
efficacy of the chlorination of Baylis–Hillman adducts.
After numerous trails, triphosgene/pyridine/DCM at
0◦C is found to be the best reaction condition for the
effective conversion (scheme 1). Comparative studies
of different bases in chlorination of Baylis–Hillman
adduct (1m) using triphosgene is tabulated in table 1.
The results of table 1 reveal that aromatic bases like
pyridine and DMAP are most effective in this chlori-
nation reaction. The other aliphatic bases viz., DBU,
DABCO and piperidine gives moderate to low yields
with more reaction time due to their higher reactivity
in the reaction. It was noticed that the reaction was
found not progressing using DIPEA and triethylamine.
In almost all cases, starting material only recovered
from the reaction mixture. Pyridine has chosen as suit-
able base for the conversion due to its inexpensiveness
and with respect to reaction yield/time. The variation
of temperature and time does not show any appreciable
change in the reaction. To demonstrate the general util-
ity of the reaction, the method was successfully applied
to various Baylis–Hillman adducts having both ester
(1a–l) and nitrile (1m–v) moieties (table 2). The reac-
tion underwent smoothly in all the cases and excellent
–
*Reaction was carried out at 0◦C in DCM as solvent
(t, J = 8.8 Hz, 2H), 7.31 (s, 1H), 7.30 (d, J = 8.8 Hz,
2H), 4.45 (s, 2H); IR (KBr): 2965, 2214, 1891, 1602,
1510, 1417, 1246, 1163 cm−1; MS (EI): m/z 195 [M+],
160 (100) 140, 133, 120,106; GC: Z:E = 2:98.
2.2u (E)-2-(Chloromethyl)-3-(4-methoxyphenyl)
acrylonitrile (2u): Colourless solid; Yield 93%; M.p.:
71–73◦C; H NMR (300 MHz, CDCl3): δ = 7.77 (d,
1
J = 8.8 Hz, 2H), 7.09 (s, 1H), 6.93 (d, J = 8.8 Hz,
2H), 4.27 (s, 2H), 3.80 (s, 3H); IR (KBr): 2962, 2841,
2214, 1601, 1511, 1260, 1179 cm−1; MS (EI): m/z
207 [M+], 172 (100), 157, 140, 128, 115, 102; GC:
Z:E = 5:95.
2.2v (E)-2-(Chloromethyl)-3-(4-nitrophenyl)
acrylonitrile (2v): Light yellow solid; Yield 90%;
M.p.: 78–80◦C; 1H NMR (300 MHz, CDCl3): δ = 8.32
(d, J = 8.8 Hz, 2H), 7.94 (d, J = 8.8 Hz, 2H), 7.29 (s,
1H), 4.32 (s, 1H); IR (KBr): 2925, 2852, 2219, 1595,
Table 2. Synthesis of allyl chlorides from Baylis–Hillman adducts.
Isolated
yield
Z:E
S. No
Substrate
Product
Ratioa
OH
COOMe
COOMe
1a
2a
Cl
1
2
3
95
92
95
97:3
95:5
96:4
OH
OH
COOMe
COOMe
1b
Cl
Cl
Cl
2b
COOMe
COOMe
1c
Cl
2c

Triphosgene mediated chlorination of Baylis-Hillman adducts
517
Table 2. (continued).
Isolated
yield
Z:E
S. No
Substrate
Product
Ratioa
OH
COOMe
1d
COOMe
Cl
2d
4
93
90
93
90
96:4
95:5
98:2
98:2
OH
COOMe
COOMe
1e
Cl
O
O
2e
5
OH
COOMe
COOMe
1f
Cl
2f
F
F
6
OH
COOMe
COOMe
1g
Cl
Cl
Cl
2g
7
OH
COOEt
COOEt
1h
Cl
Cl
Cl
2h
8
92
90
97:3
98:2
OH
OH
COOEt
COOEt
1i
Cl
2i
O
O
9
COOEt
COOEt
Cl
2j
Cl
Cl
Cl
Cl
1j
10
90
98:2
OH
COOEt
COOEt
Cl
O2N
O2N
1k
2k
11
93
89
95:5
OH
COOMe
COOMe
2l
1l
Cl
12
13
90:10
OH
Cl
CN
1m
CN
2m
95
95
3:97
5:95
OH
Cl
CN
CN
2n
1n
14
15
OH
CN
Cl
CN
1o
F
F
2o
88
10:90

518
Narender Reddy Thatikonda et al.
Table 2. (continued).
Isolated
yield
Z:E
S. No
Substrate
Product
Ratioa
OH
CN
Cl
CN
1p
2p
Cl
Br
Cl
Br
Cl
16
17
85
4:96
OH
CN
1q
CN
2q
88
92
10:90
1:99
OH
CN
1r
Cl
Cl
CN
2r
Cl
Br
Cl
18
OH
CN
CN
2s
Br
1s
19
93
96
93
5:95
2:98
5:95
OH
CN
1t
CN
CI
2t
CN
F
F
20
OH
CI
CN
2u
O
O
1u
OH
21
CN
1v
CI
CN
O N
O N
2
2
2v
22
90
6:94
aZ/E ratio was determined by 1H NMR and GC analysis
yields were obtained in short reaction times (immedi- is Z and nitrile containing Baylis–Hillman allyl chlo-
ately). Another importance of the reaction was no col- rides major isomer is E. The ratio of the E–Z products
umn chromatography is required for the isolation of as measured by GC is listed in the table 2.
product. Several functionalities such as halogen, nitro,
ether, and ester remained intact. The adducts contain-
ing electron donating as well as withdrawing groups
have been utilized effectively in this protocol and 22
examples are depicted in table 2. See supplementary
information.
The stereoselectivity of present conversion was stud-
ied in detailed. There are a few reports in the litera-
ture regarding stereochemistry of Baylis–Hillman allyl
chlorides.7–11,16 Following earlier reports, according to
1H NMR data and iterative GC analysis of prepared
chlorides, revealed that the stereochemistry of ester
containing Baylis–Hillman allyl chlorides major isomer
4. Conclusions
In summary, we have described a mild and effi-
cient method for the chlorination of Baylis–Hillman
adducts using triphosgene. The advantages of triphos-
gene/pyridine system are; more convenient to handle,
operational simplicity, excellent yields, no chromatog-
raphy, and simple workup procedure. This is a versa-
tile, inexpensive, environmentally benign method and
makes this a valid contribution in upgrading to the
existing methodologies. Application of this strategy to

Triphosgene mediated chlorination of Baylis-Hillman adducts
519
the preparation of new heterocyclic entities from allyl
chlorides is currently being pursued.
7. Das B, Chowdhury N, Damodar K and Ravikanth B
2007 Helv. Chim. Acta 90 2037
8. Li J, Li S, Jia X and Zhang Y 2008 J. Chem. Res. 1 48
9. (a) Lawrence N J, Crump J P, Mc Gown A T and
Hadfield J 2001 Tetrahedron Lett. 42 3939; (b) Biswas
K, Börner C, Gimeno J, Goldsmith P J, Ramazzotti
D, So A L K and Woodward S 2005 Tetrahedron 61
1433
10. Liu Y, Zheng H, Xu D, Xu Z and Zhang Y 2007 Org.
Prep. Proc. Int. 39 190
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Supporting information
The supplementary information for experimental pro-
cedure, characteristic data and spectra of new com-
pounds 2c, 2d and 2n can be seen in the website (www.
ias.ac.in/chemsci).
Acknowledgements
12. Ying T, Bao W, Wang Z and Zhang Y 2005 J. Chem.
Res. Synop. 2 96
The authors thank the Director, Indian Institute of
Chemical Technology (IICT) and Head, Organic-II
Division-II for encouragement. This work is the Main
Lab Project of IICT. TN, CHNSSP and BM thank the
University Grants Commission (UGC) and the Coun-
cil of Scientific and Industrial Research (CSIR), New
Delhi for fellowship.
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