Unexpected dealkylation during nucleophilic substitution: Synthesis of 2-N,N-dialkylamino benzoxazoles and benzothiazoles

Article abstract of DOI:10.1016/S0040-4020(00)00802-4

Mild reaction conditions are described for the preparation of a number of 2-alkyl- and 2-arylaminobenzoxazoles and benzothiazoles from 2-chlorobenzoxazole and 2-chlorobenzothiazole and N-methyl or other simple N-alkyl tertiary amines. The reaction proceeds neat or in THF solution and involves dealkylation of the amine reactant by nucleophilic substitution by chloride. In the case of N-methylpyrrolidine and N-methylpiperidine demethylation was not observed and the major product was formed by ring opening to give chlorobutyl- and chloropentyl-methylamino substituted benzoxazoles and benzothiazoles. Treatment of the chlorobutyl derivative with iodide in acetone afforded the new 1H,2H,3H,4H,5H-[1,3]diazepino[2,1-b][1,3]benzoxazol-6-ium ring system. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00802-4

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TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 8567±8571
Unexpected Dealkylation During Nucleophilic Substitution:
Synthesis of 2-N,N-Dialkylamino Benzoxazoles and Benzothiazoles
a
a
b
Abedawn I. Khalaf,a, Ricardo G. Alvarez, Colin J. Suckling and Roger D. Waigh
*
aDepartment of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, Scotland, UK
bDepartment of Pharmaceutical Sciences, Strathclyde Institute for Biomedical Sciences, 27 Taylor Street, Glasgow G4 0NR, Scotland, UK
Received 6 July 2000; revised 18 August 2000; accepted 30 August 2000
AbstractÐMild reaction conditions are described for the preparation of a number of 2-alkyl- and 2-arylaminobenzoxazoles and benzo-
thiazoles from 2-chlorobenzoxazole and 2-chlorobenzothiazole and N-methyl or other simple N-alkyl tertiary amines. The reaction proceeds
neat or in THF solution and involves dealkylation of the amine reactant by nucleophilic substitution by chloride. In the case of N-methyl-
pyrrolidine and N-methylpiperidine demethylation was not observed and the major product was formed by ring opening to give chlorobutyl-
and chloropentyl-methylamino substituted benzoxazoles and benzothiazoles. Treatment of the chlorobutyl derivative with iodide in acetone
afforded the new 1H,2H,3H,4H,5H-[1,3]diazepino[2,1-b][1,3]benzoxazol-6-ium ring system. q 2000 Elsevier Science Ltd. All rights
reserved.
As part of a programme of synthesis into minor groove
binders for DNA,1 we required to prepare distamycin
analogues with heterocyclic head groups. Accordingly
2-chlorobenzoxazole was reacted with
a distamycin
analogue precursor that bore both a primary and a tertiary
amine. Surprisingly, substitution to afford the corresponding
aminobenzoxazole occurred at both amino groups with
concomitant demethylation or de-ethylation of the tertiary
amine.2±6 This unexpected reaction of the tertiary amines
prompted us to investigate the generality of the reaction.
Although the products of these reactions, N,N-dialkylamino
benzoxazoles and benzothiazoles, have been prepared
before,10±12 most recently using high pressure,4 (see
Table 1 for further references) the reactions described
here offer simpler and more direct routes to these
compounds.
The scope of this substitutive dealkylation reaction was
studied to examine the in¯uence of ring alkyl substitution
in the tertiary amines. N,N-Dimethylbenzylamine under-
went substitution with loss of the benzyl group to give 3d
(87%) but N,N-dimethylaniline afforded 2-N-methyl-N-
phenylbenzoxazole (3f) in moderate yield (43%) with loss
of the methyl group. Triethylamine reacted similarly to the
other trialkylamines giving the diethylamino derivative 3e
in 89% yield. On the other hand, dicyclohexylmethylamine
and N,N-diethylaniline failed to react. These results and
others (Table 1) show that the normal effects of reactivity
in nucleophilic substitution are followed. Attack of the
nucleophile on the aryl halide is subject to steric hindrance
and substitution is preferred at benzylic sites.
Treatment of 2-chlorobenzoxazole (1a) with N-methyl-
morpholine (2a) under re¯ux in THF (or neat at 1308C)
afforded 2-N-morpholinobenzoxazole (3a) in good yield
(85%) after puri®cation through a short column. In THF
solution, 2-chlorobenzothiazole (1b) was much less reactive
giving the corresponding morpholinothiazole (3b) in only
8% yield. However in the absence of solvent a signi®cantly
increased yield (50%) was obtained. Concentration and
temperature therefore seem to be important in this new
reaction.
The reaction mechanism suggested by these observations
(Scheme 1) involves initial addition of the tertiary amine
to the heteroaryl chloride giving an adduct with a positively
charged nitrogen atom. Instead of chloride acting as a
leaving group, the adduct decomposes by nucleophilic
substitution with the quaternary ammonium salt acting as
a leaving group. Once chloride has been formed in the
aprotic reaction mixture, it is a potential nucleophile leading
to alkyl chlorides as the by-products. Benzyl chloride was
Keywords: 2-arylaminobenzoxazoles; 2-chlorobenzoxazole; 2-chloro-
benzothiazole; dealkylation; [1,3]diazepino[2,1-b][1,3]benzazoles.
* Corresponding author. Tel.: 1141-548-2271; fax: 1141-548-4733;
e-mail: c.j.suckling@strath.ac.uk
1
indeed detected from the H NMR signal at d 4.6 in the
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00802-4

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8568
A. I. Khalaf et al. / Tetrahedron 56 (2000) 8567±8571
Table 1. Synthesis of 3 from 2-chlorobenzoxazole (or 2-chlorobenzothiazole) and tertiary amines
Entry
Product
X
R1
R2
R3
Yield%
Mp (8C)
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
3g
3h
3i
O
S
O
S
O
O
O
S
O
S
Morpholino
Morpholino
CH3
CH3
CH2Ph
CH2Ph
CH2CH3
CH3
CH3
CH3
CH2CH3
CH2CH3
CH3
80
50
87
72
89
43
7e
92±95a
122±125b
89±91c
84±86d
Oil4,15
CH3
CH3
CH2CH3
CH3
CH3
CH3
CH2CH3
Ph
Oil8
Pyrrolidino
Pyrrolidino
Piperidino
Piperidino
134±135f
96±98g
72±73h
90±91i
Oilj
7e
9
10
11
86
41
17
3j
3k
S
CH3
Ph
a Lit.13 mp 88±898C.
b Lit.14 mp 126±1278C.
c Lit.13 mp 88±898C.
d Lit.13 mp 84±868C.
e Indicates that the major product was a ring opened derivative (see below).
f Lit.9 mp 136±1378C.
g Lit.16 mp 98±1008C.
h Lit.17 mp 70±718C.
i Lit.7 mp 93±958C.
j Lit.18 mp 66±678C.
A further unusual observation was made. When the products
of the reactions of 2-chlorobenzoxazole and 2-chloro-
benzothiazole with N-methylpyrrolidine or N-ethylpyrroli-
dine were puri®ed, a second product was isolated along with
the expected adducts 3g and 3h. The new products
contained covalently bound chlorine and the methyl group
was still present; they were insoluble in water and clearly
not salts. In the case of the compound derived from
N-methylpyrrolidine, high resolution mass spectroscopy
established the molecular formula C14H19ClN2O. The 13C
NMR spectrum showed four distinct methylene groups
deriving from the pyrrolidine ring suggesting that the ring
opened structure 4 (Scheme 2) represented the new
compound. This suggestion was also consistent with the
long range couplings shown by COSY experiments: an
interaction between the N-methyl protons (d 3.20) and the
methylene protons (d 3.68) was observed. What is not easily
understood is that this reaction is strongly favoured in the
case of pyrrolidine. A small amount of the analogous
product was characterised from the reaction of N-ethyl-
piperidine and 2-chlorobenzoxazole but in other cases no
ring cleavage product was detected, although it may have
been present in small quantity. Again, it is possible that
Scheme 1. Proposed mechanism of dealkylative substitution.
reaction mixture with benzyldimethylamine as substrate and
the increase of the alkyl chloride was followed during the
course of the reaction. The action of chloride and bromide as
nucleophiles in substitution reactions of ammonium salts,
sulphonium salts, and oxonium salts is well known. It is also
possible that attack by chloride on the methyl group is
internal, i.e. the two stages are concerted, a reasonable
suggestion because of the proximity of the departing
chloride and the adjacent polarised C±N bond.
Scheme 2. Proposed mechanism of formation of ring opened products and further cyclisation.

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A. I. Khalaf et al. / Tetrahedron 56 (2000) 8567±8571
8569
release of chlorine from the oxazole ring and attack on the
pyrrolidine carbon is a concerted process, which may be
sterically favoured in the ®ve-membered ring. To con®rm
the presence of the chloromethyl group, compound 4 was
treated with sodium iodide in acetone at room temperature.
This surprisingly led to the formation of a new fused
ArH); 7.25 (1H, d, Jˆ7.8 Hz, ArH); 7.36 (1H, d, Jˆ7.8 Hz,
ArH). dC (CDCl3): 37.65, 108.55, 115.98, 120.16, 123.82,
143.58, 149.07, 163.05. nmax: 1665, 1588, 1462, 1426, 901,
745 cm.21
Similarly the following compounds were prepared.
heterocyclic
system,
1-Methyl-1H,2H,3H,4H,5H-
[1,3]diazepino[2,1-b][1,3]benzoxazol-6-ium iodide, 5.
Evidence for this structure comes from the water solubility
of 5 and the down®eld shift of the methylene protons (dH
3.68±4.02 and 4.48) and carbons (dC 44.48 and 49.55±
47.14 and 54.48) and N-methyl protons (dH 3.20±3.50)
and carbons (dC 35.42±41.97). Symmetrical structures
such as pyrrolidinium salts are ruled out (Scheme 2).
2-N-Morpholinobenzothiazole (3b).14 As a pale yellow
crystalline solid (50%); dH (CDCl3): 3.64 (4H, t,
Jˆ4.8 Hz, CH2NCH2); 3.85 (4H, t, Jˆ4.7 Hz, CH2OCH2);
7.11 (1H, dt, Jˆ1.2 and 7.4 Hz, ArH); 7.32 (1H, dt, Jˆ1.2
and 7.4 Hz, ArH); 7.58 (1H, d, Jˆ7.4 Hz, ArH); 7.62 (1H, d,
Jˆ7.4 Hz, ArH). nmax: 1596, 1562, 1539, 1443, 1291, 1116,
759, 727 cm21. HREIMS: found 220.066. Calculated for
C11H12N2OS 220.067.
Recently, further reactions under high pressure have been
described for the preparation of 4-dialkyl-aminopyridines.19
It would be interesting to discover whether milder condi-
tions such as those described here would be successful in
that case also.
2-N,N-Dimethylaminobenzothiazole (3d).13 As a white
crystalline solid (72%). dH (CDCl3): 3.21 (6H, s, NMe2);
7.06 (1H, dt, Jˆ1.2 and 7.4 Hz, ArH); 7.29 (1H, dt, Jˆ1.2
and 7.4 Hz, ArH); 7.57 (1H, d Jˆ7.4 Hz, ArH); 7.60 (1H, d,
Jˆ7.4 Hz, ArH). dC (CDCl3): 40.40, 118.99, 120.81,
121.10, 126.13, 131.34, 153.47, 168.99. nmax: 1599, 1574,
1546, 1453, 1416, 1295, 750, cm21
.
Experimental
2-N,N-Diethylaminobenzoxazole (3e).4,15 As a colourless
oil (89%). dH (CDCl3): 1.27±1.31 (6H, t, Jˆ7.1 Hz,
NCH2CH3); 3.57±3.62 (4H, q, Jˆ7.1 Hz, NCH2CH3);
6.96±7.01 (1H, dt, Jˆ1.1 and 7.8 Hz, ArH); 7.12±7.16
(1H, dt, Jˆ1.1 and 7.8 Hz, ArH); 7.25 (1H, d, Jˆ7.8 Hz,
ArH); 7.36 (1H, d, Jˆ7.8 Hz, ArH). dC (CDCl3): 13.44,
42.91, 108.45, 115.77, 119.89, 123.73, 143.65, 148.81,
162.20. nmax: 2968, 2937, 1647, 1580, 1466, 1399, 1251,
The majority of compounds prepared by the new route have
been described before. Physical constants for compounds
obtained and literature comparisons are given in Table 1.
Spectroscopic data are reported below with the preparative
details. IR spectra: solids were run as KBr discs and liquids
as ®lms, using a Nicolet Impact 400D. Low- and high-
resolution (EI-MS) mass spectra were obtained on a Jeol
JMS-AX505HA mass spectrometer. NMR spectra were
obtained on a Bruker AMX 400 spectrometer operating at
400 MHz for 1H and 100.6 MHz for 13C. Column chromato-
graphy was performed with silica gel Prolabo (200±400
mesh).
784, 761, 748 cm21
.
2-N-Methyl-N-phenylaminobenzoxazole (3f).8 As
a
colourless oil (43%). dH (CDCl3): 3.64 (3H, s, NMe);
7.03±7.08 (1H, dt, Jˆ1.1 and 7.8 Hz, ArH); 7.18±7.22
(1H, dt, Jˆ1.1 and 7.7 Hz, ArH); 7.25±7.31 (2H, m,
ArH); 7.42±7.48 (5H, m, ArH). dC (CDCl3): 39.04,
108.94, 116.66, 121.07, 123.99, 124.43, 126.02, 129.24,
142.76, 142.95, 148.74, 161.26. nmax: 3063, 2940, 1632,
2-N-morpholinobenzoxazole (3a).13 N-Methylmorpholine
(329 mg, 3.256 mmol) was dissolved in THF (20 mL, dry)
to which 2-chlorobenzoxazole (504 mg, 3.256 mmol) was
added at room temperature with stirring. The reaction
mixture was heated under re¯ux for 3 h then the solvent
removed under reduced pressure at 508C. The residue was
dissolved in a small amount of ethyl acetate and applied to a
silica gel column. Ethyl acetate/n-hexane (1:1 v/v) was used
to elute the product, which was obtained as a pale yellow
solid (529 mg, 80%); dH (CDCl3): 3.62±3.65 (4H, t,
Jˆ4.8 Hz, CH2±N±CH2); 3.83±3.86 (4H, t, Jˆ4.8 Hz,
CH2±O±CH2); 7.06 (1H, dt, Jˆ1.2 and 7.8 Hz, ArH);
7.19 (1H, dt, Jˆ1.2 and 7.8 Hz, ArH); 7.26 (1H, d,
1570, 1503, 1380, 1246, 1138, 755, 747, 701 cm21
.
Reaction of N-methylpyrrolidine and (1a): formation of
N-(4-chlorobutyl)-N-methylaminobenzoxazole. 2-Chloro-
benzoxazole (460 mg, 3.0 mmol) and N-methylpyrrolidine
(260 mg, 3.0 mmol) were dissolved in THF (20 mL, dry).
The reaction mixture was heated under re¯ux for 6 h. The
solvent was removed under reduced pressure and the residue
puri®ed by column chromatography on silica eluted with
ethyl acetate/n-hexane (1:20 v/v). The ®rst fraction
(compound of type 4, N-(4-chlorobutyl)-N-methylamino-
benzoxazole) was obtained as a colourless oil (617 mg,
86%). dH (CDCl3): 1.85 (4H, m, (CH2)2CH2N); 3.20 (3H,
s, NMe); 3.68 (4H, m, CH2Cl and CH2N); 7.01 (1H,dt,
Jˆ1.2 and 7.8 Hz, ArH); 7.15 (1H, dt, Jˆ1.2 and 7.8 Hz,
ArH); 7.26 (1H, d, Jˆ7.8 Hz, ArH); 7.36 (1H, d, Jˆ7.8 Hz,
ArH). dC (CDCl3): 24.78, 29.48, 35.42, 44.48, 49.55,
108.55, 115.96, 120.18, 123.85, 143.45, 148.85, 162.65.
Jˆ7.8 Hz, ArH); 7.38 (1H, d, Jˆ7.8 Hz, ArH). nmax
1670, 1580, 1461, 1290, 1108, 763, 744 cm21
:
.
2-N,N-dimethylaminobenzoxazole (3c).13 N,N-Dimethyl-
benzylamine (507 mg, 3.750 mmol) and 2-chlorobenzoxa-
zole (576 mg, 3.750 mmol) were heated at 1308C for 3 h.
The reaction mixture was left to cool to room temperature
then the crystalline mass was dissolved in hot ethyl acetate
and applied to a silica gel column. The required benzoxa-
zole (3c) was obtained as white crystalline material by
elution with ethyl acetate/n-hexane (1:1 v/v) (527 mg,
87%). dH (CDCl3): 3.21 (6H, s, NMe2); 7.00 (1H, dt,
Jˆ1.2 and 7.7 Hz, ArH); 7.16 (1H, dt, Jˆ1.2 and 7.8 Hz,
n
max: 2956, 2867, 1598, 1567, 1544, 1447, 1293, 753,
727 cm21
. HREIMS: found 238.087, calculated for
C12H15N2O35Cl 238.087, and found 240.086 calculated for
C12H15N2O 37Cl 240.086.

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8570
A. I. Khalaf et al. / Tetrahedron 56 (2000) 8567±8571
The second fraction was obtained as white solid material
(40 mg, 7%), identi®ed as 3g.9 dH (CDCl3): 2.05 (4H, t,
Jˆ8 Hz, (CH2)2CH2N); 3.66 (4H, t, Jˆ4.0 Hz, CH2N);
6.99 (1H, t, Jˆ7.8 Hz, ArH); 7.15 (1H, t, Jˆ7.8 Hz, ArH);
7.26 (1H, d, Jˆ7.8 Hz, ArH); 7.36 (1H, d, Jˆ7.8 Hz, ArH).
dC (CDCl3): 25.58, 47.40, 108.55, 115.95, 120.04, 123.81,
143.58, 149.00, 160.98. nmax: 2922, 1642, 1584, 800, 760,
(504 mg, 2.971 mmol) and N-ethylpiperidine (1.009 g,
8.913 mmol) were heated at 1308C for ®ve days. Excess
reagent was removed under reduced pressure and the
crude product was applied to a column chromatography.
Ethyl acetate/n-hexane 1/10 was used to elute the product
which was obtained as pale yellow crystalline material (3j)
(266 mg, 41% yield), Rfˆ0.33. dH (CDCl3): 1.68 (6H, br s,
3£CH2); 3.56 (4H, br s, CH2NCH2); 7.03±7.07 (1H, dt,
Jˆ1.1 and 7.8 Hz, ArH); 7.26±7.31 (1H, dt, Jˆ1.1 and
7.8 Hz, ArH); 7.55±7.59 (2H, m, ArH). dC (CDCl3):
24.67, 25.71 (2£C), 50.02 (2£C), 119.21, 120.97, 121.44,
126.26, 131.12, 153.42, 169.25. nmax: 2945, 2924, 2846,
740 cm21
.
Reaction of N-ethylpiperidine and (1a): N-(4-chloro-
pentyl)-N-ethylaminobenzoxazole. 2-Chlorobenzoxazole
(460 mg, 3.0 mmol) and 1-ethylpiperidine (679 mg,
6.0 mmol) were dissolved in THF (20 mL, dry). The reac-
tion mixture was heated under re¯ux for 24 h. The solvent
was removed under reduced pressure and the residue puri-
®ed by column chromatography eluted with ethyl acetate/n-
hexane (1:9 v/v). The ®rst fraction was obtained as a white
solid which was identi®ed as 3i,17 (519 mg, 86%). dH
(CDCl3): 1.73 (6H, m, 3£CH2); 3.71 (4H, m, CH2N); 7.04
(1H, dt, Jˆ1.2 and 7.8 Hz, ArH); 7.19 (1H, dt, Jˆ1.2 and
7.8 Hz, ArH); 7.28 (1H, d, Jˆ7.8 Hz, ArH); 7.39 (1H, d,
Jˆ7.8 Hz, ArH). dC (CDCl3): 24.08, 25.24 (2£C); 46.62
(2£C); 108.54, 116.00, 120.26, 123.82, 143.39, 148.71,
162.47. nmax: 2941, 2854, 1643, 1576, 1454, 1275, 792,
754, 743 cm21. A second fraction (compound of type 4,
N-(4-chloropentyl)-N-ethylaminobenzoxazole) was obtained
as a colourless oil (55 mg, 7%). dH (CDCl3): 1.27±1.31 (3H,
t, Jˆ7.1 Hz, CH2CH3), 1.49±1.58 (2H, m, CH2), 1.69±1.77
(2H, m, CH2), 1.82±1.89 (2H, qt, Jˆ6.7 Hz, CH2), 3.51 (2H,
t, Jˆ7.4 Hz, CH2N), 3.53 (2H, t, Jˆ6.7 Hz, CH2Cl), 3.57
(2H, q, Jˆ7.3 Hz, NCH2CH3), 6.99 (1H, dt, Jˆ1.2 and
7.8 Hz, ArH), 7.15 (1H, dt, Jˆ1.2 and 7.8 Hz, ArH), 7.27
(1H, d, Jˆ7.8 Hz, ArH), 7.34 (1H, d, Jˆ7.8 Hz, ArH). dC
(CDCl3): 13.29, 24.09, 27.54, 32.30, 43.47, 44.80, 48.01,
1593, 1561, 1535, 1444, 1261, 762, 732 cm21
.
2-N-methyl-N-phenylaminobenzothiazole (3k).18 The
same procedure for the synthesis of (3f) was employed to
give the product as a colourless oil. dH (CDCl3): 3.66 (3H, s,
NMe); 7.09 (1H, dt, Jˆ1.1 and 7.8 Hz, ArH); 7.30±7.52
(7H, m, ArH); 7.66 (1H, d, Jˆ7.8 Hz, ArH). dC (CDCl3):
40.59, 119.36, 120.60, 121.88, 126.00, 126.12 (2£C),
127.55, 130.06 (2£C), 131.33, 145.96, 152.78, 168.37.
n
max: 3063, 1593, 1521, 755 cm21
.
1-Methyl-1H,2H,3H,4H,5H-[1,3]diazepino[2,1-b][1,3]benz-
oxazol-6-ium iodide (compound of type 5). N-(4-chloro-
butyl)-N-methylaminobenzoxazole (20 mg, 0.084 mmol)
was dissolved in dry acetone (5 mL) to which was added
anhydrous sodium iodide (25 mg, 0.10 mmol). The solution
was heated under re¯ux for 8 h and allowed to cool to room
temperature. The sodium chloride precipitate was ®ltered
and the solvent evaporated to dryness under reduced pres-
sure, to afford the product as a white solid (25 mg, 90%).
mp.2408C. dH (CDCl3): 2.27±2.39 (4H, m, 2£CH2), 3.50
(3H, s, NMe), 4.02 (2H, t, Jˆ5.6 Hz, NCH2), 4.48 (2H, t,
Jˆ5.6 Hz, N1CH2), 7.31±7.36 (1H, m, ArH), 7.39±7.47
(3H, m, ArH). dC (CDCl3): 24.60, 24.42 (CH2±CH2),
41.97 (NMe), 47.14 (NCH2), 54.48 (N1CH2), 111.46,
111.91, 125.54, 126.67 (CH of Ar), 131.92, 144.35 (C of
Ar), 158.6 (N1vC±O(N)). HRFABMS Found 203.11834
(95%, base peak), calculated for C12H15N2O 203.11844
108.53, 115.89, 120.04, 123.83, 148.82, 162.47. nmax
:
2939, 1649, 1585, 1462, 760, 745 cm21. HREIMS: found
266.119, calculated for C14H19N2O35Cl 266.119; and found
268.116, calculated for C14H19N2O37Cl 268.116.
Reaction of (1b) with N-methylpyrrolidine: formation of
N-(4-chlorobutyl)-N-methylaminobenzothiazole.
The
(M12I2). nmax 1685, 1480, 1400, 1267, 1164, 758 cm21
.
same experimental procedure as above was employed to
give two products eluted with ethyl acetate/petroleum
ether (1:3 v/v). The ®rst fraction (compound of type 4,
N-(4-chlorobutyl)-N-methylaminobenzothiazole) was obtained
as a colourless oil (83%). dH (CDCl3): 1.82±1.85 (4H, m,
2£CH2), 3.18 (3H, s, NMe), 3.56±3.59 (4H, m, NCH2 and
CH2Cl), 7.06 (1H, dt, Jˆ1.2 and 7.8 Hz, ArH), 7.29 (1H, dt,
Jˆ1.2 and 7.8 Hz, ArH), 7.55 (1H, d, Jˆ7.8 Hz, ArH), 7.59
(1H, d, Jˆ7.8 Hz, ArH). dC (CDCl3): 24.84, 29.84, 38.14,
44.78, 52.47, 118.97, 120.77, 121.14, 126.13, 131.04,
153.37, 168.50. nmax: 2956, 2867, 1598, 1544, 1447, 1293,
754, 727 cm21. HREIMS: found 254.065 calculated for
C12H15N2S35Cl 254.064; and found 256.063 calculated for
C12H15N2S37Cl 256.063. The second fraction (3h) was
obtained as a white solid (7%).16 dH (CDCl3): 2.05 (4H, t,
Jˆ8.0 Hz, 2£CH2); 3.66 (4H, t, Jˆ4.0 Hz, 2£NCH2); 7.03±
7.06 (1H, dt, Jˆ1.1 and 7.8 Hz, ArH); 7.27±7.31 (1H, dt,
Jˆ1.1 and 7.8 Hz, ArH); 7.57±7.61 (2H, m, ArH). dC
(CDCl3): 25.88, 49.71, 118.91, 120.88, 126.12, 131.96,
Acknowledgements
The authors would like to acknowledge the grant gratefully
received by R. G. A. from the D.G.U.I. (Gobierno de
Canarias).
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