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Moreover it is reported
in this publication that the reaction of trimethoxybenzene proceeds
efficiently while the reaction of 1 and
trimethoxybenzene has previously been reported to give only by-products
at room temperature.
[7a]
<A NAME="RG00403ST-8C">8c</A>
In our hands using Montmorillonite
K10 purchased from Aldrich Chemical Co. and used as received, the
reaction between 1 and anisole led to unchanged
reactants following the procedure reported.
[8a]
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<A NAME="RG00403ST-10">10</A> For a review about Friedel-Crafts
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<A NAME="RG00403ST-17">17</A>
From our experience the stability
of aryl sulfinyl chlorides seems highly unpredictable.
<A NAME="RG00403ST-18A">18a</A>
The
mass of a known amount of 3 remained unchanged after
stirring for 5 h at -5 °C with 1 in
excess and evaporation to dryness at the same temperature under
high vacuum. Moreover, this recovered 3 showed
the same 19F NMR signals than the ones reported
for 3.
[14]
Finally,
no fluorine was detected by 19F NMR in the recovered 1.
<A NAME="RG00403ST-18B">18b</A>
When a 10:2:0.4 molar
mixture of 1, 4 and 3 was stirred at -5 °C
for 2 h, the 1H NMR signals of 4 remained
unchanged.
<A NAME="RG00403ST-19A">19a</A>
Yadav JS.
Subba Reddy BV.
Srinivasa Rao R.
Praveen
Kumar S.
Nagaiah K.
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<A NAME="RG00403ST-19B">19b</A>
Unfortunately in our
hands, using scandium triflate purchased from Aldrich Chemical Co.,
used as received and following the procedure reported,
[19a]
1 failed
to react with some selected aromatic compounds (anisole, veratrole, biphenyl,
fluorobenzene, benzene, chlorobenzene).
<A NAME="RG00403ST-20">20</A>
General procedure. CAUTION: Aromatic sulfinyl chlorides are
thermolabile compounds and have been reported to explode during
distillation.
[4a]
[5a]
Thus, distillation was not attempted
in our experiments and all the yields reported have been determined
by 1H NMR (250 MHz) after addition of a known
amount of dibromomethane. To a 50 mL flask equipped with a septum
inlet and magnetic stirring bar was added 160 mg (507 µmol)
of bismuth(III) chloride. The flask was connected to an argon line
and 18 mL (247 mmol) of freshly distilled thionyl chloride were
added by syringe. To this suspension was added 2.74 g (25.3 mmol)
of anisole. The flask was equipped with a condenser, connected to
an oil bubbler and the reaction mixture was heated in an oil bath
at 60 °C for 1 h. During this time the color of the solution became
red-orange and HCl evolved from the solution. The flask was cooled
in an ice bath and the excess of thionyl chloride was removed in
vacuum (0.1 mm Hg) yielding to an orange liquid. In order to remove
the catalyst, 50 mL of pentane were added, the organic phase was
collected and evaporated under reduced pressure to give a yellow
liquid, which was characterized as 4-methoxybenzenesulfinyl chloride(4). 1H NMR (CDCl3): δ 3.84
(s, 3 H, OMe), 7.03 (d, 2 H, H3,5, J = 8.9
Hz), 7.79 (d, 2 H, H2,6, J = 8.9
Hz); 13C NMR (CDCl3): δ 55.9
(OMe), 114.9, 126.1 (CH phenyl), 139.9 (C-OMe), 164.1 (C-SO phenyl);
IR (neat): 2976, 1587, 1488, 1310, 1260, 1146, 1078, 1021, 831 cm-1.
The formation of 4 was proved after characterization
of its corresponding sulfinamide (N,N-diisopropyl-4-methoxybenzenesulfinamide
was isolated after flash chromatography over silica gel G60, eluant:
ethyl acetate) as previously reported.
[7a]
Mp = 57-58 °C; 1H
NMR (CDCl3): δ 1.09 (d, 6 H, CHMe2, J = 6.7 Hz), 1.38 (d, 6 H, CHMe2, J = 6.7 Hz), 3.58 (spt, 2 H,
CHMe2, J = 6.7 Hz),
3.83 (s, 3 H, Me), 6.98 (m, 2 H, H3,5), 7.53 (d, 2 H,
H2,6); 13C NMR (CDCl3): δ 23.7,
23.8 (CHMe2), 46.7 (CHMe2), 55.4 (OMe), 114.0,
128.1 (CH phenyl), 135.7 (C-OMe), 161.2 (C-SO phenyl); IR(neat):
2966, 1461, 1376, 1245, 1180, 1087, 831 cm-1;
MS (EI): m/z (%) = 255
(8) [M+], 240 (8), 155 (100), 58
(18), 43 (17).
4-Methoxy-2-methylbenzenesulfinyl
chloride: 1H NMR (CDCl3): δ 2.27
(s, 3 H, C-Me), 3.56 (s, 3 H, OMe), 6.53 (d, 1 H, H3, J = 2.3 Hz), 6.69 (dd, 1 H,
H5, J = 2.3 Hz and
8.8 Hz), 7.78 (d, 1 H, H6, J = 8.8
Hz); 13C NMR (CDCl3): δ 18.1 (C-Me),
55.9 (OMe), 113.0, 117.0, 126.0 (CH phenyl), 138.2, 138.6 (C-Me
and C-OMe phenyl), 164.4 (C-SO phenyl); IR (neat): 2940, 1590, 1568,
1480, 1456, 1323, 1291, 1249, 1148, 1058, 851, 814 cm-1.
N,N
-diisopropyl-4-methoxy-2-methylbenzenesulfin-amide: 1H
NMR (CDCl3): δ 1.05 (d, 6 H, CHMe2, J = 6.7 Hz), 1.38 (d, 6 H, CHMe2, J = 6.7 Hz), 2.31 (s, 3 H, C-Me), 3.56
(spt, 2 H, CHMe2, J = 6.7
Hz), 3.80 (s, 3 H, OMe), 6.67 (d, 1 H, H3, J = 2.4 Hz), 6.87 (dd, 1 H,
H5, J = 2.4 Hz and
8.5 Hz), 7.92 (d, 1 H, H6, J = 8.5
Hz); 13C NMR (CDCl3): δ 19.1 (C-Me),
23.5, 23.9 (CHMe2), 47.1 (CHMe2), 55.3 (OMe), 111.0,
116.7, 128.7 (CH phenyl), 132.6, 137.1 (C-Me and C-OMe phenyl),
161.3 (C-SO phenyl); IR (neat): 2970, 1597, 1481, 1240, 1069, 1055,
940, 861 cm-1; MS (EI): m/z (%) = 269
(16) [M+], 169 (100), 141
(19), 108 (48), 58(35), 43 (51).
4-Methoxy-3-methylbenzenesulfinyl
chloride: 1H NMR (CDCl3): δ 2.06
(s, 3 H, C-Me), 3.58 (s, 3 H, OMe), 6.72 (d, 1 H, H5, J = 8.5 Hz), 7.5 (m, 1 H, H2),
7.54 (dd, 1 H, H6, J = 2.4
Hz and 8.5 Hz); 13C NMR (CDCl3): δ 18.7
(C-Me), 56.1 (OMe), 110.5, 124.3, 126.2 (CH phenyl), 128.8, 139.6
(C-Me and C-OMe phenyl), 162.6 (C-SO phenyl); IR (neat): 2974, 1588,
1492, 1458, 1317, 1255, 1135, 1080, 1024, 808 cm-1.
N,N
-diisopropyl-4-methoxy-3-methylbenzenesulfin-amide: 1H
NMR (CDCl3): δ 1.00 (d, 6 H, CHMe2, J = 6.7 Hz), 1.28 (d, 6 H, CHMe2, J = 6.7 Hz), 2.13 (s, 3 H, Me), 3.44
(spt, 2 H, CHMe2, J = 6.7
Hz), 3.74 (s, 3 H, CH3), 6.78 (d, 1 H, H5, J = 8.5 Hz), 7.26 (m, 1 H, H2),
7.30 (dd, 1 H, H6, J = 2.4
Hz and 8.5 Hz); 13C NMR (CDCl3): δ 16.3
(C-Me), 23.7, 23.8 (CHMe2), 46.2 (CHMe2),
55.4 (OMe), 109.6, 125.6 (CH phenyl), 127.1 (C-Me or C-OMe phenyl),
128.4 (CH phenyl), 134.8 (C-Me or C-OMe phenyl), 159.3 (C-SO phenyl);
IR(neat): 2967, 1594, 1488, 1458, 1365, 1252, 1182, 1123, 1067,
944 cm-1; MS (EI): m/z (%) = 269(10) [M+],
254 (6), 169 (100), 58 (13), 43 (13).
3,4-Dimethoxybenzenesulfinyl
chloride: 1H NMR (CDCl3): δ 3.97
(s, 3 H, OMe), 3.98 (s, 3 H, OMe), 7.00 (d, 1 H, H3, J = 8.9 Hz), 7.42 (m, 2 H, H2,5); 13C
NMR (CDCl3): δ 56.0 and 56.1 (OMe), 105.5, 110.7,
117.9 (CH phenyl), 139.7, 149.8 (C-Me and C-OMe phenyl), 153.8 (C-SO phenyl);
IR(neat): 2954, 1574, 1503, 1461, 1261, 1231, 1133, 1077, 1015 cm-1.
N,N
-diisopropyl-3,4-dimethoxybenzenesulfinamide: 1H NMR
(CDCl3): δ 0.93 (d, 6 H, CHMe2, J = 6.7 Hz), 1.20 (d, 6 H, CHMe2, J = 6.7 Hz), 3.38 (spt, 2 H,
CHMe2, J = 6.7 Hz), 3.72
(s, 3 H, OMe), 3.73 (s, 3 H, OMe), 6.77 (d, 2 H, H3, J = 8.8 Hz), 6.94-7.10
(m, 2 H, H2-6); 13C
NMR (CDCl3): δ 23.6, 23.8 (CHMe2),
46.2 (CHMe2), 55.9 (OMe), 109.1, 110.7, 119.3 (CH phenyl),
136.0, 149.0 (C-Me and C-OMe phenyl), 150.4 (C-SO phenyl); IR (neat):
2964, 1588, 1504, 1268, 1254, 1229, 1182, 1088 cm-1;
MS (EI): m/z (%) = 285 (9) [M+],
185 (100), 58 (8), 43(11).
4-Ethoxybenzenesulfinyl
chloride: 1H NMR (CDCl3): δ 1.39
(t, 3 H, Me, J = 7.5 Hz), 4.07
(q, 2 H, CH2, J = 7.5
Hz), 6.98 (m, 2 H, H3,5), 7.74 (d, 2 H, H2,6); 13C
NMR (CDCl3): δ 14.7 (CH2-Me), 64.3
(CH2-Me), 109.9 (C-Me phenyl), 115.3, 126.1 (CH phenyl),
139.7 (C-OEt phenyl), 163.5 (C-SO phenyl); IR(neat): 2975, 1587,
1489, 1310, 1261, 1142, 1077, 1039, 832 cm-1.
N,N
-diisopropyl-4-ethoxybenzenesulfinamide: 1H
NMR (CDCl3): δ 0.97 (d, 6 H, CHMe2, J = 6.7 Hz), 1.25 (d, 6 H, CHMe2, J = 6.7 Hz), 1.28 (t, 3 H, Me, J = 7.0 Hz), 3.41 (spt, 2 H,
CHMe2, J = 6.7 Hz),
3.91 (q, 2 H, CH2, J = 7.0
Hz), 6.82 (d, 2 H, H3,5), 7.39 (d, 2 H, H2,6); 13C
NMR (CDCl3): δ 14.7 (CH2-Me), 23.7,
23.8 (CHMe2), 46.2 (CHMe2), 63.6 (CH2-Me),
114.4, 128.0 (CH phenyl), 135.3 (C-OEt phenyl), 160.6 (C-SO phenyl);
MS (EI): m/z (%) = 269
(9) [M+], 254 (6), 169 (89),
141 (51), 86 (72), 84 (100); IR (neat): 2964, 1590, 1487, 1472,
1385, 1364, 1303, 1246, 1179, 1113, 1082, 1061, 949, 836 cm-1.
2,4,6-trimethylbenzenesulfinyl chloride: 1H
NMR (CDCl3): δ 2.34 (s, 3 H, 4-Me), 2.63 (s,
6 H, 2,6-Me), 6.93 (s, 2 H, H3,5); 13C
NMR (CDCl3): δ 18.7 (2,6-Me), 21.5 (4-Me), 131.2,
138.0 (CH phenyl), 141.0 (C-Me), 144.6 (C-SO phenyl); IR(neat):
2919, 1598, 1454, 1379, 1292, 1151, 1052, 852 cm-1.
N,N
-diisopropyl-2,4,6-trimethylbenzenesulfinamide: 1H NMR
(CDCl3): δ 1.04 (d, 6 H, CHMe2, J = 6.7 Hz), 1.42 (d, 6 H, CHMe2, J = 6.7 Hz), 2.19 (s, 3 H, 4-Me),
2.46 (s, 6 H, 2,6-Me), 6.75 (br s, 2 H, H3,5); 13C
NMR (CDCl3): δ 20.5 (C2,6-Me), 21.0
(C4-Me), 23.7, 24.4 (CHMe2), 48.9 (CHMe2),
131.3 (CH phenyl), 134.8, 138.3, 139.9 (C2,4,6-Me and
C-SO phenyl); MS (EI): m/z (%) = 267 (60) [M+],
167 (66), 139 (100), 106 (94), 58 (80), 43 (97); IR (nujol): 2868, 1598,
1460, 1366, 1172, 1120, 1085, 935, 848 cm-1.