86
B. LIU AND H. J. SHINE
Preparation of 5-(alkyl)thianthrenium tri¯ates. An
example is given with 3a. To a stirred mixture of
1.08 g of Th (5.0 mmol) and 600 mg (10.0 mmol) of
methyl formate, cooled in an ice-bath, was added 2.5 ml
of trifluoromethanesulfonic acid (triflic acid). The
mixture was removed from the ice-bath and stirred for
10 h at room temperature, after which it was poured into
100 ml of water. The resulting suspension was extracted
with 3 Â 100 ml of dichloromethane. The combined
dichloromethane solution was concentrated to 10 ml
and poured into 200 ml of diethylether to give 1.16 g
2H, J = 7.62 (ave), 1.18 (ave); 7.707, td, 2H, J = 7.55
(ave), 1.36 (ave); 4.707, m (mainly q), 1H, J = 6.0 (ave);
1.936–1.66, m, overlapping solvent peaks.
5-(Cycloheptyl)thianthrenium triflate (3i), 17%, m.p.
1
70–71°C after reprecipitation from dichloromethane. H
NMR, 200 MHz (CD3CN), ꢀ: 8.807, dd, 2H, J = 7.73,
1.38 (ave); 7.951, dd, 2H, J = 7.83, 1.46; 7.832, td, 2H,
J = 7.62 (ave), 1.52 (ave); 7.707, td, 2H, J = 7.54 (ave),
1.50 (ave): 4.501, m. 1H: 1.759–1.441, m. 12H.
5-(Benzyl)thianthrenium triflate (3f). Thianthrene
(864 mg, 4.0 mmol) and benzyl bromide (684 mg,
4.0 mmol) were dissolved in 20 ml of dichloromethane.
The solution was stirred while 514 mg (2.0 mmol) of
silver triflate was added. After 3 h of stirring the mixture
was filtered into 80 ml of dry diethylether. The
precipitated product was reprecipitated from MeCN with
diethylether, giving 560 mg (1.23 mmol, 61%) of 3f, m.p.
1
(3.05 mmol, 61 %) of 3a, m.p. 176–178°C. H NMR,
300 MHz (CD3CN) (J in Hz throughout) ꢀ: 8.116, dd(d),
2H, J = 7.90, 1.30 (ave), 0.267 (upfield peaks split only);
7.947, dd(d), 2H, J = 7.98, 1.07 (ave), 0.228 (upfield peak
split only); 7.806, td, 2H, J = 7.69 (ave), 1.41 (ave);
7.697, td, 2H, J = 7.69 (ave), 1.35 (ave); 3.160, s, 3H. 13C
NMR, ꢀ: 136.875, 135.501, 134.547, 131.328, 130.658,
119.587, 25.610.
Attempts to prepare 5-(methyl)thianthrenium perchlo-
rate by reaction of Th with methyl chloroformate and
perchloric acid failed.
1
87–88°C. H NMR 200 MHz (CD3CN), ꢀ: 4.935, s, 2H;
the NMR spectrum of 3f in the aromatic region was a
series of overlapping multiplets, ꢀ 7.987–7.058, from the
thianthrenium and phenyl rings. Also, 3f tended to
decompose slowly in MeCN so that the aromatic region
was further complicated by a small amount of thianthrene
and the departed benzyl group. Attempts to alkylate Th
with benzyl formate failed.
5-(Ethyl)thianthrenium triflate (3b) was prepared
similarly, using 2.16 g (10.0 mmol) of Th and 1.48 g
(20.0 mmol) of ethyl formate. The first precipitate from
pouring the dichloromethene solution into diethylether
was a yellow oil. This was dissolved in dichloromethane,
cooled in an ice–salt bath and a small amount of
diethylether was added, with scratching, giving 740 mg
5-(Neopentyl)thianthrenium perchlorate (3e). To a
Á
stirred suspension of 630 mg (2.0 mmol) of Th ClO4
in 2 ml of MeCN was added dropwise a solution of
342 mg (1.0 mmol) of dineopentylmercury in 5 ml of
MeCN. The mixture was stirred until the color of Th.
had disappeared. The solvent was removed in a rotary
evaporator and the residue was dissolved in dichlor-
omethane. That solution was shaken with 1% aqueous
LiCl, separated, concentrated to about 5 ml and poured
into dry diethylether to precipitate 235 mg (0.61 mmol,
61%) of 3e, m.p. 125–127°C (decomp.). 1H NMR,
200 MHz (CD3CN), ꢀ:8.141 dd, 2H, J = 7.82, 1.42 (ave);
7.982, dd, 2H, J = 7.89, 1.229 (ave); 7.813, td, 2H,
J = 7.62 (ave), 1.52 (ave); 7.695, td, 2H, J = 7.60 (ave),
1.42 (ave); 3.710, s, 2H; 1.040, s, 9H.
1
(1.88 mmol, 19%) of pale yellow 3b, m.p. 65–67°C. H
NMR, 300 MHz (CD3CN), ꢀ: 8.098, dd, 2H, J = 7.95,
1.05 (ave); 7.945, dd, 2H, J = 7.95, 1.05 (ave); 7.829, td,
2H, J = 7.73 (ave), 1.40 (ave); 7.706, td, 2H, J = 7.65
(ave), 1.40 (ave); 3.674, q, 2H, J = 7.35 (ave); 1.179, t,
3H, J = 7.35 (ave). 13C NMR, ꢀ: 136.889, 135.714
135.353, 131.274, 130.593, 117.721, 37.115, 9.828.
5-(Isopropyl)thianthrenium triflate (3c), m.p. 75–
76°C, was obtained in 94% yield from reaction of Th
with isopropyl formate. 1H NMR, 200 MHz (CD3CN), ꢀ:
8.098, dd, 2H, J = 7.76, 1.50 (ave); 7.946, dd, 2H,
J = 7.93, 1.45 (ave); 7.845, td, 2H, J = 7.58 (ave), 1.43
(ave); 7.716, td, 2H, J = 7.58 (ave), 1.56 (ave); 4.469,
sept, 1H, J = 6.73 (ave); 1.273, d, 6H, J = 6.69 (ave).
5-(2-Butyl)thianthrenium triflate (3d), m.p. 61–62°C,
was obtained in 40% yield from alkylation of Th with 2-
butyl formate. 1H NMR, 300 MHz (CD3CN), ꢀ:8.090 and
8.055, overlapping dd, 2H, J = 7.88, 1.42 (ave) and 7.82,
1.32 (ave); 7.951, dd, 2H, J = 7.97, 1.29 (ave); 7.841, td,
2H, J = 7.58 (ave), 1.37 (ave); 7.712 and 7.164, over-
lapping td, 2H, J = 7.66 (ave), 1.26 (ave) and 7.73 (ave),
1.24 (ave). 200 MHz, ꢀ:4.402, sextet, 1H, J = 6.54 (ave);
1.600, quintet, 2H, J = 7.10 (ave); 1.214, d 3H, J = 6.89;
0.953, t, 3H, J = 7.36 (ave).
5-(Cyclohexyl)thianthrenium triflate (3h) was pre-
pared from 5.0 mmol of Th, 10.0 mmol of cyclohexyl
formate and 2.5 ml of triflic acid. The product was
reprecipitated from dichloromethane with ether three
times, giving 1.86 g (4.15 mmol, 83%) of 3h, m.p. 80–
1
81°C. H NMR, 200 MHz (CD3CN), ꢀ:8.057, dd, 2H,
J = 7.76, 1.33; 7.947, dd, 2H, J = 7.89, 1.29 (ave); 7.834,
td, 2H, J = 7.63 (ave), 1.37 (ave); 7.701, td, 2H, J = 7.56
(ave), 1.44 (ave); 4.310, quintet, 1H, J = 7.38 (ave);
1.817–1.753, m, 2H; 1.664–1.544, m, 5H; 1.413–1.268,
m 3H.
Diphenylmethylsulfonium triflate (4a). Reaction of
930 mg (5.0 mmol) of diphenyl sulfide, 600 mg
(10.0 mmol) of methyl formate and 2.5 ml of triflic acid
5-(Cyclopentyl)thianthrenium triflate (3g), 85% yield,
m.p. 90–92°C after reprecipitation from dichloro-
1
gave 1.56 g (4.46 mmol, 89%) of 4a, m.p. 95–97°C. H
1
methane. H NMR, 200 MHz (CD3CN), ꢀ:8.114, dd,
NMR, 200 MHz (CD3CN), ꢀ: 7.968–7.903, m, 4H;
7.695–7.580, m, 6H; 3.688, s, 3H. Lit. m.p. 94–97.5°C,
2H, J = 7.77, 1.40 (ave); 7.945, d, 2H, J = 7.81; 7.835, td,
Copyright 2000 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2001; 14: 81–89