Photosensitized Oxygenation of 5,6-Dihydro-1,4-oxathiins
160 (M+ - 16), 144 (M+ - 32), 116 (M+ - 60). Meth yl
[(2S*,3R*)-3-oxid o-1,3-oxa th iola n -2-yl](oxo)a ceta te (7f)
decomposed on contact with the chromatographic adsorbent,
so its spectroscopic data and yield were deduced from the crude
Starting from 1j, chromatography gave, with decreasing Rf
values, 2-({2-[m et h yl(p h en yl)a m in o]-2-oxoa cet yl}t h io)-
eth yl a ceta te (4j): yield 5%; oil; IR (CHCl3) 1745, 1670 cm-1
;
1H NMR δ 2.00 (s, 3 H), 3.04 (t, J ) 6.4 Hz, 2 H), 3.37 (s, 3 H),
4.00 (t, J ) 6.4 Hz, 2 H), 7.10-7.50 (m, 5 H); 13C NMR δ 20.7
(q), 27.3 (t), 38.0 (q), 62.0 (t), 126.4 (d), 128.2 (d), 129.5 (d),
141.7 (s), 170.5 (s), 189.1 (s); MS m/z 281 (M+), 221 (M+ - 60),
163 (M+ - 118). (2R*,3R*)-2-Acetyl-N-m eth yl-N-p h en yl-
1,3-oxa th iola n e-2-ca r boxa m id e 3-oxid e (8j): yield 15%;
131-133 °C; IR (CHCl3) 1716, 1646, 1058, 1025 cm-1; 1H NMR
δ 1.41 (s, 3 H), 3.11 (m, 1 H), 3.25 (s, 3 H), 3.52 (m, 1 H), 4.58
(m, 1 H), 4.95 (m, 1 H), 7.10-7.50 (m, 5 H); 13C NMR δ 27.4
(q), 38.4 (q), 53.7 (t), 72.0 (t), 112.4 (s), 128.9 (d), 129.4 (d),
130.0 (d), 140.0(s), 156.8 (s), 202.6 (s); MS m/z 282 (MH+), 239
(M+ - 42), 146 (M+ - 135), 134. N-Meth yl-2-[(2S*,3R*)-2-
m eth yl-3-oxid o-1,3-oxa th iola n -2-yl]-2-oxo-N-p h en yla cet-
a m id e (7j): yield 60%; 136-138 °C; IR (CHCl3) 1718, 1656,
1
oxygenation mixture: yield 75% (purity of 80%); H NMR δ
2.85 (m, 1 H), 3.22 (m, 1 H), 3.95 (s, 3 H), 4.64 (m, 2 H), 6.44
(s, 1 H); 13C NMR δ 53.5 (t), 54.1 (q), 70.0 (t), 99.6 (d), 162.0
(s), 185.0 (s).
Starting from 1g, TLC chromatography yielded only d i-
m eth yl 5,6-d ih yd r o-1,4-oxa th iin e-2,3-d ica r boxyla te 4-ox-
id e (6g): yield 10%; viscous oil; IR (CHCl3) 1752, 1723, 1100
1
cm-1; H NMR δ 2.79 (ddd, J ) 14.7, 13.7, 3.4 Hz, 1 H), 3.13
(m, 1 H), 3.87 (s, 3 H), 3.91 (s, 3 H), 4.62 (m, 1 H), 4.76 (m, 1
H);13C NMR δ 43.1 (t), 52.9 (q), 53.6 (q), 58.0 (t), 109.5 (s),
159.6 (s), 162.2 (s), 163.1 (s); MS m/z 234 (M +), 218 (M+
-
16), 203 (M+ - 31), 175 (M+ - 59). Meth yl (2R*,3R*)-2-
[m eth oxy(oxo)acetyl]-1,3-oxath iolan e-2-car boxylate 3-ox-
id e (7gt8g) decomposed on contact with the chromatographic
adsorbents, so its spectroscopic data and yield were deduced
from the crude oxygenation mixture: yield 70% (purity of 75%);
1H NMR δ 2.95-3.15 (m),* 3.30 (m, 1 H), 3.80 (s, 3 H), 3.95 (s,
3 H), 4.70-4.95 (m, 2 H)*;13C NMR δ 52.8 (q), 53.8 (t + q),
72.8 (t), 107.7 (s), 159.8 (s), 163.9 (s), 181.4 (s); [* indicates
partial overlap to signals of 6g].
1070, 1026 cm-1; H NMR δ 1.28 (s, 3 H), 2.88 (m, 1 H), 3.25
1
(m, 1 H), 3.38 (s, 3 H), 4.50-4.90 (m, 2 H), 7.20-7.50 (m, 5
H); 13C NMR δ 21.0 (q), 36.6 (q), 52.2 (t), 71.3 (t), 109.0 (s),
127.4 (d), 128.3 (d), 129.5 (d), 140.8 (s), 164.8 (s), 194.1 (s);
MS m/z 282 (MH+), 147 (M+ - 134), 134, 119; sulfoxide 6j
1
[yield 2%] was identified by comparing H and 13C NMR data
with those reported.31
Starting from 1h , chromatography by TLC gave, with
decreasing Rf values, 2-[(2-a m in o-2-oxoa cetyl)th io]eth yl
a ceta te (4h ): yield 31%; mp 95-97 °C; IR (CHCl3) 3464, 3394,
Starting from 1k , chromatography gave, with decreasing Rf
values, 2-{[2-(d im eth yla m in o)-2-oxoa cetyl]th io}eth yl a c-
eta te (4k ): yield 58%; oil; IR (CHCl3) 1739, 1674, 1653 cm-1
;
1
1745, 1687, 1568 cm-1; H NMR δ 2.07 (s, 3 H), 3.21 (t, J )
1H NMR δ 2.07 (s, 3 H), 3.04 (s, 3 H), 3.18 (s) and 3.21 (t, J )
6.3 Hz) (together 5 H), 4.23 (t, J ) 6.3 Hz, 2 H); 13C NMR δ
22.7 (q), 29.6 (t), 38.2 (q), 39.3 (q), 64.2 (t), 164.0 (s), 172.7 (s),
192.6 (s); MS m/z 220 (MH+), 160 (M+ - 59). N,N-Dim eth yl-
[(2S*,3R*)-2-m eth yl-3-oxid o-1,3-oxa th iola n -2-yl](oxo)a c-
eta m id e (7k ): yield 5%; oil; IR (CHCl3) 1723, 1651, 1063, 1014
6.5 Hz, 2 H), 4.23 (t, J ) 6.5 Hz, 2 H), 6.36 (br s, 1 H), 6.86 (br
s, 1 H); 13C NMR δ 20.7 (q), 27.9 (t), 61.9 (t), 160.3 (s), 170.7
(s), 190.4 (s); MS m/z: 192 (MH+), 149 (M+ - 42), 147 (M+
-
44), 131 (M+ - 60), 120 (M+ - 72). (2R*,3R*)-2-Acetyl-1,3-
oxa th iola n e-2-ca r boxa m id e 3-oxid e (8h ): yield 9%; oil; IR
1
(CHCl3) 3486, 3398, 1714, 1601, 1076 cm-1; H NMR δ 2.46
cm-1; H NMR δ 1.75 (s, 3 H), 3.02 (s), 3.05 (s), 3.04 (m) and
1
3.20 (m) (together 8 H), 4.62 (m, 1 H), 4.87 (m, 1 H); 13C NMR
δ 22.0 (q), 34.7 (q), 36.5 (q), 52.1 (t), 70.2 (t), 109.7 (s), 164.5
(s), 200.5 (s); MS m/z 220 (MH+), 119. N,N,2-Tr im eth yl-5,6-
d ih yd r o-1,4-oxa th iin e-3-ca r boxa m id e 4-oxid e (6k ): yield
(s, 3 H), 3.07 (m, 1 H), 3.32 (m, 1 H), 5.00 (m, 2 H), 5.71 (br s,
1 H), 7.02 (br s, 1 H); 13C NMR δ 29.5 (q), 52.7 (t), 69.9 (t),
111.7 (s), 164.5 (s), 201.3 (s); MS m/z 192 (MH+), 149 (M+
-
43), 148 (M+ - 44). [(2S*,3R*)-2-(2-Meth yl-3-oxid o-1,3-
oxa th iola n -2-yl]-2-oxoa ceta m id e (7h ): yield 8%; oil; IR
11%; oil; IR (CHCl3) 1625, 1041, 1019 cm-1; H NMR δ 1.98
1
1
(CHCl3) 3514, 3397, 1713, 1602, 1078 cm-1; H NMR δ 1.90
(s, 3 H), 2.76 (ddd, J ) 14.9, 10.2, 6.3 Hz, 1 H), 3.00 (m) and
3.11 (br s) (together 8 H), 4.55 (m, 2 H); 13C NMR δ 19.4 (q),
36.6 (br q), 38.8 (br q), 43.4 (t), 56.6 (t), 111.3 (s), 157.9 (s),
166.6 (s); MS m/z 204 (MH+), 186 (M+ - 17), 159 (M+ - 44),
131 (M+ - 72).
P h otooxygen a tion of 1b,c,i u n d er Differ en t Con d i-
tion s. Reactions were carried out as described above using
0.25 mmol of the starting oxathiin 1. When methanol, acetone,
CH3CN, or DMF-d7 was used as the solvent, methylene blue
was the sensitizer (2 × 10-3 mmol). Table 2 reports the various
conditions used as well as the product distribution, which was
deduced by 1H NMR of each reaction mixture after removal of
the solvent except for entry p. In this case, the reaction was
carried out in DMF-d7 and the mixture analyzed directly by
comparing the spectrum with those of authentic samples in
this solvent.
(s, 3 H), 2.82 (m, 1 H), 3.20 (m, 1 H), 4.53-4.72 (m, 2 H), 5.50
(br s, 1 H), 6.70 (br s, 1 H); 13C NMR δ 20.7 (q), 52.8 (t), 69.9
(t), 108.3 (s), 160.9 (s), 192.4 (s); MS m/z 192 (MH+), 163
(M+ - 28), 119 (M+ - 72). 2-Meth yl-5,6-d ih yd r o-1,4-oxa th i-
in e-3-ca r boxa m id e 4-oxid e (6h ): yield 11%; oil; IR (CHCl3)
3499, 3378, 1673, 1041 cm-1 1H NMR δ 2.37 (s, 3 H), 2.82
;
(ddd, J ) 14.6, 12.7, 3.9 Hz, 1 H), 3.08 (m, 1 H), 4.40-4.65
(m, 2 H), 6.20 (br s, 2 H); 13C NMR δ 20.8 (q), 43.3 (t), 56.8 (t),
110.0 (s), 166.9 (s), 167.1 (s); MS m/z 176 (MH+), 159 (M+
16), 131 (M+ - 44).
-
Starting from 1i, chromatography gave, with decreasing Rf
values, 2-[(2-a n ilin o-2-oxoa cetyl)th io]eth yl a ceta te (4i):
yield 29%; mp 82-83 °C; IR (CHCl3) 3377, 1741, 1703, 1677
1
cm-1; H NMR δ 2.08 (s, 3 H), 3.26 (t, J ) 6.3 Hz, 2 H), 4.27
(t, J ) 6.3 Hz, 2 H), 7.10-7.70 (m, 5 H), 8.56 (br s, 1 H); 13C
NMR δ 20.7 (q), 28.0 (t), 61.8 (t), 119.9 (d), 125.6 (d), 129.2
(d), 135.7 (s), 155.8 (s), 170.6 (s), 191.6 (s); MS m/z 267 (M+),
149 (M+ - 118), 120, 119. [(2S*,3R*)-2-Meth yl-3-oxid o-1,3-
oxa th iola n -2-yl]-2-oxo-N-p h en yla ceta m id e (7i): yield 4%;
oil; IR (CHCl3) 3380, 1732, 1697, 1078, 1054 cm-1; 1H NMR δ
1.93 (s, 3 H), 2.88 (m, 1 H), 3.23 (m, 1 H), 4.60 (m, 2 H), 7.00-
7.70 (m, 5 H), 8.81 (br s, 1 H); 13C NMR δ 20.8 (q), 52.7 (t),
69.9 (t), 108.4 (s), 120.1 (d), 125.3 (d), 129.0 (d), 136.0 (s), 156.6
(s), 193.0 (s); MS m/z 267 (M+), 149 (M+ - 118), 120. 2-Meth yl-
N-p h en yl-5,6-d ih yd r o-1,4-oxa th iin e-3-ca r boxa m id e 4-ox-
id e (6i):34 yield 34%; oil; IR (CHCl3) 3349, 1721, 1673, 1079,
1039 cm-1; 1H NMR δ 2.38 (s, 3 H), 2.90 (ddd, J ) 14.6, 13.5,
3.5 Hz, 1 H), 3.10 (m, 1 H), 4.52 (m, 2 H), 7.10-7.60 (m, 5 H),
8.35 (br s, 1 H); 13C NMR δ 20.7 (q), 43.5 (t), 56.9 (t), 110.7 (s),
120.5 (d), 124.7 (d), 129.0 (d), 137.8 (s),163.6 (s), 166.6 (s); MS
m/z 251 (M+), 234 (M+ - 17), 159 (M+ - 92), 131.
After the oxygenation of 1b in methanol, TLC of the residue
carried out as above gave, in addition to 4b (yield 40%),
3-m eth yl-2-p h en yl-5,6-d ih yd r o-1,4-oxa th iin e 4-oxid e (6b):
1
yield 37%; oil; IR (CHCl3) 1617, 1040, 1029 cm-1; H NMR δ
2.15 (s, 3 H), 2.93 (ddd, J ) 12.1, 9.5, 3.4 Hz, 1 H), 3.10 (m, 1
H), 4.52 (m, 2 H), 7.41 (s, 5 H); 13C NMR δ 16.6 (q), 45.0 (t),
57.1 (t), 108.9 (s), 128.3 (d), 128.9 (d), 129.8 (d), 134.2 (s), 154.4
(s); MS m/z 209 (MH+), 192 (M+ - 16), 191 (M+ - 17).
After the oxygenation of 1c in methanol at -40 °C, TLC of
the residue carried out as above led to the sulfoxide 6c [mp
80-82 °C (lit.35 81-82 °C)] in 87% yield.
Photooxygenation of 1i at -20 °C in acetone and separation
as above led, with a decreasing order of Rf values, to 4i (yield
10%), a mixture of 7i and 8i, and 6i (yield 14%). Subsequent
TLC of the mixture using 1:9 methanol/CHCl3 gave, with a
(34) NMR data reported in ref 31 are in DMSO-d6.
(35) King, R. R. J . Org. Chem. 1980, 45, 5347.
J . Org. Chem, Vol. 67, No. 14, 2002 4943