Tanimura et al.
JOCArticle
J=8.3 Hz, 1H), 7.19 (dd, J=8.2 and 1.7 Hz, 1H), 7.29 (d, J=1.7
Hz, 1H), 7.43 (dd with fine coupling, J=8.1 and 7.2 Hz, 1H),
7.53 (dd with fine coupling, J=8.2 and 7.2 Hz, 1H), 7.74 (d, J=
8.2 Hz, 1H), 7.92 (d with fine coupling, J=8.1 Hz, 1H), 8.01 (d
with fine coupling, J=8.2 Hz, 1H), 12.60 (s, 1H). 13C NMR (125
MHz, CDCl3):δC 17.1, 17.3, 17.5, 22.7, 30.1, 44.3, 79.9, 103.0,
115.8, 116.4, 117.4, 117.9, 121.5, 122.3, 125.8, 126.8, 128.3,
132.6, 140.2, 151.7, 157.8, 168.6. IR (KBr): ν~ 3464, 2969,
2891, 1630, 1575 cm-1. MS: m/z 398 (Mþ þ 1, 17), 397 (Mþ,
61), 272 (22), 271 (100), 255 (11), 254 (60), 227 (16), 226 (15), 198
(20). HRMS (ESI): 398.1440, calcd for C22H24NO4S [M þ Hþ]
398.1426, 420.1255, calcd for C22H23NO4SNa [M þ Naþ]
420.1246. Anal. Calcd for C22H23NO4S: C, 66.48; H, 5.83; N,
3.52. Found: C, 66.41; H, 5.77; N, 3.53.
6H), 2.60 (q, J=7.2 Hz, 2H), 4.40 (s, 2H), 7.46 (ddd, J=8.1, 7.2,
and 1.2 Hz, 1H), 7.52-7.57 (m, 2H), 7.69 (d, J=1.6 Hz, 1H),
7.75 (d, J=8.2 Hz, 1H), 7.94 (d with fine coupling, J=8.1 Hz,
1H), 8.03 (d with fine coupling, J=8.2 Hz, 1H), 12.61 (s, 1H).
13C NMR (125 MHz, CDCl3): δC 7.9, 22.0, 30.5, 47.5, 70.7,
119.0, 120.2, 120.2, 121.6, 122.5, 126.1, 126.9, 128.3, 132.8,
133.2, 151.6, 157.6, 165.3, 168.1, 213.3. IR (KBr): ν~ 3415,
3064, 2976, 2939, 2879, 1716, 1697, 1579 cm-1. MS: m/z 384
(Mþ þ 1, 13), 383 (Mþ, 54), 272 (21), 271 (100), 254 (37), 227
(23), 226 (14), 198 (23), 197 (11). HRMS (ESI): 384.1305, calcd
for C21H22NO4S [M þ Hþ] 384.1270, 406.1104, calcd for
C21H21NO4SNa [M þ Naþ] 406.1089. Anal. Calcd for
C21H21NO4S: C, 65.78; H, 5.52; N, 3.65. Found: C, 65.65; H,
5.40; N, 3.69.
1d. Colorless plates. Mp: 152.0-152.5 ꢀC dec (recrystallized
from p-xylene). 1H NMR (400 MHz, CDCl3): δH 1.05 (s, 9H),
1.17 (s, 3H), 1.40 (s, 3H), 3.85 (d, J=8.3 Hz, 1H), 4.60 (d, J=8.3
Hz, 1H), 7.24-7.26 (m, 1H), 7.38 (s, 1H), 7.44 (dd with fine
coupling, J=8.1 and 7.1 Hz, 1H), 7.53 (dd with fine coupling, J=
8.3 and 7.1 Hz, 1H), 7.72 (d, J=8.3 Hz, 1H), 7.92 (d, J=8.1 Hz,
1H), 8.01 (d, J=8.3 Hz, 1H), 12.56 (broad s, 1H). 13C NMR (125
MHz, CDCl3): δC 18.4, 25.0, 26.9, 36.8, 45.6, 80.4, 105.3, 116.1,
117.5, 118.1, 119.4, 121.6, 122.3, 125.8, 126.8, 127.9, 132.6,
140.6, 151.7, 157.4, 168.6. IR (KBr): ν~ 3442, 2967, 2892,
1631, 1573, 1481, 1371, 1322 cm-1. MS: m/z 411 (Mþ, 24), 355
(22), 271 (28), 255 (18), 254 (100), 227 (17), 226 (18), 198 (24), 197
(11), 57 (33). HRMS (ESI): 412.1554, calcd for C23H26NO4S [M
þ Hþ] 412.1583, 434.1381, calcd for C23H25NO4SNa [M þ Naþ]
434.1402. Anal. Calcd for C23H25NO4S: C, 67.13; H, 6.12; N,
3.40. Found: C, 67.13; H, 6.15; N, 3.35.
9c. Pale yellow needles. Mp: 134.5-135.0 ꢀC (from AcOEt-
hexane). 1H NMR (400 MHz, CDCl3): δH 1.10 (d, J=6.7 Hz,
6H), 1.30 (s, 6H), 3.17 (sept, J=6.7 Hz, 1H), 4.41 (s, 2H), 7.46
(dd with fine coupling, J=7.9 and 7.3 Hz, 1H), 7.52-7.57 (m,
2H), 7.70 (d, J=1.3 Hz, 1H), 7.75 (d, J=8.2 Hz, 1H), 7.94 (d with
fine coupling, J=7.9 Hz, 1H), 8.04 (d with fine coupling, J=8.2
Hz, 1H), 12.61 (s, 1H) ppm. 13C NMR (125 MHz, CDCl3): δC
20.0, 21.5, 34.4, 48.2, 70.5, 119.0, 120.2, 120.2, 121.6, 122.5,
126.1, 126.9, 128.3, 132.8, 133.2, 151.6, 157.6, 165.3, 168.1, 217.2
ppm. IR (KBr): ν~ 3394, 3065, 2970, 2930, 2873, 1712, 1577
cm-1. MS: m/z 398 (Mþ þ 1, 13), 397 (Mþ, 48), 272 (23), 271
(100), 255 (11), 254 (61), 227 (18), 226 (17), 198 (22). HRMS
(ESI): 398.1443, calcd for C22H24NO4S [M þ Hþ] 398.1426,
420.1257, calcd for C22H23NO4SNa [M þ Naþ] 420.1246. Anal.
Calcd for C22H23NO4S: C, 66.48; H, 5.83; N, 3.52. Found: C,
66.36; H, 5.71; N, 3.53.
1e. Combined with 20% of 9e. 1H NMR (500 MHz, CDCl3):
9d. Pale yellow needles. Mp: 149.5-150.0 ꢀC (recrystallized
1
δ
H 1.01 (s, 3H), 1.20 (s, 3H), 4.13 (d with fine coupling, J=8.5
from CH2ClCH2Cl). H NMR (400 MHz, CDCl3):δH 1.30 (s,
Hz, 1H), 4.67 (d, J=8.5 Hz, 1H), 5.11 (s, 1H), 7.40-7.47 (m,
2H), 7.51-7.56 (m, 2H), 7.77 (d, J=8.2 Hz, 1H), 7.93 (d with
fine coupling, J=8.0 Hz, 1H), 8.02 (d, J=8.0 Hz, 1H), 12.63 (s,
1H). 13C NMR (125 MHz, CDCl3): δC 16.0, 22.3, 41.8, 79.1,
98.2, 114.5, 116.1, 117.5, 117.7, 121.5, 122.3, 125.8, 126.8, 128.5,
132.6, 139.6, 151.7, 157.9, 168.5.
Thermal Decomposition of 1-[4-(Benzothiazol-2-yl)-3-hydroxy-
phenyl]-4,4,5-trimethyl-2,6,7-trioxabicyclo[3.2.0]heptane (1a).
Typical Procedure. A solution of 1-[4-(benzothiazol-2-yl)-3-
hydroxyphenyl]-4,4,5-trimethyl-2,6,7-trioxabicyclo[3.2.0]heptane
(1a) (59 mg, 0.16 mmol) in p-xylene (2 mL) was refluxed under a
nitrogen atmosphere for 20 min. After cooling, the reaction
mixture was concentrated in vacuo. The residue was chromato-
graphed on silica gel and eluted with AcOEt-hexane (1:2) to
give 2,2-dimethyl-3-oxobutyl 4-(benzothiazol-2-yl)-3-hydroxy-
benzenecarboxylate (9a) as a colorless solid (58 mg, 99% yield).
Dioxetanes 1b-e were similarly decomposed to give the
coresponding keto esters 9b-e in 98, 97, 100, and 96% yields,
respectively.
9a. Colorless needles. Mp: 138.0-138.5 ꢀC (from AcOEt-
hexane). 1H NMR (400 MHz, CDCl3): δH 1.29 (s, 6H), 2.25 (s,
3H), 4.40 (s, 2H), 7.47 (ddd, J=8.1, 7.2, and 1.2 Hz, 1H), 7.55
(ddd, J=8.2, 7.2, and 1.2 Hz, 1H), 7.57 (dd, J=8.2 and 1.7 Hz,
1H), 7.71 (d, J=1.7 Hz, 1H), 7.76 (d, J=8.2 Hz, 1H), 7.95 (d with
fine coupling, J=8.1 Hz, 1H), 8.05 (d with fine coupling, J=8.2
Hz, 1H), 12.63 (s, 1H). 13C NMR (125 MHz, CDCl3): δC 21.8,
25.4, 47.8, 70.5, 119.0, 120.2, 120.2, 121.5, 122.4, 126.0, 126.9,
128.3, 132.8, 133.1, 151.6, 157.6, 165.2, 168.0, 210.8. IR (KBr):
ν~ 3437, 3059, 2974, 1722, 1577 cm-1. MS: m/z 370 (Mþ þ 1, 22),
369 (Mþ, 97), 322 (13), 272 (21), 271 (100), 254 (41), 227 (22), 226
(17), 198 (23), 197 (13). HRMS (ESI): 370.1137, calcd for
C20H20NO4S [M þ Hþ] 370.1113, 392.0947, calcd for C20H19-
NO4SNa [M þ Naþ] 392.0933. Anal. Calcd for C20H19NO4S: C,
65.02; H, 5.18; N, 3.79. Found: C, 64.80; H, 4.99; N, 3.84.
9b. Pale yellow columns. Mp: 139.0-139.5 ꢀC (from AcOEt).
1H NMR (400 MHz, CDCl3): δH 1.09 (t, J=7.2 Hz, 3H), 1.29 (s,
9H), 1.41 (s, 6H), 4.43 (s, 2H), 7.46 (dd with fine coupling, J=8.1
and 7.1 Hz, 1H), 7.52-7.58 (m, 2H), 7.70 (d, J=1.5 Hz, 1H),
7.75 (d, J=8.1 Hz, 1H), 7.94 (d, J=8.1 Hz, 1H), 8.03 (d, J=8.1
Hz, 1H), 12.62 (s, 1H). 13C NMR (125 MHz, CDCl3): δC 23.6,
28.1, 45.9, 49.1, 72.3, 119.0, 120.1, 120.2, 121.6, 122.5, 126.0,
126.9, 128.3, 132.8, 133.4, 151.6, 157.6, 165.3, 168.1, 215.8. IR
(KBr): ν~ 3429, 2970, 1716, 1689, 1574, 1479, 1385 cm-1. Mass:
m/z 411 (Mþ, 21), 355 (23), 271 (31), 255 (17), 254 (100), 227 (23),
226 (22), 198 (30), 197 (13), 57 (45). HRMS (ESI): 412.1544,
calcd for C23H26NO4S [M þ Hþ] 412.1583, 434.1355, calcd for
C23H25NO4SNa [M þ Naþ] 434.1402. Anal. Calcd for
C23H25NO4S: C, 67.13; H, 6.12; N, 3.40. Found: C, 67.13; H,
6.15; N, 3.40.
9e. Pale yellow granules. Mp: 196.0-197.0 ꢀC (from AcOEt).
1H NMR (400 MHz, CDCl3): δH 1.24 (s, 6H), 4.39 (s, 2H), 7.47
(ddd, J=8.1, 7.2, and 1.2 Hz, 1H), 7.55 (ddd, J=8.2, 7.2, and 1.2
Hz, 1H), 7.57 (dd, J=8.2 and 1.5 Hz, 1H), 7.71 (d, J=1.5 Hz,
1H), 7.76 (d, J=8.2 Hz, 1H), 7.95 (d with fine coupling, J=8.1
Hz, 1H), 8.04 (d with fine coupling, J=8.2 Hz, 1H), 9.65 (s, 1H),
12.64 (s, 1H). 13C NMR (125 MHz, CDCl3): δC 19.0, 46.5, 68.6,
119.0, 120.2, 120.3, 121.5, 122.5, 126.1, 126.9, 128.3, 132.8,
132.9, 151.6, 157.6, 165.2, 168.0, 203.2. IR (KBr): ν~ 3447,
3066, 2973, 2936, 2878, 1712, 1576 cm-1. Mass: m/z 356 (Mþ
þ 1, 11), 355 (Mþ, 52), 272 (19), 271 (100), 254 (26), 227 (15), 226
(16), 199 (10), 198 (22), 197 (11), 149 (10). HRMS (ESI):
356.0975, calcd for C19H18NO4S [M
þ
Hþ] 356.0957,
378.0787, calcd for C19H17NO4SNa [M þ Naþ] 378.0776. Anal.
Calcd for C19H17NO4S: C, 64.21; H, 4.82; N, 3.94. Found: C,
64.47; H, 4.97; N, 3.93.
Time Course of the Thermal Decomposition of Dioxetanes 1.
General Procedure. A solution of dioxetane 1 (3-5 mg) in
p-xylene-d10 (0.8 mL) in an NMR sample tube was heated by
means of a liquid paraffin bath thermostatted at an appropriate
temperature range of 70-140 ꢀC. After heating at regular
1
intervals, the samples were subjected to H NMR analysis to
determine the ratio of intact 1 to the corresponding keto ester 9.
J. Org. Chem. Vol. 75, No. 11, 2010 3683