FULL PAPERS
action flask was allowed to stand until the mixture thawed
to room temperature and was then stirred at 228C for 8 h.
After that, the reaction was quenched with 1.0037 g DOAc
and then 20 mL of Et2O and 20 mL of brine were added
into the mixture. The aqueous layer was extracted with
Et2O (10 mLꢁ3) and the combined organic layer was
washed with brine (10 mLꢁ2), dried over anhydrous
Na2SO4, filtered and concentrated. The crude product was
purified by column chromatography on silica gel (eluent:
petroleum ether/ethyl acetate=20/1) to afford Z-4a-D as
a white solid; yield: 210.3 mg (60%). 1H NMR (400 MHz,
CDCl3): d=7.54–7.51 (m, 3H, ArH), 7.22–7.19 (m, 1H,
ArH), 7.19–7.10 (m, 5H, ArH), 7.10–6.97 (m, 2H, ArH),
6.93 (d, J=7.6 Hz, 2H, ArH), 6.639 (s, 0.62H, =CH), 6.57 (s,
1H, NH), 2.34 (s, 3H, CH3). The following signals are dis-
cernible for Z-4a: d=6.64 (d, J=12.8 Hz, 0.38H, =CH),
6.12 (d, J=11.6 Hz, 0.38H, =CH); 13C NMR (100 MHz,
CDCl3): d=143.8, 136.4, 135.4, 134.2, 134.02, 133.64, 133.62,
129.59, 129.57, 129.54, 129.51, 128.7, 128.5, 128.4, 128.0,
127.2, 125.1, 124.5, 121.60, 21.5. The following signals are
discernible for Z-4a: d=134.02, 133.64, 129.57 (t, J=
4.0 Hz), 121.63; IR (neat, cmÀ1) 3251, 1597, 1494, 1483,
1448, 1401, 1272, 1154, 1089; MS (ESI): m/z=374 [M(D)+
Na+H]+, 373 [M(D)+Na]+, 351 [M(D)+H]+, 350 [M(D)]+;
HR-MS: m/z=350.1196, calcd, for C21H18DNO2S [M]+:
350.1199.
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In addition, 26.8 mg of an unknown product were isolated
1
and presented unique peaks in the H NMR spectrum. This
kind of structure had never been observed by comparing
1
with all other crude H NMR spectra described previously
in this article. Further study will be continued in this group
about this unknown product.
Acknowledgements
Financial support from National Natural Science Foundation
of China (21232006) and National Basic Research Program
of China (2015CB856600) is greatly appreciated. We thank
Weilong Lin in this group for reproducing the results of E-2j
in Table 2, E-6b in Table 3 and E-2p in Scheme 3.
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