1634 J . Org. Chem., Vol. 64, No. 5, 1999
Liu et al.
combined extracts were washed with H2O (100 mL) and dried
over MgSO4. The solvent was evaporated, and the residue was
crystallized from Et2O to give 12a (4.6 g, 78%) as colorless
crystals: mp 128-130 °C; 1H NMR (CDCl3) δ 0.15 (s, 9H), 1.62
(s, 9H), 7.28 (d, J ) 2.1 Hz, 1H), 7.38 (m, 2H), 7.49-7.55 (m,
1H), 7.80-7.84 (m, 2H), 8.13 (d, J ) 2.1 Hz, 1H); 13C NMR
(CDCl3) δ -0.9, 27.7, 86.9, 89.5, 114.6, 118.1, 122.4, 125.0,
mg, 2.4 mmol) with KF (696 mg, 12 mmol) in CH2Cl2 (20 mL),
employing a procedure as described for the preparation of 13,
yielding 15 (10.7 mg, 2.2%) as colorless crystals: mp 118 °C;
1H NMR (CDCl3) δ 1.52 (s, 9H), 4.63 (tt, J ) 3.6, 3.6, 3.6, 3.6
Hz, 2H), 6.79-6.82 (m, 6H); 13C NMR (CDCl3) δ 28.0, 40.4,
82.4, 109.7, 135.6, 139.6, 145.0; MS m/z 243 (M+, 100); high-
resolution MS calcd for C15H18NO2 (MH+) m/z 244.1332, found
244.1328. Compounds 16 (59 mg, 10%) and 17 (182 mg, 25%)
were also obtained.
128.9, 131.8, 132.0, 132.4, 132.7, 146.5; MS m/z 442 (M+
-
OSO2CF3, 86). Anal. Calcd for C19H25F3INO5SSi: C, 38.58; H,
4.26; N, 2.37. Found: C, 38.59; H, 4.27; N, 2.21.
N-ter t-Bu toxyca r bon yl-7-oxa bicyclo[2.2.1]h ep t-5-en o-
2,3-[c]p yr r ole (13) P r ep a r ed u n d er High Dilu tion Con d i-
tion . To a well stirred solution of 18-crown-6 (295 mg, 0.5
mmol), KF (87 mg, 1.5 mmol), and furan (1 mL) in CH2Cl2 (5
mL) was added 12a (295 mg, 0.3 mmol) in CH2Cl2 (9 mL)
through a syringe pump at a rate of 0.9 mL/h in 10 h. The
mixture was stirred for another 14 h after the addition. The
resulting mixture was worked up as described above, yielding
13 (1.2 mg, 1%) as a colorless oil. The 1H NMR (CDCl3) and
13C NMR (CDCl3) spectra were identical to those of 13 obtained
under the regular condition. Compounds 16 (15 mg, 10%) and
P h en yl [1-tolu en esu lfon yl-4-(tr im eth ylsilyl)-1H-p yr -
r ole-3-yl]iod on iu m Tr ifla te (12b). Iodonium salt 12b was
prepared from pyrrole 11b (1.1 g, 3 mmol) with PhIO (0.66 g,
3 mmol) in CH2Cl2 (21 mL) catalyzed by BF3‚Et2O (0.57 mL,
4.5 mmol) in the same manner as for 12a , yielding 12b (1.6 g,
1
82%) as colorless crystals: mp 54-56 °C; H NMR (CDCl3) δ
0.10 (s, 9H), 2.41 (s, 3H), 7.08 (d, J ) 2.1 Hz, 1H), 7.34-7.39
(m, 4H), 7.47-7.51 (m, 1H), 7.78 (d, J ) 8.4 Hz, 2H), 7.87 (d,
J ) 8.4 Hz, 2H), 8.22 (d, J ) 2.1 Hz, 1H); 13C NMR (CDCl3) δ
-1.0, 21.7, 91.0, 114.5, 117.9, 122.2, 126.2, 127.6, 128.1, 130.5,
131.7, 131.8, 132.4, 133.0, 133.9, 146.6; MS m/z 496 (M+
OSO2CF3, 100). Anal. Calcd for C21H23F3INO5S2Si: C, 39.07;
H, 3.59; N, 2.17. Found: C, 39.07; H, 3.50; N, 1.99.
-
1
17 (57 mg, 31%) were also obtained, the H NMR (CDCl3) and
13C NMR (CDCl3) spectra of which were identical to those
obtained from the regular condition.
N-ter t-Bu toxyca r bon yl-7-oxa bicyclo[2.2.1]h ep t-5-en o-
2,3-[c]p yr r ole (13). To a well stirred solution of 12a (295 mg,
0.5 mmol), 18-crown-6 (79 mg, 0.3 mmol), and furan (1 mL) in
CH2Cl2 (5 mL) under N2 was added KF (87 mg, 1.5 mmol).
This mixture was stirred at room temperature for 17 h. The
resulting precipitate was removed by filtration. After evapora-
tion of the solvent, the residue was chromatographed on
preparative TLC (20 × 20 cm2) with hexanes-ethyl acetate
(9:1) as eluent to afford two portions. The first portion was
further purified on silica gel (7 g) with CH2Cl2-hexanes (4:1)
to give 13 as a colorless oil (1.6 mg, 1.4%): 1H NMR (CDCl3)
δ 1.59 (s, 9H), 5.61 (s, 2H), 6.85 (d, J ) 0.6 Hz, 2H), 6.90 (s,
2H); 13C NMR (CDC13) δ 28.0, 78.2, 83.1, 110.2, 136.3, 141.1,
149.8; MS m/z 233 (M+, 30); high-resolution MS calcd for
N -t er t -Bu t oxyca r b on yl-3-cya n ocyclob u t e n o[c]p yr -
r ole (14) P r ep a r ed u n d er High Dilu tion Con d ition . Com-
pound 14 was prepared by use of 12a (1.2 g, 2 mmol) in
CH2Cl2 (5 mL), 18-crown-6 (317 mg, 1.2 mmol), KF (348 mg,
6 mmol), and acrylonitrile (10 mL) in CH2Cl2 (20 mL). The
syringe pump rate was 0.2 mL/h, and the addition time was
25 h, yielding 14 (3.9 mg, 0.9%) as a colorless oil. Compounds
16 (47 mg, 8%) and 17 (153 mg, 21%) were also obtained. The
1H NMR (CDCl3) and 13C NMR (CDCl3) spectra of 14, 16,
and 17 were identical to those obtained under the regular
condition.
N -t er t -B u t o x y c a r b o n y lp y r r o [c]b ic y c lo [2.2.2]o c t a -
tr ien e (15) P r ep a r ed u n d er High Dilu tion Con d ition .
Compound 15 was prepared by use of 12a (1.2 g, 2 mmol) in
CH2Cl2 (5 mL), 18-crown-6 (634 mg, 2.4 mmol), KF (696 mg,
12 mmol), and benzene (8 mL) in CH2Cl2 (20 mL). The syringe
pump rate was 0.2 mL/h, and the addition time was 25 h,
yielding 15 (11 mg, 2.3%) as a colorless oil. Compounds 16 (100
mg, 17%) and 17 (197 mg, 27%) were also obtained. The 1H
NMR (CDCl3) and 13C NMR (CDCl3) spectra of 15, 16, and 17
were identical to those obtained under the regular condition.
Attem p ted Gen er a tion of 4 fr om 17 by TBAF . To a
solution of 17 (183 mg, 0.5 mmol) and furan (1 mL) in CH2Cl2
(2.5 mL) was added TBAF (0.6 mL, 0.6 mmol) slowly. After
30 h of stirring at room temperature and evaporation of
the solvent, the resulting residue was chromatographed on a
silica gel column (230-400 mesh, 50 g) eluted with hexanes-
CH2Cl2 (33:4) to recover the starting material (179 mg, 98%)
as a colorless oil, the 1H NMR spectrum of which was identical
to that of an authentic 17.
C
13H16NO3 (MH+) m/z 234.1125, found 234.1127.
The second portion was further purified on silica gel (20 g)
with hexanes-CH2Cl2 (33:4) as eluent to afford 1-tert-butoxy-
carbonyl-3-iodo-1H-pyrrole (16) as colorless oil (25 mg, 17%):
1H NMR (CDCl3) δ 1.59 (s, 9H), 6.29 (q, J ) 1.5 Hz, 1H), 7.13
(t, J ) 2.7 Hz, 1H), 7.32 (t, J ) 1.8 Hz, 1H); 13C NMR (CDCl3)
δ 27.9, 65.2, 84.4, 118.8, 121.4, 124.7, 147.5; MS m/z 293 (M+,
100).
Another component of the second portion was 1-tert-butoxy-
carbonyl-3-iodo-4-trimethylsilyl-1H-pyrrole (17), which formed
a colorless oil (51 mg, 28%): 1H NMR (CDCl3) δ 0.29 (s, 9H),
1.58 (s, 9H), 7.11 (d, J ) 1.8 Hz, 1H), 7.40 (d, J ) 1.8 Hz, 1H);
13C NMR (CDCl3) δ -1.1, 27.8, 71.4, 84.2, 125.7, 126.4, 126.7,
147.3; MS m/z 365 (M+, 27). Anal. Calcd for C12H20INO2Si: C,
39.46; H, 5.52; N, 3.83. Found: C, 39.41; H, 5.55; N, 3.76.
N -t er t -Bu t oxyca r b on yl-3-cya n ocyclob u t e n o[c]p yr -
r ole (14). This compound was prepared from the reaction of
12a (1.2 g, 2 mmol), acrylonitrile (10 mL), and 18-crown-6 (317
mg, 1.2 mmol) with KF (348 mg, 6 mmol) in CH2Cl2 (20 mL),
employing a procedure as described for the preparation of 13,
yielding 14 (6 mg, 1.4%) as a colorless oil: 1H NMR (CDCl3) δ
1.59 (s, 9H), 3.56-3.61 (ddd, J ) 13.8, 3.6, 1.2 Hz, 1H), 3.68-
3.75 (ddd, J ) 13.8, 6.0, 0.9 Hz, 1H), 4.24-4.28 (ddd, J ) 6.0,
3.3, 0.9 Hz, 1H), 6.86 (d, J ) 0.9 Hz, 1H), 6.99 (s, 1H); 13C
NMR (CDCl3) δ 26.7, 28.0, 34.9, 84.1, 111.8, 111.9, 119.3, 124.1,
126.5, 149.1; MS m/z 218 (M+, 41); high-resolution MS calcd
for C12H15N2O2 (MH+) m/z 219.1128, found 219.1129. Com-
pounds 16 (47 mg, 8%) and 17 (190 mg, 26%) were also
obtained.
Ack n ow led gm en t. Financial support from a Re-
search Grants Council (Hong Kong) Earmarked Grant
for Research (CUHK 77/93E) is gratefully acknowl-
edged.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra for the compounds prepared, as well as the X-ray
structural results of 10, 12a , and 15 (33 pages). This material
is contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
N -t er t -B u t o x y c a r b o n y lp y r r o [c]b ic y c lo [2.2.2]o c t a -
tr ien e (15). This compound was prepared from the reaction
of 12a (1.2 g, 2 mmol), benzene (8 mL), and 18-crown-6 (634
J O982129L