7556
K. Hemming, N. Patel / Tetrahedron Letters 45 (2004) 7553–7556
1991, 32, 2233–2236; (e) Langlois, N.; Favre, F.; Rojas, A.
Tetrahedron Lett. 1993, 34, 4635–4638.
9. (a) Harrington, P. J.; Sanchez, I. H. Synth. Commun. 1994,
24, 175–180; (b) Shi, G.; Schlosser, M. Tetrahedron 1993,
49, 1445–1456; (c) Zhu, S. Z.; Liu, X. Y.; Wang, S. W.
Tetrahedron 2003, 59, 9669–9676.
(10mL) was added the 1,2-thiazine 1-oxide 4 (0.30–
0.50g, 1equiv) in one portion and the mixture was stirred
at room temperature under an atmosphere of dry nitrogen
for 2h. The volatiles were removed by rotary evaporation
and the crude mixture was purified by silica column
chromatography
(petroleum
ether–ethyl
acetate
10. Hemming, K.; Loukou, C. Tetrahedron 2004, 60, 3349–
3357.
11. Hemming, K.; Loukou, C.; Elkatip, S.; Smalley, R. K.
Synlett 2004, 101–105.
40:60+10% triethylamine). For example, compound 11c
(0.135g, 50%) was obtained as pale yellow oil from 1,2-
thiazine 1-oxide 4c (0.350g, 1.07mmol). dH (400MHz,
CDCl3): 1.91 (6H, s, 2 · Me), 4.5–4.7 (2H, br s, NH2), 6.63
(1H, d, J 8.2, ArH), 6.71 (1H, t, J 7.6, ArH), 6.84 (2H, s,
2 · pyrrole-H), 7.25 (1H, t, J 7.4, ArH), 7.61 (1H, d, J 8.1,
ArH). dC (100MHz, CDCl3): 10.1 (Me), 117.4 (CH), 117.6
(CH), 117.8 (CH), 120.0 (q), 124.2 (q), 129.2 (CH), 135.0
(CH), 145.6 (q). mmax(thin film, cmꢀ1): 3457 (s, NH2), 3377
(s, NH2), 2966 (m), 2919 (m), 1636 (s), 1599 (m), 1484 (s),
1455 (m), 1348 (m), 1296 (m), 1068 (s), 1034 (s), 829 (s),
744 (m), 699 (m), 610 (m), 588 (m). EI+ mass spectrum
(m/z, %): 250 ([M]+, 70%), 185 (25%), 156 (20%), 108
(35%), 94 (100%), 65 (80%), 39 (50%). HRMS (ESI+):
Found [M+H+] 251.0845, C12H14N2O2S requires 251.0849.
Preparation of 1-(2-formamidobenzenesulfonyl)pyrroles
10: formic acid (2.25equiv) was added into acetic anhy-
dride (2equiv) at 0ꢁC and the solution was stirred at room
temperature for 2h. This solution was added to a solution
of the 1-(2-aminobenzenesulfonyl)pyrrole 11 (0.10–0.20g,
1equiv) in anhydrous tetrahydrofuran (5mL) and the
reaction mixture was stirred at room temperature for 20h.
The crude product was purified by silica column chroma-
tography (petroleum ether–ethyl acetate 40:60). As an
example, compound 10c (0.120g, 83%) was obtained as a
pale yellow oil from 1-(2-aminobenzenesulfonyl)pyrrole
11c (0.130g, 0.52mmol). dH (400MHz, CDCl3): 1.97 (6H,
s, 2 · Me), 6.85 (2H, s, 2 · pyrrole-H), 7.23(1H, t, J 7.7,
ArH), 7.61 (1H, t, J 7.7, ArH), 7.77 (1H, d, J 8.0, ArH),
8.52 (1H, d, J 7.9, ArH), 8.56 (1H, s, CHO), 9.45 (1H, br s,
NH). dC (100MHz, CDCl3): 10.1 (Me), 117.5 (CH), 123.0
(CH), 124.2 (CH), 125.7 (q), 125.8 (q), 126.1 (q), 128.8
(CH), 135.1 (CH), 158.8 (CHO). mmax (thin film, cmꢀ1):
3290 (m, NH), 3020 (w), 2921 (w), 1706 (s), 1674 (s), 1579
(m), 1514 (m), 1403(m), 1358 (m), 1290 (m), 1216 (s), 1160
(s), 1071 (m), 669 (m), 611 (m). EI+ mass spectrum (m/z,
%): 278 ([M+], 60%), 250 (10%), 228 (60%), 184 (85%), 156
(20%), 120 (50%), 95 (100%), 65 (85%). HRMS (CI+NH3):
Found [M+NHþ4 ] 296.1063, C13H14N2O3S requires
296.1063.
Preparation of pyrrolobenzothiadiazepines 3: A solution
of 1-(2-formamidobenzenesulfonyl)pyrrole 10 (ꢁ0.10g,
1equiv) and phosphorus oxychloride (21.6equiv) in 1,2-
dichloroethane (2mL) was heated at reflux temperature
for 3h. Evaporation of the solvent gave a residue, which
was purified by silica column chromatography (petroleum
ether–ethyl acetate, 40:60). For example, compound 3c
(0.040g, 43%) was obtained from 1-(2-forma-
midobenzenesulfonyl)pyrrole 10c (0.100g, 0.36mmol) as
a bright orange oil. dH (400MHz, CDCl3): 2.06 (3H, s,
Me), 2.26 (3H, s, Me), 7.33 (1H, s, pyrrole-H), 7.42 (1H,
dt, J 8.0, 1.0, ArH), 7.60–7.73(2H, m, 2 · ArH), 8.04 (1H,
dd, J 7.9, 1.2, ArH), 8.62 (1H, s, N@CH). dC (100MHz,
CDCl3): 9.6 (Me), 9.9 (Me), 120.8 (CH), 123.6 (q), 124.9
(q), 125.3( CH), 126.2(CH), 129.9(CH), 130.1 (q), 132.5
(q), 134.4 (CH), 144.1 (q), 148.6 (CH). mmax (cmꢀ1): 2924
(w), 1603(s), 1582 (s), 1458 (m), 1365 (s), 1294 (m), 1181
(s), 1137 (m), 1107 (m), 910 (s), 832 (m), 767 (m), 733 (m).
HRMS (ESI+): Found [M+H+] 261.0691, C13H12N2O2S
requires 261.0692.
12. Anwar, B.; Grimsey, P.; Hemming, K.; Krajniewski, M.;
Loukou, C. Tetrahedron Lett. 2000, 41, 10107–10110.
13. For some examples of this transformation, see: (a)
Gololobov, Y. G.; Kasukhin, L. F. Tetrahedron 1992,
48, 1353–1406; (b) Katritzky, A. R.; Jiang, S.; Urogdi, L.
Tetrahedron Lett. 1989, 30, 3303–3306; (c) Schoetzau, T.;
Holletz, T.; Cech, D. Chem. Commun. 1996, 387–388.
14. For a review of this type of reaction, see: Weinreb, S. M.
Acc. Chem. Res. 1988, 21, 313–318.
15. For leading references on this heterocumulene, see: (a)
Levchenko, E. S.; BalÕon, Y. G.; Kisilenko, A. A. J. Org.
Chem. USSR (English Transl.) 1965, 1, 151–155; (b)
Kresze, G.; Maschke, A.; Albrecht, R.; Bederke, K.;
Patzschke, H. P.; Smalla, H.; Trede, A. Angew. Chem., Int.
Ed. Engl. 1962, 1, 89–98; (c) Kresze, G.; Wucherpfennig,
W. Angew. Chem., Int. Ed. Engl. 1967, 6, 149–167.
16. Zwierak, A.; Piotrowicz, B. J. Angew. Chem., Int. Ed.
Engl. 1977, 16, 107.
17. Silvestri, R.; Artico, M.; Pagnozzi, E.; Stefancich, G. J.
Heterocycl. Chem. 1994, 31, 1033–1036.
18. All new compounds gave satisfactory 1H/13C NMR
spectra, mass spectra and HRMS/microanalysis.
19. Experimental procedures and typical spectroscopic details:
preparation of 1,2-thiazine 1-oxides 4. To a stirred
solution of o-azidobenzenesulfonamide (2.00g, 10.1mmol)
and anhydrous pyridine (2.0equiv) in anhydrous tetra-
hydrofuran (50mL), under an atmosphere of dry nitrogen
at 0ꢁC, was added, dropwise with stirring over a period of
3h, a solution of thionyl chloride (1.0equiv) in anhydrous
tetrahydrofuran (10mL), to yield the crude N-sulfinyl
compound 6. The appropriate 1,3-diene (1.6equiv) was
added, and the mixture was allowed to warm to room
temperature overnight. The solvent was removed by
rotary evaporation and the crude product was purified
by flash silica column chromatography (petroleum ether–
ethyl acetate/1:1). For example, 2-(o-azidobenzenesulfon-
yl)-4,5-dimethyl-1,2-thiazine-1-oxide 4c was obtained as a
yellow solid (3.06g, 93% yield). Mp: 137–138ꢁC. dH
(400MHz, CDCl3): 1.71 (3H, s, Me), 1.79 (3H, s, Me),
3.23 (1H, d, J 15.9, CH2), 3.63 (1H, d, J 14.2, CH2), 3.68
(1H, d, J 14.2, CH2), 3.86 (1H, d, J 16.2), 7.28 (1H, t, J 7.8,
ArH), 7.34 (1H, d, J 8.0, ArH), 7.66 (1H, dt, J 7.8, 1.1,
ArH), 8.01 (1H, dd, J 8.0, 0.9, ArH). dC (100MHz,
CDCl3): 16.9 (Me), 19.7 (Me), 42.9 (CH2), 55.5 (CH2),
115.0 (q), 120.3( CH), 123.5 (q), 124.6 (CH), 127.5 (q),
131.6 (CH), 135.1 (CH), 139.0 (q). mmax (chloroform,
cmꢀ1): 3006 (w), 2918 (w), 2134 (s, N3), 1585 (m), 1575
(m), 1472 (s), 1444 (m), 1351(s), 1291 (m), 1171 (s), 1102
(s), 885 (m), 758 (s), 614 (m). EI+ mass spectrum (m/z, %):
326 ([M]+, 9%), 298 (12%), 278 (10%), 156 (10%), 116
(25%), 104 (20%), 90 (40%), 76 (35%), 64 (50%), 54 (30%),
39 (100%). HRMS (ESI+): found [M+H+] 327.0587,
C12H14N4O3S2 requires 327.0585.
Preparation of 1-(2-aminobenzenesulfonyl)pyrroles 11: to
a rapidly stirring solution of triethylamine (1equiv) and
trimethylphosphite (2equiv) in anhydrous methanol