LETTER
Thiazolidine-Condensed Five-, Six-, and Seven-Membered Heterocycles
2001
(6) (a) Hart, D. J. J. Org. Chem. 1981, 46, 367. (b) Winterfeldt,
E. Synthesis 1975, 617. (c) Padwa, A.; Kappe, C. O.;
Cochran, J. E.; Snyder, J. P. J. Org. Chem. 1997, 62, 2786.
(7) Marković, R.; Baranac, M.; Steel, P. J.; Kleinpeter, E.;
Stojanović, M. Heterocycles 2005, 65, 2635.
(8) (a) Marković, R.; Džambaski, Z.; Baranac, M. Tetrahedron
2001, 57, 5833. (b) Marković, R.; Baranac, M.; Džambaski,
Z.; Stojanović, M.; Steel, P. J. Tetrahedron 2003, 59, 7803.
(9) (a) Pujari, H. K. Adv. Heterocycl. Chem. 1990, 49, 1.
(b) Köpper, S.; Lindner, K.; Martens, J. Tetrahedron 1992,
48, 10277.
CDCl3): d = 14.6 (CH3CH2), 22.0 (C3), 29.1 (C2), 33.0 (C8),
46.8 (C4), 59.3 (CH2CH3), 67.5 (C8a), 83.5 (C6¢), 162.3 (C6),
168.9 (CO2) ppm. IR: 2977, 2951, 2925, 2897, 1662, 1531,
1459, 1427, 1335, 1276, 1226, 1205, 1177, 1144, 1102,
1043, 1003, 900, 809 cm–1. HR MS (CI/TOF): m/z [M + H]+
calcd: 246.06170; found: 246.06176 0.24 ppm.
(16) Analytical Data of (Z)-Ethyl 2-{7-Methyl-2H-thiazolo[4,3-
b]thiazol-5 (3H,7H,7aH)-ylidene}acetate (9c)
Isolated in 37% yield as a mixture of trans- and cis-isomer
in a 75:25 ratio.
Compound trans-9c: 1H NMR (500 MHz, CDCl3): d = 1.26
(3 H, t, J = 7.0 Hz, CH3CH2), 1.49 (3 H, d, J = 6.5 Hz,
CH3CHS), 3.09–3.12 (1 H, m, CH2S), 3.15–3.20 (1 H, m,
CH2S), 3.26–3.32 (1 H m, CH2N), 3.66 (1 H, dq, J1 = 6.5 Hz,
J2 = 5.5 Hz, CHCH3S), 3.97 (1 H, ddd, J1 = 9.0 Hz, J2 = 6.0
Hz, J3 = 3.0 Hz, CH2N) 4.16 (2 H, q, J = 7.0 Hz, CH2CH3),
4.89 (1 H, d, J = 5.5 Hz, CHSN), 5.07 (1 H, s, = CH) ppm.
13C NMR (50.3 MHz, CDCl3): d = 14.5 (CH3CH2), 20.1
(CH3CHS), 32.0 (CH2S), 45.1 (CHCH3S), 50.7 (CH2N),
59.4 (CH2CH3), 76.8 (CHSN), 84.4 (=CH), 163.76 (C=),
168.6 (CO2) ppm.
(10) (a) Pinck, L. A.; Hilbert, G. E. J. Am. Chem. Soc. 1946, 751.
(b) McKillop, A.; Ford, M. E. Tetrahedron 1974, 30, 2467.
(c) Stetter, H.; Schwarz, M.; Hirschhorn, A. Chem. Ber.
1959, 92, 1629.
(11) Geluk, H. W.; Schlatmann, J. L. M. A. Tetrahedron 1968,
24, 5361.
(12) For this type of neighboring-group participation, see:
(a) Pasto, D. J.; Serve, M. P. J. Am. Chem. Soc. 1965, 87,
1515. (b) Cheng, X.-E.; Hui, Y.-Z.; Gu, J.-H.; Jiang, X.-K.
Chem. Commun. 1985, 71. (c) Bhatt, M. V.; Rao, G. V.;
Rao, K. S. J. Org. Chem. 1979, 44, 984. (d) Irie, T.; Tanida,
H. J. Org. Chem. 1980, 45, 1759. (e) Holum, J. R.; Jorenby,
D.; Mattison, P. J. Org. Chem. 1964, 29, 769.
Compound cis-9c: 1H NMR (500 MHz, CDCl3): d = 1.27 (3
H, t, J = 7.0 Hz, CH3CH2), 1.46 (3 H, d, J = 7.0 Hz,
CH3CHS), 3.05–3.09 (1 H, m, CH2S), 3.24–3.33 (1 H, m,
CH2S), 3.29–3.41 (1 H, m, CH2N), 3.89 (1 H, dq, J1 = 7.0
Hz, J2 = 5.5 Hz, CHCH3S), 4.00 (1 H, ddd, J1 = 9.2 Hz,
J2 = 5.8 Hz, J3 = 3.2 Hz, CH2N) 4.16 (2 H, q, J = 7.0 Hz,
CH2CH3), 5.10 (1 H, s, =CH), 5.28 (1 H, d, J = 5.5 Hz,
CHSN) ppm. 13C NMR (50.3 MHz, CDCl3): d = 14.5
(CH3CH2), 17.0 (CH3CHS), 31.0 (CH2S), 41.3 (CHCH3S),
51.0 (CH2N), 59.4 (CH2CH3), 76.8 (CHSN), 84.8 (=CH),
163.8 (C=), 168.6 ppm.
(13) Zheng, T.-C.; Burkart, M.; Richardson, D. E. Tetrahedron
Lett. 1999, 40, 603.
(14) Van Maarseveen, J. H.; Scheeren, H. W.; Kruse, C. G.
Tetrahedron 1993, 49, 2325.
(15) Typical Procedure for the Synthesis of (Z)-Ethyl 2-
(Tetrahydrothiazolo[4,3-b][1,3]thiazin-6 (2H)-
ylidene)acetate (9f)
The thioester 7f (50.5 mg, 0.17 mmol) was dissolved in dry
EtOH (5 mL) and a solution of NaOEt (0.2 M in EtOH, 0.85
mL, 0.17 mmol) was added at r.t. with vigorous stirring.
After hydrolysis to thiol, as evidenced by complete
consumption of the reactant (ca. 15 min; TLC), the reaction
mixture was cooled down to 0 °C. Twofold mass excess of
NaBH4 (101 mg, 15–20 mmol equiv) was added, followed
by 3 drops of 0.4 M HCl in EtOH. The addition of the same
amount of acid was continued in regular 10 min intervals
until the end of the reaction (45 min), when the reaction
mixture was quenched with 1 M HCl in EtOH. The
suspension was stirred for an additional 30 min at 0 °C,
diluted with H2O, extracted with CHCl3, the organic phase
separated, dried with Na2SO4, and the solvent evaporated
under reduced pressure. Purification of a crude product by
column chromatography (SiO2; PE–EtOAc solvent gradient
100:0 → 80:20) afforded the final product 9f as a white solid
(27.4 mg, 66%); mp 108–109 °C. 1H NMR (200 MHz,
CDCl3): d = 1.27 (3 H, t, J = 7.4 Hz, CH3CH2), 1.65–2.05 (2
H, m, C3H2), 2.76–2.83 (1 H, m, C2H), 2.83 (1 H, dd,
J1 = 11.8 Hz, J2 = 2.0 Hz, C8H), 3.12 (1 H, ddd, J1 = 13.6
Hz, J2 = 12.2 Hz, J3 = 3.0 Hz, C2H), 3.27 (1 H, ddd,
J1 = 14.4 Hz, J2 = 12.6 Hz, J3 = 2.6 Hz, C4H), 3.39 (1 H, dd,
J1 = 11.8 Hz, J2 = 7.2 Hz, C8H), 3.80–3.87 (1 H, m, C4H),
4.17 (2 H, q, J = 7.4 Hz), 5.05 (1 H, s, C6¢H), 5.18 (1 H, dd,
J1 = 7.2 Hz, J2 = 2.0, C8aH) ppm. 13C NMR (50.3 MHz,
(17) For recent examples of the 5-endo-trig mode ring-closing
reaction, see: (a) Fuwa, H.; Sasaki, M. Org. Lett. 2007, 9,
3347. (b) Kim, I.; Won, H. K.; Choi, J.; Lee, G. H.
Tetrahedron 2007, 63, 12954. (c) Ray, D.; Paul, S.; Brahma,
S.; Ray, J. K. Tetrahedron Lett. 2007, 48, 8005. (d) Bogen,
S.; Goddard, J.-P.; Fensterbank, L.; Malacria, M. ARKIVOC
2008, (viii), 126. (e) Ichikawa, J.; Iwai, Y.; Nadano, R.;
Mori, T.; Ikeda, M. Chem. Asian J. 2008, 3, 393.
(f) Marchand, P.; Gulea, M.; Masson, S.; Saquet, M.;
Collignon, N. Org. Lett. 2000, 2, 3757. (g) Bommezijn, S.;
Martin, C. G.; Kennedy, A. R.; Lizos, D.; Murphy, J. A. Org.
Lett. 2001, 3, 3405. (h) Chowdhury, M. A.; Reissig, H.-U.
Synlett 2006, 2383. (i) Clark, A. J.; Dell, C. P.; McDonagh,
J. M.; Geden, J.; Mawdsley, P. Org. Lett. 2003, 5, 2063.
(j) Jones, A. D.; Redfern, A. L.; Knight, D. W.; Morgan,
I. R.; Williams, A. C. Tetrahedron 2006, 62, 9247.
(k) Clive, D. L. J.; Yang, W.; MacDonald, A. C.; Wang, Z.;
Cantin, M. J. Org. Chem. 2001, 66, 1996. (l) Geyer, A.;
Moser, F. Eur. J. Org. Chem. 2000, 1113.
(18) (a) Baldwin, J. E. Chem. Commun. 1976, 736. (b) Baldwin,
J. E.; Thomas, R. C.; Kruse, L. I.; Silberman, L. J. Org.
Chem. 1977, 42, 3846.
(19) Chatgilialoglu, C.; Ferreri, C.; Guerra, M.; Timokhin, V.;
Froudakis, G.; Gimisis, T. J. Am. Chem. Soc. 2002, 124,
10765.
Synlett 2009, No. 12, 1997–2001 © Thieme Stuttgart · New York