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Chart 3. The Proposed Mechanism for the Tandem Staudinger/aza-Wittig Reactions to Produce 3a
reduced pressure and the residue was purified by silica gel column chro-
matography (CHCl3/n-Hexaneꢂ1 : 3) to afford 5b as a colorless oil (0.78 g,
27%). 1H-NMR (CDCl3) d: 3.81 (2H, d, Jꢂ5.8 Hz), 4.09 (2H, d, Jꢂ5.8 Hz),
5.10—5.90 (2H, m). 13C-NMR (CDCl3) d: 44.06, 52.10, 128.07, 130.89. IR
(neat) cmꢃ1: 2102, 1442, 1350, 1255, 971. FAB-MS m/z: 131.0275 (Calcd
for C4H6ClN3: 131.0250). MS m/z: 131 (Mꢀ).
General Procedure Utilizing Method I for the Preparation of ((E)-3-
Isothiocyanatoprop-1-enyl)benzene (3c)23) To a solution of ((E)-3-azido-
prop-1-enyl)benzene 5c (78.5 mg, 0.5 mmol) and CS2 (0.24 ml, 4.0 mmol) in
CHCl3 (1.0 ml) was added Ph3P (131.1 mg, 0.5 mmol) at room temperature.
The mixture was stirred for 1.5 h, and the reaction mixture was directly sub-
jected to preparative TLC with AcOEt–hexane (1 : 10, v/v) to give 3c as a
1
colorless oil (65.4 mg, 75%). H-NMR (CDCl3) d: 4.31 (2H, d, Jꢂ5.5 Hz),
6.17 (1H, dd, Jꢂ5.5, 15.7 Hz), 6.66 (1H, d, Jꢂ15.7 Hz), 7.25—7.39 (5H,
m). IR (neat) cmꢃ1: 3027, 2093, 1495, 1448, 1350, 964. EI-MS m/z:
175.0351 (Calcd for C10H9NS: 175.0456). MS m/z: 175 (Mꢀ).
(Z)-1-Chloro-4-isothiocyanatobut-2-ene (3b): Colorless oil. 1H-NMR
(CDCl3) d: 4.09 (2H, d, Jꢂ6.5 Hz), 4.18 (2H, d, Jꢂ4.9 Hz), 5.82 (1H, dt,
Jꢂ4.9, 15.1 Hz), 5.97 (1H, dt, Jꢂ6.5, 15.1 Hz). 13C-NMR (CDCl3) d: 43.77,
46.17, 127.02, 129.55, 133.25. IR (neat) cmꢃ1: 2120, 1437, 1348, 1297,
1252. EI-MS m/z: 146.9919 (Calcd for C5H6ClNS: 146.9909). MS m/z: 147
(Mꢀ).
Spectral data of the known compounds 3a,14) 3d,24) 3e,25) 3f,26) and 3g27)
agree with those of the disclosed data.
General Procedure Utilizing Method II for the Preparation of ((E)-3-
Isothiocyanatoprop-1-enyl)benzene (3c)23) To a solution of ((E)-3-azido-
prop-1-enyl)benzene 5c (78.5 mg, 0.5 mmol) in CHCl3 (1.0 ml) was added
Ph3P (131.1 mg, 0.5 mmol) at room temperature, and the mixture was stirred
for 2 h. To the reaction mixture was added CS2 (0.24 ml, 4.0 mmol) at room
temperature. After being stirred for 1 h, the reaction mixture was directly
subjected to preparative TLC with AcOEt–hexane (1 : 10, v/v) to give 3c
(58.0 mg, 66%).
(Z)-2-Thioxo-1,3-thiazepin-3(2H,4H,7H)-yltriphenylphosphonium chlo-
ride (6) was obtained from the reaction of 5b (77.9 mg, 0.59 mmol) as a col-
orless oil (39.9 mg, 15%). 1H-NMR (CDCl3) d: 3.69—3.74 (2H, m), 3.89
(2H, d, Jꢂ7.0 Hz), 5.50 (1H, dt, Jꢂ7.0, 15.3 Hz), 5.86—5.93 (1H, m),
7.61—7.66 (6H, m), 7.69—7.71 (3H, m), 7.74—7.86 (6H, m). 13C-NMR
(CDCl3) d: 43.87, 44.51, 121.64, 122.66, 128.55, 130.15, 130.29, 132.17,
133.90, 134.01, 135.06. IR (neat) cmꢃ1: 2929, 1588, 1440, 1116. FAB-MS
m/z: 366 (MꢀꢀHꢃPh), 330 (MꢀꢀHꢃPhꢃCl).
Fig. 1. 1H-NMR Spectrum (400 MHz, CDCl3) of Chloroethylazide (5a),
Some Reaction Mixtures, and Chloroethylisothiocyanate (3a) in the Range
between 3 and 4 ppm
References and Notes
1) Kürti L., Czakó B., “Strategic Applications of Named Reactions in
Organic Synthesis,” Elsevier Academic Press, New York, 2005, pp.
428—429, and references cited therein.
2) Isolation of stable phosphazides and their reactivity, see: Molina P.,
López-Leonardo C., Llamas-Botía J., Foces-Foces C., Fernández-
Castaño C., Tetrahedron, 52, 9629—9642 (1996).
3) Bollens E., Szönyi F., Cambon A., J. Fluorine Chem., 53, 1—14
(1991).
(a) The chart of 5a, (b) that of the reaction mixture after 0.5 h when Ph3P was added
to a solution of 5a, (c) that of the reaction mixture after 3.0 h when CS2 was added to
the mixture of 5a and Ph3P, (d) that of the reaction mixture after 0.5 h when Ph3P was
added to a premixed solution of 5a and CS2, and (e) that of 3a are depicted. All reac-
tions were carried out at room temperature.
Experimental
4) Alajarín M., Vidal A., Ortín M., Org. Biomol. Chem., 1, 4282—4292
(2003).
5) For review of Staudinger reaction, see: Gololobov Y. G., Kasukhin L.
F., Tetrahedron, 48, 1353—1406 (1992).
6) Tsuge O., Kanemasa S., Matsuda K., J. Org. Chem., 49, 2688—2691
(1984).
The NMR spectra were obtained using a Bruker Avance DPX400
(400 MHz) spectrometer with tetramethylsilane (TMS) as the internal stan-
dard. The IR spectra were recorded by a JASCO FT-IR (VALOR-III) spec-
trometer. The Mass spectra were recorded using a JMS-SX102A spectrome-
ter.
(Z)-1-Azido-4-chlorobut-2-ene (5b) To a solution of (Z)-4-azidobut-2-
en-1-ol28) (2.5 g, 22.1 mmol) and pyridine (1.95 ml, 24.3 mmol) in CH2Cl2
(22 ml) was added SOCl2 (1.77 ml, 24.3 mmol) at 5 °C, and the mixture was
stirred for 30 min. The reaction mixture was then treated with excess satu-
rated aqueous ammonium chloride. The organic layer was washed with
brine, dried over MgSO4, and filtered. The filtrate was concentrated under
7) Zhu J., Bouillon J. P., Singh G. P., Chastanet J., Beugelmans R., Tetra-
hedron Lett., 36, 7081—7084 (1995).
8) Chu C., Ramamurthy A., Makriyannis A., Tius M. A., J. Org. Chem.,
68, 55—61 (2003).
9) Kötter S., Krallmann-Wenzel U., Ehlers S., Lindhorst T. K., J. Chem.
Soc. Perkin Trans. 1, 1998, 2193—2200 (1998).