Zhou et al.
629
Reduction of (Z)-2,3-dichloropropenoic acid (2) to (Z)-1,2-
dichloro-3-hydroxy-1-propene (17c or 3)
were obtained by slow evaporation of a solution of 12 in hex-
anes.
To a cooled (ice water bath) suspension of lithium alumi-
num hydride (0.84 g, 95% purity, 21 mmol) in dry diethyl
ether (20 mL) was added dropwise a solution of (Z)-2,3-di-
chloropropenoic acid (2, 3.00 g, 21.3 mmol) in dry diethyl
ether (20 mL). After stirring, first at 0 °C for 20 min and
then at room temperature for 2 h, the reaction mixture was
cooled (ice water bath), followed by sequential addition of
methanol (0.5 mL) and water (20 mL). When the evolution
of hydrogen gas ceased, dilute hydrochloric acid (approxi-
mately 3 N) was added to acidify the mixture until all precip-
itate dissolved. The layers were separated and the aqueous
layer was back-extracted with diethyl ether (50 mL). The
combined organic layers were washed with brine (2 ×
20 mL), dried (MgSO4), and evaporated under reduced pres-
sure. The residue was distilled to give (Z)-1,2-dichloro-3-hy-
droxy-1-propene as a colourless oil (1.62 g, 45–48 °C/2 mm
Hg (1 mm Hg = 133.3224 Pa), 61%). The NMR spectra were
identical to those of 17c.
X-ray diffraction experiment
Data were collected on a Nonius Kappa-CCD diffractome-
ter using monochromated Mo Ka radiation and were meas-
ured using a combination of f scans and u scans with k
offsets, to fill the Ewald sphere. The data were processed us-
ing the Denzo-SMN package.17 Absorption corrections were
carried out using SORTAV.18 The structure was solved and
refined using SHELXTL V6.119 for full-matrix least-squares
refinement that was based on F2. All H atoms were included
in the calculated positions and allowed to refine in riding-
motion approximation with Uiso tied to the carrier atom.
Supplementary data
Supplementary data are available with the article through
10.1139/v2012-041. CCDC 859121 contains the X-ray data
in CIF format for this manuscript. These data can be ob-
ucts/csd/request (Or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK;
fax: +44 1223 33603; or e-mail: depost@ccdc.cam.ac.uk.
(Z)-1,2,3-Trichloro-propene (4)
To a cooled (ice water bath) solution of (Z)-1,2-dichloro-3-
hydroxy-1-propene (3, 3.00 g, 23.6 mmol) in dry dichloro-
methane (12 mL) and dry pyridine (2.7 mL) was added drop-
wise thionyl chloride (2.4 mL, 33 mmol). After the reaction
mixture was stirred, first at 0 °C for 20 min and then at room
temperature for 2 h, nitrogen gas was bubbled into the reac-
tion mixture. The products were then evaporated under re-
duced pressure, and the residue was extracted with diethyl
ether (3 × 50 mL). The combined ether layers were concen-
trated under reduced pressure. The residue was purified by
column chromatography on silica gel. The appropriate frac-
tions, which were eluted with hexanes–dichloromethane (3:2
v/v), were evaporated under reduced pressure to give the title
compound as a colourless oil (1.30 g, 38%). dH (CDCl3):
4.67 (2 H, s), 6.64 (1 H, s). dC (CDCl3): 63.5, 120.9, 130.7.
HR-MS (EI) calcd for C3H3Cl3: 143.93003; found:
143.92975.
Conclusion
In conclusion, an approach for the synthesis of the thermo-
dynamically disfavoured (Z)-1,2-dichloroalkenes was devel-
oped. Chloroboration of terminal alkynes gives
corresponding (Z)-chloroboronic acids, which are readily
transformed into potassium trifluoro organoborate. Subse-
quent chlorodeboronation gives (Z)-1,2-dichloroalkenes in a
stereospecific manner.
Acknowledgments
The authors thank the Natural Sciences and Engineering
Research Council of Canada (NSERC) for funding this work.
References
(Z)-3,4-Dibromo-3-buten-1-tosylate (12)
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Single crystal growth: Single crystals of the tosylate 12
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