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26th July 2016 @ 02:13

Procedure:

NBS was recrystallized before the reaction. Water (25ml) was added to NBS (2g). The mixture was stirred and heated at 100 celsius degree until NBS was dissolved to make a homogeneous orange solution. The solution was then cooled down to room temperature. Bright white crystals crystallized in the solution. The crystals were then filtered out and washed with ice water. 

5-chloro-[1,2,4]triazolo[4,3-a]pyrazine (1 g, 6.49 mmol) and N-bromosuccinimide (1.04 g, 5.82 mmol, 0.9equiv.) were placed in chloroform (50 mL) and refluxed for 44 h.

The reaction mixture was then diluted with chloroform (50 mL), washed with sodium carbonate solution (15 mL), and the aqueous layer re-extracted with chloroform (2 x 20 mL). The combined organic portions were concentrated under reduced pressure

 

HIRAC

HM3-2.docx

Log

Reaction started at 4:30pm 26th Jul

27th Jul 

TLC was performed, showing much of starting material existed. Another 0.5equiv of NBS was added.

 

28th Jul

TLC was performed at 9:50. Reaction was almost completed, so that it was swtiched and cooled down to room temperature.( Then I have to attend a talk about safty in the afternoon and work up the reaction tomorrow )

29th Jul

The reaction mixture was then diluted with chloroform (50 mL), washed with sodium carbonate solution (15 mL), and the aqueous layer re-extracted with chloroform (2 x 20 mL). The combined organic portions were concentrated under reduced pressure.

NMR was performed and two major peaks matched with Tom's though there was another peak whose shift was 2.78ppm, which might result from the residual succinimide. Product was dissolved in Chloroform and washed with sodium carbonate solution again and concentrated. Then the peak on 2.78ppm was gone but other peaks(assumed to be oxethyl group) appeared. Maybe NMR tube was not clean enough.So NMR was performed a second time, indicating impurity still exist but it's quite promising. Sample weight:1.25g, yield:82.8%

(product)

 NMR

HM 3-2.png
HM3-2.zip
(before washing)

HM 3-2 washed.png
HM3-2 washed.zip
(after washing)

HM3-2 washed\'.zip
HM 3-2 washed (2nd).png
(after washing)

 

two spectra.png
(Though different solvent in the nmr of SM and NMR of Product were used it still looks promising! Waiting for single crystal ;-) )

 


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Attached Files
HM3-1.png
HM3-2.docx
IMG_2163.JPG
IMG_2155.JPG
HM 3-2.png
HM3-2.zip
IMG_2200.JPG
HM 3-2 washed (2nd).png
HM3-2 washed\'.zip
HM3-2 washed.zip
HM 3-2 washed.png
two spectra.png
Comments
Re: Synthesis of 3-bromo-5-chloro-[1,2,4]triazolo[4,3-a]pyrazine (HM 3-2) by Matthew Todd
26th July 2016 @ 05:42
HIRAC approved - on assumption that the product is also assumed to be harmful/toxic and handled accordingly.