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10th August 2016 @ 01:53

Procedure:

NBS was recrystallized before the reaction. Water (125ml) was added to NBS (10g). 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 (2 g, 12.98 mmol) and N-bromosuccinimide (3.5 g, 19.4 mmol, 1.5equiv.) were placed in chloroform (100 mL) and refluxed for 48 h.

The reaction mixture was then diluted with chloroform (100 mL), washed with sodium carbonate solution (30 mL), and the aqueous layer re-extracted with chloroform (2 x 40 mL). The combined organic portions were concentrated under reduced pressure

HIRAC

See  HM 3-2 Synthesis of 3-bromo-5-chloro-[1,2,4]triazolo[4,3-a]pyrazine (HM 3-2)

(2X the scale)


Log

10th Aug

The reaction was started at 2:50pm. And the temperature reached 70 degree celcious at 3:15. A dark red solution was formed.

11th Aug

Precipitant was observed and the reaction mixture was organge, which looked not like the previous one. TLC was performed under condition of 67% of ethyl acetate in hexane.TLC looked not as good and there was still SM left.50ml more chloroform was added to the solution.

(It probably needs column this time.  Next time, dissolve the starting material in chloroform first, then add 0.9equiv NBS first and add another 0.6equiv the next day.)

     

12th Aug


TLC was performed at 11:30. Reaction hasn't gone to completion.There was much precipitant sticked on the flask. Another 0.2 equiv of NBS was added.

 

The reation was switched off at 4:00pm,much precipitant was formed. After filteration, orange solid and light yellow solution was afforded.The solid could not dissolve in chloroform,so that it's probably not desired product.The solution was concentrated to afford dark red oil. 

In the H-NMR of the orange solid, the intensity of peaks was so low for the concentration of NMR sample, which could be a sign that no proton exists.

15th Aug

The oil was solidated. And TLC showed there was no obvious difference from the reation mixture. 

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