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10th August 2015 @ 03:23

Very clean desired product was obtained with no further purification. Mass of crude is 188mg and yield of product is 62%. Optimization of condesation reaction (see TZ5-1) is necessary.

Reaction started at 14:10.

 

Procedure:

N'-(6-chloropyrazin-2-yl)formohydrazide (1.97 mmol, 338 mg) and phosphorus oxychloride (46.4.3 ml) were combined under argon atmosphere in a flask. The reaction mixture was then heated at reflux for 4 hours and was stirred at room temperature overnight.

Phosphorus oxychloride was removed under reduced pressure to give dark brown solid. Ice-water (8ml) was added to the solid residue dropwise. The resulting aqueous solution was adjusted to pH 6 using concentrated sodium hydroxide silution under external cooling and then extracted with choloroform (3*60ml). The organics were collected in a flask and dried over sodium sulfate. The solvent (chloroform) was then removed under reduced pressure to give brown solid (188mg, 62%).

NMR of the brown solid (crude) was clean apart form the peak of solvent (ethyl acetate) and showed that the desired product was obtained compared to NMR of TZ 2-1 frac 4 (see TZ 2-1). The yield of the desired product is terrible. Further optimization of the first step (see TZ 5-1) was needed to improve the reaction.

 

 

Data

NMR data of crude:

TZ 6-1 crude.pdf

HIRAC

 

HIRAC 5-2.pdf

 

Srings:

ClC1=CN=CC(NNC([H])=O)=N1

TO

ClC1=CN=CC2=NN=CN21

 

InChI=1S/C5H5ClN4O/c6-4-1-7-2-5(9-4)10-8-3-11/h1-3H,(H,8,11)(H,9,10)

TO

InChI=1S/C5H3ClN4/c6-4-1-7-2-5-9-8-3-10(4)5/h1-3H

Attached Files
TZ 5-2.png
HIRAC 5-2.doc
HIRAC 5-2.pdf
TZ 6-1 crude.pdf
TZ 6-1 crude.rar
Comments
Re: Synthesis of 5-Chloro-[1,2,4]triazolo[4,3-a]pyrazine (TZ 5-2) by Alice Williamson
10th August 2015 @ 05:33
HIRAC seen and approved with addition of use of blast shield as a secondary shield in case of explosion during reflux