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20th March 2018 @ 14:15

Method:

2-chloro-6-(2-hydrazinyl(4-(dimethylamino)benzylidene))pyrazine) (52 mg, 0.18 mmol, 1.00 equiv.) was dissolved in chloroform (20 mL) forming a yellow solution. PIDA (62 mg, 0.19 mmol, 1.1 equiv.) was then added. The reaction was stirred at 50°C and the yellow solution became progressively red-orange within an hour. The reaction was monitored by TLC (3:7 Ethyl acetate: PET ether) and after 4 hours the TLC showed that no starting material remained. The reaction was quenched with saturated sodium hydrogen carbonate solution. The organic layer was isolated by separation with brine before drying over MgSO4. The dried filtrate was concentrated in vacuo to a dark brown crude oil. The crude product was characterised by IR and 1HNMR before purification by silica column (10 g silica) with an initial 1:1 Ethyl acetate: PET ether solvent system, then 7:3 Ethyl acetate : PET ether after starting material had been eluted; this was monitored by TLC. Many fractions were obtained and dried in vacuo, forming dark brown powders. Fraction A (34 mg, 65 %) and Fraction B (32 mg, 62%), were then characterised by IR, 1H NMR, and 13C NMR, DEPT and MS. 5-chloro-3-(4-(dimethylamino)phenyl)-[1,2,4]triazolo[4,3-a]pyrazine. IR taken immediately after their isolation showed presence of product, while NMR spectra showed the absence of aromatic signals, suggesting degradation overnight within the NMR tubes.


Attached Files
19:3-1.png
(4-dimethylamino)5.png
(4-dimethylamino)6.png
1HNMR Spectrum of 5-chloro-3-(4-(dimethylamino)phenyl)-[1,2,4]triazolo[4,3-a]pyrazine-2.pdf