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20th March 2018 @ 14:18

Method:

2-chloro-6-(2-hydrazinyl(2,4-dimethoxybenzylidene))pyrazine) (C) (51.8 mg, 0.177 mmol, 1.0 equiv.) was dissolved in dry dichloromethane (15 mL) forming a yellow solution. Diacetoxyiodobenzene (PIDA) (62.8 mg, 0.195 mmol, 1.1 equiv.) was then added and the solution was stirred at room temperature under nitrogen for approximately 16 hours. After this time, the reaction mixture was exposed to air and analysed by TLC (pure EtOAc) showing a clear product peak as well as some residual PIDA. The reaction mixture was quenched by the addition of a saturated aqueous solution of sodium hydrogen carbonate (~15 mL). Aqueous layers were separated and then extracted with DCM (2 x 15 mL). The organic layers were combined and washed with brine (1 x 20 mL), dried with MgSO4, filtered and evaporated in vacuo, yielding the crude product as orange plate-like crystals (28.8 mg, 56.0%). The crude product was characterised using 1H NMR, 13C NMR, DEPT 90 + 135, GC-MS and IR, all of which showed a complicated array of signals, suggesting significant impurity. Attempts were made to isolate the product by recrystallisation in ethanol and by using a silica column, neither of which were successful. Since TLC showed that the reaction mixture contained only one product after stirring overnight, but many compounds were present upon TLC analysis of the same mixture later in the same day, it may be that the product decomposed considerably in the presence of air.


Attached Files
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2,4 dimethoxy triazolopyrazine formation 1H NMR.pdf