Studies on pyrazines, Part 39.¹ Synthesis and acidic hydrolysis of 2-hydroxy-5-methoxypyrazine

Abstract

2-Hydroxy-5-methoxypyrazine was synthesised in a three-step reaction sequence starting from aminopyrazine. The product was extensively destroyed on acidic workup without forming 2,5-dihydroxypyrazine.

Solubility Measurement and Correlation of 2-Amino-5-bromopyrazine in Methanol/Ethanol/Isopropanol/Propylene Glycol Plus Water and 10 Pure Solvents at (278.15–323.15) K

“…The result in Figure indicates that the temperature at the inflection point of the curve is 386.15 K (standard uncertainty, 0.5 K), which is the melting point ( T m ) of 2-amino-5-bromopyrazine, and the fusion enthalpy (Δ fus H ) of 2-amino-5-bromopyrazine is 10.01 kJ mol –1 (standard uncertainty, 0.3 kJ mol –1 ). Besides, some previous publications have reported the melting points of 2-amino-5-bromopyrazine. ,,,− The T m value of 2-amino-5-bromopyrazine obtained in this work was similar to the values 387.65–388.65 K, 386.75 K, 386.15–387.15 K, and 385.15–387.15 K ,, in the literature. However, there are no data related to the fusion enthalpy of 2-amino-5-bromopyrazine in the database, so the data measured this time cannot be compared with the literature value.…”

“…Besides, some previous publications have reported the melting points of 2-amino-5-bromopyrazine. 13,14,16,26−28 The T m value of 2-amino-5-bromopyrazine obtained in this work was similar to the values 387.65−388.65 K, 13 386.75 K, 26 386.15−387.15 K, 16 and 385.15−387.15 K 14,27,28 in the literature. However, there are no data related to the fusion enthalpy of 2-amino-5-bromopyrazine in the database, so the data measured this time cannot be compared with the literature value.…”

“…Nevertheless, the product has a high content of impurities, which can be found in some reports concerning the synthesis methods of 2-amino-5-bromopyrazine. − After the synthesis section of 2-amino-5-bromopyrazine, the product with a yield of 36–65% is crystallized in heptane or cyclohexane. − Whatever areas 2-amino-5-bromopyrazine is applied in, the purity of 2-amino-5-bromopyrazine must be high in demand. Meanwhile, to achieve the high-purity 2-amino-5-bromopyrazine product, it is necessary to select the best solvent systems to separate and purify.…”

Solubility and Data Correlation of 2-Bromo-5-hydroxypyrazine in Four Cosolvent Mixtures and Ten Mono-Solvents from 278.15 to 323.15 K

“…The test curves of DSC are illustrated in Figure S1, from which the following information can be obtained: melting point ( T m ) of 391.65 K (standard uncertainty 0.5 K) and enthalpy of fusion (Δ fus H ) of 11.64 kJ·mol –1 (standard uncertainty 0.4 kJ·mol –1 ). In addition, some previous publications have reported the melting point but no fusion enthalpy of C 4 H 3 BrN 2 O . The T m of C 4 H 3 BrN 2 O obtained in this work was greater than the value in ref (388.15–389.15 K).…”

“… a High-performance liquid chromatography. b Gas chromatography. c Measured by this work. d Taken from ref . …”