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16.14.4.1.5.2 Method 2: Halogenation

DOI: 10.1055/sos-SD-016-00919

Sato, N.Science of Synthesis, (200416815.

The most important reaction in this section is certainly halogenation of pyrazinols, because pyrazinols are readily prepared from aliphatic components, and, additionally, halopyrazines are versatile intermediates for the synthesis of less accessible pyrazines. Chloropyrazines 165 are generally synthesized by treatment of pyrazinol 55 with phosphoryl chloride at reflux or at elevated temperature in a sealed vessel (Scheme 95),[‌42‌,‌126‌‌128‌,‌132‌,‌286‌,‌287‌,‌359‌,‌385‌] in which a trace of sulfuric acid or hydrochloric acid is sometimes added. Several pyrazine-2,3-diols are likewise chlorinated to afford 2,3-dichloropyrazines.[‌179‌,‌284‌] The chlorination is occasionally effected by addition of phosphorus pentachloride to the phosphoryl chloride solution.[‌126‌,‌356‌]

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Meeeeeeeeeeeee 888; Meeeeee Meeeeeeee:[‌888‌]

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