Preparation of Extranuclear Hydroxyquinoxalines

Many such hydroxyquinoxalines have been made by primary synthesis (see Chapter 1) and some by hydrolysis of extranuclear halogenoquinoxalines (see Section 3.4.2) in addition, during extranuclear alkylidenation of methylquinox-alines (see Section 2.2.1.4) the intermediate secondary alcohols may sometimes be isolated, especially with heavily substituted aldehydes, when dehydration can be difficult or even impossible. °  

Other methods of preparation that have been used recently (as of 2003) are illustrated by the following classihed examples. 

2-(4 -Acetoxybiphenyl-4-yl)quinoxaline (152, R = Ac) gave 2-(4 -hydroxybi-phenyl-4-yl)quinoxaline (152, R = H) (NaOH, MeOH, H2O, reflux, 30 min  

2-Quinoxalinecarbaldehyde 1,4-dioxide (153) gave 2-(hydroxymethyl)quinoxa-line 1,4-dioxide (154) (NaBH4, MeOH, 20°C, 30 min 78%).  

3-(ot-Formyl-a-phenylhydrazonomethyl)-2(177)-quinoxalinone (155, R = H) gave 3-(2-hydroxy-1 -phenylhydrazonoethyl)-2( l//)-quinoxalinone (156, 

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