Nuclear Halogenoquinoxalines by Transhalogenation

The replacement of one halogeno substituent by another at the 2- or 3-position may be done directly by several methods similar transformations at the 5- to 8-positions normally require an indirect route. The following examples illustrate typical procedures. [Pg.142]

2-Chloro-3-methyl- (46, R = Me) gave 2-iodo-3-methylquinoxaline (47, R = Me) (Nal, trace HCl, MeCN, reflux, 2h 83%) 3-chloro-2-quinoxaline-carbaldehyde (46, R = CHO) gave 3-iodo-2-quinoxalinecarbaldehyde (47, R = CHO) (likewise 60%) and 2-chloro- (46, R = H) gave 2-iodoquinoxa-line (47, R = H) (somewhat similarly 79%). [Pg.143]

6-Dichloroquinoxaline (49, R = Cl) gave 6-chloro-2-fluoroquinoxaline (49, R = F) (CsF, 18-crown-6, THF, 20°C, 20 h 87%) 6-bromo-2-chloroqui-noxaline gave 6-bromo-2-fluoroquinoxalme (likewise 87%) and other [Pg.143]

6-Bromo-2,3-diphenylquinoxaline (51, R = Br) gave 6-lithio-2,3-diphenylqui-noxaline (51, R = Li) (BuLi 80%) and thence 6-iodo-2,3-diphenylquinoxa- [Pg.144]

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