Reactions of Extranuclear Halogenoquinoxalines

Note The introduction of extranuclear halogeno substituents into quinoxalines by halogenoalkylation, halogenoacylation, halogenoarylaminolysis, and the like is well illustrated in appropriate chapters of this book. A single atypical example is given here. 

3-Methyl-2-quinoxalinecarbaldehyde 1,4-dioxide (235) and A-(2-chloroethyl)-hydroxylamine hydrochloride (236) gave the nitrone, 2-(2-chloroethylimino-methyl)-3-methylquinoxahne l,4,A(-trioxide (237) (NaHCOa, 95% EtOH, warm then 20°C, 1 h 70% after separation from a byproduct).  

These halogenoquinoxalines undergo all the reactions that would be expected of a carbocyclic analog (e.g., 2-chloromethylnaphthalene) and at comparable rates unless the activity of an individual substrate is affected appreciably by an adjacent passenger group. 

The alkanelysis of extranuclear halogenoquinoxalines has been covered in Section 2.2.1.4. Other reactions are discussed in the following subsections. 

7-Dichloro-5-(l-hydroxypropyl)-2,3-dimethoxyquinoxaline (234, R = OH) gave 5-(l-bromopropyl)-6,7-dichloro-2,3-dimethoxyquinoxaline (234, R = Br) (CBr4, Ph2P, CH2C12, 20°C, 18 h 46%).1039 

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Reactions of Extranuclear Halogenoquinoxalines Conversion into Extranuclear Acylquinoxalines... 

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