3- Amino-2-chloro-7-nitroquinoxaline

The methylamination is less selective. This lower selectivity is due to the stronger nucleophilicity of methylamine as also shown by the methylamino-dehalogenation occurring with 2-chloro-5-nitroquinoxaline and 2-chloro-7-nitroquinoxaline into 2-amino-5-nitroquinoxaline and 2-amino-7-nitroquinoxaline, respectively. Amino-dehydrogenations with these compounds were not observed (see Scheme 22). It is important to note that 5-nitroquinoxaline gives methylamination at position ortho and para... 

Chloro-7-nitroquinoxaline (103, Q = Cl, R = H) gave a separable mixture of 6-nitro-3-piperidinoquinoxaline [103, Q = N(CH2)2, R = H] (product of amino-lysis) and 6-nitro-2,3-dipiperidinoquinoxaline [103, Q = R = N(CH2)s] (product of an additional amination) [excess HN(CH2)5, Et20, 20°C, <4h the amination product was least in an inert atmosphere and most in an oxygen atmosphere, inferrring an addition-oxidation mechanism]. 

SnH amination of 2-R-7-nitroquinoxalines (R = C1, OH, OMe) provides the corresponding 3-amino-2-R-7-nitroquinoxalines. No replacement of the chloro or methoxy group at position 2 takes place (Scheme 22). 

Amino-7-halo-6-nitro derivatives are prepared similarly.Excess piperidine and 2-chloro-7-nitroquinoxaline (11) give 7-nitro-2-piperidinoquinoxaline (12) and large amounts of 6-nitro-2,3-dipiperidinoquinoxaline (13). The mechanism of this unusual nucleophilic substitution of hydrogen is proposed to involve the oxidation of the dipiperidinodihydroquinoxaline intermediate by dissolved oxygen.The relative yields of both products depends on the ratio of the... 

The nitro group in 2-chloro-7-nitroquinoxaline (58) is aminated by piperidine at C-3 carbon and then displacement of the chloro substituent ensues to afford 2,3-dipiperidino-6-nitroquinoxaline as well as the normal 2-piperidino-7-nitro product (Equation (5)) <9lTLl3ll>. In contrast, 2-chloro-3-nitroquinoxaline (59) undergoes displacement of the nitro group with amines to form 2-amino-... 

Dichloro-6-nitroquinoxaline reacts with aziridine(ethyleneimine) in benzene solution at room temperature, in the presence of triethylamine as acid scavenger, to give the 2-aziridinyl derivative, the 6-nitro group thus selectively activating the 2-chloro substituent. Chlorine activation is also apparent in the substitution reactions of 2-chloroquinoxaline 1-oxide, which is converted into the 2-amino 1-oxide by treatment with aqueous or ethanolic ammonia at 60-80° and thus under much milder conditions than those used for the conversion of 2-chloroquinoxaline into 2-aminoquinoxaline. 

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