5-chloro-4-nitro

Halogen atoms on benzazole rings can be activated toward nucleophilic displacement by electron-withdrawing groups. Thus azide ion displaces chlorine from 5-chloro-4-nitro- and 4-chloro-7-nitro-benzofuroxan (65JCS5958). 

Several examples of nucleophilic displacement of nitro-activated leaving groups have been recorded. 5,6-Dinitrobenzofuroxan with aniline and p-bromoandine gives the corresponding substitution product (50). Azide ion displaces chloride from both 5-chloro-4-nitro- and 4-chloro-7-nitrobenzofuroxan (51 and 52) the product from the former loses nitrogen spontaneously to give furoxanobenzo-furoxan (benzobisfuroxan, 17), which is also formed, although in poor... 

Although derivatives of 2,1,3-benzoxadiazole have been used extensively to make quinoxalines (see Section 1.6.7), the corresponding selena and thia systems have been paid scant attention for that purpose. However, 5-chloro-4-nitro-2,l,3-benzoselenadiazole (456) has been used as a convenient source of 4-chloro-3-nitro-1,2-benzenediamine (457) (HCl + HI, 20°C, 2 h 88%), which was then converted into 6-chloro-5-nitro-2,3(l//,4//)-quinoxalinedione (458) (oxalic acid, 2M HCl, reflux, 2.5 h 23%). ° In addition, irradiation of 2,1,3-benzoselenadiazole (460, X = Se) or 2,1,3-benzothiadiazole (460, X = S) with dimethyl acetylenedicarboxy-late afforded, among other products, dimethyl 2,3-quinoxalinedicarboxylate (459)... 

The submitters have found that this procedure works equally well with many substituted anthranilic acids however, it does not work with 3-chloro-, 5-chloro-, 4-nitro-, 5-nitro-, and 4,5-benzoanthranilic acids. 

When heated with potassium iodide in dimethylformamide, l-alkyl-4-chloro- (or bromo)-5-nitroimidazoles were converted into the 4-iodo analogues (79JGU1251). One would expect the 5-chloro-4-nitro isomers to be even more susceptible to this replacement (87AJC1399). 

Nucleophilic substitution has been used for the preparation of many thiophenes. For instance, 2-phenylthio-3,4-dinitro-5-piperidino-thiophene (155) has been prepared " through stepwise reaction of (150) with different nucleophiles. Nitrothienols and derivatives of them have been obtained from halogenated nitrothiophenes. Allyl ethers have been prepared by the reaction of 5-chloro-4-nitro-2-acetylthiophene, 3-nitro-2-chlorothiophene, and 2-nitro-3-bromothio-... 

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