Phenanthridine nitration

Phenanthridine-6-carboxylic acids synthesis, 2, 415 Phenanthridines amination, 2, 236 bromination, 2, 320 hydrogenation, 2, 328 nitration, 2, 319 nomenclature, 2, 5 5-oxides... 

Phenanthridine (74) was converted by NBS into the 2-bromo derivative (40%) (55JA6379), but the bromine-sulfuric acid-silver sulfate reagent gave low yields of 1-, 4-, and 10-bromophenanthridines in the ratio (1 6.4 9.5), a reactivity order which contrasts with that found in nitration (1 > 10 > 4 > 2) (69AJC1105). Phosphoryl chloride converted phenanthridine 5-oxide into the 6-chloro derivative, but when that position was blocked by a phenyl substituent, the reductive chlorination process gave a 2-chloro compound (84MI2). 

Whereas treatment of phenanthridine with AT-bromosuccinimide gives only 2-bromo-phenanthridine, use of bromine and silver sulfate in 92% sulfuric acid gives, in low yields, 10-, 4- and 1-bromo-phenanthridines in the ratio 9.5 6.4 1 together with some dibromo products (Scheme 11) (69AJC1105). This order of reactivity contrasts with that observed for nitration of phenanthridine (Section 2.06.2.1.2). 

Nitric acid alone is without effect on phenanthridine, but nitration occurs quite readily in sulfuric acid solution. The use of not more than one equivalent of nitric acid results in mononitration only, but a mixture of products is obtained and a quantitative recovery of the individual isomers has not been achieved. Valid assessments of reactivity are not possible from the available data, but the major products are certainly 1- and 10-nitrophenanthridine with smaller amounts of the 8-nitro isomers. To this extent the results are in agreement with localization energy calculations for the cation227 2-, 3-, and 4-nitrophenanthridine have also been isolated, but in minor amounts which could not be determined accurately.89... 

Reports of bromination of phenanthridine (11.14) are contradictory, claiming (1) a 40% yield of 2-bromophenanthridine (55JA6379) and (2) a positional reactivity order of 10 > 4 > 2, the isomer yields being 6, 4, and 0.7%, respectively, with —1% of dibromo products (69AJCI105). These reports both contrast with nitration, in which positional order is I > 10 > 8 > 3. 

Acridine 613, phenanthridine 614, cinnoline 615, and quinazoline 616 are nitrated as shown in Figure 3. 

Reactions of dibenzopyridines show analogies with pyridine, quinoline and isoquinoline. Acridine and phenanthridine are A-protonated by strong protic acids, iV-alkylated by alkyl halides and A-oxidized by peroxy acids. Electrophilic substitutions of acridine often result in disubstitution at the 2- and 7-positions (e.g. nitration giving 3), whereas those of phenanthridine occur at different positions (e.g. nitration mainly at the 1- and 10-position yielding 4 and 5) ... 

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