Phenanthridines, alkyl-, reactions

Isocyanides, which are isoelectronic with carbon monoxide, can undergo insertion reactions to provide Af-containing heterocycles. In 2013, Yu and coworkers [46] developed a photoredox catalytic, somophilic isocyanide insertion (HAS) yielding 6-alkylated phenanthridine derivatives from biphenyl isocyanide and electron-deficient bromides (Eq. (13.14)). Interestingly, when ethyl bromoflu-oroacetate or ethyl bromodifluoroacetate were used as the substrate [47], a subsequent decarboxylation efficiently produced mono- and difluoromethylated phenanthridine derivatives (Eq. (13.15)). 

The synthesis of selectively substituted benzoxepines from ortho-substituted aryl iodides and bromoenoates has been achieved by Lautens and coworkers by palladacycle alkylation followed by an intramolecular Heck reaction under the modified conditions reported in Eq. (8) for synthesis of l-(l-ethoxycarbonylmethy-lene)-9-methyl-4,5-dihydro-3-benzoxepine [8]. In the second example (Eq. 9) the palladium-bonded biphenylyl inserts diphenylacetylene to form 1,5-di-i-propyl-9,10-diphenylphenanthrene[9]. In the last case the synthesis of 4-methyl-5H-phenanthridin-6-one is achieved by palladium-catalyzed sequential C-C and C-N bond formation starting from o-iodotoluene and o-bromobenzamide [10]. 

The conversion of the phenanthridones obtained by both Beckmann and Schmidt procedures into the parent bases is described in Section II, D. Alternatively, phenanthridines (and their 6-alkyl derivatives) can be obtained directly by a variation of the Schmidt reaction... 

ET-initiated alkylation of azines in the presence of alkyl halides has been found to occur under electrochemical conditions according to Scheme 43. Either alkylated dihydroheterocycles or the rearomatized products are obtained. As an example, electroreduction of quinoline in the presence of 1-bromoadamantane gives alkylated quinolines (10 % in position 2, 5 % in position 7) and 2-methyl- and 2-methoxyquinoline give the 7-adamantyl derivative in 20 and 23 % yield, respectively. 1,10-Phenanthroline gives bis(adamantyl) derivatives, whereas isoquinoline and phenanthridine give the 6-adamantyl-5,6-dihydro and the 9-adamantyl-9,10-dihydro derivatives, respectively [132]. Reaction with terr-butyl chloride also gives alkylated dihydroheterocycles [133]. Arylation has also been performed, e.g. in the synthesis of pyrazolophenanthridines (62, Scheme 44) [134]. 

A number of polymers containing a heterocyclic group have been prepared using the Reissert alkylation sequence.92 94 Thus, for example, the reaction of the isoquinoline Reissert anion (26) with polyfvinylbenzyl chloride) and sodium hydride gave 36, which on hydrolysis with base gave 37.92,93 A similar condensation takes place with quinoline, phenanthridine, and benzo-[/Jquinoline Reissert compounds.94 The Reissert anion 26 has also been alkylated with a mixture of m- and p-vinylbenzyl chloride and the product polymerized to a polymer of type 37.93 Copolymerization has also been studied.93... 

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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