Potential Building Blocks for 1,4‐Dihydro‐N‐heteroacenes

Abstract

Studies have been performed aimed at the synthesis of N‐heteroacenes via substitution reactions of 4,5‐difluoro‐1,2‐dinitrobenzene with a diamine. The fluorine atoms are displaced first, followed by an activated nitro group. Two intermediates have been characterised by X‐ray single‐crystal structure determinations. Their intermolecular interactions were examined by Hirshfeld surfaces to assess their suitability for organic molecular electronics. The high reactivity of the phenazine, which is prone to oxidise and rearrange, as are displacement products prepared from it, is explained by the formation of a cis‐aci‐nitro form from the secondary amine of the phenazine and a nitro group.

Reactions of 4,5-difluoro-1,2-dinitrobenzene with amines in dimethylformamide or EtOH

“…Our studies so far making phenazines have shown that the fluorine atoms displace in preference to a nitro group in EtOH. 6,7 Exploratory studies on reactions of compound 7 in dimethylformamide (DMF) with nucleophiles are reported here. DMF might be a better dipolar aprotic solvent for substitution reactions because it does not hydrogen bond to the nucleophile in the same manner that it is a better solvent than methanol (MeOH) for certain nucleophilic substitution reactions.…”

“…These studies are helpful for our ongoing work on an iterative approach to NOS-heteroacenes using 4,5-difluoro-1,2-dinitrobenzene 7 as a building block. 6,7…”

“…A literature survey of some reactions of fluorinated and nitrated aromatic compounds with amines. 1–11 …”

“…5 The reaction of N-methyl-o-phenylenediamine 6 with 4,5-difluoro-1,2-dinitrobenzene 7 was studied as a potential iterative approach to 1,4-dihydro-N-heteroacenes, which may have interesting electronic properties. 6,7 The reaction of 2-fluoronitrobenzene 9 with enaminones gave aposafranones and their N-oxides, with butylamine and other amines gave 2-aminobenzimidazoles, with butylamine and other amines gave isoalloxazines and with aminomethylpyrazoles gave more complex medicinally active heterocycles [8][9][10][11] (Scheme 2). 4-Fluoronitrobenzene 10 has been used to explore the reactivity sequence of aromatic halides, to make N-alkyl-p-nitroanilines for second harmonic generation and in molecular recognition-based catalysis in nucleophilic aromatic substitution.…”

“…A literature survey of some reactions of fluorinated and nitrated aromatic compounds with amines. [1][2][3][4][5][6][7][8][9][10][11] Scheme 2. Some commercially available nitrated fluorobenzenes.…”