Chemical and electrochemical reduction of pyrazino[2,3-b]quinoxalines

Abstract

JOSEPH ARMAND, LINE BOULARES, KHALED CHEKIR, and CHRISTIAN BELLEC. Can. J . Chem. 59, 3237 (1981). The hydrogenation of 2,3-dimethylpyrazino[2,3-blquinoxaline 1 and 2-phenylpyrazino[2,3-b]quinoxaline 2 leads to the corresponding 5,lO-dihydroderivatives 3b and 4b. LiAlH, reduction of 2, of 2.3-dimethyl-6,7-diphenylpyrazino[2,3-b]pyrazne 8 and 2,6,7-triphenylpyrazino[2,3-blpyrazine 9 furnishes the corresponding 1,2,3,4-tetrahydroderivatives 7,10, and 11. NaBH, reduction of 2 leads to a mixture of 4b and 7. In hydroorganic medium 1 and 2 are electrochemically reduced to 36 and 46 with which they form a redox system. Although the synthesis of pyrazino[2,3-blquin-1). The reduction products of 1 and 2 have two oxalines has been investigated (1) neither their amino protons which are readily exchanged by chemical nor their electrochemical reduction has addition of D,O so that the isomeric structures been studied.shown below have to be considered:We report the hydrogenation, the reduction with LiAlH, and NaBH,, and the electrochemical reduction of compounds 1 and 2. Concerning the electrochemical reduction, the presence of two condensed pyrazine rings made possible two reaction paths, either a reduction into a 1,4-(or 5.10-) dihydro derivative as in the case of pyrazines, or a behaviour similar to that of flavines leading to a 1 3 -(or 4, lo-) dihydro compound. HydrogenationIn the presence of Pd/C, hydrogenation of 1 and 2 leads to the dihydro derivatives 3b and 4b, the structures of which were determined by nmr (Table k I A rapid equilibrium on the nmr time scale of the two tautomers 3c and 3c' cannot be excluded on the grounds of the nmr spectrum. However, acetylation gives a diacetylated compound to which the nmr spectrum permits assigning the 1 ,Cdiacetyl-1 ,4-dihydro structure or the 5,lO-diacetyl-5,lOdihydro structure (see Experimental). Thus, the reduction product of 1 must have a plane of symmetry, which rules out structure 3c. Structures 3a and 3b can be discriminated by examination of the chemical shifts. The aromatic protons of 1,2,3,4-tetrahydrophenazine 5 give evidence of a multiplet

Polyazaacenes – On the Way to Stable, Fluorescent and Redox‐Active Derivatives

“…This is in agreement with experimental findings for other tetraaminoethenes derived from imidazoles [18] and 2,2Ј-biimidazoles. [19] Furthermore, these observations were proposed by earlier works of Armand and Badger [20,21] who reported structures and stabilities of ring-fused pyrazines and their 1,4-dehydroderivates connected with their redox behaviour.…”

Electrochemical behavior of conjugated quinoxaline derivatives

“…The reduction of quinoxalines in aprotic media produces the radical species [11][12][13][14], and is different from that in protic media [15][16][17][18][19][20][21][22]. For this reason, 98% H 2 SO 4 was used to adjust the solution pH and to act as the proton source of the electrochemical reaction.…”

A Hydrogen-Bonded Organic Framework Based on Pyrazinopyrazine

“…IR spectrum data were obtained from Thermo Scientific Nicolet 6700 FTIR spectrometer. 1 H and 13 C NMR spectra were measured by AV 400 MHz JEOL ECX-400 NMR spectrometers. Residual proton and carbon of deuterated solvents were used as internal standards for the measurements (for 1 H NMR, CDCl 3 , δ = 7.26 ppm; DMSO−d 6 , δ = 2.5 ppm: for 13 CNMR, CDCl 3 , δ = 77.16 ppm; DMSO−d 6 , δ = 39.52 ppm).…”

“…1 H and 13 C NMR spectra were measured by AV 400 MHz JEOL ECX-400 NMR spectrometers. Residual proton and carbon of deuterated solvents were used as internal standards for the measurements (for 1 H NMR, CDCl 3 , δ = 7.26 ppm; DMSO−d 6 , δ = 2.5 ppm: for 13 CNMR, CDCl 3 , δ = 77.16 ppm; DMSO−d 6 , δ = 39.52 ppm). 38 Mass spectrum data were obtained from Thermo Scientific Exactive mass spectrometers with ESI and APCI ionization methods.…”

“…8−12 For example, pyrazinoquinoxaline was reported by Armand and co-workers to form a redox system in the aqueous organic medium. 13 Tadokoro, Isoda, and co-workers reported that tetraazatetracene (TANC) and tetraazapentacene (BTANC) show electron acceptors functioning as novel ntype semiconductors with field-effect transistor (FET) activity. 14 Bonifazi and co-workers also constructed solidstate supramolecular structures based on TANC and boronic acids through strong hydrogen bonding.…”