Syntheses and Properties of S2-Bridged Benzidines

Abstract

The syntheses of 1,2‐benzodithiino[5,4,3‐cde][1,2]benzodithiin‐2,7‐diamine (1) and dithio‐bridged benzidine 2 have been achieved. The starting material for the synthesis of 1 was 1,3‐diiodo‐5‐nitrobenzene (15) which was transformed by conventional means into 1,2‐bis[3,5‐bis(ethylthio)phenyl]diazane (19). The benzidine rearrangement of 19 in the presence of HBF4 at –30 °C yielded 4,4′‐diamino‐2,2′,6,6′‐tetraethylthiobiphenyl (20) in 50 % yield. Treatment of 20 with sodium in ammonia and work‐up in the presence of air yielded 1. The latter compound could be reduced with LiAlH4 to the tetrathiol 20a. The starting material for the preparation of 2 was 3‐chloro‐1‐iodo‐5‐nitrobenzene (23), a side product of the preparation of 15. It was transformed analogously to the preparation of 1 into 1,2‐bis(3‐ethylthiophenyl)diazane (28). The benzidine rearrangement of 28 in presence of HBF4 at –30 °C afforded 4,4′‐diamino‐2,2′‐bis(ethylthio)biphenyl (29) in 49 % yield. Treatment of 29 with sodium in ammonia and work‐up under aerobic conditions yielded 2. Quantitative reduction of 2 to the thiol 29a could be achieved with LiAlH4. The reversible electrochemical reduction of 1 on unmodified glassy carbon electrodes leads to a product to which the structure of 3 was assigned.

2,2′‐Bipyridine Equipped with a Disulfide/Dithiol Switch for Coupled Two‐Electron and Two‐Proton Transfer

“…The DFT calculated minimum energy structure of 1 (see the Supporting Information for details) shows a S−S bond length of 2.076 Å and tilting of the two pyridine rings with a C‐S‐S‐C torsion angle ϕ =22.3°, which is similar to the experimentally observed values for a S 2 ‐bridged benzidine (2.053 Å, ϕ =29°), A (2.059 Å, ϕ =30.4°) and for B (2.056 Å, ϕ =32°) . The LUMO of 1 has antibonding character with respect to the S−S bond and bonding character with respect to the C−C bond linking the pyridine rings (Figure ).…”

Five varieties of hydrogen bond in 1-formyl-3-thiosemicarbazide: an electron density study

“…In the shorter one (D, 3.40 Å ), the S-H group is disordered. The longer one (3.84 Å ) might correspond to a weak S-HÁ Á ÁN interaction (Zhu-Ohlbach et al, 1998). In the third compound (Ambalalavanan et al, 2003), 3-(p-tolyl)-4amino-5-mercapto-1,2,4-triazole (ILOQEF), the R factor is perhaps high (0.066) and there is a possibility of tautomerism so that instead of an S-HÁ Á ÁN bond, an N-HÁ Á ÁS bond could be formed instead.…”

Spring Open Two-plus-Two Electron Storage in a Disulfide-Strapped Methyl Viologen Derivative

“…In essence, the molecule “springs open” to assist this process (see the Supporting Information for more details). Again, such behavior is dissimilar to dibenzo[1,2]dithiine where only after concurrent two-electron reduction does the molecule twist to alleviate electrostatic repulsion …”