N -[ g-(Dimethylamino)phenyl]-a-(2-amino-3-cyano-5-pyr-aziny1)nitrone (5). To a suspension of 2.63 g (10.6 mmol) of the pyridinium salt 4 and 1.64 g (11.0 mmol) ofp-dimethylaminonitrosobenzene in 50 mL of ethanol was added 8.33 g (60.4 mmol) of potassium carbonate in 30 mL of water. The reaction mixture became homogeneous, changed in color from green to brown, and the orange-brown nitrone started to separate. After 30 min of stirring at room temperature followed by ice cooling, the mixture was filtered and the collected solid was washed with water followed by ethanol and then ether and air-dried: yield 2.86 g (96%) of a dull orange powder, mp 219-222 OC (dec). Recrystallization from a large volume of acetonitrile (Norite) gave dark-orange needles: mp 227-228 OC (dec); NMR (Me2SO) F 2.95 (s, 6), 6.68 (d, 2), 7.72 (m, 4) (2 Ar protons + -NH2), 8.15 (s, l), 9.92 (9, 1); UV A , , ,(acetonitrile) (log
Various pyrazino[ 1,2-~:4,5'-a']diindoles have been synthesized corresponding in structure t o the diketopiperazine type dimers o f indole-and indoline-2-carboxylic acids. 7,14-Dihydroxy-6H,13H-pyrazino[l,2-a:4,5-~']diindole-6,13-dione reacted w i t h sulfur monochloride and pyridine t o give epidithio and epitrithio derivatives. These are aromatic analogues o f the aranotins. T h e structure o f the epitrithio derivative was verified by single-crystal x-ray crystallography. T h e space group is P?,P21Pz, w i t h pertinent cell data as follows: a = 9.199 (4), b = 13.846 (4), c = 13.248 (3) A, and 2 = 4.
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