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2004
Pyrazine derivatives
R 0550
Fused Polycyclic Nitrogen-Containing Heterocycles. Part 7. Reaction Products of
and Thioureas as Key Interme46- 155 3-(α-Chlorobenzyl)-1,2-dihydroquinoxalin-2-one
diate Compounds in the Synthesis of Thiazolo[3,4-a]quinoxalines. — Quinoxalinone derivative (I) is subjected to reactions with reagents which are equivalents of the
NCS species, in particular with (II), (V), 2-sulfanylbenzimidazole, and 2-sulfanylbenzothiazole. Attempted intramolecular cyclization reactions of the latter compounds fail.
Heating thiourea (II) or N,N'-diphenylthiourea (VI) with quinoxalinone (I) in dioxane
with subsequent addition of acetic anhydride affords the thiazoloquinoxalines (IV) and
(VII). Unfortunately, the yield of (IV) for this one-pot procedure is considerably lower
than in the two-step synthesis via isothioureide (V). Also, structures containing no heterocyclic system can be regarded as precursors of the title compounds. For example,
synthetic equivalents for the required synthons are chloropyruvate (VIII), potassium
thiocyanate (IX), and o-phenylenediamine (X). — (KALININ, A. A.; MAMEDOV, V.
A.; RIZVANOV, I. K.; LEVIN, Y. A.; Russ. J. Org. Chem. 40 (2004) 4, 527-533;
Arbuzov Inst. Org. Phys. Chem., Kazan Res. Cent., Russ. Acad. Sci., Kazan' 420088,
Russia; Eng.) — H. Hoennerscheid
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