3-Aryl-1-imino-4-oxo-4,5-dihydrothiazolo-[3,4a]quinoxalines. Retrosynthetic approach

Fused polycyclic nitrogen-containing heterocycles 15.* 1,3-bis(4-hydroxy-4-methoxycarbonyl-3,5-diphenylthiazolidin-2-ylideneamino)-benzene in the synthesis of thiazolo[3,4-a]quinoxalines

“…15 However, the case of bishydroxythiazolidine 9 is more complicated than that of its prototype 7 (see Scheme 4). For the latter, a structure analogous to E contain phenyl substituents at both N atoms of the isothioureido group, while in intermedi ate E derived from compound 9, one of these N atoms is still bound to phenyl, while the other bears 3 substituted phenyl.…”

“…17) and X = OMe, Y = S, and Ar = Ph or 2,4 Cl 2 C 6 H 3 (see Ref. 18)) easily undergo acid catalyzed cyclization into thiazolo[3,4 a]quinoxa lines 1 [15][16][17][18] (except for X = Me, Y = NAc, and R = H or Et). Thioureido derivatives 4, which predominantly exist as tautomeric spirothiazolinoquinoxalines, isomer ize in acidic media to give thiazolo[3,4 a]quinoxalines 1 (X = Me, Y = NAc, and R = H or Et) in high yields.…”

Fused polycyclic nitrogen-containing heterocycles 21. Condensation of 4-hydroxy-3,5-diphenyl-2-phenyliminothiazolidine with 5-fluoro-4-morpholino- and 4-(4-methylpiperazino)-1,2-phenylenediamines

“…This allowed the differentiation of the atoms С(6) and С(9) and the assign ment of the corresponding protons Н(6) and Н (9). 15 N NMR data for compound 4a additionally support the assignment of the proton Н(6): in the 2D HMBC 1 H-15 N spectrum (see Fig. 1, b) a cross peak between the atom N(5) (the signal of which was determined from the 2D HSQC 1 Н-15 N spectrum) and the proton Н(6) is present, whereas for the proton Н(9) there is no such a peak ( 3 J N,Н > 4 J N,Н ).…”

Fused polycyclic nitrogen-containing heterocycles 11. 4-Hydroxy-3,5-diphenyl-2-phenyliminothiazolidines as new key compounds in the synthesis of thiazolo[3,4-a]quinoxaline derivatives

“…with DMSO in the monoclinic system, the DMSO molecule in the crystal being disor dered over two positions with occupancies of 0.7 and 0.3. It should be noted that the thiazoloquinoxaline ring in compound 5b, as in analogous compounds studied ear lier,14 is planar (to within 0.03(3) Å). The phenyl substitu ents (C(12)-C(17) and C(18)-C(23)) are twisted with respect to the plane of the thiazoloquinoxaline moiety by 81.3° and 51.2°, respectively.…”