Quinoxaline reaction with dimethyl acetylenedicarboxylate

Methyl- and 2,3-dimethylquinoxaline also undergo interesting addition reactions with dimethyl acetylenedicarboxylate. Addition of 2-methylquinoxaline to two molecules of the ester results in the formation of the isomeric azepino[l,2-a]quinoxalines 61 and 62. Addition is accom-... 

B. Reaction of 2-Phenyl- and 2,3-Diphenyl-quinoxaline with Dimethyl Acetylenedicarboxylate.221... 

Attack at the heteroatoms was observed in the reactions of (1) and (2) with dimethyl acetylenedicarboxylate and with benzyne (78JCS(P1)1006). Compound (2) behaves as a heterodiene toward the acetylene ester, producing the quinoxaline (25) and selenium. The diester (25) was obtained only in trace amounts from (1). These reactions, and the failure of (1) and (2) to react with maleic anhydride, contrast with the behavior of naphtho[2,3-c] [l,2,5]thiadiazole which reacts with maleic anhydride across the center ring (64TL3815). 

In the reaction of dimethyl acetylenedicarboxylate with 2,1,3-benzoselenadiazole (8) attack proceeds at the heteroatoms compound 8 behaves as a heterodiene towards dimethyl acetylenedicarboxylate, producing the quinoxaline derivative 9 and selenium. 

The adduct 14, from the reaction of the amino compound 6 with dimethyl acetylenedicarboxylate, was cyclized to the pyrrolo[l,2-a]quinoxaline 15 using polyphosphoric acid. The anilino compound 17... 

The iV-oxides not only of quinoxalines but also of 1,4-benzodiazepines can serve as excellent 1,3-dipoles in the synthesis of derivatives of pyrrolo[l,2-fl]quinoxa-lines. For example, the reaction of chlorodiazepineoxide 133 with dimethyl acetylenedicarboxylate takes place by a scheme of 1,3-dipolar addition with the... 

Diphenylfuro[3,4-6 ]quinoxaline (207) has been obtained (70TL1409) from the phthalide (206) as a green crystalline, quite stable solid (m.p. 244-246 °C). In DMSO (deep blue solution), (207) reacts instantaneously with such dienophiles as maleic anhydride, maleimide, dimethyl acetylenedicarboxylate and others to give crystalline adducts which, when heated to or above their melting points, decompose giving a blue color presumably due to reversal of the Diels-Alder reactions. 

Pyridazino[3,4-i)]quinoxalines and pyrazolo[3,4-i)]qumoxalme hydrochloride are synthesized by the 1,3-dipolar cycloaddition reaction of 6-chloro-2-(l-methylhydrazino)quinoxaline 4-ox-ide with dimethyl or diethyl acetylenedicarboxylate and a-chloroacrylonitrile, respectively. ... 

A series of complex derivatives (18) of the ring system have been prepared by reaction of the pyranylidene compounds 17 with o-phenylenediamine." The only other pyrido[l,2-a]quinoxaline to be reported is compound 19, obtained from the reaction of quinoxaline with two molecular equivalents of dimethyl acetylenedicarboxylate. ... 

Two procedures of synthesis of aminomethylquinoxalines 1 have been developed. One of them involves three stages (a) condensation of ethyl ethoxalylacetate 4 or dimethyl acetylenedicarboxylate with 1,2-DAB to give quinoxalines 5, (b) the reaction of the latter with isopentyl nitrite, and (c) reduction of resulting oximes 6 (Scheme 4.2) (Danswan et al. 1982 Ager et al. 1988). 

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