Pyrrolo quinoxalines

Thermal decomposition of 2-azidophenazine in hydrocarbon solvents e.g. tetralin) gives 2-aminophenazine photolysis in undegassed cyclohexane, however, gives an excellent yield of the pyrrolo-quinoxaline (290) A possible mechanism, passing through the nitrile oxide (289), has been proposed. ... 

Interesting constructs of molecules such as pyrrolo-pyridines, pyrrolo-quinolines, pyrrolo-pyrazines, pyrrolo-quinoxalines and pyrrolo-pyrimidines could be constructed by intramolecular Chichibain-type reaction. Davis and co-workers were the first to show the first of these examples, where p-methylazines react with nitriles to give the corresponding fused bicycle in the presence of excess base (2.5 equiv). For example, P-picoline reacts with benzonitrile in the presence of LDA to give the pyrrolo-pyridine adduct 61 in a 90% yield and traces of 62a. Under similar conditions and if... 

Another example of the modification of a tricyclic compound is the transformation of pyridazinoquinoxaline 103 in an acidic medium into the pyrrolo-quinoxaline 105 (Scheme 3.34) (Abbott et al. 1972). 

In the opinion of the authors of (Zhang and Huang 1997, 1998), the pyrrolo-quinoxaline system is formed from the benzimidazole system according to the scheme presented below (Scheme 3.88). 

Pyrrolo[3,4-6]quinoxaline, 2-/-butyl-1,3-dihydro-oxidation, 4, 509 Pyrrolo[3,2-d Jselenazoles synthesis, 6, 344, 1009... 

Denitrocyclization involving the primary amide group in 437 gave good yields of pyrrolo[l,2-<2]quinoxaline derivatives 438 (Eq. 39) (9ISC 1567). 

Phenyl-l//-pyrrolo[3,4-h]quinoxaline-l,3(2//)-dione (589) gave 3-(A(-phenyl-carbamoyl)-2-quinoxalinecarboxylic acid (590, R = H) initially as the crude ammonium salt (590, R = NH4) (NH3, H2O, reflux, 4 h ... 

Benzenesulfonyloxy-1 //-pyrrolo[3,4-/>]quinoxaline-1,3(2F/)-dione (591) gave //-phenyl-3-(A( -phenylureido)-2-quinoxalinecarboxamide (592) (PI1NH2, PhH, 20°C, 6 h 82% the mechanism probably involved Lossen rearrangement at an intermediate stage but remains unprove) A(-p-tolyl-3-(A( -p-tolyl-ureido)-2-quinoxalinecarboxamide (87%) was made similarly using p-toluidine. ... 

Dimethylquinoxaline (147) gave 2-ethoxycarbonyl-2-hydroxy -methyl-2,3-dihydro-[l/ ]-pyrrolo[l,2-u]quinoxalin-10-ium bromide (148) (BrCH2CO-C02Et, AcEt, reflux, 3h, then 20°C, 12 h 72%) and thence successively ethyl 4-methylpyrrolo[l,2-fl]quinoxaline-2-carboxylate (149) (EtONa, EtOH, 20°C, 4h 93% note oxidation by loss of H2O), the uncharacterized quaternary salt (150) (as the first step but 6h 50%), and diethyl dipyr-rolo[l,2-fl 2, l -c]quinoxaline-2,ll-dicarboxylate (151) (KOH, H2O, reflux, 1 h 56%). ° " - ... 

A-Allyl-A-benzylamino)-3-bromoquinoxaline (202) gave l-benzyl-3-methyl-l//-pyrrolo[2,3-/7]quinoxaline (203) [Pd(OAc)2, K2CO3, Bu NBr, Me2NCHO, 80°C, 30 min 83%] analogs likewise. 

In contrast, the same substrate (291) gave trimethyl 8-chloro-4-piperidinopyr-rolo[l,2-fl]quinoxaline-l,2-3-tricarboxylate (293) [Me02CC=CC02Me (2 mol), dioxane, reflux, 6 h 30%]" ° " or dimethyl 8-chloro-4-piperidino-pyrrolo[l,2-fl]quinoxaline-l,3-dicarboxylate (294) [HC=CC02Me (2 mol), dioxane, reflux, 10 h 16%] ° mechanisms are suggested." °... 

Azido-6-nitro-3-styrylquinoxaline (298) underwent thermal cyclization with loss of N2 to afford 6-nitro-2-phenyl-l//-pyrrolo[2,3-h]quinoxaline (299) (PI1NO2, reflux, 90 min 54%). ... 

Ethyl 3-bromomethyl-6,7-difluoro-2-quinoxalinecarboxylate 1,4-dioxide (84) gave 6-fluoro-2-methyl-7-methylamino-2,3-di hydro-1 //-pyrrolo 3,4-h]quinoxalin-l -... 

A Cu-catalyzed domino reaction has been developed by Cacchi and his group [305] for the synthesis of pyrrolo[2,3-b]quinoxalines 6/4-101 using a 2-bromo-3-tri-fluoroacetamido quinoxaline 6/4-98 and a tolane 6/4-99 containing electron-donating or -withdrawing groups as substrates, and with 6/4-100 as a proposed intermediate (Scheme 6/4.24). 

Thermolysis of 3-alkyloxy- and 3-aroyloxy-5-phenyl-l,2,4-pyrrolo[l,2- ]quinoxaline-l,2,4-triones afforded 5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-6,8,10-trioxo-5,6,9,10-tetrahydro-87/-pyrido[l,2-tf ]quinoxaline-7,9-dicarboxylates <2000CHE615, 2004CHE1295> and 7-aroyl-8-aroyloxy-5-phenyl-9-(4-phenyl-3-oxo-3,4-dihydro-2-quinoxalinyl)-5,6-dihydro-1077-pyrido[l,2- ]quinoxaline-6,10-diones <2002CHE498>, respectively. Thermolysis of 3-aryl-2-(5-aryl-2,3-dioxo-2,3-dioxo-4-furanyl)quinoxalines gave 7-aroyl-8-aroyloxy-6-aryl-9-(3-aryl-2-quinoxalyl)-10/7-pyrido[l,2- ]quinoxalin-10-ones <2001CHE1314, 2002RCB850>. 

Condensed quinoxalines have been synthesized using 2-chloro-3-alkynylquinoxalines as common intermediates. 2-Chloro-3-phenylethynylquinoxaline 98 was prepared from 2,3-dichloroquinoxaline (97). Action of methylamine on 98 gave 1,2-disubstituted pyrrolo[2,3-fcjquinoxaline 99. Similarly, 2-phenylthieno[2,3-fc]quinoxaline 100 was synthesized by treating 98 with ethanolic sodium sulfide. 

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