1//-Pyrroles, 4,5-dioxo-4,5-dihydro

Methyl 3-acyl-l-diphenylmethyleneamino-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 489 are formed from 488 and oxalyl chloride in good yields. Preparative thermolysis of these compounds at 130-140°C gives mixtures of dipyrazolo[l,2- l,2- [l,2,4,5]tetrazines 491 as major products and pyrazoles 492 as minor hydrolytic by-products. The intermediacy of mesoionic compound 490 is expected (Scheme 83) <2004T5319>. 

In a similar manner, aminotriazole 260 has been condensed with 1 -mcthyM-m ethyl sulfanyl-2,5-dioxo-2,5-dihydro-17/-pyrrole-3-carbonitrile 262 to give rise to analogous product 263 (Equation 72) <1996H(43)1597>. 

PQQ (methoxatin 4,5-dihydro-4,5-dioxo-lH-pyrrolo [2,3-f] quinoline-2,7, 9-tricarboxylic acid), 2-(dimethylamino) ethanethiol (DMAET), 2-(diethylamino) ethanethiol (DEAET), and pyrrole were purchased from Sigma (St. Louis, MO). Potassium hydrogen phthalate was purchased from Acros (Pittsburgh, PA). Pyrrole was distilled every time immediately before use. All other regents were used without further purification. 

Pentan 3-Aminomethylen-2,4-dioxo-1-ethoxy- XI/1. 199 4H-Pyran 6-(Ethoxycarbonyl-amino)-5,6-dihydro- Vl/4, 363 3H-Pyrrol... 

H-(Furo[3,4-e indol> l,3-Dioxo-6-methyl-1,3-dihydro- E6b/1, 823 (aus Pyrrol-Der.)... 

Benzoyl-l-phenyl-5-methoxycarbonyl-2,3-dihydro-pyrrole-2,3-dione was reacted with 5/5-dimethyl-3-p-methoxyphenylamino-2-cyclohexen-l-one in boiling benzene to afford 6,6-d imethyl-1 -p-methoxyphenyl-2,4-dioxo-2,3,4,5,6,7-hexahydro-lH-indole-3-spiro-2-(3-benzoyl-5-oxo-4-phenyl-amino-2,5-dihydrofuran) in high yield. The reaction proceeded by the enamine addition to the 2-carbonyl group with ring opening, followed by double cyclization (06RJOC772). 

Thermolysis of methyl l-methyleneamino-4,5-dioxo, 5-dihydro-lW-pyrrole-2-carboxylates 123 led to substituted dimethyl 3,9-dioxo-l,5,7,ll-tetrahydro-lA/,7A/-dipyrazolo l,2-a r,2 -<3 ][l,2,4,51tetrazine-l,7-dicarboxylates 124 <04T5319>. 

Similarly, heating of methyl 3-acyl-l-(diphenylmethyleneamino)-4,5-dioxo-4,5-dihydro-l//-pyrrole-2-carboxylates 96 gave the corresponding dimethyl 2,8-diacyl-3,9-dioxo-5,5,ll,ll-tetraphenyl-3,5,9,lTtetrahydrodipyrazolo[l,2- 7 l, 2 -i [l,2,4,5]tetrazine-l,7-dicarboxylates 99 in good yields. The proposed mechanism involves thermal decarbon-ylation to give the ketene intermediate 97, which cyclizes into the azomethine imine 98, followed by dimerization (Scheme 24) <2004T5319>. 

X. Huang, J.-R Xu, Solid-phase synthesis of 2,5-dihydro-l//-pyrroles,l,3-dioxo-2,3,5,7a-tetra-hydro-l/f-pyrrolo[l,2-c]imidazoles and l,4-dioxo-l,2,3,4,6,8a-hexahydropyirolo[l,2-a]pyra-zines using a supported selenium resin. J. Comb. Chem. 2009, 11, 350-354. 

Retrospectively, we showed the modification of functional groups, which were in many cases directly introduced by the initiators of the polymerization. In the same way, activated esters could be inserted. Using this strategy. Junker and Conradi synthesized poly(butyl acrylates) bearing W-hydroxysuccinimide at the a-chain end [32]. The activated ester was substituted with 2-(2,5-dioxo-2,5-dihydro-l//-pyrrol-l-yl) ethanaminiumtrifluoroacetate (Scheme 17). This additional step was necessary to avoid the copolymerization of maleimide and butyl... 

CA Index Name 2i7-l-Benzopyran-3-carboxamide, A-[5-(2,5-dihydro-2,5-dioxo-l//-pyrrol-l-yl)pentyl]-6,8-difluoro-7-hydroxy-2-oxo-... 

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