Dipyrrolo[1,2-a;2':,1'-c]pyrazines. 7. Electrophilic Substitution of Dipyrrolo[1,2-a;2',1'-c]pyrazines and 5,6-Dihydrodipyrrolo[1,2-a;2',1'-c]pyrazines via Formylation of Dipyrrolo[1,2-a;2':,1'-c]pyrazines

A series of previously unreported aldehydes has been prepared by the formylation reaction of dipyrrolo[1,2-a;2':,1'-c]pyrazines and their 5,6-dihydro analogs by DMF and phosphorus oxychloride.     

Dipyrrolo[1,2-a;2',1'-c]pyrazines. 6. Electrophilic Substitution in a Series of Dipyrrolo[1,2-a;2',1'-c]pyrazine and 5,6-Dihydrodipyrrolo[1,2-a;2',1'-c]pyrazine Derivatives. Phosphorylation of Dipyrrolo[1,2-a;2',1'-c]pyrazines

We have studied the behavior of asymmetrically substituted dipyrrolo[1,2-a;2',1'-c]pyrazines and their 5,6-dihydro analogs under phosphorylation reaction conditions.     

Acylation of pyrrolo[1,2-a]pyrazines

The acylation of pyrrolo[1,2-a]pyrazines with acetic anhydride and the acid chlorides of various carboxylic acids has been studied. It has been shown that pyrrole[1,2-a]pyrazines are selectively acylated at the α-position of the pyrrole ring when it is free. Products of the condensation of 1-methylsubstituted pyrrolo[1,2-a]pyrazines have been obtained for the first time in the process of acetylation. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 263–272, February, 2008.     

Acylation of 3,4-Dihydropyrrolo[1,2-a]pyrazines

The direction of trifluoroacetylation with trifluoroacetic anhydride of 3,4-dihydropyrrolo[1,2-a]pyrazines containing an alkyl or aralkyl substituent in position 1 depends on both the structure of the 3,4-dihydropyrrolo[1,2-a]pyrazine starting materials and on the ratio of reagent:substrate. It may lead to both mono- and disubstituted products. Trifluoroacetylation of 1-methyl-3,4-dihydropyrrolo[1,2-a]pyrazines occurs at the methyl group. Acetylation of 3,4-dihydropyrrolo[1,2-a]pyrazines leads only to N-acetyl-substituted reaction products.     

Formylation of 3,4-Dihydropyrrolo[1,2-a]pyrazines

Formylation of 3,4-dihydropyrrolo[1,2-a]pyrazines containing alkyl or aryl substituents at position 1 has been studied under the conditions of the Vilsmeier reaction. The direction of the reaction depends on the structure of 3,4-dihydropyrrolo[1,2-a]pyrazine starting materials. Formylation of 1-methyl-substituted 3,4-dihydropyrrolo[1,2-a]pyrazines occurs at the methyl group.     

Reactions of 1-Substituted Benzo[4,5]imidazo[1,2-a]pyridines

Bromination of 1-oxo(imino, amino)benzo[4,5]imidazo[1,2-a]pyridines gave the corresponding 2-bromo derivatives. Acylation using the Vilsmeier complex in acetic anhydride gave the N-formyl and N-acetyl derivatives. The reaction of the amine with the Vilsmeier complex, acetyl acetone, ethyl acetoacetate, and 2,5-dimethoxytetrahydrofuran occurs at the amino group.     

Formylation of Furyl-substituted Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine and Imidazo[2,1-b]thiazole

Vilsmeier formylation of 2-(2-furyl)-substituted imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, and also 6-(2-furyl)imidazo[2,1-b]thiazole with 1 mole of reagent occurs at the free position of the imidazole ring, while with an excess of the reagent it also occurs at the position 5 of the furyl group.     

Nitration of Pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]pyrazines

We have synthesized nitro derivatives of pyrrolo[1,2-a]pyrazines using a nitrating mixture and acetyl nitrate. We have obtained the products of oxidation of the side chain of 1,6-substituted pyrrolo[1,2-a]-pyrazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1579–1586, October, 2005.     

Synthesis and Structure of Di-N-arylpyrrolo[1,2-c;5,6-c]cyclooctanes

Di-N-arylpyrrolo[1,2-c;5,6-c]cyclooctanes were synthesized for the first time by the cyclization of N,N-dipropynylarylamines in a superbasic medium.     

Research on heterocyclic compounds,XXXV. Synthesis of 2-phenylimidazo[1,2-a]pyrazine-3-acetates

Summary Prompted by the remarkable pharmacological activity shown by the corresponding carboxylic acids and other analogues, a series of 2-phenylimidazo[1,2-a]pyrazine-3-acetic acids has been prepared. A multi-step method similar to a synthetic procedure used to obtain Zolpidem, an imidazo[1,2-a]pyridine with hypnotic properties has been developed.

---

Untersuchungen an heterocyclischen Verbindungen, 35. Mitt. Synthese von 2-Phenylimidazo[1,2-a]pyrazin-3-acetaten

Zusammenfassung Angeregt durch die bemerkenswerte pharmakologische Aktivität der entsprechenden Carbonsäuren, wurde eine Reihe von 2-Phenylimidazo[1,2-a]pyrazin-3-acetaten synthetisiert. Zu diesem Zweck wurde eine mehrstufige Methode analog zu jener zur Herstellung von Zolpidem, einem Imidazo[1,2-a]pyridin mit hypnotischen Eigenschaften, entwickelt.

     

Properties of 8-Cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

The alkylation, acylation, halogenation, nitration, oxidation, and hydrolysis reactions of 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine have been studied. It was found that the 6-halo derivatives add alcohol to give covalent solvates. X-ray analysis has been carried out on one of the solvates (6-chloro-8-cyano-7-ethoxy-5-phenyl-7-trifluoromethyl-1,2,3,7-tetrahydroimidazo[1,2-a]pyridine) as well as on 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine trifluoroacetate.     

A new, one-pot, multi-component synthesis of imines of 3-amino-2-arylimidazo[1,2-a]pyridines, 3-amino-2-arylimidazo[1,2-a]pyrazines, and 3-amino-2-arylimidazo[1,2-a]pyrimidines

An efficient, one-pot, multi-component synthesis of 3-amino-2-arylimidazo[1,2-a]pyridines, 3-amino-2-arylimidazo[1,2-a]pyrazines, and 3-amino-2-arylimidazo[1,2-a]pyrimidines is described. Heating a mixture of a 2-aminopyridine, 2-aminopyrazine or 2-aminopyrimidine, a benzaldehyde, and imidazoline-2,4,5-trione under solvent-free conditions afforded imine derivatives of the title compounds in excellent yields. Single-crystal X-ray analysis conclusively confirms the structure of these bridgehead bicyclic 5-6 heterocycles.     

Synthesis of 5-Phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridines

Syntheses are reported for a series of 2-alkylamino-6-phenyl-4-trifluoromethylpyridines. The reaction of 3-cyano-2-(hydroxyalkylamino)-6-phenyl-4-trifluoromethylpyridines with thionyl chloride gave the corresponding 2-(chloroalkylamino)pyridines, 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydro-imidazo[1,2-a]pyridines, and 9-cyano-6-phenyl-8-trifluoromethyl-2,3,4-trihydropyrido[1,2-a]-pyrimidines. X-ray diffraction structural analysis was used to study 8-cyano-5-phenyl-7-trifluoromethyl-2,3-dihydroimidazo[1,2-a]pyridine.