Pyrrolo indolizine

Pyrrolopyridines — see Indolizines Pyrrolo[l,2-a]pyridines — see Indolizines Pyrrolo[2,3]pyridines alkylation, 4, 504 synthesis, 4, 528... 

The mechanism of attack of 1,3-dipolar reagents on fluoroalkenes can be considered to be either stepwise or concerted. Heteroaromatic N-imines react by a stepwise 1,3 addition to perfluoroalkenes and -alkynes to give fluorinated pyrazolo[l,5-a]pyridines [82JCS(P1)1593]. Pyridinium /-butoxycarbonylmethylide with fluoroalkenes gave pyrrolo[l,2-a]pyri-dines [86JCS(P 1) 1769] and indolizines (22) are obtained with pyridinium phenacylide [91JFC(51)407]. 

Pyrido[2, 3 4,5]pyrrolo[2,l-A][l,3]oxazine <2002TL1205, 2003USP2003105087, 2005BP74> Pyridazino[4,5- ]indolizine <1998USP5756501>... 

The sulphur TT-electron analogue of indolizine, pyrrolo [2,1-6 ]-thiazole [ 178], and some methyl substituted derivatives protonate in... 

The nitrogen rr-electron analogue of indolizine, pyrrolo[l,2-a]-imidazole [180], shows more complicated protonation behaviour... 

Alekseeva et al. (1972b) have carried out a comparison of calculated values of localization energies and free valency indices of pyrrolo[ 1,2-a] imidazole, pyrrolo[l,2-a] benzimidazole and indolizine. In all these molecules the a-position of the pyrrole ring is calculated to be more reactive than the / -position. The free valence indices increase in the order indolizine < pyrrolobenzimidazole < pyrroloimidazole, which is also the order of increasing basicity. 

A vinylogous indole derivative like 264 reacts with DMAD to give a phenanthridone derivative (267) (Scheme 42). An interesting case of the reaction of an enamine system is observed in the case of the 2H-pyrrolizine (268), which gives a mixture of the azepino[2,l,7-crflpyrrolizine derivative (271) and the 1 1 adduct (275) (Scheme 43) 164,165 reaction of 3-ethoxycarbonylmethylene-3 -pyrrolizine, on the other hand, yields a pyrrolo[2,l,5-croom temperature, the primary adduct (278) is isolated and undergoes thermal cyclization to 281 (Scheme 44). ... 

In the thioaldehyde of pyrrolo[2,l-h]thiazole (73JCS(P1)657) (150), the C=S group is directed preferentially toward nitrogen (Z-form), as occurs in the aldehyde of indolizine 10, while bulky R substituents change this... 

Further substitution of the peripheral carbon atoms of the cyclazines by heteroatoms (N, S, etc.) is indicated in this chapter according to the replacement nomenclature system (aza, thia, etc.). Although, strictly, this runs contrary to the rules,lc since it is a heterocyclic, not a hydrocarbon, system which is replaced, the connection between closely related compounds can more clearly be seen. It should be noted that Chemical Abstracts employs the systematic fusion nomenclature I, for instance, is pyrrolo[2,l,5-cd]indolizine. 

Several names have been used in the chemical literature for pyrrolo[l,2-a]pyridine including pyrrocoline, pyrindole, pyrrodine and 8-pyrrolopyridine, but the one which is now used by Chemical Abstracts, and which will be used in this chapter, is indolizine. The numbering of the system is shown in formula (1). The denomination of aza derivatives follows the replacement nomenclature system, e.g. 1-azaindolizine, etc. It should be noted that Chemical Abstracts follows the systematic fusion nomenclature 1-azaindolizine, for instance, is imidazo[l,2-a]pyridine. The cyclazine nomenclature is treated in Section 3.08.9.1. 

Indolizine Pyrrolo[2,3-]pyridine Pyrrolo[2,3-d]pyrimidine Purine... 

Vilsmeier reaction, 4, 1051 Furo[3,2-6]pyrroles MO calculations, 6, 979 synthesis, 4, 1069 6, 1009 Furo[3,4-a]pyrrolo[2,1,5-cd]indolizine nomenclature, 1, 22 Furopyrylium salts, 4, 993-995 Furoquinolines biosynthesis, 4, 992 occurrence, 4, 988 pharmacology, 4, 992 reactions, 4, 988 synthesis, 4, 989 Furo[3,2-c]quinolines, 4, 991 Furo[3,4-fe]quinoxaline, 1,3-diphenyl-synthesis, 4, 993 Furoquinoxalines, 4, 992 Furo[2,3-6]quinoxalines synthesis, 4, 992 Furosemide toxicity, 1, 136 Furospinulosin UV spectra, 4, 587 Furospongin-I mass spectrometry, 4, 583 Furo[3,4-d][l,2,3]triazole, 2,6-dihydro-synthesis, 6, 996 Furo[3,4 -d][ 1,2,3]triazoles synthesis, 6, 996 Furoxan, 4-amino-3-aryl-tautomerism, 6, 404 Furoxan, 4-amino-3-methyl-synthesis, 4, 414 Furoxan, 4-aryl-3-methyl-rearrangement, 6, 408 Furoxan, 3-aryl-4-nitro-synthesis, 6, 414 Furoxan, 4-benzoyl-3-methyl-oxime... 

Pyrrolo[l, 2-a]imidazoI-2(3 ff)-ones synthesis, 6, 1001 Pyrrolo[3,2-6]indoles synthesis, 4, 243 Pyrrolo[3,2-/]indolizines synthesis, 4, 274, 296 Pyrroloisoquinolines synthesis, 4, 513... 

Other products from pyridine and its 3- and 4-methyl and 3,5-dimethyl derivatives and MP are cyclazines (e.g., 100),291 which are probably formed from indolizines of type 97 by further reaction with MP and subsequent aromatization. This type of reaction has been achieved by heating appropriate indolizines with DMAD293 or MP in the presence of palladized charcoal, and the direction of the addition, as shown below, has been established in several instances.294 Heating MP with diethyl-2-pyridylmethylene malonate gave the pyrrolo[2,l,5- /]indolizine corresponding to 100, no trace of the expected indolizine intermediate (cf. 97) being observed.292... 

Refluxing 2-acetylpyridine (111) with MP gives a remarkable 29% yield of pyrrolo[2,1,5-< /]indolizine (112), which may be formed by the route (Scheme 5) outlined.296 Ethyl pyridine-2-carboxylate, presumably by a similar mechanism, yields a mixture of three pyrrolo[2,l,5-crf]-indolizines (113,114, and 115).296... 

Methylphenanthridine with DMAD in benzene yields the 9a-methyl-9ai/-quinolizine (cf. 306, Section V,G,2) and a cyclobuta[4,5]-pyrrolo[l,2-/]phenanthridine (cf. 312, Section V,G,2) DEAD in ether gives the corresponding cyclobuta derivative, whereas 6-ethylphenan-thridine with DMAD in acetonitrile yields only the quinolizine as isol-able product. With MP, phenanthridine, like pyridine, yields indolizines,... 

Pyrrolo[l,2-ci]quinoline is a benzo derivative of indolizine and its 2,7-dimethyl derivative (8.65) is nitrosated, acetylated. diazo coupled, and formylated in the expected 1-position in 90, 40, 90, and 70% yields, respectively (79JHC393). Nitration also goes in the 1-position if the conditions are not strongly acidic, in which case it goes in the 6-position. This... 

Substituted indolizines 18 are formed in Chichibabin reactions of l-[alkyl(aryl)carbonylmethyl]-2-alkylpyridinium halides 17 (Scheme 11) <1972AJC1003>. Various modifications of this method are used for the preparation of many other pyrrolo[l,2-< ]azines and pyrrolo[l,2- ]azoles. Indolizines can also be made by intramolecular Michael additions, e.g., by the cyclization of 2-acylpyridine 19 (Scheme 12). 

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