Pyrrolo pyridines, synthesis

Pyrrolo[3,2-c]pyridines — see also 5-Azaindoles hydrogen exchange, 4, 502 reactions, 4, 526 synthesis, 4, 514, 523 UV spectra, 4, 501 Pyrrolo[3,4-c]pyridines synthesis, 4, 517... 

Pyrrolo[3,4-d]pyridazinium salts, 2,3-dimethyl-synthesis, 4, 291 Pyrrolo[ 1,2-6]pyridazinones oxidation, 4, 298 Pyrrolo[2,3-6]pyridine, 1-acetyl-cycloaddition reactions, 4, 509 Pyrrolo[2,3-6]pyridine, 3-bromo-nitration, 4, 505... 

Pyrrolo[2,3-6]pyridine, 2,3-dihydro-electrophilic substitution, 4, 503 nitration, 4, 512 synthesis, 4, 520... 

Pyrrolo[2,3-6]pyridine, 6-methyl-reaction with aldehydes, 4, 503 reaction with benzaldehyde, 4, 511 Pyrrolo[2,3-6]pyridine, 7-methyl-hydrogenation, 4, 508 Pyrrolo[2,3-6]pyridine, 3-nitro-2-phenyl-reduction, 4, 511 Pyrrolo[2,3-6]pyridine, 2-phenyl-nitrosation, 4, 506 quatemization, 4, 503 synthesis, 4, 522... 

Pyrrolo[3,2-6]pyridine, 2-methyl-synthesis, 4, 527 Pyrrolo[3,2-c]pyridine, 4-amino-nucleophilic reactions, 4, 507 Pyrrolo[3,2-c]pyridine, 2,3-dihydro-reactions, 4, 512... 

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

Pyrrolo[2,3-c]pyridines — see also 6-Azaindoles reaction with O-mesitylhydroxylamine, 4, 508 synthesis, 4, 516, 522 tautomerism, 4, 502 UV spectra, 4, 501... 

H-Pyrrolo[3,2-6]pyridin-2( 1 H)-ones synthesis, 6, 630 1 H-Pyrrolo[3,2-c]pyridin-4-ones synthesis, 4, 277... 

The derivative from an isomeric fused system has been described as a sedative-hypnotic compound. The synthesis starts by condensation of the aminopicoline 32 with the haloketone 33. The resulting pyrrolo[l,2-a]pyridine 34 then undergoes a Mannich reaction with formaldehyde and dimethylamine to give the aminomethylated derivative 35. After quatemization of the di-methylamino group in 35 with methyl iodide, the ammonium group is displaced by cyanide to... 

Furthermore, oxazoles of type 9-82 bearing a secondary amino functionality can be converted into pyrrolo[3,4-b]pyridines 9-86 by reaction with appropriate acid chlorides 9-83 in a triple domino process consisting of amide formation/hetero Diels-Alder reaction and retro-Michael cycloreversion via 9-84 and 9-85 (Scheme 9.17). The pyrrolo[3,4-fc]pyridines can be obtained in even higher yields when the whole sequence is carried out as a four-component synthesis in toluene. Here, 1.5 equiv. NH4C1 must be added for the formation of the now intermediate oxazoles [56b]. 

An alternative strategy for the synthesis of these tricyclic compounds involves the reaction of the azidoalkenyl-functionalized furo[3,2-A]pyrrole 30, which reacts with triphenylphosphine to give the corresponding iminophos-phoranes 31 these upon reaction with aryl isocyanates give the pyrrolo[2, 3 4,5]furo[3,2-r-]pyridines 32, via the corresponding carbodiimides which are not isolated < 1994H(37) 1695, 1992M807> (Scheme 9). 

This method was extended to the synthesis of not only pyrrolo[3,4-c]pyridine (8a) and pyrrolo[3,4-l ]pyridine (8b) (4a), but also the salt of several labile heteroaromatic pyrroles 9-11 (4b) (Scheme 9.3). 

A practical synthesis of pyrrolo[2,3- ]pyridine from succinonitrile and ethyl formate has been reported <20030PD209>. The multistep synthesis proceeds via a substituted cyanopyrtole intermediate to give 3-cyanopyrrolo[2,3- ]pyridine, 67. As shown in Equation (12), 67 can be quantitatively converted into the unsubstituted compound, 1, by heating at reflux in concentrated acid. 

A novel solid-phase synthesis of pyrrolo[3,4- ]pyridines using a sequence of Knoevenagel and Hantzsch condensation reactions has been reported <199981951 >. The reactions lead to a variety of highly substituted pyrrolo[3,4- ]pyridines, 70. 

Cyanopyrroles, formed from malononitrile and phenacyl halides, offer another route to the synthesis of pyrrolo[2,3-3]pyridines <2004MI15>. Treatment of the cyanopyrroles with ethyl acetoacetate leads to propenylamino-pyrroles which undergo further cyclization to form highly functionalized pyrtolo[2,3-3]pyridine derivatives. 

A microwave-assisted synthesis of several isomeric pyrrolopyridines ([2,3-3], [2,3-c], [3,2-3], and [3,2-r ]) has been reported starting from aminohalopyridines <2005S2571>. Intramolecular palladium-catalyzed Heck reactions leading to substituted pyrrolo[3,2-3]pyridines from ketones and aminopyridines have been described <2003JME4702>. 

A cyclization of enecarbamates leads to the synthesis of pyrrolo[2,3-f]pyridines (Equation 40) <2005TL8877>. The reaction is catalyzed by a copper(l) iodide/L-proline catalyst system. 

Pyridinedicarboxylic acids and amino acids serve as useful starting materials for the synthesis of pyrrolo[3,4-f]-pyridines. The reactions proceed at relatively high temperatures (Equation 43) <19%EJM49>. 

A synthesis of pyrrolo[2,3-, ]pyridine derivatives from nicotinic acid or 2,6-dichloropyridine affords 1,3- and 1,3,6-substituted pyrrolo[2,3-, ]pyridines <2006JOC5538>. 

Aminopyridines and 3-aminopyridines are used in a regioselective synthesis of pyrrolo[2,3-, ]pyridines and pyrrolo[3,2-, ]pyridines that proceeds via a palladium catalyzed cross-coupling reaction with aromatic alkynes <2007TL6951>. 

The /V-acyl compounds are very suitable for the synthesis of pyrrolo[3,4-b]pyridines (10). As a rule, these compounds are synthesized starting from 2,3-disubstituted pyridines (69BCJ2996 75CB1003 77CCC283). Only a... 

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