Pyrrolo pyridine-carboxylic acids

An alternative approach (1991JHC81) to the construction of the thieno[3,2-c] pyridine system is based on C(6)-C(7) bond formation (approach S). For example, heating carboxylic acid 279 in PPA resulted in its cyclization giving 9-oxo-4H, 9f/-pyrrolo[l,2-a]thieno[2,3-<7]pyridine (280) in low yield. An attempt to prepare this compound by an independent synthesis, viz., by cyclization of isomeric acid 281 under analogous conditions, failed. 

Amino-l,5-naphthyridin-4 (1 //)-one (21) underwent diazotization to 3-diazo-nio-l,5-naphthyridin-4(1//)-one chloride (22) (substrate, Me2NCHO, 0°C, Me2CHCH2CH2ONO [, HCI/btOH [ 75%), which on irradiation gave 177-pyrrolo[3,2-b]pyridine-3-carboxylic acid hydrochloride (23) [substrate, AcOH, H20, 0°C, hv (arc lamp), h %].722... 

Amino-l,5-naphthyridin-4 (1 //)-one gave crude 3-diazonio-l,6-naphthyridin-4(l//)-one chloride (HC1, NaN02, 5°C, 12 h) and thence 3-diazonio-l,6-naphthyridin-4-olate (26) (NaHC03, Et20 70% overall) 726 subsequent irradiation caused ring contraction to pyrrolo [3,2-[Pg.133]

Amino-l,7-naphthyridin-4(l//)-one (10) underwent diazotization to give 4-oxo-3,4-dihydro-l,7-naphthyridin-3-ylidendiazonium chloride hydrochloride (11) (NaN02, HC1, 0°C 80%) and subsequent ring contraction on irradiation to afford pyrrolo[2,3-c]pyridine-3-carboxylic acid (12) (AcOH, H20, hv,... 

Preparation of 5-methyl-4-(lH-pyrrolo[2,3-b]pyridin-5-yloxy)-pyrrolo [2,l-f][l,2,4]triazine-6-carboxylic acid ethyl ester... 

According to Chemical Abstracts 3-Hydroxy-lfl -pyrrolo[2,3-b]pyridine-2-carboxylic acid. The common names indoxyl, oxindole, and isatin will be used as they do not imply which tautomer is predominant. It is noted that the tautomers shown are in accord with current theory for indoles and have not been established as such. 

AUTONOM 6-Acetyl-3-(2-(3-lttert -butyl-phenyl)-ethylidene)-l-(2-fluoro-2-phenyl-thyl)-5-(8-nethyl-octahydro 2,5-nethano-isoqui olin-3-yl)-7 thioacryloyloxy-2, dihydro-l H pyrrolo[3,2 ltb ]pyridine-2 carboxylic acid vinyl ester... 

Cyclization of diethyl N-[cyclohepta(6)pyrrrol-2-yl]aminomethylene-malonates (1676), by heating in xylene, t-butylbenzene, or tetralin at reflux temperature, gave cyclohepta[4,5]pyrrolo[l, 2-a]pyrimidine-3-carboxyl-ates (1677) in 46-90% yields (87BCJ1053). Cyclization were also carried out in a mixture of phosphoryl chloride and polyphosphoric acid. While compound 1676 (R = COOEt) gave 1677 (R = COOEt) in 95% yield, the unsubstituted 1676 (R = H) afforded a mixture of 1677 (R = H) and 4-hydroxycyclohepta[4,5]pyrrolo[2,3-b]pyridine-3-carboxylate (1678) in 7% and 48% yields, respectively. The nitrogen bridgehead compound (1677, R = H) could not be transformed into pyridine derivative (1678). 

---