Pyrazolo-pyridines, halogenation

Conversions of diazonium salts into halogenated derivatives have been reported for compounds of type 128 and 129 [73JCS(P1)2901 80JCS(P 1)2398], Although some 7-substituted pyrazolo[ 1,5-u]pyridines have been made from the lithiated precursors, no halogeno products have been reported (92JOC5538). 

Halogenation of pyrazolo[4,3-c]pyridines has not been reported, but all other isomers, as with pyrrolopyridines, undergo substitution mainly in the 3-position. 

No halogenations of the pyrazolo[4,3-c]pyridine ring system have been reported. 

Acylation and metallation studies on monomers, dimers, trimers, and tetramers containing linked thiophen, pyridine, pyrimidine, furan, benzofuran, benzothiophen, and indole moieties have been published/ Deuteriation, halogenation, and diazo-coupling reactions of 2-oxo- and 2-thioxo-l,2-dihy-dropyrimidinium salts have been studied and compared with results for 2,2-dialkyl-1,2-dihydropyrimidinium and 2,3-dihydro-1,4-diazepinium salts in order to demonstrate the effect of an adjacent 0x0- or thioxo-group on the properties of a 1,5-diazopentadienium system/ Vilsmeier formylation of, and tautomerism in, 2-hydroxypyrazolo[5,l-h]quinazolone and l-phenylpyrazolo[5,l-A]-quinazoline-2,9-dione have been studied/ The pyrazolo[3,4-c]pyrazole (71) has been methylated and acetylated, the major products being (72)/ ... 

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