Synthesis of 2-Aryl-1-hydroxyazaindolesand 2-Arylazaindoles via Oxidation of o-Hydroxyaminostyrylpyridines

2-Aryl-1-hydroxyazaindoles (pyrrolopyridin-1-ols) are prepared via an oxidation/cyclization of o-hydroxyaminostyrylpyridines with DDQ. Reduction of the N-OH bond affords the corresponding 2-arylazaindoles (1H-pyrrolopyridines). The scope of the cyclization is explored via (i) the condensation of 4-methyl-3-nitropyridine with various aryl aldehydes to afford 2-aryl substituted 6-azaindoles and, (ii) the synthesis of 2-phenyl-4-, 5- and 7-azaindoles.