Knorr quinoline synthesis
Knorr quinoline synthesis | |
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Named after | Ludwig Knorr |
Reaction type | Ring forming reaction |
Identifiers | |
RSC ontology ID | RXNO:0000394 |
The Knorr quinoline synthesis is an
2-hydroxyquinoline using sulfuric acid. This reaction was first described by Ludwig Knorr (1859–1921) in 1886[1]
The reaction is a type of
polyphosphoric acid (PPA) but 4-hydroxyquinoline 3 when the amount of PPA is small. A reaction mechanism identified a N,O-dicationic intermediate A with excess acid capable of ring-closing and a monocationic intermediate B which fragments to aniline and (ultimately to) acetophenone
. Aniline reacts with another equivalent of benzoylacetanilide before forming the 4-hydroxyquinoline.
A 2007 studysuperelectrophile) over the N,O dicationic intermediate . For preparative purposes triflic acid is recommended: