| abstract |
Provided is a method for industrially advantageously synthesizing a production intermediate of a quinolinecarboxamide derivative or a salt thereof. The present invention provides a method for producing a quinolinecarboxylic acid derivative of formula (4) or a salt thereof, including reacting an aniline of the following formula (1), in the presence of boron trifluoride-tetrahydrofuran complex or boron trifluoride-diethyl ether complex, with an aldehyde of formula (2) and subsequently reacting the resulting compound with an α-keto acid of formula (3), wherein R<sup>1</sup>, R<sup>2</sup>, R<sup>3</sup> and R<sup>4</sup> are the same or different and each represent a hydrogen atom, a halogen atom, a lower alkyl group, or the like, R<sup>5</sup> represents a hydrogen atom, a lower alkyl group, or the like, and R<sup>6</sup> represents a hydrogen atom, a lower alkyl group, or the like. |