A mild and efficient synthesis of substituted quinolines via a cross-dehydrogenative coupling of (Bio)available alcohols and aminoarenes

A ruthenium-catalysed dehydrogenative cross-coupling of primary alcohols and imines in the presence of TFA provided a library of differently substituted quinolines. Imines can be prepared in situ from various anilines and several benzyl alcohols using a ruthenium-catalysed hydrogen-transfer procedure. Without changing the catalyst, quinolines can be obtained in moderate to good yields by adding various primary alcohols in the presence of TFA (30 mol%) via a "telescopic" protocol. The use of alcohols, the absence of strong oxidants and the diversity of potential starting materials make this modern version of the Skraup reaction superior to most of the conventional quinoline syntheses.