Dehydrogenative Cyclization of 2-Aminobenzyl Alcohols with Ketones or Secondary Alcohols to Construct Quinolines

Herein, we present an environmentally friendly and sustainable approach for accessing functionalized quinolines through the dehydrogenative cyclization of 2-aminobenzyl alcohols with ketones or secondary alcohols. This reaction does not require transition metal catalysts, utilizes oxygen from the air as an oxidant, and is performed at room temperature. Notably, the lignin β-O-4 model compounds can be directly converted into a variety of quinolines by using this method. Mechanistic studies reveal that the reaction proceeds through a cascade of dehydrogenation, aldol condensation, and ketoamine condensation.