Metal-Free, Ionic Liquid-Mediated Synthesis of Functionalized Quinolines

An expedient and metal-free synthetic protocol for construction of substituted quinolines has been developed from anilines and phenylacetaldehydes using imidazolium cation-based ionic liquids as the reaction medium. Mechanistic analysis indicated that the reaction occurs through C–C and C–N bond formation to produce isolable 2,3-disubstituted quinoline intermediates, which undergo C–C bond cleavage to produce 3-substituted quinolines. The reaction proceeds smoothly with a range of functionalities in good to excellent yields. Advantages of this protocol include metal-free, environmentally friendly, recyclable reaction media, higher yields and shorter reaction times, and thus is promising for the efficient combinatorial synthesis of structurally diverse 2,3-disubstituted and 3-substituted quinolines

<i>ortho</i>-Amidoalkylation of Phenols via Tandem One-Pot Approach Involving Oxazine Intermediate

A new and efficient method for <i>ortho</i>-amidoalkylation of phenols via Mannich-type condensation with formaldehyde and lactams using recyclable solid acid catalyst is described. This is the first report for <i>ortho</i>-amidoalkylation of phenols by lactams via Mannich-type condensation. LC-ESI-MS/MS based mechanistic study revealed that reaction proceeds through <i>o</i>-quinone methide (<i>o</i>-QM) and an oxazine intermediate via tandem Knoevenagel condensation, formal [4 + 2]-Diels–Alder cycloaddition and acid catalyzed oxazine ring-opening