Triflic acid promoted fries rearrangement of C-3 vinyl/isopropenyl-azetidin-2-ones: single-pot synthesis of C-3 functionalized-2-aryl-2,3-dihydro-quinoline-4(1H)-ones†
Abstract
The β-lactam-synthon-interceded synthesis of C-3 functionalized 2-aryl-2,3-dihydro-quinoline-4(1H)-ones has been described via the Fries rearrangement of C-3 vinyl/isopropenyl substituted β-lactams. The reaction at 0 °C resulted in the isolation of a tautomeric mixture, and the preferential formation of the conjugated product was observed at higher temperatures. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations were additionally performed to explain the preferential formation of product 2 over 3. The proposed mechanism was further validated via the base-induced isomerisation of the mixture of 2a and 3a.