Alkylation of 2-and 3-alkoxycarbonyl-4-quinolinones. DFT study on the regioselectivity

The reaction of 2-alkoxycarbonyl-4-quinolinones (1) with a variety of alkylating reagents under different conditions, lead to the corresponding O-alkylated products. The behavior in basic medium of compounds 1 differs from the 3-alkoxycarbonyl-4-quinolinones (4) isomers suggesting that the position of the carboxylate group determines the regioselectivity of the reaction. OFT calculations allow us to conclude that for 3-alkoxycarbonyl-4-quinolinones, the N-alkylation would be thermodynamically and kinetically favored. But for 2-alkoxycarbonyl-4-quinolinones the side chain in the 2-position of the ring prevents the planar approximation to the contiguous heteroatom leading to a more favorable O-alkylation transition state. Crystal structure of an O-alkylated product is determined by single crystal X-ray diffractometry. (C) 2016 Elsevier B.V. All rights reserved.