Recent Advances in the Catalytic Synthesis of 4-Quinolones

The 4-quinolones and their analogs are a heterogeneous group of biologically active compounds that have evolved in modern days to provide utilities at the forefront of antibiotic research. They have been used to combat Gram-negative or Gram-positive bacteria, suppress tumor growth, and treat many serious infections. These antimicrobial agents have also been used to promote apoptosis and DNA repair for the treatment of cancer. This review summarizes the experimental progress made in the synthetic development of various catalytic routes to preparing 4-quinolones and their analogs; discusses our current understanding of the reaction mechanisms involving biocatalytic synthesis, general catalytic synthesis, and asymmetric synthesis; and finally presents the future prospects of the emerging field. Quinolones and their analogs are an important class of organic compounds that can be prepared by a wide range of synthetic approaches. These organic molecules have a number of applications—including combating malarial infection, suppressing tumor growth, and promoting apoptosis and DNA repair—that are frequently required for the treatment of cancer. Quinolone-based drugs, when used alone or in combination with existing antiretroviral drugs, can also be useful in the treatment of patients with human immunodeficiency virus infection. Despite all the benefits, it has been challenging to substitute the quinolone scaffold with diverse chemical functionality through a short step under mild reaction conditions. One proposed approach to tackling this is to utilize catalytic transformations, which is attractive from an environmental and industrial perspective. The aim of this review is to highlight and better understand the recent development of catalytic synthesis of 4-quinolones and their analogs, in compliance with the principle of green chemistry. This review provides a recent overview of various catalytic routes for preparing 4-quinolones with a particular emphasis on biocatalytic synthesis, general catalytic synthesis, and asymmetric synthesis. The mechanisms are delineated for most of the reactions that lead to 4-quinolone-based analogs. The synthesis of a number of natural products and medicinally important drugs comprising 4-quinolone moieties is also included.