Synthesis of 3,5,6-trisubstituted α-pyrones from Baylis–Hillman adducts

Emergence of 2-Pyrone and Its Derivatives, from Synthesis to Biological Perspective: An Overview and Current Status

Pyrone moieties are present in natural products and can be synthesized by a diverse range of synthetic methods, resulting in the formation of various derivatives through chemical modifications. Many pyrone-based derivatives are commercially available and are biocompatible. They are building blocks of various intermediates in organic synthesis. They possess remarkable biological properties including antimicrobial, antiviral, cytotoxic, and antitumor activity. These characteristics have made them valuable for the development of drugs. We have summarized recent developments in the synthesis of 2-pyrone and its derivatives and their potential applications. With regard to synthetic approaches, the focus has been on metal-free and transition metal-catalyzed reactions.

Synthesis of Highly Functionalized 2-Pyranone from Silyl Ketene

We report a highly functionalized 2-pyranone small molecule prepared from tert-butyl diphenyl silyl ketene using an alkoxide catalyst and thermally induced rearrangement. Treatment of the silyl ketene with a substoichiometric amount of alkoxide led to the formation of a trimer which was isolated and fully characterized; heating this trimer in a 1,4-dioxane solution induced a thermal rearrangement, yielding the product 2-pyranone. The isolated intermediate and product are characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopies, mass spectrometry, and single crystal X-ray diffraction. A mechanism for the thermally induced rearrangement is proposed based on ¹H NMR studies, and a rate law is derived from the proposed mechanism with steady-state approximation. This work illustrates a route for the formation of highly functionalized and modifiable 2-pyranone motifs with potential biological activity. The formation of the trimer, and thus the functionalized 2-pyranone, is highly dependent on the silyl substituents and alkoxide counterion and thus indicates the intriguing reactivity of highly functionalized small molecules.

Recent advances in the synthesis of 2-pyrones

The present review summarizes the recent progresses in the synthesis of 2-pyrones and the application to the synthesis of marine natural products. Especially, much attention was placed on the transition metal catalyzed synthetic methodologies in this review.