Development of solvent-free HWE reaction

Solvent-free reaction has drawn great attention in recent years for a range of reasons, such as environmental concerns, safety consideration, reduction of costs, simplicity of process. In this study, we have developed a solvent-free Horner-Wadsworth-Emmons reaction that gives a,b-unsaturated esters and ketones in good yields with excellent E-selectivity as shown below (Scheme 1, 2). DBU can be recovered almost quantitatively by a simple procedure. Additionally, we found that virtually the same results were obtained by using K₂CO₃ and catalytic amount of DBU (Scheme 3). Highly E-selective solvent-free HWE reaction of ketones was also achieved by using Cs₂CO₃ in place of K₂CO₃.

Ando, K.; Yamada, K. Tetrahedron Lett. 2010, 51, 3297–3299.

Ando, K.; Yamada, K. Green Chem. 2011, 13, 1143–1146.