Electrochemical Corey–Winter reaction. Reduction of thiocarbonates in aqueous methanol media and application to the synthesis of a naturally occurring α-pyrone

• Main Authors: Ernesto Emmanuel López-López, José Alvano Pérez-Bautista, Fernando Sartillo-Piscil, Bernardo A. Frontana-Uribe
• Format: Article
• Language: English
• Published: Beilstein-Institut 2018-03-01
• Series: Beilstein Journal of Organic Chemistry
• Subjects: Corey–Winter reaction; electrosynthesis; 6-pentyl-2H-pyran-2-ones; reduction; thiocarbonates
• Online Access: https://doi.org/10.3762/bjoc.14.41

An electrochemical version of the Corey–Winter reaction was developed giving excellent results in aqueous methanol media (MeOH/H2O (80:20) with AcOH/AcONa buffer 0.5 M as supporting electrolyte), using a reticulated vitreous carbon as cathode in a divided cell. The electrochemical version is much more environmentally friendly than the classical reaction, where a large excess of trialkyl phosphite as reducing agent and high temperatures are required. Thus, cathodic reduction at room temperature of two cyclic thiocarbonates (−1.2 to −1.4 V vs Ag/AgCl) afforded the corresponding alkenes, trans-6-(pent-1-enyl)-α-pyrone and trans-6-(pent-1,4-dienyl)-α-pyrone, which are naturally occurring metabolites isolated from Trichoderma viride and Penicillium, in high chemical yield and with excellent stereo selectivity.