One-Pot O2-Oxidation and the Horner-Wadsworth-Emmons Reaction of Primary Alcohols for the Synthesis of (Z)-α,β-Unsaturated Esters

We developed one-pot oxidation/olefination procedures of primary alcohols giving Z-alpha,beta-unsaturated esters 3. TEMPO-(CuCl or CuBr2)-(2,2'-bipyridine) (1:1:1) catalyzed O-2 oxidation of primary alcohols in the presence of Z-selective Horner-Wadsworth-Emmons reagent lb and K3PO4 or NaH gave 3 with Z/E = 84:16 to 96:4 in high yields. A stepwise reaction was also developed. After TEMPO-CuBr2-(2,2'-bipyridine)-K3PO4 (1:1:1:1) catalyzed O-2 oxidation of alcohols in MeCN, the resulting mixture was treated with a THF solution of lb and t-BuOK at -78 degrees C to 0 degrees C, giving 3 with higher selectivity (Z/E = 91:9 to 99:1).

Automated summary

In this study, a convenient and high-yield synthesis method for Z-α,β-unsaturated esters was developed. By using a one-pot oxidation/olefination reaction with suitable catalysts and reagents, the desired product with high selectivity could be obtained.