A Straightforward, Purification-Free Procedure for the Synthesis of Ando and Still-Gennari Type Phosphonates

Z -Selective Still-Gennari and Ando modifications of the typically E -selective Horner-Wadsworth-Emmons reaction are highly valuable synthetic tools in organic chemistry. These procedures are based on application of bis(2,2,2-trifluoroethyl) phosphonates or diaryl phosphonates, respectively, for the olefination of carbonyl groups. In our research, we present an improved, straightforward, purification-free procedure for the synthesis of these reagents. The key step of our procedure is the reaction of phosphonic dichlorides with the appropriate sodium alkoxides, which results in 52-97% isolated yields of the desired products on a gram scale. The whole three-step process is performed in one pot. Most importantly, the product is obtained in over 95% purity after simple extraction, avoiding column chromatography and distillation. Moreover, we present the synthesis of a novel Still-Gennari type reagent, bis(1,1,1,3,3,3-hexafluoroisopropyl) phosphonates, which may exhibit improved Z -selectivity in Still-Gennari olefinations.

Automated summary

The Z-selective Still-Gennari and Ando modifications of the Horner-Wadsworth-Emmons reaction are valuable synthetic tools in organic chemistry. A purification-free procedure for the synthesis of these reagents has been presented, resulting in high purity products on a gram scale. Additionally, a novel Still-Gennari type reagent has been synthesized, which may exhibit improved Z-selectivity in olefinations.