Condensation of Long-Chain α-Phosphono Carboxylates with Aldehydes

Article abstract of DOI:10.1021/jo00360a019

The condensation of several long-chain α-phosphono carboxylates with propanal was examined as a prototype route to trans and cis α-substituted conjugated esters.With the diisopropylphosphono and the dimethylphosphono bis-homogeranic esters A6 and A7, the trans product predominated by ca. 9:1.A similar trend was observed with the diisopropyl and dimethyl α-phosphono-ω-undecylenates B3 and B4.The bis(trifluoroethyl) α-phosphono-ω-undecylenate B5 afforded the cis product B11 as the major isomer with 8:1 stereoselectivity.Condensations of the α-(triphenylphosphorylidene)-ω-dodecenylate C3 with several representative aldehydes gave only trans products within the limits of detection.Thus, α-phosphorylidene esters show uniformly high trans stereoselectivity regardless of α-alkyl substitution.The phosphonates, on the other hand, show markedly diminished stereoselectivity when long-chain α-substituents are present.