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Thermal Arndt–Eistert reactions of N ‐tosyl cyclic α‐amino acids were studied to explore the preparation of α,β‐unsaturated esters bearing a terminal tosylamino group. For L‐ N ‐tosyl‐aziridine 2‐carboxylic acid and L‐ N ‐tosyl‐azetidine 2‐carboxylic acid, the corresponding ( E )‐α,β‐unsaturated esters were obtained stereospecifically. [ABSTRACT FROM AUTHOR]

Stereoselective synthesis of α,β-unsaturated esters 7 and 8 was achieved through Horner–Wadsworth–Emmons reaction of β,β-disubstituted α,β-unsaturated aldehydes. Thus, aldehydes 6 undergo olefination with phosphonate carbanion generated from triethyl phosphonoacetate 3 and lithium hydroxide or butyl lithium/DMPU to give (E)-α,β-unsaturated esters 7 with excellent selectivity. The treatment of 6 with the new Horner–Emmons reagents, ethyl(diphenylphosphono)acetate 4a and ethyl (di-o-tolyl-phosphono) acetate 4b in the presence of benzyltrimethyl ammonium hydroxide (Triton B) afforded (Z)-α,β-unsaturated esters 8 with 73–89% selectivity. The esters 7 and 8 were converted to (2E)- and (2Z)-4-cycloalkylidenebut-2-enoic acids 9 and 10, respectively. [ABSTRACT FROM AUTHOR]