Abstract
This review is comprised of seven topics: (1) Reactivity of O-acylTEMPOs towards nucleophiles and application to chemoselective transformations, (2) reactivity of anionic species derived from O-acylTEMPOs, (3) E-selective Knoevenagel condensation of acetoacetylTEMPOs and furan synthesis, (4) electrocyclization of 2,4-dienones derived from acetoacetic derivatives and 2-substituted enals, (5) diastereoselective addition of amide to O-(2-alkenoyl)TEMPOs and β-amino acids synthesis, (6) thermal stability of O-acylTEMPOs, and (7) reactivity of TEMPO anion and use of O-alkylTEMPOs as a latent carbonyl function. O-AcylTEMPOs were stable towards hydride-transferring and metallic alkylating reagents, allowing chemoselective transformation of diacid mixed alkyl/TEMP-1-yl esters. The lithium anionic species of O-acylTEMPOs were employed for alkylation, Michael addition, direct aldol reaction, and others. Knoevenagel condensation of O-acetoacetylTEMPOs with aldehydes substituted with an electron-withdrawing group led preferentially to E-adducts. The AlMe3-treated O-(2-alkenoyl)TEMPOs underwent smooth addition of the Mg amide. O-Alkylated TEMPOs were oxidized with mCPBA to afford the corresponding aldehydes, thus accomplishing a new protocol for the halide-carbonyl conversion.
