Triphenylphosphine-mediated chemoselective synthesis of functionalized thiazol-2(5H)-ones
摘要:
Stabilized phosphoranes, obtained from three-component reaction between dialkyl acetylenedicarboxylates and thiazolidine-2,4-dione in the presence of triphenylphosphine, undergo a smooth intramolecular Wittig reaction in boiling toluene to produce functionalized thiazol-2(5H)-ones in good yields. When alkyl propiolates were employed in these reactions, only the (E)-isomer of alkyl 3-(2,4-dioxothiazolidin-3-yl)acrylates were isolated. A dynamic effect was observed in the (1)H nuclear magnetic resonance (NMR) spectrum of ethyl (E)-3-(2,4-dioxothiazolidin-3-yl)-3-phenylacrylate as a result of restricted rotation (Delta G(not equal) = 77 kJ/mol) around the N-C bond between the thiazolidine moiety and the vinyl group.