A Single-Step Synthesis of 4-Oxazolin-2-ones and Their Use in the Construction of Polycyclic Structures Bearing Quaternary Stereocenters
作者:Blanca M. Santoyo、Carlos González-Romero、Omar Merino、Rafael Martínez-Palou、Aydeé Fuentes-Benites、Hugo A. Jiménez-Vázquez、Francisco Delgado、Joaquín Tamariz
DOI:10.1002/ejoc.200900114
日期:2009.5
for the synthesis of 4-oxazolin-2-ones by a one-pot MW-promoted condensation of α-ketols and isocyanates is reported. An alternative thermal approach using the same starting materials is also described. These cyclic enamides were efficient nucleophiles, reacting with Michael acceptors and prenyl bromide to give a variety of polycyclicstructuresbearing one or two quaternarystereocenters. The selectivity
Regioselective Synthesis of N-Substituted 4-Methylene-2-oxazolidinones and 4-Oxazolin-2-ones. Study of Reactivity in Thermal Michael Conjugate Additions
作者:Rafael Martı́nez、Hugo A. Jiménez-Vázquez、Joaquı́n Tamariz
DOI:10.1016/s0040-4020(00)00311-2
日期:2000.6
N-Substituted 4-methylene-2-isoxazolidinones 9a–9e have been prepared from the tandem condensation of isocyanates 3 with α-ketol 7. In a more polar solvent (DMF) the same reaction led to stereoisomeric alcohols 11 and 12, which could be transformed to the thermodynamically more stable isomers 4-oxazolin-2-ones 10 in good yield. Thermal conjugate additions of both heterocycles 9a and 10a to enone 13