Synthesis of di- and cis-triaryl-3a,4,5,6-tetrahydroimidazo1,5-bisoxazoles and their ring-opening reactions

摘要

The Delta (3)-imidazoline 3-oxides I undergo diastereoselective cycloaddition with dimethyl acetylenedicarboxylate 2 to give 3a,4,5,6-tetrahydroimidazo1,5-bisoxazoles 3. Thermally and base induced ring-opening reactions of compounds 3 were demonstrated. cis-6-Phenyl substituted adducts 3d,e undergo ring opening with secondary but not with ternary amines. The same adducts undergo regio- and diastereoselective Michael addition with sodium methoxide to give 2-methoxy-3a,5,6-triphenyl-hexahydro-imidazo1,5-bisoxazole-2,3-dicarboxy lic acid dimethyl esters 6. (C) 2001 Elsevier Science Ltd. All rights reserved. References: 19