RHODIUM-CATALYZED HETEROCYCLOADDITION ROUTE TO 1,3-OXAZOLES AS BUILDING-BLOCKS IN NATURAL-PRODUCTS SYNTHESIS

Rhodium(II) acetate serves as a catalyst for the heterocycloaddition r eaction of diazodicarbonyl compounds with nitriles to give functionali zed 1,3-oxazole derivatives in a simple one-step procedure. In particu lar, dimethyl diazomalonate undergoes this reaction to give 2-aryl-, 2 -alkenyl-, or 2-alkyl-4-carbomethoxy-5-methoxy-1,3-oxazoles, and ethyl fomyldiazoacetate (diazomalonate half-ester half-aldehyde) gives 2-ar yl-, 2-alkenyl-, or 2-alkyl-4-carboethoxy-1,3-oxazoles. These products are of potential importance as key intermediates in the synthesis of several oxazole-containing natural products and other heterocyclic sys tems.