INTRAMOLECULAR AND INTERMOLECULAR MN(III)-INDUCED CARBON-MONOXIDE TRAPPING REACTIONS OF ALKYNES WITH MALONATE AND CYANO ESTER UNITS

Intra- and intermolecular carbon monoxide trapping reactions of alkyne s with malonates and cyano esters were developed using a Mn(III)-induc ed oxidative system. Phenylacetylene was treated with diethyl ethylmal onate in the presence of Mn(OAc)(3) . 2H(2)O, in AcOH-CH3CN (1:1) unde r carbon monoxide, affording (Z)-4,4-dicarbethoxy-2-phenyl-2-hexenoic acid. Similarly, intramolecular reactions of 4-alkynylmalonates and cy anoacetates proceeded regio- and stereoselectively under the same cond itions to afford the corresponding methylenecycloalkanecarboxylic acid s in moderate yields. The reaction involves carbon monoxide trapping o f vinyl radicals which are formed by the addition of malonate or cyano acetate radicals induced by Mn(III) to alkynes.