Cyclopropanation reactions catalysed by copper and rhodium complexes homogeneous and heterogenised on a modified USY-zeolite. Influence of the catalyst on the catalytic profile

The reaction of alkyl diazoacetate (ethyl and t-butyl diazoacetate) with st yrene and 1,2-dihydropyrane is catalysed by Cu- and Rh-complexes, homogeneo us and heterogenised on a modified USY-zeolite. A comparative study (homoge neous vs. supported) was made for the catalytic activity and selectivity in cyclopropanation reactions. High activities and selectivity (cyclopropanat ion vs, dimerisation) were obtained at 1:150 catalyst:substrate relationshi p, with the Cu catalysts being remarkably more active than the Rh-ones. The enantioselectivity in the tested conditions was low. The reactivity and se lectivity for zeolite-heterogenised catalysts do not deviate significantly from that obtained using the corresponding homogeneous complexes, though th ey could be used without loss of cyclopropanation activity and metal leachi ng at least in five successive runs. (C) 1999 Elsevier Science B.V. All rig hts reserved.