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 styrene and 1,2-dihydropyrane is catalysed by Cu- and Rh-complexes, homogeneous and heterogenised on a modified USY-zeolite. A comparative study (homogeneous vs. supported) was made for the catalytic activity and selectivity in cyclopropanation reactions. High activities and selectivity (cyclopropanation vs, dimerisation) were obtained at 1:150 catalyst:substrate relationship, with the Cu catalysts being remarkably more active than the Rh-ones. The enantioselectivity in the tested conditions was low. The reactivity and selectivity for zeolite-heterogenised catalysts do not deviate significantly from that obtained using the corresponding homogeneous complexes, though they could be used without loss of cyclopropanation activity and metal leaching at least in five successive runs. (C) 1999 Elsevier Science B.V. All rights reserved.