Cyclopropanation reactions catalysed by copper and rhodium complexes homogeneous and heterogenised on a modified USY-zeolite. Influence of the catalyst on the catalytic profile
Mj. Alcon et al., Cyclopropanation reactions catalysed by copper and rhodium complexes homogeneous and heterogenised on a modified USY-zeolite. Influence of the catalyst on the catalytic profile, J MOL CAT A, 144(2), 1999, pp. 337-346
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.