NUCLEOPHILIC CATALYSIS WITH PI-BOUND NITROGEN-HETEROCYCLES - SYNTHESIS OF THE FIRST RUTHENIUM CATALYSTS AND COMPARISON OF THE REACTIVITY AND THE ENANTIOSELECTIVITY OF RUTHENIUM AND IRON COMPLEXES

Three ruthenium complexes that bear pi-bound nitrogen heterocycles hav e been synthesized. It is established that these complexes serve as ef fective nucleophilic catalysts for a range of processes, including the acylation of alcohols with diketene, the ring opening of azlactones, and the addition of alcohols to ketenes; their activity is comparable to or somewhat greater than the corresponding iron catalysts. The rela tive efficiency of the ruthenium complexes as asymmetric catalysts is also evaluated: in the kinetic resolution of secondary alcohols, ruthe nium is markedly less effective than iron, but in the deracemization/r ing opening of azlactones, ruthenium is slightly more enantioselective . This study documents for the first time the impact of the metal on t he reactivity and on the enantioselectivity of nucleophilic catalysts based on pi-bound nitrogen heterocycles.