RESUMO
Polymeric and monomeric V(V) chiral salen complexes-catalyzed enantioselective ethyl cyanoformylation of aldehydes using ethyl cyanoformate as a source of cyanide was accomplished in the presence of several basic cocatalysts viz., NaOH, KOH, basic Al2O3 and hydrotalcite. Excellent yield (>95%) of chiral ethyl cyanohydrincarbonate with high enantioselectivity up to 94% was achieved in 24-36 h when hydrotalcite was used as an additive. The polymeric catalyst 1 is more reactive than the monomeric catalyst 2 to produce chiral ethyl cyanohydrincarbonate in high optical purity. The chiral polymeric catalyst 1 and cocatalysts hydrotalcite and basic alumina used in this study were recoverable and recyclable several times with retention of its performance.
RESUMO
Chiral polymeric Mn(III) salen complexes were used efficiently for oxidative kinetic resolution of racemic secondary alcohols at room temperature. High chiral purity (ee; >99%) was achieved for the oxidative kinetic resolution of racemic secondary alcohols with 0.6 mol % catalyst loading in 60 min. The catalyst was easily recycled for five successive catalytic experiments.
RESUMO
New polymeric Zn(salen) complex was employed in the enantioselective phenylacetylene addition to aldehydes and ketones to produce corresponding chiral secondary propargylic alcohols with yields (up to 96%) and enantioselectivity (up to 72%) and tertiary propargylic alcohols with yields (up to 79%) and enantioselectivity (up to 68%) at room temperature, with added advantage of four times reuse with retention of enantioselectivity.
