Optically active spirocyclopropyloxindole derivatives were efficiently synthesized from diazooxindoles and olefins in the presence of a Ru(ii)-Pheox catalyst.
A reusable and highly enantioselective catalyst for the intramolecular cyclopropanation of various diazo ester and Weinreb amide derivatives was developed. The reactions catalyzed by a water-soluble Ru(II)-Amm-Pheox catalyst proceeded smoothly at room temperature, affording the corresponding bicyclic cyclopropane ring-fused lactones and lactams in high yields (up to 99%) with excellent enantioselectivities (up to 99% ee). After screening of various catalysts, the Ru(II)-Amm-Pheox complex having an ammonium group proved to be crucial for the intramolecular cyclopropanation reaction in a water/ether biphasic medium. The water-soluble catalyst could be reused at least six times with little loss in yield and enantioselectivity.
Oxindole derivatives were efficiently synthesized from diazoamides derived from aniline derivatives in the presence of a Ru(II)-Pheox catalyst. Ru(II)-Pheox was found to be one of the most efficient catalysts so far for the synthesis of oxindole derivatives from the diazoamides in high yields (up to 99%) with high regioselectivity. Furthermore, the reaction was rapid and no substituent effects on the aromatic ring.
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