Asymmetric Synthesis of 3‐Amino Oxindoles Using Isatin‐Derived N‐Boc Ketimines with Activated Nitroolefin Catalyzed by Organocatalysts. Issue 7 (2nd March 2017) - Choudhary, Manoj K.
Abstract: Asymmetric synthesis of 3‐aminooxindole via aza‐MBH reaction by using isatin‐derived N ‐Boc ketimines with activated nitroolefin (2 and3 ) is reported for the first time by using various organocatalysts where chiral thiourea‐based organocatalystOC‐7 was found to be better catalyst to give the products in high yield with high diastereoselectivity (up to >99:1) and good enantioselectivity (up to 97:3 er). A probable mechanism for the formation of 3‐aminooxindole is established by 1 H & 13 C NMR studies. Abstract : In this work, enantioselective aza‐MBH reaction of isatin‐derived N ‐Boc ketimines with activated nitroolefins are reported for the first time by using various organocatalysts (OC‐1 to OC‐7). Among these, chiral thiourea‐based organocatalyst OC‐7 was delivered high yield with high diastereoselectivity (up to >99:1) and good enantioselectivity (up to 97:3 er) in corresponding products. End product of this reaction, chiral quaternary 3‐aminooxindole is active intermediates in valuable pharmaceutical candidates and bioactive molecules.