Organocatalytic asymmetric synthesis of dihydrofuran-spirooxindoles from benzylidene malononitriles and dioxindoles

Abstract

The first organocatalytic asymmetric synthesis of dihydrofuran-spirooxindoles having a linkage at the 2-position of the dihydrofuran motif has been developed from dioxindoles and benzylidene malononitriles.

Stereoselective synthesis and applications of spirocyclic oxindoles

“…57 (Scheme 58). 274 Deng reported an asymmetric Michael/ lactonization procedure between 3-hydroxyoxindoles and 3-methylene oxindoles which resulted in ring opening of the oxindole coupling partner (Scheme 58). 275,276 Similar to ref.…”

Organocatalytic Synthesis of Chiral Spirooxindoles with Quaternary Stereogenic Centers

“…Balha and co‐workers also described the first organocatalytic asymmetric synthesis of a dihydrofuran spirooxindole 129 from the reaction of N ‐benzyldioxindole 120 and benzylidene malononitrile 127 in the presence of a catalytic amount of bifunctional catalyst cinchonidine‐derived squaramide (20 mol‐%) 128 in toluene for 1 h at room temperature to give spirooxindole 129 in 80 % yield and with a moderate diastereoselectivity (1.7:1 dr) and high enantioselectivity (95 % ee) for the majority spirooxindole 129 , as shown in Scheme . The scope of the reaction was studied with different substituents in different positions in both starting materials 120 and 127 and in all cases the reactions led spirooxindole compounds with high enantioselectivies and moderate to good diastereoselectivies.…”

“…In the reaction mechanism, the bifunctional catalyst 128 activated the benzylidene malononitrile 127 via hydrogen bonding and the tautomeric enol of 120 attacked via Michael addition reaction to deliver the intermediate II . A subsequent Pinner reaction is carried out to provide III and isomerization reaction in III gave spirooxindole 129 , as shown in Scheme …”

Advances in the Synthesis of Benzo‐Fused Spiro Nitrogen Heterocycles: New Approaches and Modification of Old Strategies

“…Other catalysts, including Takemoto's thiourea 114, were less efficient in this reaction (Scheme 62). [256] A fairly simple method for the synthesis of spiro-fused oxetane-2-oxindole heterocycles is proposed. The Michael addition/intramolecular etherification cascade reaction of phenyl vinyl selenone 237 with 3-hydroxyindolones 234 under aqueous basic conditions at room temperature leads to spiro-fused oxindole-oxetanes 238 in moderate to good yields (Scheme 63).…”

“…Other catalysts, including Takemoto ’s thiourea 114 , were less efficient in this reaction ( Scheme 62). [256] …”