Catalytic Asymmetric Tandem Cycloisomerization/[5+2] Cycloaddition Reaction of N-Aryl Nitrone Alkynes with Methyleneindolinones

Abstract

An asymmetric tandem cycloisomerization and intermolecular [5+2] cycloaddition reaction of 2-ethynylphenyl-substituted nitrones with methyleneindolinones was realized. The process includes the palladium­(II)-promoted in situ formation of azomethine ylide and the following chiral N,N′-dioxide-Co­(II) complex-catalyzed regio-, diastereo-, and enantioselective [5+2] cycloaddition reaction. The desired spiro-tropanyl oxindoles were obtained in good yields with excellent dr and ee values. On the basis of the determination of the catalyst structure, a possible transition state model was proposed.

Diversified Transformations of Tetrahydroindolizines to Construct Chiral 3-Arylindolizines and Dicarbofunctionalized 1,5-Diketones

“…The sequential reaction for the synthesis of 3-arylindolizine atropisomers could further be simplified into a three-component one-pot process of enone A , ethyl diazoacetate and isonicotinonitrile via a bimetallic relay catalysis , (Scheme ). In the presence of a catalytic amount of Fe­(TPP)Cl (TPP = tetraphenylporphyrin), pyridinium ylide can be generated in situ via the reaction of iron-carbene species with isonicotinonitrile.…”

Stereoselective synthesis of fused-, spiro- and bridged heterocycles via cyclization of isoquinolinium salts: a recent update

“…57 In the presence of the chiral N,N′-dioxide/Mg(OTf ) 2 catalytic system, the An asymmetric tandem cycloisomerization and intramolecular [5 + 2] cycloaddition reaction of 2-ethynylphenyl substituted nitrones 141 with arylideneindolinones 103 by dual metallic relay catalysis was investigated by Feng's group (Scheme 40). 58 The reaction comprises the palladium(II)-promoted in situ formation of the isoquinolinium salt 142 followed by the chiral N,N′-dioxide-Co(II) complex-catalyzed regio-, diastereo-and enantioselective [5 + 2] cycloaddition process. The desired spiro-tropanyl oxindoles 143 containing four contiguous chiral centers were produced in good yields with excellent dr and ee values (up to 87% yield, 98% ee, >19 : 1 dr).…”

Stereoselective Synthesis of Azacycles Induced by Group 8–11 Late Transition Metals

“…The Feng group demonstrated a strategy to form diverse spiro-tropanyl oxindoles in the reaction of substituted nitrones and methyleneindolinones in a Pd-Co-catalyzed synthesis utilizing chiral N,N'-dioxide ligand 30. [40] In the tandem process Pd(OAc) 2 induces the formation of azomethine ylide int-8. It reacts further through intermolecular [5 + 2] cycloaddition promoted by the cobalt complex delivering the desired products in high yields with high enantio-and diastereoselectivities (Scheme 33).…”

“…[48] Again, Cu(MeCN) 4 PF 6 was used with ligand 38 and chiral NHC precatalyst 39 serving both as a Lewis base and a coordinating ligand. Kinetic resolutions taking place with isatinderived enals through [3 + 3] annulation gave spiro-oxindoles (40) and N-tosylaziridine derivatives (41) with high selectivities (Scheme 41). Two catalytic cycles are involved in product formation (Scheme 42).…”