Asymmetric Synthesis of Spiropyrazolones by Sequential Organo‐ and Silver Catalysis

Abstract

A stereoselective one-pot synthesis of spiropyrazolones through an organocatalytic asymmetric Michael addition and a formal Conia-ene reaction has been developed. Depending on the nitroalkene, the 5-exo-dig-cyclization could be achieved by silver-catalyzed alkyne activation or by oxidation of the intermediate enolate. The mechanistic pathways have been investigated using computational chemistry and mechanistic experiments.

Enantioselective Tandem Cyclization of Alkyne‐Tethered Indoles Using Cooperative Silver(I)/Chiral Phosphoric Acid Catalysis

“…[4b,14] However,a sc arbophilic catalysts,s ilver species are understudied, mainly because of their significantly lower reactivity compared to that of related gold complexes. [15] Silver chiral phosphates have been reported as effective catalysts in asymmetric transformations. [16] However,t he origin of the enantioselectivity is unclear.We envisioned that silver-catalyzed tandem cyclization of alkyne-tethered indoles could be accelerated by the addition of aB rønsted acid, ac ommon means to accelerate gold catalysis.…”

Combining Organocatalysis and Lanthanide Catalysis: A Sequential One‐Pot Quadruple Reaction Sequence/Hetero‐Diels–Alder Asymmetric Synthesis of Functionalized Tricycles

“…[5] Moreover, common problems such as mutual catalyst deactivation and solvent compatibility have to be addressed to provide efficient sequential or relay catalysis. [6] Based on our previous work on organocatalyzed domino and sequential catalysis procedures, [7,8] we envisioned building the functionalized tricyclic polyethers A in ao ne-pot procedure (Scheme 1). This fused tricycle contains six stereogenic centers and resembles the framework of xylocarponoids Aa nd B.…”

Asymmetric Synthesis of Spiropyrazolones by Rhodium‐Catalyzed C(sp2)−H Functionalization/Annulation Reactions

“…In 2014, Lu and co‐workers developed an elegant phosphine‐catalyzed [4+1] annulation for the asymmetric synthesis of spiropyrazolones (Scheme a) . Later, Enders and co‐workers reported a highly efficient one‐pot enantioselective synthesis of spiropyrazolones by sequential organo‐ and silver catalysis (Scheme b) . Very recently, the same group also synthesized spiropyrazolones by NHC‐catalyzed asymmetric [3+2] annulation reactions (Scheme c) …”