Asymmetric Spirocyclization Enabled by Iridium and Brønsted Acid-Catalyzed Formal Reductive Cycloaddition

Abstract

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Palladium-Catalyzed Asymmetric Domino Heck/Carbocyclization/Suzuki Reaction: A Dearomatization of Nonactivated Naphthalenes

“…45 Very recently, elegant examples of Pd-catalyzed dearomative 1,4-difunctionalization of naphthalenes for the diastereoselective formation of 1,4-dihydronaphthalene-based spirocycles have emerged (Scheme 1b). 46,47 Based on our recent interest in the field, 35,48 we hypothesized that the β-naphthyl group might be activated by the key alkyl-Pd species in domino Heck reaction through an intramolecular coordination interaction (Scheme 1c). As such, an intramolecular dearomative migratory insertion of the nonactivated naphthyl ring into the alkyl-Pd bond might be achieved in certain cases.…”

endo-5-Norbornene-2,3-dimethanol-promoted asymmetric Heck/Suzuki cascade reaction of N-(2-bromophenyl)acrylamides

“…Recently, we developed monodentate-phosphoramidite-ligand-assisted palladium-catalyzed asymmetric Heck/carbonylation(carbocyclization)/Suzuki domino reactions of N -(2-bromophenyl)acrylamides for the synthesis of oxindoles (Scheme 1c). 11 In these reactions, the CO or naphthyl ring can inhibit transmetalation of the aryl-palladium complex by occupying coordination sites at the palladium center, 9 b ,11 reducing the negative impact of arylboronic acids on the enantioselectivity. Based on this observation, as well as the significance of the optically active oxindoles in natural products and pharmaceuticals (Fig.…”

“…However, the catalyst and solvent had little influence on the enantioselectivity. Next, various phosphoramidite ligands were screened, 11,14 but unfortunately, no improvement was achieved (see Table S2 in the ESI†). In this context, we speculated that an auxiliary ligand would suppress the transmetalation of the aryl-palladium complex, which might improve the efficiency of the asymmetric Heck/Suzuki reaction.…”

Highly Enantioselective Three-Component Povarov Reaction for Direct Construction of Azaspirocycles

“…Subsequently, aided by the CPA catalyst, nucleophilic addition of complex I gives intermediate II . The C–H⋯F hydrogen bonds formed between the substrate and the CF 3 group on OCF- CPA and between the reactants in the enantio-determining transition states may be crucial for the enantioselectivity of the reaction . Additionally, there may be π–π stacking between the reactants and cyclic enamide.…”

“…In this respect, although the threecomponent Povarov reaction has been used to construct C-2spiro tetrahydroquinolines (Scheme 1B), 4 the formation of chiral C-4-spiro tetrahydroquinolines via a Povarov reaction has rarely been developed. Based on our recent Ir/CPA cocatalyzed reductive spirocyclization of tertiary formanilides, 8 , we envision that the Povarov reaction of cyclic enamides might offer an enantioselective approach to forming azaspirocycles. 9 The C-4-spiro tetrahydroquinolines are valuable compounds in pharmacological studies.…”