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Catalytic Asymmetric Friedel–Crafts Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The enantioselective Friedel–Crafts fluoroalkylation of indoles 4 by employing chiral phosphoric acid C3 has been described by Lin and Xiao (Scheme 5.11).30 Chiral phosphoric acid C3 assists the reaction as a bifunctional catalyst and activates the nucleophile as well as the electrophile by hydrogen bonding. It was found that the absence of a hydrogen atom on the nitrogen atom or the presence of a methyl group at the 2-position of indole 4 considerably decreases the enantioselectivity as the N–H moiety is involved in hydrogen bonding.
Synthesis of six- and seven-membered and larger heterocylces using Au and Ag catalysts
Published in Inorganic and Nano-Metal Chemistry, 2018
Povarov[16g] reactions occurred with chiral phosphoric-acid catalyst. For hydroamination/transfer hydrogenation of alkynes We[16h] and Che and Liu[16i] have respectively reported that Bronsted acid and Au complexes worked compatibly in relay catalysis. A three-component enantioselective [4 + 2] cycloaddition reaction of aldehyde, 2-(2-propynyl)aniline derivatives, and enecarbamates occurred with chiral phosphoric acid and a subsequently a catalytic intramolecular hydroamination proceeded with Au(I) complex (Scheme 10). This is a unique approach for the generation of structurally complex and diverse julolidine derivatives in high optical purity.[16j] Bronsted acid acted as chiral catalyst for asymmetric cycloaddition and also assisted Au complex catalyzed hydroamination. Kinetic studies have demonstrated that phosphoric acid acted as chiral catalyst for Povarov reaction as well as assisted the hydroamination reaction with Au complex.[16k]