Gold‐Catalyzed [3+2]/Retro‐[3+2]/[3+2] Cycloaddition Cascade Reaction of N‐Alkoxyazomethine Ylides

• Published in: Angewandte Chemie 2017-02, Vol.129 (9), p.2509-2512
• Main Authors: Sugita, Shoichi, Takeda, Norihiko, Tohnai, Norimitsu, Miyata, Mikiji, Miyata, Okiko, Ueda, Masafumi
• Format: Article
• Language: eng ; ger
• Subjects: Azomethin-Ylide; Bonding; Carbon-carbon composites; Cascade chemical reactions; Chemical bonds; Chemical synthesis; Chemistry; Cleavage; Cycloaddition; Cycloadditionen; Gold; Heterocyclen; Hydrogen bonds; Synthesemethoden; Synthesis; Synthesis (chemistry)
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201611816

A novel cascade reaction has been developed for the synthesis of 2,6‐methanopyrrolo[1,2‐b]isoxazoles based on the gold‐catalyzed generation of an N‐allyloxyazomethine ylide. This reaction involves sequential [3+2]/retro‐[3+2]/[3+2] cycloaddition reactions, thus providing facile access to fused and bridged heterocycles which would be otherwise difficult to prepare using existing synthetic methods. Notably, this reaction allows the efficient construction of three C−C bonds, one C−O bond, one C−N bond and one C−H bond, as well as the cleavage of one C−C bond, one C−O bond and one C−H bond in a single operation. The intermolecular cycloaddition of an N‐allyloxyazomethine ylide and the subsequent application of the product to the synthesis of tropenol is also described. Retro‐Chic: In einer Reaktionskaskade werden unter Goldkatalyse N‐Allyloxyazomethin‐Ylide erzeugt, die über eine [3+2]‐Retro‐[3+2]‐[3+2]‐Cycloadditionssequenz überbrückte Isoxazolidine liefern. Bei diesem Prozess werden drei C‐C‐Bindungen, eine C‐O‐Bindung, eine C‐N‐Bindung und eine C‐H‐Bindung geknüpft, während eine C‐C‐Bindung, eine C‐O‐Bindung und eine C‐H‐Bindung gespalten werden.