Asymmetric, Three‐Component, One‐Pot Synthesis of Spiropyrazolones and 2, 5‐Chromenediones from Aldol Condensation/NHC‐Catalyzed Annulation Reactions. Issue 15 (18th February 2016)

• Record Type: Journal Article
• Authors: Wang, Lei; Li, Sun; Chauhan, Pankaj; Hack, Daniel; Philipps, Arne R.; Puttreddy, Rakesh; Rissanen, Kari; Raabe, Gerhard; Enders, Dieter
• Is Part Of: Chemistry. Volume 22:Issue 15(2016)
• Page Start: 5123
• Page End: 5127
• Publication Date: 2016-02-18
• Subjects: asymmetric synthesis -- chromenedione -- multicomponent reaction -- N-heterocyclic carbene -- spiropyrazolone; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201600515
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α, β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good to excellent stereoselectivities. Alternatively, starting from cyclic 1, 3‐diketones, 2, 5‐chromenediones are available through [2+4] annulation. Abstract : Aldol/NHC cooperation : Three‐component, one‐pot, aldol condensation/N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation reations have been developed to steroselectively assemble spiropyrazolones through an azolium homoenolate pathway. By simply replacing the pyrazolones by diketones, highly substituted 2, 5‐chromenediones are obtained through a [2+4] annulation reaction by an azolium enolate route.