Catalytic Regioselective Isomerization of 2, 2‐Disubstituted Oxetanes to Homoallylic Alcohols. (12th March 2020)

• Record Type: Journal Article
• Authors: Cabré, Albert; Rafael, Sergi; Sciortino, Giuseppe; Ujaque, Gregori; Verdaguer, Xavier; Lledós, Agustí; Riera, Antoni
• Is Part Of: Angewandte Chemie. Volume 132:Number 19(2020)
• Page Start: 7591
• Page End: 7597
• Publication Date: 2020-03-12
• Subjects: Allylverbindungen -- Asymmetrische Katalyse -- Bor -- Hydrierung -- Isomerisierung; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201915772
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The selective isomerization of strained heterocyclic compounds is an important tool in organic synthesis. An unprecedented regioselective isomerization of 2, 2‐disubstituted oxetanes into homoallylic alcohols is described. The use of tris(pentafluorophenyl)borane (B(C6 F5 )3 ), a commercially available Lewis acid was key to obtaining good yields and selectivities since other Lewis acids afforded mixtures of isomers and substantial polymerization. The reaction took place under exceptionally mild reaction conditions and very low catalyst loading (0.5 mol %). DFT calculations disclose the mechanistic features of the isomerization and account for the high selectivity displayed by the B(C6 F5 )3 catalyst. The synthetic applicability of the new reaction is demonstrated by the preparation of γ‐chiral alcohols using iridium‐catalyzed asymmetric hydrogenation. Abstract : Ringspannung : 2, 2‐Disubstituierte Oxetane, die leicht durch eine doppelte Corey‐Chaykovsky‐Reaktion zugänglich sind, isomerisieren zu homoallylischen Alkoholen mit B(C6 F5 )3 als Katalysator. DFT‐Rechnungen belegen eine intramolekulare Protonenmigration als Schlüsselschritt. Das Synthesepotenzial wurde durch die Herstellung mehrerer chiraler disubstituierter Alkohole mittels asymmetrischer Hydrierung demonstriert.