Asymmetric Catalytic Formal 1, 4‐Allylation of β, γ‐Unsaturated α‐Ketoesters: Allylboration/Oxy‐Cope Rearrangement. (12th July 2019)

• Record Type: Journal Article
• Authors: Tang, Qiong; Fu, Kai; Ruan, Peiran; Dong, Shunxi; Su, Zhishan; Liu, Xiaohua; Feng, Xiaoming
• Is Part Of: Angewandte Chemie. Volume 131:Number 34(2019)
• Page Start: 11972
• Page End: 11977
• Publication Date: 2019-07-12
• Subjects: Allylverbindungen -- Asymmetrische Katalyse -- Nickel -- Reaktionsmechanismen -- Umlagerungen; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201905533
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: A highly enantioselective formal conjugate allyl addition of allylboronic acids to β, γ‐unsaturated α‐ketoesters has been realized by employing a chiral Ni II / N, N ′‐dioxide complex as the catalyst. This transformation proceeds by an allylboration/oxy‐Cope rearrangement sequence, providing a facile and rapid route to γ‐allyl‐α‐ketoesters with moderate to good yields (65–92 %) and excellent ee values (90–99 % ee ). The isolation of 1, 2‐allylboration products provided insight into the mechanism of the subsequent oxy‐Cope rearrangement reaction: substrate‐induced chiral transfer and a chiral Lewis acid accelerated process. Based on the experimental investigations and DFT calculations, a rare boatlike transition‐state model is proposed as the origin of high chirality transfer during the oxy‐Cope rearrangement. Abstract : Eine hocheffiziente Sequenz aus katalytischer asymmetrischer Allylborierung und Oxy‐Cope‐Umlagerung von β, γ‐ungesättigten α‐Ketoestern mit Allylboronsäuren gelang mithilfe eines Ni II / N, N ′‐Dioxid‐Komplexes als Katalysator. Diese Transformation bietet eine leichte und schnelle Route zu chiralen γ‐Allyl‐α‐ketoestern als Produkten einer formalen konjugierten Allyladdition.