Enantiodifferentiating endo‐Selective Oxylactonization of ortho‐Alk‐1‐enylbenzoate with a Lactate‐Derived Aryl‐λ³‐Iodane

Abstract

Erfolg mit Lactat: Die asymmetrische Synthese von 3‐Alkyl‐4‐oxyisochroman‐1‐on gelingt durch die Titelreaktion mit einer Serie optisch aktiver hypervalenter Iod(III)‐Reagentien, die aus Lactat oder Valin als chiraler Quelle präpariert wurden. Die Oxylactonisierung ist hoch regio‐, diastereo‐ und enantioselektiv.

Enantioselective Oxidation of Alkenylbenzoates Catalyzed by Chiral Hypervalent Iodine(III) To Yield 4‐Hydroxyisochroman‐1‐ones

“…Despite the simple structures and promising biological properties of the oxyisochromanones, the synthesis of this class of natural products remains a significant challenge, and only a few successful total syntheses have been reported. [13] Using lactate-based chiral hypervalent iodine reagents led to high levels of enantioselectivity in the oxylactonization of ortho-alkenylbenzoate 1. However, an enantioselective transformation has not been achieved using either of these strategies.…”

“…However, an enantioselective transformation has not been achieved using either of these strategies. [9,13] Scheme 1. [13] Using lactate-based chiral hypervalent iodine reagents led to high levels of enantioselectivity in the oxylactonization of ortho-alkenylbenzoate 1.…”

“…Thus, the catalytic route provides simpler and more efficient protocols than traditional reactions based on a stoichiometric amount of the hypervalent iodine reagent. [13,23] If the structural requirements for a successful chiral catalyst are clarified, the catalytic system may be extended to various reactions, including those that have already been reported using stoichiometric asymmetric induction. In the case of the reaction of alkenylbenzoate substrate 1, as illustrated in Scheme 2, the direct oxidation reaction must yield by-products (e.g., Scheme 4).…”

Diastereoselective IBX Oxidative Dearomatization of Phenols by Remote Induction: Towards the Epicocconone Core Framework

“…Among them, IBX (2-iodoxybenzoic acid, l5-iodane) is used in numerous classical oxidation reactions, but a particular case is the oxidative dearomatization, which almost only hypervalent iodine reagents can perform (less used reagents are: PbA C H T U N G T R E N N U N G (OAc) 4 , Ph 2 Se 2 O 3 , NaIO 4 and Cu I /O 2 ). Although the mechanism of oxidative dearomatization is still unclear and depends on the oxidant, hypervalent iodine reagents are nowadays commonly used.…”

Flexible stereoselektive Funktionalisierung von Ketonen durch Umpolung mit hypervalenten Iodreagentien

“…Chirale hypervalenten Iodverbindungen auf Milchsäurebasis wurden von Fujita [27] und Ishihara [28] entwickelt und wurden bereits für hocheffiziente Diaminierungen, [29,30] Aminofluorierungen, [31] Aminohydroxylierungen [32] und für Umlagerungsreaktionen verwendet. [33] Während Verfahren zur stereoselektiven a-Hydroxylierungen existieren, [34] stellt die direkte und stereoselektive Einführung einer einfachen Aminogruppe neben Ketonen eine neue Synthesestrategien dar, die den Aufbau wichtiger Strukturen gestattet.…”