Catalytic Synthesis of Potassium Acyltrifluoroborates (KATs) through Chemoselective Cross‐Coupling with a Bifunctional Reagent

Abstract

Potassium acyltrifluoroborates (KATs) are increasingly important functional groups,a nd general methods for their preparation are of great current interest. We report abifunctional iminium reagent bearing both atin nucleophile and at rifluoroborate,w hichw as applied in chemoselective Pd 0 -catalyzed Migita-Kosugi-Stille cross-coupling reactions owitha ryl and vinyl halides.T his method gives access to previously inaccessible aromatic and a,b-unsaturated acyltrifluoroborates,i ncluding precursors to amino-acid derived KATs.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Scheme 4. Analysis on the effect of copper. Scheme 5. Direct synthesis of a-aminotrifluoroborates from aryl iodides. Scheme 3. Synthesis of amino acid derived KATs by hydrogenation. Angewandte Chemie Communications

Diversity‐Oriented Synthesis of α‐Functionalized Acylborons and Borylated Heteroarenes by Nucleophilic Ring Opening of α‐Chloroepoxyboronates

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The ring-opening reactions of N-methyliminodiacetyl (MIDA) a-chloroepoxyboronates with different nucleophiles allowt he modular synthesis of ad iverse arrayo f organoboronates.T hese include seven types of a-functionalized acylboronates and seven types of borylated heteroarenes, some of which are difficult-to-access products using alternative methods.T he common synthons, a-chloroepoxyboronates, could be viably synthesized by at wo-step procedure from the corresponding alkenyl MIDAb oronates.M ild reaction conditions,g ood functional-group tolerance,a nd generally good efficiency were observed. [8] By taking advantage of the stability of boronates with sp 3 -hybridized B, several conceptually new routes to acylborons based on the late-stage functional-group manipulation of ab oron-containing organic precursor were also developed (Scheme 1a). [1] Their synthetic value,e xemplified by their involvement in chemoselective amide formation, [1b,d,2] as well as in the synthesis of borylated heterocycles [3] and a-aminoboronic acids, [4] have rendered them appealing targets in organic synthesis.T wo classic approaches toward acylboron preparation include the reaction of ab oryl metal species [5] with ac arbonyl electrophile,a nd the reaction of an acyl anion equivalent (generated under strong basic conditions) with an electrophilic boryl reagent.

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“…[2a, 6] An elegant alternative to these approaches is the Bode acylboron synthesis,wherein an electrophilic zwitterionic boronate reagent is used to react with organometallic reagents to afford potassium acyltrifluroborates (KATs). [8] By taking advantage of the stability of boronates with sp 3 -hybridized B, several conceptually new routes to acylborons based on the late-stage functional-group manipulation of ab oron-containing organic precursor were also developed (Scheme 1a). Very recently,B ode invented an ew trifluoroborate iminium reagent bearing at in moiety which could undergo Stille coupling with aryl-or vinylhalides to provide KATs.…”

Katalytische Synthese von Kaliumacyltrifluoroboraten mithilfe chemoselektiver Kreuzkupplung eines bifunktionalen Reagenzes

“…Dieser Tr end bestätigt die Beobachtungen von Jutand und NØgri, die folgende Reaktivitätstrends festgestellt haben:V inyl-OTf @ Vinyl-Br @ Ar-Br sowie Vinyl-OTf @ Ar-OTf, wenn koordinierende Lçsungsmittel wie DMF verwendet werden. [21] Thermische Ellipsoide sind mit einer Wahrscheinlichkait von 50 %dargestellt. Wiee rwartet wurde die Doppelbindung durch die elektronenziehende KAT-Gruppe aktiviert und reagierte daher leicht in einer konjugierten Addition mit Wasser oder Aminen, was die Ausbeute fürweniger substituierte Derivate oder Verbindungen mit elektronenarmen aromatischen Gruppen verringerte.Nichtsdestotrotz konnte eine Reihe von interessanten KATs zum ersten Mal isoliert werden.…”

“…Wire rhielten die erste Molekülstruktur eines ungesättigten KATi mK ristall durch einen Einkristall von 7g. [21] Das Moleküll iegt in der s-trans-Konformation vor,u nd die Länge der C2-C3-Doppelbindung beträgt 1.334 ,w as mit den bisher publizierten KAT-Kristallstrukturen gut übereinstimmt. [4a] Die Hydrierung der Enamine 7h und 7i ergab die Substrate 8h und 8i,d ie den Aminosäure-KAT-Analogen in [f ]ORTEP-Darstellung von 7g ist dargestellt.…”

Diversity‐Oriented Synthesis of α‐Functionalized Acylborons and Borylated Heteroarenes by Nucleophilic Ring Opening of α‐Chloroepoxyboronates

“…Very recently,B ode invented an ew trifluoroborate iminium reagent bearing at in moiety which could undergo Stille coupling with aryl-or vinylhalides to provide KATs. [8] By taking advantage of the stability of boronates with sp 3 -hybridized B, several conceptually new routes to acylborons based on the late-stage functional-group manipulation of ab oron-containing organic precursor were also developed (Scheme 1a). In this regard, the groups of Yudin and Ito reported the oxidation reaction of a-hydroxy boronates into acylboron compounds.T he key a-hydroxy boronate intermediates were prepared by Barton radical decarboxylation of MIDA a-borylcarboxylic acid, [3a] ringopening of 2-boryl oxirane, [3b] dihydroxylation of alkenyl boronates, [3c] oxidation of unsymmetrical geminal diborylalkanes, [9] and copper(I)-catalyzed borylation of aldehydes.…”