Many boronic acids, including 2-heterocyclic, vinyl, and cyclopropyl derivatives, are inherently unstable, which can limit their benchtop storage and/or efficient cross-coupling. We herein report the first general solution to this problem: in situ slow release of unstable boronic acids from the corresponding air-stable MIDA boronates. This remarkably general approach has transformed all three classes of these unstable boronic acids into shelf-stable and highly effective building blocks for cross-coupling with a wide range of aryl and heteroaryl chlorides.
[Show abstract][Hide abstract] ABSTRACT: Repetition does not hurt! New strategies for the modulation of the reactivity of difunctional building blocks are discussed, allowing the palladium-catalyzed controlled iterative cross-coupling and, thus, the efficient formation of complex molecules of defined size and structure (see scheme). As in peptide synthesis, this development will enable the automation of these reactions. M(PG)=protected metal, M(act)=metal.
[Show abstract][Hide abstract] ABSTRACT: Wiederholung schadet nicht! Neue Strategien für die Modulierung der Reaktivität von difunktionellen Bausteinen ermöglichen die Pd-katalysierte, kontrollierte iterative Kreuzkupplung und dadurch die effiziente Synthese komplexer Moleküle von definierter Größe und Struktur (siehe Schema). Diese Arbeiten sollten zur Automatisierung dieser Kreuzkupplungen analog zu der Peptidsynthese führen.
[Show abstract][Hide abstract] ABSTRACT: A catalyst system for the Suzuki-Miyaura cross-coupling reactions of aryl and vinyl tosylates and mesylates has been developed. This catalyst displays excellent functional group tolerance and allows the coupling of heteroarylboronic acids with aryl tosylates and mesylates to be performed in high yields. Moreover, reactions employing alkylboronic acids, as well as heteroaryl, vinyl, and allylic pinacol boronate esters, were conducted with high efficiencies.
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