Polyfluorinated biphenyls are interesting and promising substrates for many different applications. Unfortunately, all current methods for the syntheses of these compounds only work for a hand full of molecules or only in very special cases. Thus, many of these compounds are still inaccessible to date. Here we report a general strategy for the synthesis of a wide range of highly fluorinated biphenyls. In our studies we investigated crucial parameters, such as different phosphine ligands and the influence of various nucleophiles and electrophiles with different degrees of fluorination. These results extend the scope of the already very versatile Suzuki–Miyaura reaction toward the synthesis of very electron-poor products, making these more readily accessible. The presented methodology is scalable and versatile without the need for elaborate phosphine ligands or Pd-precatalysts.

Only a few studies on the use of halogen bonding in catalysis have been published so far. Herein, (benz)imidazolium-based halogen bond donors are used as catalysts in a Michael addition reaction. The most potent catalyst, a rigid atropisomer featuring two iodobenzimidazolium moieties, provided a rate acceleration versus a reference compound of ca. 50.

AbstractChalkogenbrücken sind bisher wenig erforschte nichtkovalente Wechselwirkungen, welche vergleichbar mit Halogenbrücken sind. Diese Arbeit beschreibt die erste Anwendung selenbasierter Chalkogenbrückendonoren als Lewis-Säuren in der organischen Synthese. Als Testreaktion zur Halogenidabstraktion diente die Solvolyse von Benzylhydrylbromid. Chalkogenbrückendonoren, welche auf einem Bis(benzimidazolium)-Grundgerüst basieren, ergaben Reaktionsbeschleunigungen in einer Größenordnung von 20–30 im Vergleich zur Hintergrundreaktion. Mehrere Vergleichsexperimente lieferten klare Hinweise darauf, dass die beobachtete Aktivierung auf Chalkogenbrücken zurückgeführt werden kann. Zudem sind die eingesetzten Chalkogenbrückendonoren dem entsprechenden bromierten Halogenbrückendonor in ihrer Aktivität überlegen.

Selenium compounds may form noncovalent interactions, so-called chalcogen bonds, with Lewis bases under certain conditions. In their Communication on page 12009 ff., S. M. Huber and co-workers show that such chalcogen bond donors activate a benchmark reaction. Control experiments with non-selenated reference compounds confirmed the crucial role of the selenium substituent. The corresponding brominated halogen bond donor was somewhat less active.

AbstractChalcogen bonding is a little explored noncovalent interaction similar to halogen bonding. This manuscript describes the first application of selenium-based chalcogen bond donors as Lewis acids in organic synthesis. To this end, the solvolysis of benzhydryl bromide served as a halide abstraction benchmark reaction. Chalcogen bond donors based on a bis(benzimidazolium) core provided rate accelerations relative to the background reactivity by a factor of 20–30. Several comparative experiments provide clear indications that the observed activation is due to chalcogen bonding. The performance of the chalcogen bond donors is superior to that of a related brominated halogen bond donor.

Selenverbindungen können nichtkovalente Wechselwirkungen (Chalkogenbrücken) mit Lewis-Basen eingehen. S. M. Huber und Mitarbeiter zeigen in ihrer Zuschrift auf S. 12172, dass solche Chalkogenbrückendonoren eine Testreaktion aktivieren. Kontrollexperimente mit nichtselenierten Referenzverbindungen bestätigen die entscheidende Rolle des Selensubstituenten. Der entsprechende bromierte Halogenbrückendonor war etwas weniger aktiv.

In contrast to hydrogen bonding, which is firmly established in organocatalysis, there are still very few applications of halogen bonding in this field. Herein, we present the first catalytic application of cationic halogen-bond donors in a halide abstraction reaction. First, halopyridinium-, haloimidazolium-, and halo-1,2,3-triazolium-based catalysts were systematically tested. In contrast to the pyridinium compounds, both the imidazolium and the triazolium salts showed promising potency. For the haloimidazolium-based organocatalysts, we could show that the catalytic activity is based on halogen bonding using, e.g., the chlorinated derivatives as reference compounds. On the basis of these studies, halobenzimidazolium organocatalysts were then investigated. Monodentate compounds featured the same trends as the corresponding imidazolium analogues but showed a stronger catalytic activity. In order to prepare bidentate versions which are preorganized for anion binding, a new class of rigid bis(halobenzimidazolium) compounds was synthesized and structurally characterized. The corresponding syn isomer showed unprecedented catalytic potency and could be used in as low as 0.5 mol % in the benchmark reaction of 1-chloroisochroman with a silyl enol ether. Calculations confirmed that the syn isomer may bind in a bidentate fashion to chloride. The respective anti isomer is less active and binds halides in a monodentate fashion. Kinetic investigations confirmed that the syn isomer led to a 20-fold rate acceleration compared to a neutral tridentate halogen-bond donor. The strength of the preorganized halogen-bond donor seems to approach the limit under the reaction conditions, as decomposition is observed in the presence of chloride in the same solvent at higher temperatures. Calorimetric titrations of the syn isomer with bromide confirmed the strong halogen-bond donor strength of the former (K ≈ 4 × 106 M–1, ΔG ≈ 38 kJ/mol).

Affinity materials based on halogen bonds turned out to be a powerful tool for the molecular recognition of acetone or related carbonyl compounds in the presence of ubiquitous protic molecules. The superior selectivity and sensitivity were found by the gravimetric detection of volatile organic compounds by quartz crystal microbalances.

A well-defined three-point interaction based solely on halogen bonding is presented. X-ray structural analyses of tridentate halogen bond donors (halogen-based Lewis acids) with a carefully chosen triamine illustrate the ideal geometric fit of the Lewis acidic axes of the former with the Lewis basic centers of the latter. Titration experiments reveal that the corresponding binding constant is about 3 orders of magnitude higher than that with a comparable monodentate amine. Other, less perfectly fitting multidentate amines also bind markedly weaker. Multipoint interactions like the one presented herein are the basis of molecular recognition, and we expect this principle to further establish halogen bonding as a reliable tool for solution-phase applications.

Using a prototypical Diels–Alder reaction as benchmark, we show that dicationic halogen-bond donors are capable of activating a neutral organic substrate. By various comparison experiments, the action of traces of acid or of other structural features of the halogen-bond donor not related to halogen bonding are excluded with high certainty.

Using a prototypical Diels–Alder reaction as benchmark, we show that dicationic halogen-bond donors are capable of activating a neutral organic substrate. By various comparison experiments, the action of traces of acid or of other structural features of the halogen-bond donor not related to halogen bonding are excluded with high certainty.

Affinity materials based on halogen bonds turned out to be a powerful tool for the molecular recognition of acetone or related carbonyl compounds in the presence of ubiquitous protic molecules. The superior selectivity and sensitivity were found by the gravimetric detection of volatile organic compounds by quartz crystal microbalances.