Asymmetric Counteranion-Directed Lewis Acid Catalysis with α,β-Unsaturated Esters

The fundamental substrate class of α,β-unsaturated esters offers extraordinary synthetic potential for carbon-carbon bond forming reactions, such as cycloadditions and conjugate additions, however is rarely applied in asymmetric catalysis due to its relatively low reactivity. By expanding the concept of silylium-ACDC to non-silicon transfer reactions (catalytic in silicon), the introduction of chiral C–H acids into asymmetric catalysis and the identification of two distinct families of imidodiphosphorimidates (IDPi) catalysts, we could report unprecedented highly enantio- and diastereoselective Diels–Alder and Mukaiyama–Michael reactions of simple α,β-unsaturated methyl esters. The developed extremely active chiral Lewis acids represent the most efficient catalysts for asymmetric Diels–Alder reactions of α,β-unsaturated esters to date while tolerating a very broad scope on a variable scale with catalyst loadings as low as 0.1 mol%. Kurzzusammenfassung Die grundlegende Substratklasse der α,β-ungesättigten Ester bietet herausragendes synthetisches Potential für Kohlenstoff-Kohlenstoff Bindungsknüpfungsreaktionen wie Cycloadditionen und konjugierte Additionen, wird jedoch in der asymmetrischen Katalyse aufgrund ihrer relativ niedrigen Reaktivität kaum angewendet. Durch die Erweiterung des Konzept der asymmetrischen Gegenanion-vermittelten Katalyse mit Silylium-Equivalenten (silylium-ACDC) hin zu Reaktionen mit katalytischen Mengen Silizium, die Einführung von chiralen C–H Säuren in die asymmetrische Katalyse und die Identifizierung von zwei separaten Familien an Imidodiphosphorimidat-Katalysatoren, konnten bisher beispiellose hoch enantio- und diastereoselektive Diels–Alder und Mukaiyama–Michael Reaktionen beschrieben werden. Die entwickelten chiralen Lewis Säuren stellen die bis dato effizientesten Katalysatoren für asymmetrische Diels–Alder Reaktionen von α,β-ungesättigten Estern dar und tolerieren trotzdem ein sehr breites Substratspektrum auf verschiedenen Reaktionsmaßstäben mit sehr niedrigen Katalysatorbeladungen von bis zu 0.1 mol%

The Catalytic Asymmetric Mukaiyama–Michael Reaction of Silyl Ketene Acetals with α,β-Unsaturated Methyl Esters

α,β-Unsaturated esters are readily available but challenging substrates to activate in asymmetric catalysis. We now describe an efficient, general, and highly enantioselective Mukaiyama–Michael reaction of silyl ketene acetals with α,β-unsaturated methyl esters that is catalyzed by a silylium imidodiphosphorimidate (IDPi) Lewis acid

Asymmetric Counteranion-Directed Lewis Acid Catalysis with α,β-Unsaturated Esters

The fundamental substrate class of α,β-unsaturated esters offers extraordinary synthetic potential for carbon-carbon bond forming reactions, such as cycloadditions and conjugate additions, however is rarely applied in asymmetric catalysis due to its relatively low reactivity. By expanding the concept of silylium-ACDC to non-silicon transfer reactions (catalytic in silicon), the introduction of chiral C–H acids into asymmetric catalysis and the identification of two distinct families of imidodiphosphorimidates (IDPi) catalysts, we could report unprecedented highly enantio- and diastereoselective Diels–Alder and Mukaiyama– Michael reactions of simple α,β-unsaturated methyl esters. The developed extremely active chiral Lewis acids represent the most efficient catalysts for asymmetric Diels–Alder reactions of α,β-unsaturated esters to date while tolerating a very broad scope on a variable scale with catalyst loadings as low as 0.1 mol%

Straightforward Pentafluorosulfanylation for Molecular Design

Pentafluorosulfanylation is a powerful boost of molecular properties for many applications. In order to leverage its full potential, a direct and high-yielding synthetic strategy is in great demand. We report here how the discovery of a direct pentafluorosulfanylation of thiolated arenes led to a generalized synthetic approach toward aryl– and heteroaryl pentafluorosulfanyl (SF5) compounds from various common building blocks. The combination of onium halides with silver(II) fluoride (AgF2) provided drastically enhanced oxidative fluorination conditions that enabled the single-step conversion of various thiophenol derivatives to SF5-compounds in high yields and broad scope. The particularly high reaction rate is accounted to an onium fluoroargentate(II)-mediated fluorination mechanism. The recycling potential of inorganic silver byproducts furthermore offers an avenue into industrial-scale production

Asymmetric Lewis acid organocatalysis of the Diels-Alder reaction by a silylated C-H acid

Silylium ion equivalents have shown promise as Lewis acid catalysts for a range of important C-C bond-forming reactions. Here we describe chiral C-H acids that upon in situ silylation, generate silylium-carbanion pairs, which are extremely active Lewis acid catalysts for enantioselective Diels-Alder reactions of cinnamates with cyclopentadiene. Enantiomeric ratios of up to 97: 3 and diastereomeric ratios of more than 20: 1 are observed across a diverse set of substitution patterns with 1 mole percent (mol %) of C-H acid catalyst and 10 mol % of a silylating reagent. The results show promise for broad applications of such C-H acid-derived silylium ion equivalents in asymmetric Lewis acid catalysis