Gold(I)‐Catalyzed Enantioselective Synthesis of Pyrazolidines, Isoxazolidines, and Tetrahydrooxazines

Abstract

Auf das Substrat abgestimmt: Chirale Liganden L* und chirale Anionen, wie in (S)‐TriP Ag, wurden in Gold(I)‐katalysierten enantioselektiven intramolekularen Additionen von Hydrazinen und Hydroxylaminen an Allene eingesetzt. Diese komplementären Ansätze ebnen den Weg zu den Titelverbindungen in chiraler Form. PNB=para‐Nitrobenzoyl.

Enantioselective Rhodium‐Catalyzed Synthesis of Branched Allylic Amines by Intermolecular Hydroamination of Terminal Allenes

“…[4] Despite extensive effort, efficient methods for catalytic enantioselective intermolecular hydroamination are rare. [5] Although the enantioselective intermolecular hydroamination of allenes would be an efficient method for the synthesis of a-chiral allylic amines, [6,7] only one example has been reported, which requires internal allenes, has a limited scope, and provides only moderate levels of enantioselectivity (Scheme 1 a). [8,9] To date, the enantioselective intermolecular hydroamination of mono-substituted allenes has not been reported, owing to the propensity of many hydroamination catalysts to form achiral products (either imines or linear allylic amines) from such substrates (Scheme 1 b).…”

Inter‐ and Intramolecular Hydroamination of Unactivated Alkenes Catalysed by a Combination of Copper and Silver Salts: The Unveiling of a Brønstedt Acid Catalysis

“…Other chlorinated solvents were also suitable (entries 3,4,7,8) with the exception of chloroform. Toluene (entries 1 and 2) and 1,4-dioxane (entry 13) led to good conversions as well.…”

“…[3h] With the exception of 2-vinylpyridine leading to the linear "anti-Markovnikov" product (entry 6), conjugated olefins (e.g., styrene, 1,3-cyclohexadiene, 4-vinylpyridine) did not react (entries [8][9][10].…”

“…The usefulness of gold was pointed out on alkene [7] and allene [8] substrates for both intra-and intermolecular hydroamination reactions as well as for diaminations. Silver was recently shown to be active for the hydroamination of alkenes.…”

Hoch enantioselektive Overman‐Umlagerung durch asymmetrische Gegenanionen‐vermittelte Palladium‐Katalyse

“…In Anbetracht des gut etablierten Mechanismus dieser durch eine Pd II -p-Lewis-Säure vermittelten Cyclisierung [3,4] sahen wir hier eine Einsatzmçglichkeit für unser Konzept der asymmetrischen Gegenanionen-vermittelten Katalyse (ACDC). [5][6][7][8][9][10] Vor kurzem haben wir diese Strategie erfolgreich bei mechanistisch verwandten Pd-katalysierten Tsuji-Trost-Reaktionen eingesetzt. [8] Gegebenenfalls kçnnte die ACDC-Strategie zur Entwicklung von vereinfachten, aber dennoch hoch enantioselektiven Katalysatoren verwendet werden.…”