An Efficient Approach to the Securinega Alkaloids Empowered by Cooperative N‐Heterocyclic Carbene/Lewis Acid Catalysis

Abstract

Alles fügt sich zusammen: Die meisten der bisherigen Synthesen der Securinega‐Alkaloide erforderten längere Sequenzen zum Aufbau der verbrückenden Butenolid‐Domäne. Ein neuartiger Ansatz wird nun beschrieben, der mithilfe von N‐heterocyclischen Carbenen (NHCs) und Lewis‐Säuren die gesamte Domäne in einem einzigen Schritt aufbaut (siehe Schema). Die Synthese demonstriert, dass von Inalen abgeleitete Homoenolate als Nucleophile an intramolekularen Reaktionen teilnehmen können.

Aminomethylation of Enals through Carbene and Acid Cooperative Catalysis: Concise Access to β2‐Amino Acids

“…Notably, the combined use of NHC and either Lewis or Brønsted acid catalysts have recently been described by the groups of Scheidt, [15] Rovis, [16] You, [17] Xu, [18] Snyder, [19] Yao, [20] as well as our own group. [21] In the previous studies, the acid cocatalysts were used to improve the reaction yields or selectivities.…”

The Combination of Lewis Acid with N-Heterocyclic Carbene (NHC) Catalysis

“…Eventually, the tricyclic butenolide 36 product was isolated by slowly adding starting material into a suspension of catalyst and Ti(Oi-Pr)4 in toluene with the concentration of 0.03 M. Surprisingly, an exogenous base was not necessary, probably due to the Ti(Oi-Pr)4 was basic enough to facilitate the generation of the active carbene. In this dual catalysis strategy, ynals were used as nucleophilic homoenolate precursors to synthesize securinega alkaloids in only nine steps from commercial materials, which could provide opportunities for the further development of NHC-catalyzed reactions in total synthesis of fused bicyclic butenolide domains [50]. Scheme 8.…”

Kooperative Katalyse mit N‐heterocyclischen Carbenen

“…[30] Mit den Standardmethoden zur Optimierung,w ie z. [30] Mit den Standardmethoden zur Optimierung,w ie z.…”