Rhodium-Catalyzed Domino Hydroformylation/Double-Cyclization Reaction of Arylacetylenecarboxamides: Diastereoselectivity Studies and Application in the Synthesis of 1-Azabicyclo[x.y.0]alkanes

An aza-Robinson Annulation Strategy for the Synthesis of Fused Bicyclic Amides: Synthesis of (±)-Coniceine and Quinolizidine

An aza-Robinson annulation strategy is described using a NaOEt-catalyzed conjugate addition of cyclic imides onto vinyl ketones, followed by a TfOH-mediated intramolecular aldol condensation to afford densely functionalized fused bicyclic amides. The potential use of these amides in the synthesis of alkaloids is demonstrated by the sequential conversion of appropriate precursors to (±)-coniceine and quinolizidine in two additional steps, thus allowing their preparation in overall 40 and 44% yields, respectively.

Activating Imides with Triflic Acid: A General Intramolecular Aldol Condensation Strategy Toward Indolizidine, Quinolizidine, and Valmerin Alkaloids

A simple, inexpensive, step economic, and highly modular synthetic strategy to access izidine alkaloids is described. The key step is a TfOH-promoted intramolecular aldol condensation between enol and cyclic imide moieties. This cyclization strategy can be employed within an aza-Robinson annulation framework and represents a general tool to build fused bicyclic amines. To illustrate the power of this method, we describe the preparation of (±)-coniceine, (±)-quinolizidine, (±)-tashiromine, (±)-epilupinine, and the core of (±)-valmerins.