Enantioselective Construction of Bridged Multicyclic Skeletons: Intermolecular [2+2+2] Cycloaddition/Intramolecular Diels–Alder Reaction Cascade

Abstract

Brückenbau: Ein kationischer Rhodium(I)‐Ligand‐Komplex katalysiert die Titelreaktion zwischen Alkinen und 1,5‐Dienen mit einer Amidbrücke, bei der verbrückte Polycyclen mit hoher Chemo‐, Regio‐ und Enantioselektivität entstehen (siehe Schema; Bn=Benzyl).

Carbon‐Nanotubes‐Supported Pd Nanoparticles for Alcohol Oxidations in Fuel Cells: Effect of Number of Nanotube Walls on Activity

“…In addition, regioselectivities are insufficient in some cases. Recently, our research group accomplished the rhodium‐catalyzed enantioselective cross‐cyclotrimerization of electron‐rich terminal alkynes, acetylenedicarboxylates, and enamides, however the product yields were low to moderate 7. 8 Herein, we disclose the unprecedented highly chemo‐, regio‐, and enantioselective catalytic cross‐cyclotrimerization of two different alkynes with an alkene.…”

Renoprotective effect of Tanshinone IIA, an active component of Salvia miltiorrhiza, on rats with chronic kidney disease

“…As an example, Tanaka et al. have recently reported an efficient enantioselective domino intermolecular [2+2+2] cycloaddition–intramolecular Diels–Alder cycloaddition reaction occurring between 1,6‐diynes 81a – d and amide‐linked 1,5‐dienes 82a – c bearing two sterically and/or electronically different alkene units 54. This domino reaction was induced by a cationic rhodium(I)/( R )‐Segphos complex and provided the corresponding amides 83a – g in moderate to high yields and excellent enantioselectivities of up to 99% ee , as shown in Scheme .…”

Rhodium‐Catalyzed [3+2+2] and [2+2+2] Cycloadditions of Two Alkynes with Cyclopropylideneacetamides

“…[2f, 5] Importantly,both cycloheptane [6] and spiro-cyclohexane [7] skeletons are frequently found in biologically active natural products.T herefore,t heir selective syntheses are important targets for organic synthesis.H erein, we have applied ac ationic rhodium(I)/biaryl bis(phosphine) catalyst, which is known to be ah ighly active catalyst for the [2+ +2+ +2] cycloaddition, [8,9] to the cycloaddition reactions involving cyclopropylidene compounds. [11] Therefore,w e first examined the reaction of the 1,6-diyne 1a and N-methyl-N-phenylcyclopropylidene-acetamide (2a)inthe presence of cationic rhodium(I)/bisphosphine complexes,a ss hown in Table 1. [11] Therefore,w e first examined the reaction of the 1,6-diyne 1a and N-methyl-N-phenylcyclopropylidene-acetamide (2a)inthe presence of cationic rhodium(I)/bisphosphine complexes,a ss hown in Table 1.…”