Ruthenium Carbene-Mediated Construction of Strained Allenes via the Enyne Cross-Metathesis/Cyclopropanation of 1,6-Enynes

Abstract

Herein, we report on the unprecedented dimerization of 1,6-enynes using a commercially available ruthenium complex RuCl2(PPh3)3, which results in a series of bicyclo[3.1.0]­hexyl allene derivatives in moderate to excellent yields. Mechanistic investigation indicates that the in-situ-generated ruthenium vinylidene undergoes a site-selective metathesis process to provide allenyl ruthenium carbene, which can be intramolecularly trapped by the pendent C=C bond of enyne through a [2 + 2] cycloaddition/metal elimination process.

Base-Promoted Intramolecular Addition of Vinyl Cyclopropanecarboxamides to Access Conformationally Restricted Aza[3.1.0]bicycles

“…A literature review indicates that the metal-mediated cyclopropanation domino reaction of chain enynes is the most commonly used strategy for the construction of aza [3.1.0]bicycle derivatives in terms of scalability and substrate scope, which highly rely on the in situ-generated metal carbene species in the presence of Pd, Au, Ru, Co, Ni, and Rh salts as catalysts [20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Occasionally, the same conversion starting from enyne analogues has also been achieved by a photocatalytic pathway [34][35][36] as well as metal-free organocatalytic processes [37][38][39][40][41][42], mechanisms that are similar to the metal carbene A literature review indicates that the metal-mediated cyclopropanation domino reaction of chain enynes is the most commonly used strategy for the construction of aza [3.1.0]bicycle derivatives in terms of scalability and substrate scope, which highly rely on the in situgenerated metal carbene species in the presence of Pd, Au, Ru, Co, Ni, and Rh salts as catalysts [20][21][22][23][24][25][26][27][28][29][30][31][32][33]. Occasionally, the same conversion starting from enyne analogues has also been achieved by a photocatalytic pathway [34]…”

Ruthenium-Catalyzed Tandem Carbene/Alkyne Metathesis/N–H Insertion: Synthesis of Benzofused Six-Membered Azaheterocycles

“…In particular, the in situ generation of metal vinyl carbenes through carbene/alkyne metathesis (CAM) represents a versatile route for alkyne bifunctionalization . These intermediates are known to react with olefins to give dienes (Scheme a) or vinyl cyclopropa­(e)­nes (Scheme b) with nucleophiles to afford ylide intermediates (Scheme c) or with C–H bonds to give new C–C bonds (Scheme d). However, as far as we know, a tandem CAM process ending up in a N–H insertion reaction has never been reported (Scheme e).…”