Ruthenium-Catalyzed Cycloadditions to Form Five-, Six-, and Seven-Membered Rings

Abstract

Ruthenium-catalyzed cycloadditions to form five-, six-, and seven-membered rings are summarized, including applications in natural product total synthesis. Content is organized by ring size and reaction type. Coverage is limited to processes that involve formation of at least one C–C bond. Processes that are stoichiometric in ruthenium or exploit ruthenium as a Lewis acid (without intervention of organometallic intermediates), ring formations that occur through dehydrogenative condensation-reduction, σ-bond activation-initiated annulations that do not result in net reduction of bond multiplicity, and photochemically promoted ruthenium-catalyzed cycloadditions are not covered.

Understanding Halide Counterion Effects in Enantioselective Ruthenium-Catalyzed Carbonyl (α-Aryl)allylation: Alkynes as Latent Allenes and Trifluoroethanol-Enhanced Turnover in The Conversion of Ethanol to Higher Alcohols via Hydrogen Auto-transfer

“…Specifically, using iridium catalysts, methanol was coupled to dienes and allenes to form primary neopentyl alcohols, and ethanol was coupled to allylic acetates to form branched secondary homoallylic alcohols. As reflected by annual production rates, ruthenium (30 tons/yr) is more abundant than iridium (3 tons/yr), yet the use of ruthenium catalysts in asymmetric conversion of methanol or ethanol to higher alcohols is unknown . Recent advances in our laboratory on ruthenium-catalyzed alkyne−alcohol carbonyl reductive coupling via hydrogen auto-transfer support the feasibility of converting ethanol and 1-aryl-1-propynes to higher enantiomerically enriched alcohols. ,, However, our previously reported catalytic system was inefficient, requiring high loadings of ruthenium (10 mol%)…”

The synthesis of seven- and eight-membered rings by radical strategies

“…Furthermore, the preparation of seven- and eight-membered rings from acyclic precursors or some high-energy unsaturated compounds (such as alkenes, alkynes, or small cyclic compounds) is efficiently realized by metal-mediated cyclization because of the properties of metal coordination. 9 Nevertheless, considering the economy and environmental friendliness in green chemistry, the synthesis of seven- and eight-membered rings requires more flexible, practical, and efficient strategies.…”

Facile Generation of Fused Seven-Membered Polycyclic Systems via Ring Expansion and Application to the Total Synthesis of Sesquiterpenoids

“…A scarce number of catalytic methods are available to overcome the unfavorable enthalpic and entropic challenges of such organic reactions. [17][18] Over the past decades, a vast array of approaches have been devoted to developing effective strategies for synthesizing the benzocycloheptane motif and other fused bicyclo[m.n.0] ring systems, [19][20][21][22][23][24][25][26][27][28] including intramolecular cycloadditions, transition-metal catalyzed intermolecular [5+2] annulation, and other methods (Scheme 1a). [29][30][31][32] Very recently, Dong and co-workers reported a straightforward and distinct approach for accessing benzene-fused scaffolds between 1-indanones and ethylene gas or internal alkynes via intermolecular reactions (Scheme 1b).…”