Recent applications of ring-rearrangement metathesis in organic synthesis

Abstract

SummaryRing-rearrangement metathesis (RRM) involves multiple metathesis processes such as ring-opening metathesis (ROM)/ring-closing metathesis (RCM) in a one-pot operation to generate complex targets. RRM delivers complex frameworks that are difficult to assemble by conventional methods. The noteworthy point about this type of protocol is multi-bond formation and it is an atom economic process. In this review, we have covered literature that appeared during the last seven years (2008–2014).

Application of Fischer Indolization under Green Conditions using Deep Eutectic Solvents

“…A readily available dicyclopentadiene derivative 31 in the presence eutectic melt L‐(+)‐TA:DMU was converted to indole derivative 32 (79 %), which on further allylation followed by ring‐rearrangement metathesis (RRM) with the aid of G‐II catalyst gave indole‐fused polycyclic framework 33 . This indole derivative is generated by two atom‐economic reactions [40] such as FI and RRM as key steps (Scheme ).…”

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

“…The metathesis of norbornene derivatives having an alkene side-chain on the norbornene nucleus with Grubbs’ ruthenium catalysts has been extensively investigated. Generally the reaction proceeds through a domino process involving a ring opening of the norbornene nucleus and ring closing with the alkene side chains to produce ring rearrangement products (path 1, Scheme 1 ) [ 1 – 4 ]. This protocol has been employed by several groups [ 5 – 22 ] as well as by our group [ 23 – 33 ] for the synthesis of a variety of complex ring systems such as condensed, bridged and spirocycles difficult to obtain otherwise.…”

Syntheses of functionalised β-amino acids through ring-opening/cross metathesis

“…[25][26][27][28][29][30][31] In this field Ring-Rearrangement Metathesis (RRM) is especially useful, because it enables the formation of highly diverse unsaturated ring systems in a tandem fashion. [115][116] This reaction has many advantages over the usual stepwise approach, such as decreasing the number of steps, and minimizing the necessary reagent, solvent, and purification. These benefits were utilised in 1999 by Granja et al when "taxosteroid" containing the same [5,3,1] bicyclic ring system as taxol was synthesised via cascade dienyne metathesis reaction ( Fig.…”

“…Thanks to their high ring strain, bridged bicyclic frameworks such as norbornene and oxanorbornene provide a great possibility toward condensed 5-or 6-membered carbo-or heterocyclic systems. [115][116] Winkler et al utilised the benefits of the oxanorbornene framework for the syntheses of novel tri-and pentaheterocyclic ring systems via tandem metathesis. 138 Nadany and Mckendrick applied a similar pathway towards constrained bicyclic β-amino acid derivatives.…”

“…The driving force of these reactions is the formation of thermodynamically more stable molecules, which have lower ring strain than the bi-or tricyclic starting materials. [115][116] During these ring-opening processes mediated by Ru-alkylidene complexes, epimerisation was not observed, that is the stereochemistry of the starting β-lactams was conserved and determined the configuration of the chiral centres in the end-products. In Racemic monocyclic azetidinone (±)-131 with alkenyl moieties at the end of the alkyl chains was accessed through metathesis in dry CH 2 Cl 2 at 20 °C.…”