Ring Rearrangement Metathesis in 7-Oxabicyclo[2.2.1]heptene (7-Oxanorbornene) Derivatives. Some Applications in Natural Product Chemistry

Abstract

Metathesis reactions is firmly established as a valuable synthetic tool in organic chemistry, clearly comparable with the venerable Diels-Alder and Wittig reactions and, more recently, with the metal-catalyzed cross-coupling reactions. Metathesis reactions can be considered as a fascinating synthetic methodology, allowing different variants regarding substrate (alkene and alkyne metathesis) and type of metathetical reactions. On the other hand, tandem metathesis reactions such Ring Rearrangement Metathesis (RRM) and the coupling of metathesis reaction with other reactions of alkenes such as Diels-Alder or Heck reactions, makes metathesis one of the most powerful and reliable synthetic procedure. In particular, Ring-Rearrangement Metathesis (RRM) refers to the combination of several metathesis transformations into a domino process such as ringopening metathesis (ROM)/ring-closing metathesis (RCM) and ROM-cross metathesis (CM) in a one-pot operation. RRM delivers complex frameworks that are difficult to assemble by conventional methods constitutingan atom economic process. RRM is applicable to mono-and polycyclic systems of varying ring sizes such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, pyran systems, bicyclo[2.2.1]heptene derivatives, bicyclo[2.2.2]octene derivatives, bicyclo[3.2.1]octene derivatives and bicyclo[3.2.1]octene derivatives. In this review our attention has focused on the RRM reactions in 7-oxabicyclo[2.2.1]heptene derivatives and on their application in the synthesis of natural products or significant subunits of them.

Stereocontrolled synthesis of some novel functionalized heterocyclic amino ester and amide derivatives with multiple stereocenters

“…With everything taken into account, it is not surprising that olen metathesis became a powerful and increasingly applied tool in organic synthesis during the last decades. [1][2][3][4][5][6][7][8][9][10][11] Ring-rearrangement metathesis (RRM) is a domino process, where ring-opening metathesis is followed by closure of a new ring via another olen metathesis process. The most common RRM sequences are ROM/RCM and ROM/RCEYM (see Scheme 1).…”

“…Ring-rearrangement metathesis excels in fast and efficient generation of structurally complex frameworks. [8][9][10][11] Scheme 2 depicts the synthesis of some natural products via RRM. 10 Lactones or lactams are widespread amongst natural products.…”

“…With everything taken into account, it is not surprising that olefin metathesis became a powerful and increasingly applied tool in organic synthesis during the last decades. 1–11…”

Molecular Acrobatics in Polycyclic Frames: Synthesis of “Kurmanediol” via Post-synthetic Modification of Cage Molecules by Olefinic Metathesis

“…22 In addition, suitably oriented norbornene derivatives are valuable substrates for the RRM process to generate intricate targets. 23 A number of reports are available involving RRM strategy starting with simple norbornene derivatives. 24 However, there are no reports of norbornene moiety attached to cage systems such as 13 or 14.…”

“…Tam and co-workers have used the inherent ring strain of bicyclo[2.2.1]­heptene derivatives to design various polycycles, catalyzed by transition-metal catalysts . In addition, suitably oriented norbornene derivatives are valuable substrates for the RRM process to generate intricate targets . A number of reports are available involving RRM strategy starting with simple norbornene derivatives .…”