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In the ring closing metathesis step, a ruthenium indenylidene complex was used as the precatalyst to afford the desired 7-member ring in 87% yield. [55] In 2002, Stephen F. Martin and others reported the 24-step synthesis of manzamine A with two ring-closing metathesis steps to access the polycyclic alkaloid. [56]
In one study published by Grubbs and Hong in 2006, a water-soluble Grubbs catalyst was prepared by attaching a polyethylene glycol chain to the imidazolidine group. [20] This catalyst is used in the ring-closing metathesis reaction in water of a diene carrying an ammonium salt group making it water-soluble as well.
Grubbs was instrumental in developing a family of ruthenium catalysts, including Grubbs catalyst for olefin metathesis. [36] He studied olefin transformations for ring-closing metathesis (RCM), [37] cross-metathesis reaction (CMR), [38] and ring-opening metathesis polymerization (ROMP) with cyclic olefins such as norbornene. [39]
An enyne metathesis is an organic reaction taking place between an alkyne and an alkene with a metal carbene catalyst forming a butadiene. This reaction is a variation of olefin metathesis. [1] The general scheme is given by scheme 1: When the reaction is intramolecular (in an enyne) it is called ring-closing enyne metathesis or RCEYM (scheme 2):
Alkyne metathesis can be used in ring-closing operations and RCAM stands for ring closing alkyne metathesis. The olfactory molecule civetone can be synthesised from a di-alkyne. After ring closure the new triple bond is stereoselectively reduced with hydrogen and the Lindlar catalyst in order to obtain the Z -alkene (cyclic E -alkenes are ...
The mechanism of homogeneous ring-opening metathesis polymerization is well-studied. It is similar to any olefin metathesis reaction. Initiation occurs by forming an open coordination site on the catalyst. Propagation happens via a metallacycle intermediate formed after a 2+2 cycloaddition. When using a G3 catalyst, 2+2 cycloaddition is the ...
The Zhan catalysts were inspired by previous work in the olefin metathesis field. Robert H. Grubbs first reported the first and second generation of Ru catalysts in 1992, with good metathesis activity. However, the catalysts containing the tricyclohexylphospine ligand were unstable to air and water, and the catalytic activity is not good enough ...
Pages in category "Ring forming reactions" The following 75 pages are in this category, out of 75 total. ... Ring-closing metathesis; Robinson annulation; S.