In this short review, a brief description about olefin metathesis (OM) by transition metal complexes is
presented. Metathesis reactions in olefin (organic eye compounds) are mostly carried out using transition
organic-metal complexes (OMC) such as ruthenium, rhenium, molybdenum and tungsten based, schorock,
grubb’s, Hoveyda-grubb’s catalyst etc. These catalysts cause redistribution of π-bond of alkene by cross
scission and rearrangement in compounds by the formation of cyclic (2+2cycloaddition) intermediate.
OM reactions are efficiently used for the synthesis of neohexene by dimers of isobutene, conversion of
detergent by shell higher olefin process and synthesis of many drugs.
Graphical abstract
Keywords: Metathesis; Olefin; Metal catalyst; Cross-coupling reaction
Metathesis of olefins is developed as catalytic synthesis method which is applied for
synthesis in organic compounds like basic and fine laboratory chemicals, active pharmaceutical
ingredients and it may also use as polymeric, noble materials. Olefin metathesis reactions
are following particular mechanism just like ring-opening metathesis reaction, ring closing
metathesis reaction, and acyclic diene metathesis reaction, cross metathesis reactions are
following the formation of met allocyclic intermediate [1-9]. By the development in the
structure of transition metal complexes, they get catalyze enzyme metathesis reactions with
high turnover, and emerged a high interesting research area to produce various substitution
in olefins. Organometallic catalysts are very efficient for these reactions like ruthenium
hydrides [10-14], Grubbs-I catalyst [15], palladium [16], Hoveyda-Grubbs pre-catalyst on
zirconia membrane [17]. Fogg et al. [18] have reported that olefin metathesis is used as a
technology for Industrial production of derivative of olefin.
For the cross synthesis of cyclic and bicyclic compounds via Pd-catalyzed alkene [19,20]
with N-alkylureas and alkenyl halides, they give the mixture of products of acyclic or cyclic
compounds [21-22]. Such types of reactions show the cross-metathesis reaction, in the
method of preparations of cyclic or acyclic compound via cross metathesis, use simpler
methods as synthesis of cyclic urea’s using α, β-unsaturated carbonyl compounds with pentad
dentate ligand in metal complexes followed by cross-metathesis reaction. In these reactions, formation of C-N and C-C bond formation takes place [23]; (Figure
1).
Figure 1:
Ring-opening metathesis (ROM)
For the synthesis of long chain polymers ring-opening
metathesis polymerization (ROMP) method is used which is firstly
introduced by Hillmyer et al. [24-26] via using 4-cis-butenediols
using ruthenium carbine organometallic complexes. Heterodontieschain
polymers are carrying two different functional groups at the
end of chain (Figure 2). Such types of polymerization methods are,
mostly applicable for the synthesis of flexible biologically active
molecules [27,28].
Figure 2:
Ring-closing metathesis (RCM)
In the synthesis of ring closing reactions stereo-specific
skeleton structure is found in bio-active compounds, it’s very
unique synthetic procedure in the field of polymer chemistry, via
development into synthetic method (Figure 3), which is limiting
the potential for biomedical applications. Here we have discussed
about the synthesis of a stereo-selective compound by 1,4-linkage
in six-membered cycle polyether which is prepared by the method
of ring-closing metathesis (RCM) [29].
Figure 3:
Ring-opening metathesis polymerization (ROMP)
Figure 4:
Ring-opening metathesis polymerization (ROMP) is an efficient
method for the formation of practically important in various fields
of applied science, as functionalization in polymeric materials to
form advance material structures [30-32]. ROMP of norbornadiene
(NBD) in the presence of [RuCl2(PPh3)2(pyrrolidine)] as the starting complex and catalyst and the reaction at room temperature with
2mL of CHCl3, for 30 minutes. Measured yields of poly-NBD were
found in inert argon atmosphere [33]; (Figure 4).
A cyclic diene metathesis (ADMET)
Acyclic diene metathesis (ADMET) is a method of synthesis of
cyclic and acyclic end compound via fragmentation of α, ω-diene
monomer. These types of polymers can be self-interconvertible or
by the use of catalyst, which causes the pi-pi interaction between
conjugated diene, and the movement of electron is enhanced [34].
These reactions are carried out in presence of 2mol% of WOCl2sub>
(2,6-Br2C6H3O)2 as catalyst, α, ω-diene monomer for 1 hour into the
corresponding in 68-70% isolated yield [35]; (Figure 5).
Here we are describing some new methods for synthesis of
alkenes by metathesis. These new methods are having versatile
application in the field of industry, biomedical and other porous
material synthesis. Ring-opening metathesis polymerization
process give an opportunity, with which we can develop nanoporous
polymers with the structure having high surface area. Ringclosing
metathesis is very ease for the synthesis of co-polymerized
material and the ring size can be modulated or multi-functionalized
by use of different solvent cause di-hydroxylation for example olefin
group converted into sugar like structure as polyethylene glycol.
Modification in bioactive molecule like amylase, via change in
configuration of STERI GENIC center in cyclo-polymers. New crossmetathesis
reactions are used as a transformation effect for the
synthesis of derivatives of olefin with diene and allyl group for the
formation of bi-cyclic and mono-cyclic ends. Metathesis reactions
are highly emerging area in the field of pure organic synthesis.
It can be further improved for the symmetric and asymmetric
synthesis of olefins.
Grela K (2014) Olefin metathesis: Theory and practice. In: Grela K (Ed.), Olefin metathesis. Hoboken, New Jersey, USA.
Grubbs RH, Wenzel AG (2015) Handbook of metathesis. In: Grubbs RH, Anna GW, Ezat K(Eds.), Wenzel focusses on catalyst development and mechanism (2nd edn), Columbia University, USA.
Zhang S, Zhang W, Nomura K (2017) Synthesis and reaction chemistry of alkylidene complexes with titanium, zirconium, vanadium, and niobium: Effective catalysts for olefin metathesis polymerization and the other organic transformations. Adv Organomet Chem 68: 93-136.
Fürstner A (2000) Olefin metathesis and beyond. Angew Int Ed Chem 39(17): 3012-3043.
Professor, Chief Doctor, Director of Department of Pediatric Surgery, Associate Director of Department of Surgery, Doctoral Supervisor Tongji hospital, Tongji medical college, Huazhong University of Science and Technology
Senior Research Engineer and Professor, Center for Refining and Petrochemicals, Research Institute, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia
Interim Dean, College of Education and Health Sciences, Director of Biomechanics Laboratory, Sport Science Innovation Program, Bridgewater State University