olefin metathesis
TRANSCRIPT
Organic Pedagogical Electronic Network
Olefin Metathesis
Created by Elizabeth BillingsEdited by Margaret Hilton
Honors Organic ChemistryChem 2321 (Sigman), 2013
Olefin MetathesisOverview: Olefin metathesis is a powerful reaction catalyzed by transition metals, in which two olefins can form a ring or rearrange their connectivity, or a double bond in a ring can be opened. These types of metathesis are called ring closing metathesis, cross metathesis or ring opening polymerization, respectively.
Mechanism
MRM
R
MR
Initiation:
Catalytic Cycle: M CH2
M
CH2 CH2
MM
Wiki Page: http://en.wikipedia.org/wiki/Olefin_metathesisOther References: "BIg Deal Reaction (ACS)”, Mechanism and More
Olefin MetathesisOverview: Olefin metathesis is a powerful reaction catalyzed by transition metals, in which two olefins can form a ring or rearrange their connectivity, or a double bond in a ring can be opened. These types of metathesis are called ring closing metathesis, cross metathesis or ring opening polymerization, respectively.
Types of Metathesis
Ring Opening Metathesis
Truett, et al. JACS, 1960, 19, 2337.
Ziegler catalyst
TiCl4/AlR3
*
Cross Metathesis
Zhang et al. JACS, 1993, 115, 10998. Ph
Ph +Catalyst
+
Ring Closing Metathesis
Forbes et al. JACS, 1992, 114, 10978.
SiO
SiSchrock's catalyst Si
OSi
Wiki Page: http://en.wikipedia.org/wiki/Olefin_metathesisOther References: "BIg Deal Reaction (ACS)”, Mechanism and More
Catalysts
References: 2005 Nobel Prize Lecture and Slides
Titanium Tungsten Molybdenum Ruthenium
Aldehydes Aldehydes Aldehydes OlefinsKetones Ketones Olefins AldehydesEsters, Amides Olefins Ketones KetonesOlefins Esters, Amides Esters, Amides Esters, Amides
Ru
PCy3ClCl
PCy3
PhH
Grubb's First Generation•Kinetically controlled products•Selective for alkyl substituted double bonds
N N
Ru
PCy3Cl H
Cl Ph
Grubb's Second Generation•Thermondynamical control of products•Reacts with e- deficient double bonds
Ring Opening Polymerization: Ballistic Protection
References: ”Self-Healing Composite Armor”, ”New Developments in Olefin Metathesis Technology”
9 mm bullets stopped by DCPD
DCPD, when imbedded with a chemical catalyst, is considered a “self-healing polymer.” When it is hit, the catalytic trigger is activated and the resulting cracks are filled in with newly formed polymer via ring-opening metathesis. This makes it incredibly strong, as well as potentially useful in combat situations.
CHR(PR3)2Cl2Ru(C6H5)3P
RuCl2P2 Cross-link
*P2Cl2Ru
RuCl2P2
Dicyclopentadiene (DCPD)-Thermoset Polymer
Problems
References: 1- Fürstner, Alois et al. CEJ, 2013, 2- Grubbs, et al. Tetrahedron, 2004, 60, 7117, 3- Grubbs, et al. JACS, 1993, 115, 9856
O
OO
O
O
BnO
BnOOBn
Bn
BnO
BnO
OO
O
O
1)Ru
PCy3Cl
ClPCy3
Ph
2) H2, Pd/C MeOH/EtOAc/HCOOH
???
1- Propose a product and a mechanism for the final two steps in the total synthesis of Nominal Gobienine A. 1
2- List all possible metathesis results.2
AcO CO2Me+2nd Generation Grubb's
???
3- Predict the product of ring closing metathesis for each of the three molecules and draw their mechanisms. 3
OPh N
N
O
O
N X
O
Solutions
1- 2-
3-
OO
O
O
O
HO
HOOHH
HO
HO
OO
O
O
AcOOAc
AcOCO2Me
AcO
MeO2CCO2Me
OPhN
N
O
ON X
O
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Contributed by: Created by Elizabeth Billings
Edited by Margaret HiltonHonors Organic ChemistryChem 2321 (Sigman), 2013
University of Utah