“Olefin Metathesis” R. H. Grubbs, Tetrahedron, 2004 , 60 , 7117-7140.
IMPROVED RUTHENIUM CATALYSTS FOR Z-SELECTIVE OLEFIN METATHESIS Benjamin K. Keitz, Koji Endo, Paresma...
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Transcript of IMPROVED RUTHENIUM CATALYSTS FOR Z-SELECTIVE OLEFIN METATHESIS Benjamin K. Keitz, Koji Endo, Paresma...
IMPROVED RUTHENIUM CATALYSTS IMPROVED RUTHENIUM CATALYSTS FOR FOR
Z-SELECTIVE OLEFIN METATHESISZ-SELECTIVE OLEFIN METATHESISBenjamin K. Keitz, Koji Endo, Paresma R. Patel, Myles B.
Herbert, and Robert H. Grubbs J. Am. Chem. Soc. 2012, 134, 693–699.
Shawn K. CollinsShawn K. CollinsUniversitUniversitéé de Montr de Montrééalal
Department of ChemistryDepartment of ChemistryCentre for Green Chemistry and CatalysisCentre for Green Chemistry and Catalysis
[email protected]@umontreal.caWeb: http://www.mapageweb.umontreal.ca/collinss/Web: http://www.mapageweb.umontreal.ca/collinss/
CHARETTE/COLLINS LITERATURE MEETINGCHARETTE/COLLINS LITERATURE MEETINGUniversité de Montréal (UdeM)Université de Montréal (UdeM)
October 11October 11thth, 2012, 2012Montréal, QuébecMontréal, Québec
CROSS METATHESIS: GENERALIZED MECH USING GRUBBS II
For a review on catalytic cross-metathesis, see: (a) Blechert, S.; Connon, S. J. Angew. Chem., Int. Ed. 2003, 42, 1900;
(b) Vernall, A. J.; Abell, A. D. Aldrichimica Acta 2003, 36, 93; (c) For industrial applications of cross metathesis, see: Pederson, R. L.; Fellows, I. M.; Ung, T. A.; Ishihara H.; Hajela, S. P. Adv. Synth. Catal. 2002, 344, 728.
First proposed by Chauvin: Herrison, J. L.; Chauvin, Y. Makromol. Chem. 1970, 141, 161. and later expanded upon by Katz: Katz, T. J.; McGinnis, J. L. J. Am. Chem. Soc. 1975, 97, 1592.
MesN NMes
RuR
Cl H
MesN NMes
RuR
MesN NMes
RuCl
MesN NMes
Ru
R1
R2
R1Cl
Cl
ClCl
R1
ClR1
R2Cl
MesN NMes
RuR
Cl
Cl
H MesN NMes
RuR
Cl
Cl
H
R1side-binding model bottom-binding
model
or
or
MesN NMes
RuCl
ClR1
side-binding model
bottom-binding model
MesN NMes
RuR
Cl
Cl
H
PCy3
R1
R2
initiation step
propagation step
R2
R1
R2
R1 Z:EYield of cis-product
(%)
(CH2)5CH3 9:1 56
(CH2)7CH3 8.5:1 72
(CH2)3Br 7.3:1 45
(CH2)2Br 9:1 17.5
(CH2)4OTBS 6.7:1 90
(CH2)3OTBS 5.6:1 68
(CH2)2OTBS 5.3:1 73
CH2TMS 3:1 76
o-MeOC6H4CH2 9:1 72
(CH2)6CH=CH2 8:1 53
(CH2)2C(O)OBn 5.6:1 44
(CH2)3CH(OMe)2 7: 1 79
CH2CMe2CH2CH(OMe)2 3: 1 64
Crowe, W. E.; Goldberg, D. R. J. Am. Chem. Soc. 1995, 117, 5162.
Z-SELECTIVE METATHESIS (PREVIOUS): SUBSTRATE CONTROL
+
(1 equiv.)
CN
MoN
Ph
O
O
F3CCF3
F3C
F3C
(5 mol %)rt, CH2Cl2, 3 h
R1
(1 equiv.)
CN
R1
Schrock
Z-SELECTIVE METATHESIS (PREVIOUS): SUBSTRATE CONTROL
Product Z:E Yield
(%)
Product Z:E Yield
(%)
4:1 88 3:1 76
3:1 81 3:1 79
4:1 91 9:1 83
Randl, S.; Gessler, S.; Wakamatsu, H.; Blechert, S. Synlett 2001, 430.
(5 mol %)CH2Cl2
reflux, 2 h+
(2 equiv.)
Substrate Product
Ru
O
NMesMesN
Cl
Cl
CN
GH2
OH
CN
CHO
CN
CO2H
CN
OCOPh
CN
OO
CO2Me
CNCO2Et
CO2Et
CN
Product E:Z Yield
(%)
Product E:Z Yield
(%)
43:57 79 96:4 80
42:58 78 >98:
2
94
1:99 59 >99:
1
86
83:17 74 93:7 60
Kim, M.; Lee, D. Org. Lett. 2005, 7, 1865.
Z-SELECTIVE METATHESIS (PREVIOUS): SUBSTRATE CONTROL
(5 mol %)
CH2Cl2reflux, 4-6 h
+(2-2.5 equiv.)alkynyl boronate
Ru
PCy3
NMesMesN
Cl
Cl
Ph
alkene
1,3-diene product
R2
BPin
R1R2
R1 BPin
BPin
OBn
OTBDMS
BnO
OTBDMS
OAc
BPin
BPin O
OTBDMS
BPin
BPin
TBDMSO
TMS
BPin
MeO
Br
BPin
Br
BPin
MeO
Jiang, A. J.; Zhao, Y.; Schrock, R. R.; Hoveyda, A. H. J. Am. Chem. Soc. 2009, 131, 16630.
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST CONTROL
C6D6, 22oC
catalyst(4 mol %)
R1 R1 R1
MoN
Ph
N
OBr
TBSO
Br
WN
Ph
N
Cl
Cl
O
MesTBSO
Mes
WNN
O
i-Pr
i-Pr
i-Pr
i-Pri-Pr
i-Pri-Pr
i-Pr
TMSTMS
3h, 33% conv, 98% Z
PhPh
3h, 62% conv, 93% Z
PhPh
14h, 52% conv, 94% Z
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST CONTROL
MoN
Ph
N
OBr
TBSO
Br
On-Bu or OPMB
+
R
(1.2 - 5.0 mol%)
C6H6, 22C, 2 hOn-Bu OPMB+
R R
On-Bu
OPMB
C8H17
Bn
76% conv., 68% yield98% Z
71% conv., 57% yield>98% Z
On-Bu
OPMB
76% conv., 73% yield98% Z
74% conv., 70% yield>98% Z
Br( )6
PhO2C
On-Bu
OPMB
86% conv., 77% yield94% Z
66% conv., 59% yield>98% Z
TMSCC( )6
TIPSO
On-Bu
OPMB
Cy
57% conv., 51% yield>98% Z
81% conv., 75% yield>98% Z
PhHN
Meek, S. J.; O'Brien, R. V.; Llaveria, J.; Schrock, R. R.; Hoveyda, A. H. Nature 2011, 471, 461-466.
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST CONTROL
WNN
O
Cl
Cl
i-Pr
i-Pri-Pr
i-Pri-Pr
i-Pr
(7.5 mol%)C6H6 (1M), 0.02 torr, 22C, 4h
82%, 94% Z
(5 mol%), C6H6 (1 mM), 16 h, 22C
96%, 34% Z
O OO
Me
TBSO
Me
MeMe
Me
N
SMe
TBSO OO
Me
TBSO
Me
MeMe
Me
N
SMe
TBS
Ru
O
NMesMesN
Cl
Cl
WNN
O
Cl
Cl
i-Pr
i-Pri-Pr
i-Pri-Pr
i-Pr
NO
N
H
NO
N
H
(5 mol%)PhMe (1M), 1.0 torr, 22C, 8h
63%, 94% Z
(20 mol%), slow additionCSA (300 mol%)
CH2Cl2 (0.2mM), 3.5 h, 40C62%, 63% Z
Ru
PCy3
NMesMesN
Cl
Cl
Ph
Yu, M.; Wang, C.; Kyle, A. F.; Jakubec, P.; Dixon, D. J.; Schrock, R. R.; Hoveyda, A. H. Nature 2011, 479, 88-93.
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST SYNTHESIS
Ru
O
NMesN
OO
t-Bu
NMesN
Cl
1. KOCMe2Et, hexanes, rt, 1h
2. hexanes, 60C, 4 h
Ru
PCy3
OCl
Cl92 %
Ru
O
NMesN
Cl
Cl
tBuCOOAg (3 eq.)
THF, 10 min59 %
Ru
O
NMesN
OO
t-Bu
Ru
O
NMesMesN
Cl
Cl
tBuCOOAg (2 eq.)
THF, 2 h41 %
Me
Me
Modification of adamantyl group or mesityl group either destroyed reactivity or
prevented metalation of the adamantyl group…
…current manuscript focuses on modification of the anionic group!
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST SYNTHESIS
Ru
O
NMesN
OO
t-Bu
Me
Me
Ru
O
NMesN
OO
t-Bu
Ru
O
NMesMesN
Cl
ClEtO2C CO2EtEtO2C CO2Et
Z-SELECTIVE METATHESIS (PREVIOUS): SUBSTRATE CONTROL
Ru
O
NMesN
OO
t-Bu
R R R
catalyst(0.1 mol%)
THF [3M], 35C
Ph
3h, 86% Z, 73%
MeO2C
12h, 90% Z, 13%
( )8 Me
12h, 94% Z, 30%
( )5 HO
12h, 43% Z, 81%
( )3
AcO
4h, 89% Z, 62%
PhHN
2h, 71% Z, 67%
Bpin
4h, 94% Z, 74%
TMS
3h, 95% Z, 54%2 mol% 2 mol% 2 mol% 2 mol%
Z-SELECTIVE METATHESIS (PREVIOUS): OLEFIN BINDING
Z-SELECTIVE METATHESIS (PREVIOUS): OLEFIN BINDING
Z-SELECTIVE METATHESIS (PREVIOUS): CATALYST SYNTHESIS
Bulky ligands caused faster
initiation …strange for Hov-type cats
Ru
O
NMesN
OO
t-Bu
NaITHF65%
Ru
O
NMesN
I
AgNO374%
Ru
O
NMesN
OO
NO
NH4NO382%
Monodentate ligands were essentially non-metathesis active…
Faster initiation did not guarantee better catalysts…
Some changes to aryl group (that did give catalysts) did not affect rate (ie Cl
sub for Me)…
Z-SELECTIVE METATHESIS (PREVIOUS): SUBSTRATE CONTROL
Ru
O
NMesN
OO
t-Bu
R R R
catalyst(0.1 mol%)
THF [3M], 35C
Ph
3h, 86% Z, 73%
MeO2C
12h, 90% Z, 13%
( )8 Me
12h, 94% Z, 30%
( )5 HO
12h, 43% Z, 81%
( )3
AcO
4h, 89% Z, 62%
PhHN
2h, 71% Z, 67%
Bpin
4h, 94% Z, 74%
TMS
3h, 95% Z, 54%2 mol% 2 mol% 2 mol% 2 mol%
Ru
O
NMesN
OO
NO
3h, 92% Z, 91% 12h, 91% Z, 85% 12h, 92% Z, 83% 12h, 81% Z, 67%
12h, 95% Z, 8% 12h, 91% Z, 12% 3h, 95% Z, 36% 9h, 95% Z, 14%
NO2 cat. has little secondary metathesis events
SUMMARY.
1) New C−H activated ruthenium catalysts for Z-selective olefin metathesis. Adjusting the ligand environment around the metal center has yielded significant insight into the initiation behavior, activity, and selectivity.
2) Catalysts are capable of ca. 1000 turnovers in several cross-metathesis reactions with very low loadings and do not require reduced pressures, high temperatures, or rigorous exclusion of protic solvents in order to operate effectively.
3) Secondary metathesis events are also relatively slow for the majority of substrates, meaning that significant reaction optimization should not be required.