Ruthenium olefin metathesis catalysts with N-Heterocyclic carbene ligands bearing N-Naphthyl side chains

Article abstract of DOI:10.1021/om9009697

A series of second-generation ruthenium-based olefin metathesis catalysts bearing N-naphthyl-substituted N-heterocyclic carbene (NHC) ligands have been prepared and fully characterized. By reaction with the appropriate NHC, these complexes are readily acc

Full text of DOI:10.1021/om9009697

Organometallics 2010, 29, 775–788 775
DOI: 10.1021/om9009697
Ruthenium Olefin Metathesis Catalysts with N-Heterocyclic Carbene
Ligands Bearing N-Naphthyl Side Chains
†
Ludovic Vieille-Petit, Herve Clavier,‡,§ Anthony Linden,† Sascha Blumentritt,†
ꢀ
Steven P. Nolan,*,‡ and Reto Dorta*,†
†Organic Chemistry Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zu€rich, Switzerland and
‡
§
ꢀ
School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, U.K. Present address: Universite
Aix-Marseille, UMR CNRS 6263 - Institut des Sciences Moleꢀculaires de Marseille, Av. Escadrille
Normandie Niemen, 13397 Marseille Cedex 20, France.
Received November 5, 2009
A series of second-generation ruthenium-based olefin metathesis catalysts bearing N-naphthyl-
substituted N-heterocyclic carbene (NHC) ligands have been prepared and fully characterized. By
reaction with the appropriate NHC, these complexes are readily accessible in one synthesis step from
the commercially available first-generation precursors [RuCl2(dCHPh)(PCy3)2] (Grubbs I, GI) or
[RuCl2(dCH-o-iPrO-Ph)(PCy3)] (Hoveyda-Grubbs I, HGI) by simple exchange of one phosphine
ligand with the free NHCs. Time-dependent conversions in the ring-closing metathesis (RCM) of
standard substrates leading to di- as well as trisubstituted olefins have been measured for these
catalysts. When benchmarked against the parent SIMes-containing the Grubbs II precatalyst (GII),
most of these new NHC structures show enhanced reactivity in RCM. From these comparative studies,
valuable information was gathered which shows that the alkyl substitution on the naphthyl side chains
can enhance or lower the catalytic performance, depending on the bulk and the position of these alkyl
groups. Thebehaviorofthebestperformingprecatalystshasbeeninvestigatedinthe RCM of aseriesof
representative substrates, in enyne metathesis reactions as well as in cross-metathesis (CM).
1. Introduction
higher compatibility with functional groups as well as an
increased ease of handling compared to the Schrock family
of catalysts.4 Subsequently, the Grubbs first-generation cata-
lyst 2 (GI)5 and second-generation catalysts 3 and 4 (GII),6,7
containing N-heterocyclic carbene (NHC) ligands,8 were
reported between 1995 and 1999 (eq 1).
Olefin metathesis represents one of the most useful and
versatile tools in organic synthesis for the formation of
carbon-carbon double bonds. Numerous types of metathesis
reactions such as ring-closing metathesis (RCM), enyne me-
tathesis, ring-opening metathesis polymerization, and cross-
metathesis (CM) have been developed.1 Most prominent in
synthetic organic chemistry is the RCM reaction, which gives
access to an impressive range of unsaturated carbo- and
heterocyclic ring systems.2 The discovery of the well-defined
ruthenium carbene catalyst 1 by Grubbs in 1992 generalized
their use,3 the properties of the Grubbs catalyst leading to
*To whom correspondence should be addressed. E-mail: snolan@
st-andrews.co.uk (S.P.N.); dorta@oci.uzh.ch (R.D.).
(1) For reviews on applications, see: (a) Diver, S. T.; Giessert, A. J.
Chem. Rev. 2004, 104, 1317. (b) Nakamura, I.; Yamamoto, Y. Chem. Rev.
2004, 104, 2127. (c) Dieters, A.; Martin, S. F. Chem. Rev. 2004, 104, 2199.
(d) McReynolds, M. D.; Dougherty, J. M.; Hanson, P. R. Chem. Rev. 2004,
104, 2239. (e) Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int.
Ed. 2005, 44, 4490. (f) Donohoe, T. J.; Orr, A. J.; Bingham, M. Angew.
Chem., Int. Ed. 2006, 45, 2664. (g) Michaut, A.; Rodriguez, J. Angew.
Chem., Int. Ed. 2006, 45, 5740. (h) van Otterlo, W. A. L.; de Koning, C. B.
Chem. Rev. 2009, 109, 3743.
(2) For reviews on Ru-based metathesis catalysts, see: (a) Trnka, T. M.;
Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18. (b) Grubbs, R. H. Handbook of
Metathesis;Wiley-VCH: Weinheim, Germany, 2003. (c) Connon, S. J.;
Blechert, S. Angew. Chem., Int. Ed. 2003, 42, 1900. (d) Astruc, D. New J.
Chem. 2005, 29, 42. (e) Samojzowicz, C.; Bieniek, M.; Grela, K. Chem. Rev.
2009, 109, 3708.
Successful variations of the original second-generation
catalysts 3 and 4 have since then appeared and have led,
(4) (a) Schrock, R. R.; Murdek, J. S.; Bazan, G. C.; Robbins, M.;
DiMare, M.; O’Regan, M. J. Am. Chem. Soc. 1990, 112, 3875. (b) Schrock,
R. R. Chem. Rev. 2009, 109, 3211.
(5) Schwab, P.; France, M. B.; Ziller, J. W.; Grubbs, R. H. Angew.
Chem., Int. Ed. Engl. 1995, 34, 2039.
(6) (a) Huang, J.; Stevens, E. D.; Nolan, S. P.; Peterson, J. L. J. Am.
Chem. Soc. 1999, 121, 2674. (b) Scholl, M.; Trnka, T. M.; Morgan, J. P.;
Grubbs, R. H. Tetrahedron Lett. 1999, 40, 2247.
(7) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999, 1,
953.
(8) For a review on the use of NHCs in late-transition-metal catalysis
(3) (a) Nguyen, S. T.; Johnson, L. K.; Grubbs, R. H. J. Am. Chem.
Soc. 1992, 114, 3974. (b) Fu, G. C.; Nguyen, S. T.; Grubbs, R. H. J. Am.
Chem. Soc. 1993, 115, 9856.
ꢀ
´
see: Dıez-Gonzalez, S.; Marion, N.; Nolan, S. P. Chem. Rev. 2009, 109,
3612.
r
2010 American Chemical Society
Published on Web 01/21/2010
pubs.acs.org/Organometallics

776 Organometallics, Vol. 29, No. 4, 2010
Vieille-Petit et al.
Chart 1. Imidazolin-2-ylidenes with Phenyl (Left) and Naphthyl
(Right) Side Chains
to SIMes-containing Grubbs II complexes in simple RCM
reactions leading to disubstituted olefins.17
In the present contribution, we give a full overview of
the preparation and characterization as well as on detailed
RCM studies involving these new Grubbs II type ruthenium
complexes, with both substrates giving disubstituted and
trisubstituted olefins. We show that, in contrast to what
has been observed with the SIPr-modified Grubbs II type
catalyst,12a,13 correctly substituted naphthyl side chains of
the NHC ligand indeed lead to complexes with better overall
catalytic behavior in the RCM reaction. These findings were
then applied to the synthesis, characterization, and catalytic
behavior of some Hoveyda-Grubbs II type ruthenium
complexes (type HGII, see above) containing the best per-
forming of our naphthyl-substituted NHCs. In addition, we
present the synthesis of a ligand incorporating the naphthyl
side chain motif with an unsaturated central N-heterocycle
and compare the corresponding second-generation ruthe-
nium metathesis catalyst with its saturated congener. To
obtain a more complete picture on their activity, we inves-
tigated the performance of these catalysts in the RCM of a
wider range of substrates as well as in selected enyne and
cross-metathesis reactions.
inter alia, to indenylidene precatalysts (IndII) and to phos-
phine-free Hoveyda-Grubbs II type precatalysts (HGII).9
Modification of the NHC ligand (SIMes/IMes; IMes=1,3-bis-
(2,4,6-trimethylphenyl)imidazol-2-ylidene; SIMes = 1,3-bis-
(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) has also
been studied. For example, modifying the central five-mem-
bered N-heterocycle (four- and six-membered rings),10 or
substituting one or two side chains with alkyl groups,11 have
typically led to decreased activity and/or faster decomposi-
tion of the corresponding ruthenium catalysts. On the other
hand, introducing the more bulky SIPr ligand did lead to
increased activity for simple RCM reactions,11a,12 but steri-
cally more demanding substrates again led to decreased
catalyst stability and lower product yields.13 Very small
modifications of the original SIMes ligand architecture seem
more successful, as shown by Grubbs et al., who have
recently identified a series of ligands with slightly higher
reactivity or better activity for the RCM of hindered sub-
strates.14,15
Recent work in our laboratories has led to the synthesis of
promising members of a new family of stable, saturated
NHC ligands that incorporate bulky naphthyl side chains.16
The introduction of the naphthyl moieties generates atropi-
someric ligands with C2-symmetric (anti) and Cs-symmetric
(syn) conformations (Chart 1). In a preliminary communica-
tion, we reported on the use of these new NHCs as ligands in
Grubbs second-generation ruthenium type complexes and
showed how some of the new catalyst precursors are superior
2. Results and Discussion
2.1. Synthesis and Characterization of Grubbs II Type
Ruthenium Complexes. Precatalysts of general formula
[RuCl2(NHC)(dCHPh)(PCy3)] (Grubbs II type ruthenium
complexes, 6a-e) were prepared from [RuCl2(dCHPh)-
(PCy3)2] (Grubbs I, GI) by simple exchange of one phosphine
ligand with the corresponding NHCs 5a-e at room tem-
perature in toluene (Scheme 1). The syn:anti ratio of the free
NHCs is maintained during synthesis of the complexes,
which are therefore present as isomeric mixtures, as shown
by 1H and 31P{1H} NMR spectroscopy. Completion of the
reactions was monitored by 31P{1H} NMR spectroscopy
(disappearance of the signal corresponding to GI). It is of
note that GI should be completely consumed before workup
and the reaction may be driven to completion by adding a
slight excess of the corresponding NHC ligand. Analytically
pure complexes were best obtained via crystallization/pre-
cipitation of the respective compounds by fast diffusion of
methanol into a highly concentrated CH2Cl2 solution con-
taining 6a-e.18 This synthetic procedure also led to crystal-
line material for X-ray diffraction studies, and complexes
anti-6b, syn-6c, anti-6d, and anti-6e were unambiguously
identified by X-ray structure analysis.
Atomic displacement ellipsoid drawings of the complexes,
together with the most relevant bond lengths and angles, are
given in Figure 1 and confirm the structural assignment. The
compounds exhibit a distorted-square-pyramidal geometry,
with the ruthenium-benzylidene bond occupying the apical
position and with the two chloride ligands trans to one
another. The relative bulk of the alkylated naphthyl side
chains of the NHC ligand forces the benzylidene moiety to
arrange away from the 2-isopropyl/2-cyclohexyl moieties
and to position itself parallel to the second aromatic ring
(9) For a review on catalysts of the IndII type, see: (a) Boeda, F.;
Clavier, H.; Nolan, S. P. Chem. Commun. 2008, 2726. For selected catalysts
of the HGII type, see: (b) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.;
Hoveyda, A. H. J. Am. Chem. Soc. 2000, 122, 8168. (c) Wakamatsu, H.;
Blechert, S. Angew. Chem., Int. Ed. 2002, 41, 2403. (d) Grela, K.;
Harutyunyan, S.; Michrowska, A. Angew. Chem., Int. Ed. 2002, 41, 4038.
(10) (a) Yang, L.; Mayr, M.; Wurst, K.; Buchmeiser, M. R. Chem.
Eur. J. 2004, 10, 5761. (b) Despagnet-Ayoub, E.; Grubbs, R. H. Organo-
metallics 2005, 24, 338.
€
(11) (a) Furstner, A.; Ackermann, L.; Gabor, B.; Goddard, R.;
Lehmann, C. W.; Mynott, R.; Stelzer, F.; Thiel, O. R. Chem. Eur. J.
2001, 7, 3236. (b) Dinger, M. B.; Nieczypor, P.; Mol, J. C. Organometallics
2003, 22, 5291. (c) Yun, J.; Marinez, E. R.; Grubbs, R. H. Organometallics
2004, 23, 4172. (d) Ledoux, N.; Allaert, B.; Pattyn, S.; Vander Mierde, H.;
Vercaemst, C.; Verpoort, F. Chem. Eur. J. 2006, 12, 4654. (e) Vehlow, K.;
Maechling, S.; Blechert, S. Organometallics 2006, 25, 25.
(12) (a) Dinger, M. B.; Mol, J. C. Adv. Synth. Catal. 2002, 344, 671.
(b) Banti, D.; Mol, J. C. J. Organomet. Chem. 2004, 689, 3113. (c) Clavier,
H.; Urbina-Blanco, C. A.; Nolan, S. P. Organometallics 2009, 28, 2848.
(13) Ritter, T.; Hejl, A.; Wenzel, A. G.; Funk, T. W.; Grubbs, R. H.
Organometallics 2006, 25, 5740.
(14) (a) Ritter, T.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc.
2006, 128, 11768. (b) Vougioukalakis, G. C.; Grubbs, R. H. Organometallics
2007, 26, 2469. (c) Vougioukalakis, G. C.; Grubbs, R. H. Chem. Eur. J.
2008, 14, 7545.
(15) (a) Berlin, J. M.; Campbell, K.; T. Ritter, T.; Funk, T. W.;
Chlenov, A.; Grubbs, R. H. Org. Lett. 2007, 9, 1339. (b) Stewart, I. C.;
Ung, T.; Pletnev, A. A.; Berlin, J. M.; Grubbs, R. H.; Schrodi, Y. Org. Lett.
2007, 9, 1589. (c) Chung, C. K.; Grubbs, R. H. Org. Lett. 2008, 10, 2693.
(16) (a) Luan, X.; Mariz, R.; Gatti, M.; Costabile, C.; Poater, A.;
Cavallo, L.; Linden, A.; Dorta, R. J. Am. Chem. Soc. 2008, 130, 6848.
(b) Vieille-Petit, L.; Luan, X.; Mariz, R.; Linden, A.; Blumentritt, S.; Dorta,
R. Eur. J. Inorg. Chem. 2009, 1861.
(17) Vieille-Petit, L.; Luan, X.; Gatti, M.; Blumentritt, S.; Linden, A.;
Clavier, H.; Boeda, F.; Nolan, S. P.; Dorta, R. Chem. Commun. 2009,
3783.
(18) In contrast to the synthesis of SIPr-containing second-genera-
tion ruthenium catalysts, decomposition of the complex when using
MeOH is not observed here.

Article
Organometallics, Vol. 29, No. 4, 2010 777
Figure 1. ORTEP diagrams (30% probability ellipsoids) of complexes 6b (top left), 6c (top right), 6d (bottom left), and 6e (bottom
right). Selected bond lengths (A) are as follows. Ru-CNHC: 6b, 2.074(2); 6c, 2.069(4); 6d, 2.080(5); 6e, 2.067(3). Ru-Cbenzylidene: 6b,
1.847(2); 6c, 1.830(4); 6d, 1.846(5); 6e, 1.834(4). Ru-P: 6b, 2.4180(5); 6c, 2.434(1); 6d, 2.432(1); 6e, 2.4191(9). Selected bond angles (deg)
are as follows. CNHC-Ru-Cbenzylidene: 6b, 99.94(9); 6c, 98.9(2); 6d, 100.2(2); 6e, 99.6(1).
Scheme 1. Free N-Heterocyclic Carbenes Used (Top) and Grubbs II Type Ruthenium Precatalysts Synthesized (Bottom)
of the naphthyl moiety. The overall geometry around the
transition-metal center and bond lengths and angles in the
complexes are similar to those of the parent Grubbs II
catalyst [RuCl2(SIMes)(dCHPh)(PCy3)] (GII).17,19
2.2. Ring-Closing Metathesis (RCM) Activity of Selected
Substrates. The best method to compare the catalytic beha-
vior of different ruthenium precatalysts in the RCM reaction
is to directly follow the conversion of standard substrates to
1
product via H NMR spectroscopy.13 This allows one not
only to understand the overall performance of a catalyst but
also to monitor subtle differences such as the ease of initia-
tion of the precatalyst or possible decomposition and differ-
ences in stability of the catalysts during the transformation.
We initially studied the behavior of 6a-e in the RCM
reactions of diallyltosylamide (7) and diethyl diallylmalonate
(8) using 1 mol % of precatalyst (27 °C, 0.1 M substrate/
solvent) and benchmarked the runs against the Grubbs II
(19) Love, J. A.; Sanford, M. S.; Day, M. W.; Grubbs, R. H. J. Am.
Chem. Soc. 2003, 125, 10103.

778 Organometallics, Vol. 29, No. 4, 2010
Vieille-Petit et al.
Figure 2. Time-conversion plots for the RCM of 7 (left) and 8 (right), using 1 mol % (top) and 0.1 mol % (bottom) of catalyst
precursor.
(GII) catalyst.20 The plots of cycloalkene concentration
versus time in Figure 2 (top) revealed that the four catalysts
6b-e, namely the ones incorporating bulky isopropyl or
cyclohexyl groups on the 2-position of the naphthyl side
chains of the NHC ligand, effect the cyclization of substrates
7 and 8 with a markedly increased initial reaction rate
compared to GII. However, complex 6a not only turned
out to be less active than its congeners but also needed longer
reaction times to reach full conversion in comparison to GII
(30 min for 7, 50 min for 8). The shape of the curves indicates
that the initial reaction rate for 6a is significantly slower than
for the other precatalysts. This may be directly related to the
fact that sterically more demanding NHCs enhance phos-
phine dissociation and consequently increase initial reac-
tion rates of olefin metathesis. Indeed, 6d,e are the fastest
precatalysts for these transformations, with reaction times
of <20 min for both substrates.
We therefore wondered whether more detailed informa-
tion could be gained by lowering the amount of precatalyst
by an order of magnitude (0.1 mol %, Figure 2 bottom). For
these runs, the catalytic profile of [RuCl2{(2)-SIMePh}-
(dCHPh)(PCy3)] (GII0), a slightly less bulky analogue of
GII recently synthesized by Grubbs et al. for the RCM giving
tetrasubstituted olefins,15b was also analyzed. These studies
uncovered the following trends: first, precatalysts 6e and
especially 6d are still extremely active and show conversion
times comparable to the values obtained for GII at 1 mol %.
Second, compounds 6b and especially 6c are clearly less
active under these more demanding conditions. A careful
analysis of the shape of the curves shows that while the initial
reaction rate is once again higher than for GII, the activity of
6c decreases considerably with increasing conversion and
reaction time. This indicates that at least some of the
precatalyst is deactivated over time as 6c reaches complete
conversion only after prolonged reaction times. Further-
more, once again, complex 6a turned out to be slower than
the other new catalysts. Nevertheless, and in contrast to the
case for 6c, it does not decompose over time and for both
substrates 7 and 8 complete conversion is observed after
longer reaction times. Not surprisingly, GII0, which behaves
very well with bulky diene substrates, also needs longer
reaction times than GII and apparently decomposes with
the tosylamide-derived substrate 7 before complete conver-
sion of the substrate.
It is well-known that a GII analogue with a bulky SIPr
ligand effects the cyclization of 7 and 8 with an increased
reaction rate compared to that for the orginal SIMes-derived
GII catalyst but fails to completely ring-close substrates that
give trisubstituted olefins.13 This behavior was interpreted in
terms of steric effects that render the approach of the bulkier
substrate more difficult and thus lead to decomposition of
the active ruthenium species during catalysis. It was there-
fore of interest to see how precatalysts 6a-e behave with
such substrates. RCM studies of allylmethallyl tosylamide
(11) and diethylallylmethallyl malonate (12) were performed
using 0.5 mol % of the respective precatalyst (27 °C, 0.1 M
substrate/solvent) and were once again benchmarked against
GII. In contrast to the results obtained by Grubbs et al. with
the SIPr-modified ruthenium catalyst, the overall catalytic
profiles of 6a-e when compared to that of GII do not change
with substrates 11 and 12 and reactivity trends for these
more demanding RCM reactions were found to be similar to
those observed for the RCM of 7 and 8. Thus, especially
catalysts 6d,e show excellent activity, being the most efficient
catalysts in this study. Reaction times required for full
(20) Syn/anti mixtures of complexes have been used throughout the
present study. For preliminary results showing that there are differences
in reactivity between the two conformers, see: Gatti, M.; Vieille-Petit, L.;
Luan, X.; Mariz, R.; Drinkel, E.; Linden, A.; Dorta, R. J. Am. Chem.
Soc. 2009, 131, 9496.

Article
Organometallics, Vol. 29, No. 4, 2010 779
Figure 3. Kinetic data for the RCM of 11 (left) and 12 (right), using 0.5 mol % of catalyst precursor.
Figure 4. Order of catalytic performance for Grubbs II catalysts based on the structure of the side chain of the NHC ligand or RCM
giving di- and trisubstituted double bonds.
Scheme 2. Synthesis of Hoveyda-Grubbs II Type Ruthenium
Precatalysts 15d (Top) and 15e (Bottom)
Figure 5. ORTEP diagrams (30% thermal ellipsoids) of complexes
anti-15d (left) and anti-15e (right). Selected bond lengths (A) are as
follows. Ru-CNHC: 15d, 1.970(2); 15e, 1.972(2). Ru-Cbenzylidene
:
15d, 1.828(3); 15e, 1.835(2). Ru-O: 15d, 2.247(2); 15e, 2.297(1).
Selected bond angles (deg) are as follows. CNHC-Ru-Cbenzylidene
:
15d, 101.6(1); 15e, 101.08(7).
conversion are typically one-third of what is needed with GII.
Catalyst 6b also shows good activities, and only 6c once again
suffers from somewhat lower stability due to its peculiar
substitution pattern on the naphthyl side chains. Interest-
ingly, precatalyst 6a with the less bulky NHC ligand does not
perform better with these sterically more demanding sub-
strates and needs longer reaction times for full conversion
than does GII (full conversion not shown in Figure 3).
Overall, the studies performed for both standard (7, 8) and
more challenging (11, 12) substrates show that Grubbs II
type precatalysts with NHC ligands containing correctly
substituted naphthyl side chains can clearly improve the
catalytic behavior of these ruthenium complexes without
loss of catalyst stability during the transformation. Figure 4
gives a ranking based on the structure of the side chains in
these saturated NHC ligands.
2.3. Synthesis and Characterization of Selected Hoveyda-
Grubbs II Type complexes and of a Grubbs II Type Complex
with an Unsaturated NHC Ligand. The studies above showed
that the NHC ligands (2,7)-SIPrNap (5d) and (2)-SICyNap
(5e) contain the preferred side chain geometries for ruthe-
nium metathesis precatalysts. We applied this finding to the
synthesis of two new Hoveyda-Grubbs II type precatalysts
with ligands 5d,e as well as to the synthesis of an analogue of
precatalyst 6d which incorporates an unsaturated NHC
counterpart of (2,7)-SIPrNap (5d). In the case of Hoveyda-
Grubbs II type ruthenium catalysts, the mechanism by which
the precatalyst is activated is still unclear and we believed
that time-conversion studies with our new NHC ligands
might reveal interesting insights into differences between the
two catalyst families. Similarly, very different reactivities

780 Organometallics, Vol. 29, No. 4, 2010
Vieille-Petit et al.
Scheme 3. Synthesis of (2,7)-IPrNap (20)a
a Legend: (a) HNO3, AcOH, 0 °C to room temperature; (b) cat. Pd/C, H2, MeOH, room temperature; (c) glyoxal, cat. HCOOH, MeOH, room
temperature; (d) (CH2O)n, HCl/dioxane, EtOAc, 0 °C to room temperature; (e) tBuOK, THF, room temperature; (f) [RuCl2(dCHPh)(PCy3)2] (GI),
toluene, room temperature.
have been reported for SIMes- and IMes-derived second-
generation Grubbs II type catalysts,13 prompting us to
synthesize the unsaturated homologue of 5d.
2.3.1. Hoveyda-Grubbs II Complexes. The Hoveyda-
Grubbs II type ruthenium complex [RuCl2{(2,7)-SIPrNap}-
(dCH-o-iPrO-Ph)] (15d) was prepared from [RuCl2(dCH-
o-iPrO-Ph)(PCy3)] (Hoveyda-Grubbs I, HGI) by simple
exchange of the phosphine ligand with (2,7)-SIPrNap (5d)
in the presence of CuCl (Scheme 2, top). For the synthesis of
precatalyst [RuCl2{(2)-SICyNap}(dCH-o-iPrO-Ph)] (15e),
we chose the alternative pathway which starts with the
Grubbs II type complex 6e that subsequently undergoes
cross metathesis with 2-isopropoxystyrene in the presence
of CuCl (Scheme 2, bottom).9b-d,21 In both cases, complete
reaction was monitored by 31P{1H} NMR spectroscopy
(disappearance of the signal corresponding to bound tri-
cyclohexylphosphine). The air-stable complexes 15d,e were
purified by column chromatography on silica gel with
CH2Cl2/hexane (1:1) as eluent, leading to pure green micro-
Figure 6. ORTEP diagram (30% ellipsoids) of complex 21.
crystalline products in moderate (51% for 15e) to good (76%
Selected bond lengths (A): Ru-CNHC, 2.091(8); Ru-Cbenzylidene
1.841(6); C(2)-C(3), 1.33(1). Selected bond angle (deg):
CNHC-Ru-Cbenzylidene, 99.5(3).
,
for 15d) yield. While the syn:anti ratio of the ligands was
maintained during the synthesis of these complexes, syn-15e
could not be eluted from the column, justifying the lower
overall yield in this case.
sopropylnaphthalene (16) under hydrogen pressure in the
presence of catalytic amounts of Pd/C23 gave amine 17
in >50% yield over these two steps (Scheme 3). Condensa-
tion with glyoxal and ring closing with paraformaldehyde
using a patented procedure24 resulted in clean (2,7)-IPr-
Full characterization of the new Hoveyda-Grubbs type
complexes included X-ray structure analyses of crystals
obtained by slow diffusion of hexane into concentrated
solutions of 15d,e in dichloromethane (Figure 5). The overall
geometry around the transition-metal center and most of the
bond lengths and angles are similar to those of the parent
Hoveyda-Grubbs II catalyst [RuCl2(SIMes)(dCH-o-iPrO-
Ph)] (HGII).9b The Ru-CNHC bond distances in these com-
plexes are slightly shorter than for Grubbs II type complexes,
indicating a tighter binding situation due to the replacement
of the bulky phosphine trans to the NHC with the chelating
ether fragment of the benzylidene moiety.
Nap HCl (19) that was subsequently deprotonated to give
3
(2,7)-IPrNap (20). Not surprisingly, both 19 and 20 were
obtained as a ca. 1:1 mixture of syn and anti isomers, as
evidenced by 1H and 13C NMR spectroscopy.
Free carbene 20 was then incorporated into the complex
[RuCl2{(2,7)-IPrNap}(dCHPh)(PCy3)] (21) by following
the synthetic procedure reported above for the other Grubbs
II type precatalysts (Scheme 3). The structure of 21 was
unambiguously assigned by X-ray diffraction studies on
single crystals grown by diffusion of methanol into a con-
centrated dichloromethane solution containing the complex.
A representation of anti-21 is shown in Figure 6 together
with a list of selected bond lengths and angles. The overall
geometry around the transition-metal center and most of
the bond lengths and angles in 21 are comparable to those of
the parent complex [RuCl2(IMes)(dCHPh)(PCy3)] (3),6a
2.3.2. Grubbs II Complex Containing an NHC with an
Unsaturated N-Heterocycle. The ligand (2,7)-IPrNap (20)
featuring an unsaturated central N-heterocycle and its pre-
cursor imidazolium salt (2,7)-IPrNap HCl (19) were ob-
3
tained by adapting literature procedures. Most importantly,
the naphthylamine derivative 17 was synthesized via a rather
selective nitration step, where the unwanted 4-nitro-2,7-dii-
sopropylnaphthalene derivative was eliminated by column
chromatography.22 Subsequent reduction of 1-nitro-2,7-dii-
(21) Schoeps, D.; Buhr, K.; Dijkstra, M.; Ebert, K.; Plenio, H. Chem.
Eur. J. 2009, 15, 2960.
(22) For nitration of similar naphthalene derivatives, see: Erichomo-
(23) For reduction of tert-butyl-substituted nitronaphthalenes, see:
€
Quast, H.; Nudling, W.; Klemm, G.; Kirschfeld, A.; Neuhaus, P.;
Sander, W.; Hrovat, D. A.; Thatcher Borden, W. J. Org. Chem. 2008,
73, 4956.
ꢀ
ꢀ
vitch, L.; Menard, M.; Chubb, F. L.; Pepin, Y.; Richer, J.-C. Can. J.
Chem. 1966, 44, 2305.
(24) Nolan, S. P. International Patent WO 2008/036084 A1, 2008.

Article
Organometallics, Vol. 29, No. 4, 2010 781
Figure 7. Time-conversion plots for the RCM of 7 (left) and 8 (right), using 1 mol % of catalyst precursor.
Figure 8. Time-conversion plots for the RCM of 7 (left) and 8 (right), using 1 mol % of 21 as catalyst precursor.
and of complexes 6b-e that feature NHC ligands with
saturated N-heterocycles. The only noticeable difference
consists of the obviously shorter carbon-carbon distance
in the backbone of the unsaturated NHC (1.33(1) A in
anti-21 compared to 1.505(8) A in anti-6d).
made the same observation in the RCM of 8 catalyzed by
ruthenium complexes bearing unsymmetrical N-heterocyclic
carbene ligands.14b,c In their study and in contrast to the
results presented here, these modified catalysts have been
shown to be clearly less active than HGII. In our case, 15d,e
still perform slightly better than the parent HGII complex.
Overall, however, the differences in activity are much less
pronounced than for phosphine-containing Grubbs II type
precatalysts and the curves indicate little difference in the initial
reaction rate among HGII and 15d,e. The most plausible
explanation for this behavior might be that bulky ligands 5d,e
lead to a clear initial rate enhancement in the case of phosphine-
containing catalysts, where a well-established dissociative
mechanism is at work, whereas Hoveyda-Grubbs II type
catalysts possibly initiate via an associative mechanism of the
olefin and NHC ligand sterics would consequently play a less
important role in the activation of the precatalyst.
To complete our time-conversion studies, the catalytic
potential of [RuCl2{(2,7)-IPrNap}(dCHPh)(PCy3)] (21) was
recorded for diallyltosylamide (7) and diethyl diallylmalonate
(8) using 1 mol % of catalyst loading (27 °C, 0.1 M sub-
strate/solvent). Figure 8 represents the data and compares
them to those for both GII and its ruthenium analogue 6d,
which features the saturated NHC ligand. The differences
in overall activity between saturated and unsaturated
NHC-containing ruthenium catalysts (6d vs 21) are truly
remarkable. While these activity trends have been reported
2.4. Time-Conversion studies of Precatalysts 15d,e and 21
for the RCM of Substrates 7 and 8. Conversions of the
substrates diallyltosylamide (7) and diethyl diallylmalonate
(8) using 1 mol % of catalysts 15d,e (27 °C, 0.1 M substrate/
solvent) were once again followed by 1H NMR spectroscopy.
Parallel reactions were also performed with the SIMes-
containing Hoveyda-Grubbs II catalyst [RuCl2(SIMes)-
(dCH-o-iPrO-Ph)] (HGII), and kinetic data were also recor-
ded for the more recently reported and commercially available
[RuCl2{(2)-SIMePh}(dCH-o-iPrO-Ph)] (HGII0).15b For bet-
ter comparison, Figure 7 also contains the kinetic runs of
6d,e and GII. Several observations can be made when examin-
ing the plots. First, modified HGII0, which was developed
for RCM of highly substituted dienes,15b is clearly not a good
candidate for the ring closing of normal substrates. Second
and somewhat surprising is the fact that HGII performs
slightly better than GII for both substrates 7 and 8. The inverse
trend is followed with the ruthenium catalysts containing
(2,7)-SIPrNap (5d) and (2)-SICyNap (5e), meaning that an
overall lower catalytic activity of Hoveyda-Grubbs type
complexes (15d,e) compared to their Grubbs II analogues
(6d,e) can be observed. It should be noted that Grubbs et al.

782 Organometallics, Vol. 29, No. 4, 2010
Table 1. Comparative Study in the RCM of Dienesa
Vieille-Petit et al.
a Reactions performed in CH2Cl2 at room temperature using 1 mol % of precatalyst, unless noted otherwise. b Reaction performed in CH2Cl2 at 40 °C
using 2 mol % of precatalyst.
for SIMes/IMes and SIPr/IPr modified benzylidene,13
indenylidene,25 and Hoveyda-type complexes,26 a satisfac-
tory interpretation of these differences remains elusive.
Both electronic and steric factors of a given pair of
unsaturated and saturated NHCs have been shown for
other systems to be practically undistinguishable27 and
cannot explain the kinetic data obtained here. An espe-
cially noteworthy feature of the graphs depicted in Figure 8
is the very different initial reaction rates between 6d and 21,
(27) (a) Dorta, R.; Stevens, E. D.; Scott, N. M.; Costabile, C.;
Cavallo, L.; Hoff, C. D.; Nolan, S. P. J. Am. Chem. Soc. 2005, 127,
ꢀ
(25) Clavier, H.; Nolan, S. P. Chem. Eur. J. 2007, 13, 8029.
(26) (a) Bieniek, M.; Michrowska, A.; Usanov, D. L.; Grela, K.
2485. (b) Díez-Gonzalez, S.; Nolan, S. P. Coord. Chem. Rev. 2007, 251, 874.
(c) Kelly, R. A.III; Clavier, H.; Guidice, S.; Scott, N. M.; Stevens, E. D.;
Bordner, J.; Samardjiev, I.; Hoff, C. D.; Cavallo, L.; Nolan, S. P. Organo-
metallics 2008, 27, 2002.
ꢀ
Chem. Eur. J. 2008, 14, 806. (b) Clavier, H.; Caijo, F.; Borre, E.; Rix, D.;
Boeda, F.; Nolan, S. P.; Mauduit, M. Eur. J. Org. Chem. 2009, 4254.

Article
Organometallics, Vol. 29, No. 4, 2010 783
Table 2. Comparative Study in the RCM of Enynesa
a Reactions performed in CH2Cl2 at room temperature using 1 mol % of precatalyst, unless noted otherwise. b Reaction performed in CH2Cl2 at 40 °C
using 2 mol % of precatalyst.
which either suggests that the ease of initial phosphine
dissociation is very different for these two catalysts or,
perhaps more likely, that the activation step of precatalyst
21 follows an associative mechanism instead. Another
intriguing point may be made regarding the activity of 21
toward the two model substrates. While the times needed
for full conversion of 8 with 21 or GII are similar, the new
catalyst does not perform as well with the tosylamide-
based substrate 7. Nonetheless, catalyst 21 seems to be
rather robust and does not decompose during these RCM
reactions.
2.5. Scope Investigation in Ring-Closing Metathesis and
Cross-Metathesis. The detailed studies above indicate that
Grubbs II type complexes 6d,e show the best activity in the
RCM of standard substrates leading to five-membered rings,
outperforming both the Hoveyda-Grubbs II type com-
pounds 15d,e and the unsaturated benzylidene-type preca-
talyst 21. To assess the overall metathesis performance of
these new compounds, we therefore investigated their cata-
lytic behavior in RCM of a wider range of substrates. At the
same time, we tested them in a range of enyne ring-closing
metathesis reactions as well as in the cross-metathesis of
selected olefins. Precatalysts 6d,e were directly compared to
the less active 6a in order to assess whether some substrates
preferentially lead to RCM product with 6a containing a less
bulky NHC ligand. An abridged study was performed for
precatalysts 15d,e and benzylidene-type catalyst 21 contain-
ing the unsaturated NHC ligand. In order to facilitate
assessment, all catalytic runs were carried out at standard
dilution (0.1 M) and at room temperature unless noted
otherwise.28 As can be seen from the results below, catalytic
data with the different precatalysts follow the same trends
observed for the runs shown above.
2.5.1. Ring-Closing Metathesis. Special attention was fo-
cused on tolerance toward functional groups, on the influ-
ence of ring size as well as the degree of substitution of the
unsaturated bonds. The results are depicted in Table 1. As a
general trend, differences between precatalysts 6d,e were
found to be minute, which confirms the results obtained
through kinetic studies. On the other hand, the (2,7)-SIMe-
Nap-containing ruthenium complex 6a displayed a signifi-
cantly reduced activity compared to 6d,e. This could be
directly related to the fact that sterically demanding NHCs
enhance phosphine dissociation and consequently increase
the rate of the initiation step of olefin metathesis. As
commonly encountered, RCM leading to the formation of
seven-membered rings necessitated longer reaction times
(entries 2, 4, and 9).25 Excellent product yields with trisub-
stituted olefins were isolated after short reaction times
(entries 3 and 5), confirming the precedent study. RCM
leading to a tetrasubstituted cyclic olefin was found to be
more difficult, and reactions were carried out at 40 °C
using 2 mol % of catalyst (entry 6). Despite this, product
yields were moderate and entry 6 highlights a current short-
coming of these new catalysts. Interestingly, complex 6e with
a bulky NHC ligand surpassed 6a (and 6d) in this transfor-
mation. While an interpretation is rather speculative at this
point, it should be noted that in contrast to 6a,d, which are
present as a 1:1 mixture of syn and anti NHC isomers, 6e
(28) Higher concentrations seem to be beneficial in metathesis reac-
tions; see ref 20.

784 Organometallics, Vol. 29, No. 4, 2010
Table 3. Comparative Study in Cross-Metathesisa
Vieille-Petit et al.
a Reactions performed in CH2Cl2 at room temperature using 1 mol % of precatalyst. b Traces of dimer (E/Z = 5:1) were isolated (4-8%). c 20% of the
dimer (E/Z = 5:1) was isolated.
consists of predominantly anti-(2)-SICyNap ligand and
this spatial arrangement of the NHC has already been shown
to be beneficial for these challenging substrates.20 In addition
to ester- and tosylamide-based substrates, catalysts 6a,d,e
were found to be tolerant to various functional groups such
as amides (entry 7), nitriles (entry 8), ethers (entries 9-11),
and alcohols (entry 12). Three of the substrates in Table 1
were also tested with precatalysts 15d,e and 21 (entries 3, 4,
and 10). Product yields are high when these catalysts are
employed, but in accordance with the results obtained
above, slightly longer reaction times were needed to reach
full conversion.
2.5.2. Ring-Closing Enyne Metathesis. Ring-closing enyne
metathesis represents a powerful method for the synthesis of
exocyclic 1,3-dienes, which can go on to react further in
Diels-Alder reactions or Claisen rearrangements.1a,29 We
investigated the RCM of various enynes (Table 2). The
substrate presented in entry 1 reacts in a straightforward
manner, and consequently no activity difference could be
observed between the catalysts. Overall, the same trend was
found as for the RCM of dienes; i.e., catalysts 6d,e exhibited
activities superior to that of 6a (entries 2 and 4). Enormous
reactivity differences exist, though, which are not linked to
the differences in precatalyst structure but originate from
subtle changes in both the double and triple bonds of the
substrates. Introducing a fully methylated double bond into
tosylamide-derived substrates (entry 4) surprisingly leads to
high conversions to product, in comparison to the very poor
reactivities seen for the double bond featuring a methylene
end group (entry 3). Likewise, introduction of a terminal
methyl group onto the triple bond leads to enhanced reac-
tivity in comparison to the parent triple bond (entry 5 vs 3).30
Entry 5 also indicates that especially 6e performs better
than other second-generation ruthenium catalysts, which
for this and similar substrates show various amounts of side
(30) (a) Kitamura, T.; Sato, Y.; Mori, M. Adv. Synth. Catal. 2002,
344, 678. For a discussion on the reaction mechanism in enyne metathesis,
see: (b) Lloyd-Jones, G. C.; Marque, R. G.; de Vries, J. G. Angew. Chem.,
Int. Ed. 2005, 44, 7442.
(29) (a) Poulsen, C. S.; Madsen, R. Synthesis 2003, 1, 18. (b) Clark,
D. A.; Kulkarni, A. A.; Kalbarczyk, K.; Schertzer, B.; Diver, S. T. J. Am.
Chem. Soc. 2006, 128, 15632.

Article
Organometallics, Vol. 29, No. 4, 2010 785
products.31 Unfortunately, in the case of the ether-contain-
ing substrate depicted in entry 6, only traces of product were
observed with 6a,d,e, as analyzed by 1H NMR of the crude
reaction mixture. Interestingly, Hoveyda-Grubbs II type
precatalysts 15d,e give slightly better results in enyne meta-
thesis reactions than their Grubbs II analogues 6d,e. This is
apparent in entry 4, where their higher reactivity allowed
reduction of the reaction time required for the isolation of
the product in quantitative yields. Unsaturated 21 once again
performed well but showed lower overall reactivity.
NHC ligand. Better reactivity combined with at least equal
stability makes the best NHC structures reported here very
interesting alternatives to commercially available SIMes-
derived precatalysts. A more scalable synthesis of these
ligands that does not require chromatographic purification
steps and further fine-tuning of the substitution pattern on
the naphthyl side chains are underway and will be reported in
due course.
4. Experimental Section
2.5.3. Cross-Metathesis. In comparison to RCM, cross-
metathesis (CM) is certainly an underutilized olefin metath-
esis transformation.2c The basic reason for this underutiliza-
tion lies in the fact that CM lacks the entropic driving force of
RCM and often leads to relatively low statistical yields of the
desired cross-product, as well as poor E/Z cross-product
selectivity.32 Table 3 gives an overview on the scope and
limitations of the new catalysts in cross-metathesis reactions
of terminal alkenes and R,β-unsaturated olefins. Of note, for
all reactions carried out, the secondary reaction product was
isolated and identified as the starting material except where
noted. Overall, examples shown in Table 3 corroborate the
trend observed in the RCM of dienes and enynes, as we see
noticeably superior catalytic performances of catalysts 6d,e
in comparison to 6a. Whereas methyl acrylate and methyl
vinyl ketone were well tolerated (entries 1 and 2), the use of
acrolein as a less activated olefin partner led to a dramatic
reduction of the isolated yields (entry 3). On the other hand,
cis-2-butene-1,4-diol (only 1 equiv used) gave excellent yields
without any traces of isomerization (entry 4). In addition to
aliphatic partners, we engaged a styrene derivative in the
cross-metathesis, with methyl acrylate leading to good iso-
lated yields with 6d,e and slightly lower ones with complex 6a
(entry 5). An allylamide-type olefin has been tried as a
coupling partner but provided poor yields (entry 6). Eugenol
(entries 7 and 8) can also be used to good effect as a CM
partner, although some dimeric material was formed due to
self-cross-metathesis. It is interesting to note that the amount
of byproducts in the CM in entries 7 and 8 is lowest for 6e and
highest for 6d. Finally, entry 1 also shows that the less active
benzylidene-type complex 21 is still a better choice for cross-
metathesis reactions than the Hoveyda-Grubbs II precata-
lyst 15d.
4.1. Materials and General Considerations. All manipulations
were carried out under an inert atmosphere of nitrogen using
Schlenk or glovebox (Mecaplex or Innovative Technology)
techniques, unless otherwise noted. Solvents were either distilled
from appropriate drying agents or purged with argon and
collected after passage through alumina columns in a solvent
purification system (Innovative Technology). Deuterated NMR
solvents were purchased from Armar Chemicals, degassed,
and dried over activated molecular sieves of appropriate size.
NMR spectra were recorded using Bruker ARX-300, AV2-400,
and AV-500 spectrometers and treated with MestReC or 1D
WINNMR. Mass spectra and elemental analyses were recorded
by the analytical services of the Institute of Organic Chemistry
(UZH). [RuCl2(dCHPh)(PCy3)2] (GI), [RuCl2(dCH-o-iPrO-Ph)-
(PCy3)] (HGI), [RuCl2(SIMes)(dCH-o-iPrO-Ph)] (HGII), and
[RuCl2{(2)-SIMePh}(dCH-o-iPrO-Ph)] (HGII0) were purchased
from Aldrich and used as received. [RuCl2(SIMes)(dCH-Ph)-
(PCy3)] (GII),7,33 [RuCl2{(2)-SIMePh}(dCH-Ph)(PCy3)] (GII0)15b
and 2-isopropoxystyrene34 were prepared according to literature
procedures. The syntheses of compounds [RuCl2{(2,7)-SIMe-
Nap}(dCH-Ph)(PCy3)] (6a),16a [RuCl2{(2)-SIPrNap}(dCH-Ph)-
(PCy3)] (6b),17 [RuCl2{(2,6)-SIPrNap}(dCH-Ph)(PCy3)] (6c),17
[RuCl2{(2,7)-SIPrNap}(dCH-Ph)(PCy3)] (6d),17 [RuCl2{(2)-SI-
CyNap}(dCH-Ph)(PCy3)] (6e),17 and (2,7)-SIPrNap (5d)16a were
reported elsewhere. 2,7-Diisopropylnaphthalene was purchased
from TCI Laboratory Chemicals, and all other chemicals were
obtained from Aldrich or Acros and used without further pur-
ification. Silica gel for flash chromatography was purchased from
Macherey-Nagel. The data for the crystal structure determina-
tions were collected on a Nonius KappaCCD area-detector
diffractometer using graphite-monochromated Mo KR radiation
(λ = 0.710 73 A) and an Oxford Cryosystems Cryostream 700
cooler. Data reduction was performed with HKL Denzo and
Scalepack.35 The SHELXL97 program was used for structure
refinement.36 Detailed crystallographic data for complexes 6b-e
can be found in ref 17. The CCDC files 749672-749674 contain
the supplementary crystallographic data for compounds 15d-f.
These data can be obtained free of charge from the Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif. For the structures of 6b-e, see ref 17.
3. Conclusions
A series of second-generation ruthenium-based olefin
metathesis catalysts bearing N-naphthyl-substituted N-het-
erocyclic carbene (NHC) ligands has been prepared and
completely characterized. The starting point of the present
investigation was the synthesis of a series of Grubbs II type
precatalysts with NHCs containing naphthyl side chains
alkylated at the ortho position (2-position) and optionally
at the second aromatic ring (6- or 7-position). Detailed
kinetic data on the RCM reactions revealed how these
substitution patterns affect the catalytic performance of the
catalysts and identified two preferred NHC architectures.
This finding was then applied to the synthesis of the corres-
ponding Hoveyda-Grubbs II type complexes and for the
synthesis of a Grubbs II catalyst featuring an unsaturated
4.2. Synthetic Procedures. 4.2.1. [RuCl2{(2,7)-SIPrNap}-
(dCH-o-iPrO-Ph)] (15d; ca. 1:1 Syn/Anti). In 20 mL of toluene,
a mixture of the free carbene (2,7)-SIPrNap (5d, mixture of
isomers; 120 mg, 0.245 mmol), [RuCl2(dCH-o-iPrO-Ph)(PCy3)]
(HGI; 100 mg, 0.166 mmol), and CuCl (18 mg, 0.182 mmol) was
stirred at room temperature. After 40 h, the 31P NMR spectrum
of the dark solution showed complete consumption of [RuCl2-
(dCH-o-iPrO-Ph)(PCy3)] and the solution was filtered and
evaporated to dryness. The green-brown residue was dissolved
(33) Trnka, T. M.; Morgan, J. P.; Sanford, M. S.; Wilhelm, T. E.;
Scholl, M.; Choi, T.-L.; Ding, S.; Day, M. W.; Grubbs, R. H. J. Am.
Chem. Soc. 2003, 125, 2546.
(34) Krause, J. O.; Nuyken, O.; Wurst, K.; Buchmeiser, M. R. Chem.
Eur. J. 2004, 10, 777.
(35) Otwinowski, Z.; Minor, W. In Macromolecular Crystallography,
Part A; Carter, C. W., Jr., Sweet, R. M., Eds.; Academic Press: New York,
1997; Methods in Enzymology Vol. 276, pp 307-326.
(31) Sashuk, V.; Grela, K. J. Mol. Catal. A 2006, 256, 59.
(32) Chatterjee, A. K.; Choi, T. L.; Sanders, D. P.; Grubbs, R. H.
J. Am. Chem. Soc. 2003, 125, 11360.
(36) Sheldrick, G. M. SHELXL97. Acta Crystallogr. 2008, A64, 112.

786 Organometallics, Vol. 29, No. 4, 2010
Vieille-Petit et al.
in a minimum amount of CH2Cl2/hexane (1:1), and this solution
was subjected to column chromatography on silica gel, in air,
using the same system of solvent for the elution. The green
fraction was collected and evaporated to dryness to give 15d as
a fine green powder. Yield: 103 mg (76%). Crystals suitable for
X-ray structure analysis were obtained by slow diffusion of
hexane into a concentrated solution of 15d in CH2Cl2. 1H NMR
(400 MHz, CD2Cl2, 27 °C): δ 16.40 and 16.22 (2s, 1H, RudCH),
8.39-6.64 (series of m, 14H, Harom), 4.69 (m, 1H, OCH(CH3)2),
4.59-4.32 (m, 4H, N(CH2)N), 4.13 (m, 1H, ArCH(CH3)2), 3.69
(m, 1H, ArCH(CH3)2), 3.25 (m, 1H, ArCH(CH3)2), 3.13 (m, 1H,
ArCH(CH3)2), 1.43-1.37 (series of d, 24H, ArCH(CH3)2),
1.11-0.90 (series of d, 6H, OCH(CH3)2) ppm. 13C{1H} NMR
(CD2Cl2, 125 MHz, 27 °C): δ 291.7, 291.1, 213.8, 213.4, 152.1,
152.0, 146.8, 146.5, 146.1, 144.3, 131.8, 131.4, 129.5, 129.3,
129.0, 127.6, 127.5, 126.1, 125.3, 123.4, 123.3, 122.1, 121.8,
112.7, 74.9, 35.8, 35.6, 34.8, 34.4, 32.0, 30.1, 29.7, 29.4, 29.1,
29.0, 27.9, 27.8, 26.4, 25.5, 24.0, 23.4, 23.3, 23.2, 22.6, 22.4, 21.9,
21.1, 20.9, 20.7. 14.0 ppm. MS (CHCl3/MeOH): m/z 775.4 [M -
technical methanol. This solution was transferred into a high-
pressure autoclave, and Pd on carbon (5% wt. Pd, 210 mg) was
added. After it was purged repeatedly with hydrogen, the
autoclave was charged with 30 bar of H2. After the mixture
was stirred at room temperature for 24 h, the pressure was
released and the reaction mixture filtered through Celite. After
concentration, the residue was dissolved in a minimum amount
of hexane and the solution filtered on a silica gel plug, first
washing with hexane/CH2Cl2 (10/0.1 to 10/1) and subsequently
eluting the expected product with CH2Cl2. Evaporation of
volatiles and drying under vacuum led to 17 as a red-brown
oil (3.37 g, 81%). 1H NMR (CDCl3, 300 MHz): δ 7.67 (d, 1H,
Har), 7.58 (m, 1H, Har), 7.30-7.22 (m, 3H, Har), 4.13 (br, 2H,
NH2), 3.08 (m, 2H, 2 ꢀ CH(CH3)2), 1.31 (d, 3J = 6.9 Hz, 6H,
CH(CH3)2), 1.30 (d, 3J = 6.8 Hz, 6H, CH(CH3)2) ppm. 13C{1H}
NMR (CDCl3, 125 MHz): δ 145.4, 137.1, 131.3, 128.4, 126.5,
124.5, 123.8, 123.0, 118.6, 117.0 (Car), 34.7, 27.9 (CH(CH3)2),
24.0, 22.5 (CH(CH3)2) ppm. HRMS (ESI): m/z calcd for
C16H22N [M þ H]þ 228.174 68, found 228.174 30.
Cl]þ. Anal. Calcd for C45H55Cl2N2ORu 0.5C6H12: C, 67.43; H,
4.2.5. N,N0-Bis(2,7-diisopropylnaphthalene)ethylenediimine (18).
In air, amine 17 (3.71 g, 16.3 mmol) was dissolved in 100 mL of
technical methanol and treated with aqueous glyoxal solution
(40 wt %, 1.18 g) and a few drops of formic acid. The reaction
mixture was stirred overnight at room temperature. The yellow
precipitate was filtered off, washed with cold methanol, and dried
under vacuum to give 18 as a fine yellow powder (2.7 g, 69%). 1H
NMR (CDCl3, 300 MHz): δ 8.26 (s, 2H, N(CH)2N), 7.81-7.39
(series of m, 10H, Har), 3.31 (sept, 3J = 6.9 Hz, 2H, CH(CH3)2),
3.07 (sept, 3J = 6.9 Hz, 2H, CH(CH3)2), 1.34 (d, 3J = 6.9 Hz, 12H,
CH(CH3)2), 1.33 (d, 3J = 6.9 Hz, 12H, CH(CH3)2) ppm. 13C{1H}
NMR (CDCl3, 75 MHz): δ 164.7 (N(CH)2N), 146.6, 144.7, 132.4,
131.2, 127.8, 125.3, 125.1, 123.2, 119.3 (Car), 34.5, 28.3
(CH(CH3)2), 23.9, 23.5 (CH(CH3)2) ppm. HRMS (ESI): m/z calcd
for C34H40N2Na [M þ Na]þ 499.308 37, found 499.308 24.
3
7.31; N, 3.28. Found: C, 67.43; H, 7.24; N, 3.33.
4.2.2. [RuCl2{(2)-SICyNap}(dCH-o-iPrO-Ph)] (15e; Anti
Isomer). The complex [RuCl2{(2)-SICyNap}(dCH-Ph)(PCy3)]
(6e; 200 mg, 0.195 mmol) and CuCl (22 mg, 0.222 mmol) were
placed in a Schlenk tube, and CH2Cl2 (10 mL) was added. 2-
Isopropoxystyrene (56.9 mg, 0.390 mmol) dissolved in CH2Cl2
(10 mL) was then added, and the resulting bright violet solution
was stirred at 45 °C for 90 min. During that time, the color
changed to brown and then to dark green. After evaporation to
dryness, the green residue was dissolved in a minimum amount
of CH2Cl2/hexane (1:1) and this solution was subjected to
column chromatography on silica gel, in air, using the same
system of solvent for the elution. The green fraction was
collected and evaporated to dryness to give 15e as a fine green
powder. Yield: 80 mg (51%). Crystals suitable for X-ray struc-
ture analysis were obtained by slow diffusion of hexane into a
4.2.6. 1,3-Bis(2,7-diisopropylnaphthalen-1-yl)imidazolium Chlo-
ride [(2,7)-IPrNap HCl] (19; ca. 1:1 Syn/Anti). In air, diimine
3
1
concentrated solution of 15e in CH2Cl2. H NMR (400 MHz,
18 (1 g, 2.1 mmol) was dissolved/suspended in 20 mL of technical
ethyl acetate and the resulting mixture was cooled to 0 °C.
Separately, paraformaldehyde (82 mg, 2.7 mmol) was suspended
in HCl (4 N in dioxane, 1 mL) and the reaction mixture was stirred
until complete dissolution. The resulting clear solution was added
dropwise to the solution of 18 at 0 °C. After addition, the mixture
was stirred for 1 h at 0 °C and 2 h at room temperature. Then, the
resulting brown solution/suspension was evaporated to dryness;
the dark brown residue was dissolved in 10 mL of methanol and
the solution treated with NaHCO3. After filtration and concentra-
tion to around 2 mL, the concentrate was precipitated into ether
(ca. 100 mL). The pale brown precipitate was filtered off and
washed several times with ether until a white powder was obtained,
which was dried under vacuum. 19 was thus obtained with yields
ranging from 18% to 40%. 1H NMR (CDCl3, 300 MHz): δ 9.81
(s, 0.45H, N-CHdN of the minor isomer), 9.44 (s, 0.55H, N-
CHdN of one isomer), 8.60-7.52 (series of m, 10H, Har), 7.06 (s,
0.9H, N(CH)2N of the minor isomer), 6.89 (s, 1.1H, N(CH)2N of
the major isomer), 3.12-2.69 (series of sept, 4H, CH(CH3)2),
1.47-1.29 (series of d, 24H, CH(CH3)2) ppm. 13C{1H} NMR (125
MHz, CDCl3): δ 149.8, 149.7, 143.5, 143.1, 138.8, 138.0, 131.9,
131.8, 131.1, 131.0, 129.4, 129.1, 128.7, 128.5, 128.0, 127.5, 127.0,
126.3, 126.2, 126.1, 122.6, 122.5, 117.0, 116.2 (Car), 35.0, 34.5, 29.4,
29.3 (CH(CH3)2), 24.1, 24.0, 23.8, 23.7, 23.2 (CH(CH3)2) ppm.
HRMS (ESI): m/z calcd for C35H41N2 [M]þ 489.326 43, found
489.326 91.
CD2Cl2, 27 °C): δ 16.08 (s, 1H, RudCH), 8.32-6.52 (series of m,
16H, Harom), 4.73 (sept, 1H, OCH(CH3)2), 4.46-4.32 (m, 4H,
N(CH2)N), 3.67 (m, 2H, Ar(C6H11)), 2.03-1.28 (series of m,
20H, Ar(C6H11)), 1.10 (d, 3H, OCH(CH3)2), 1.03 (d, 3H, OCH-
(CH3)2) ppm. 13C{1H} NMR (CD2Cl2, 125 MHz, 27 °C): δ
290.8, 214.3, 152.1, 145.2, 144.1, 134.2, 133.1, 132.1, 129.6,
129.2, 127.6, 126.5, 125.9, 125.6, 125.2, 122.1, 121.8, 112.8,
74.9, 54.6, 39.7, 36.3, 32.4, 27.5, 26.7, 26.4, 21.2, 21.0 ppm.
MS (CHCl3/MeOH): m/z 771.3 [M - Cl]þ. Anal. Calcd for
C45H51Cl2N2ORu 0.33CH2Cl2: C, 65.12; H, 6.23; N, 3.35.
3
Found: C, 65.22; H, 6.33; N, 3.35.
4.2.3. 1-Nitro-2,7-diisopropylnaphthalene (16). In air, acetic
acid (glacial, 20 mL) and fuming HNO3 (2 mL) were mixed at
0 °C. (2,7)-Diisopropylnaphthalene (5 g, 23.5 mmol) was added
dropwisewhile the temperaturewas keptat0 °C. The mixturewas
kept at 0 °C for an additional 1 h, stirred for 1 h at room
temperature, and then neutralized with NaOH (2 N). The pH
was raised to 9-10 and the mixture extracted twice with dichlor-
omethane. The organic phase was washed with water, dried over
anhydrous MgSO4, filtered, and concentrated. The resulting
crude yellow-orange oil was subjected to column chromatogra-
phy on silica gel (hexane/CH2Cl2, 10/0.1 to 10/0.5), and the first
fraction contained pure 16 as a yellow oil after evaporation of
volatiles (4.26 g, 70%). 1H NMR (CDCl3, 400 MHz): δ 7.89 (d,
J = 8.6 Hz, 1H, Har), 7.80 (d, 8.6 Hz, 1H, Har), 7.47-7.41 (m,
3H, Har), 3.08 (m, 2H, 2 ꢀ CH(CH3)2), 1.34 (d, 3J = 6.8 Hz, 6H,
CH(CH3)2), 1.31 (d, 3J = 6.8 Hz, 6H, CH(CH3)2) ppm. 13C{1H}
NMR (CDCl3, 125 MHz): δ 149.3, 146.7, 136.6, 130.9, 130.2,
127.8, 126.4, 124.4, 122.3, 117.6 (Car), 34.5, 29.4 (CH(CH3)2),
23.6, 23.3 (CH(CH3)2) ppm. HRMS (EI): m/z calcd for
C16H19NO2 257.1416, found 257.1415.
4.2.7. 1,3-Bis(2,7-diisopropylnaphthalen-1-yl)imidazol-2-ylidene
[(2,7)-IPrNap] (20; ca. 1:1 Syn/Anti). [(2,7)-IPrNap HCl] (19;
3
200 mg, 0.38 mmol) was suspended in 5 mL of THF, and the
suspension was stirred for 15 min at room temperature. Freshly
sublimed KOtBu (46 mg, 0.42 mmol) was added. The initial
suspension turned instantaneously to a yellow solution. After
2 h of stirring at room temperature, the reaction mixture was
filtered through Celite and evaporated to dryness and the residue
4.2.4. 1-Amino-2,7-diisopropylnaphthalene (17). In air, nitro-
naphthalene 16 (4.7 g, 18.3 mmol) was dissolved in 100 mL of

Article
Organometallics, Vol. 29, No. 4, 2010 787
was extracted with toluene. After filtration of the toluene solu-
tion through Celite and evaporation to dryness, 20 was obtained
as a yellow-orange powder (128 mg, 69%). 1H NMR (C6D6,
400 MHz): δ 7.84-7.35 (series of m, 10H, Har), 6.87 (s, 0.9H,
N(CH)2N of one isomer), 6.86 (s, 1.1H, N(CH)2N of other
isomer), 3.63-3.00 (series of m, 4H, CH(CH3)2), 1.55-1.37
(series of d, 24H, CH(CH3)2) ppm. 13C{1H} NMR (125 MHz,
C6D6): δ 221.6, 221.3 (N-C-N), 147.4, 147.3, 143.1, 143.0, 135.9,
135.8, 132.7, 132.3, 131.9, 131.8, 128.6, 128.3, 128.1, 127.9, 126.1,
125.3, 123.3, 123.2, 122.4, 122.3, 120.7, 120.0 (Car), 35.2, 34.8, 29.0,
28.9 (CH(CH3)2), 24.4, 24.3, 24.25, 24.2, 24.1, 23.9, 23.7, 23.6
(Ar-CH(CH3)2) ppm.
started at this point) and introduced to the spectrometer, and
conversions were obtained by 1H NMR.
4.3.3. RCM of Allylmethallyl Tosylamide (11) and Diethyl
Allylmethallylmalonate (12). 4.3.3.1. Catalyst Loading of 0.5
mol %. To obtain the required catalyst amount, a solution of the
appropriate ruthenium complex (4 ꢀ 10-3 mmol) in 2 mL of
CH2Cl2 was prepared. A 200 μL portion of this solution was
transferred to a NMR tube and evaporated to dryness, and the
residue was dried for 1 h under vacuum. The tube was then
closed with a screw-cap septum top. Separately, in a small vial,
substrates 11 and 12 (0.08 mmol, 21.2 and 20.3 mg, respectively)
were dissolved in 0.8 mL (0.1 M) of CD2Cl2 and then transferred
via syringe to the respective NMR tubes containing the catalyst.
The tube was vigorously stirred for a few seconds (the reaction
time was started at this point) and introduced to the spectro-
meter, and conversions were obtained by 1H NMR.
4.4. Preparative Metathesis Reactions. 4.4.1. General Re-
marks. A Schlenk flask, under argon, was charged with the sub-
strate (0.5 mmol) and dry dichloromethane (5 mL, C=0.1 M),
and then the precatalyst (0.005 mmol) was added. The progress
of the reaction was monitored by TLC. The solvent was removed
under vacuum, and the crude residue was purified by flash
column chromatography to yield the pure product. Most sub-
strates and products have been previously described.3b,24,37-40
Characterization of new catalytic products is as follows.
4.4.2. (E)-6-Hydroxyhex-4-enyl benzoate (Table 3, Entry 4).
Colorless oil. 1H NMR (300 MHz, CDCl3): δ 7.98-7.94 (m, 2H,
HPh), 7.50-7.44 (m, 1H, HPh), 7.38-7.32 (m, 2H, HPh), 5.64-5.60
(m, 2H, CHdCH), 4.24 (t, J(H,H) = 6.5 Hz, 2H, O-CH2), 4.00
(d, J(H,H) = 4.3 Hz, 2H, CH2-OH), 2.16-2.10 (m, 2H, CH2-
CHdCH), 1.97 (s bd, 1H, OH), 1.78 (quint, J(H,H) = 7.0 Hz, 2H,
CH2-CH2-CH2) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ
167.1 (C), 133.3 (CH), 131.7 (CH), 130.7 (C), 130.5 (CH), 129.9
(CH), 128.8 (CH), 64.7 (CH2), 58.7 (CH2), 29.0 (CH2), 28.5 (CH2)
ppm. HRMS (ESI): m/z calcd for C13H16O3Na 243.0997 [M þ
Na]þ, found 243.0991.
4.4.3. (E)-N-(4-Oxopent-2-enyl)benzamide (Table 3, Entry 6).
Colorless oil. 1H NMR (300 MHz, CDCl3): δ 7.74-7.72 (m, 2H,
HPh), 7.48-7.43 (m, 1H, HPh), 7.39-7.35 (m, 2H, HPh), 6.74 (td,
J(H,H) = 16.1 and 5.1 Hz, 1H, CHdCH-CO), 6.57 (s br, 1H,
NH), 6.11 (td, J(H,H) = 16.1 and 1.7 Hz, 1H, CO-CHdCH),
4.19 (dt, J(H,H) = 6.0 and 0.9 Hz, 2H, CH2-NH), 2.18 (s, 2H,
CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ 198.6 (C), 167.9
(C), 143.3 (CH), 134.2 (C), 132.3 (CH), 131.4 (CH), 129.1 (CH),
128.9 (CH), 127.4 (CH), 41.2 (CH2), 27.6 (CH3) ppm. HRMS
4.2.8. [RuCl2{(2,7)-IPrNap}(dCHPh)(PCy3)] (21; ca. 1:1
Syn/Anti). In 20 mL of toluene, a mixture of the free carbene
(2,7)-IPrNap (20; 128 mg, 0.262 mmol) and [RuCl2(dCHPh)-
(PCy3)2] (GI; 166 mg, 0.201 mmol) was stirred at room tempera-
ture. After 24 h, complete consumption of [RuCl2(dCHPh)-
(PCy3)2] was observed by 31P NMR spectroscopy; the solution
was evaporated to dryness and dried overnight under vacuum.
The dark red residue was washed with 10 mL of methanol and
dissolved in a minimum of CH2Cl2. Diffusion of MeOH into this
concentrated solution gave 21 as dark red crystals suitable for
1
X-ray structure analysis. Yield: 100 mg (48%). H NMR (400
MHz, CD2Cl2, 27 °C): δ 19.43 (s, 1H, RudCH-Ph), 8.03-6.61
(m, 17H, Harom and N(CH)2N), 3.98-3.01 (series of m and sept,
4H, ArCH(CH3)2), 2.03-0.55 (series of m, 57H, ArCH(CH3)2
and P(C6H11)3) ppm. 13C{1H} NMR (125 MHz, CD2Cl2): δ
192.2, 191.6, 150.6, 150.5, 147.2, 146.4, 146.2, 146.1, 145.5, 143.7,
143.5, 133.7, 133.6, 132.1, 131.5, 131.4, 131.3, 131.2, 130.8, 130.7,
130.5, 130.3, 129.7, 127.2, 127.0, 126.8, 126.6, 126.5, 126.3, 126.2,
125.9, 125.8, 125.4, 124.8, 123.8, 122.9, 122.1, 122.0, 121.5, 119.9,
34.7, 34.3, 34.2, 34.1, 31.7, 31.6, 31.55, 31.5, 29.4, 29.2, 28.9, 28.6,
28.1, 27.7, 27.65, 27.6, 27.5, 26.2, 26.0, 25.8, 25.4, 25.0, 23.75, 23.7,
23.6, 23.5, 23.4, 23.0, 22.8, 22.5, 22.4, 21.9, 13.8. 31P{1H} (162
MHz, CD2Cl2, 27 °C): δ 31.37 and 31.19 (2s). MS (ESI, MeOH/
CH2Cl2): m/z 995.6 [M - Cl]þ. Anal. Calcd for C60H79Cl2N2-
PRu 1.5MeOH: C, 68.44; H, 7.94; N, 2.60. Found: C, 68.11; H,
3
7.80; N, 2.74.
4.3. Time-Conversion Studies. 4.3.1. General Remarks.
All catalytic samples were prepared under an inert atmosphere
of nitrogen using gloveboxes. All reactions were run in NMR
tubes equipped with a screw-cap septum top at 300 K (27 °C) at
a 0.1 M substrate/solvent ratio, and the conversions were
1
followed by H NMR spectroscopy. Substrates 7,36 8,12 11,38
and 1239 were synthesized according to literature procedures.
4.3.2. RCM of Diallyltosylamide (7) and Diethyl Diallylma-
lonate (8). 4.3.2.1. Catalyst Loading of 1 mol %. To obtain the
required catalyst amount, a solution of the appropriate ruthe-
nium complex (4 ꢀ 10-3 mmol) in 2 mL of CH2Cl2 was pre-
pared. A 400 μL portion of this solution was transferred to a
NMR tube and evaporated to dryness, and the residue was dried
for 1 h under vacuum. The tube was then closed with a screw-cap
septum top. Separately, in a small vial, substrates 7 and 8
(0.08 mmol, 20.1 and 19.2 mg, respectively) were dissolved in
0.8 mL (0.1 M) of CD2Cl2 and then transferred via syringe to the
respective NMR tubes containing the catalyst. The tube was
vigorously stirred for a few seconds (the reaction time was
started at this point) and introduced into the spectrometer,
and conversions were obtained by 1H NMR.
(37) Terada, Y.; Mitsuhiro, M.; Nishida, A. Angew. Chem., Int. Ed.
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10222.
(40) (a) Kirkland, T. A.; Grubbs, R. H. J. Org. Chem. 1997, 62, 7310.
(b) Bien, S.; Ovadia, D. J. Chem. Soc., Perkin Trans. 1 1974, 333.
(c) Baylouny, B. A. J. Am. Chem. Soc. 1971, 93, 4621. (d) F€urstner, A.;
Guth, O.; D€uffels, A.; Seidel, G.; Liebl, M.; Gabor, B.; Mynott, R. Chem.
Eur. J. 2001, 7, 4811. (e) Garbacia, S.; Desai, B.; Lavastre, O.; Kappe, C. O.
J. Org. Chem. 2003, 68, 9136. (f) Tamaru, Y.; Hojo, M.; Yoshida, Z. J. Org.
Chem. 1988, 53, 5731. (g) Brace, N. O. J. Org. Chem. 1971, 36, 3187.
(h) Edwards, P. G.; Paisey, S. J.; Tooze, R. P. J. Chem. Soc., Perkin Trans. 1
2000, 3122. (i) Diez-Barra, E.; de la Hoz, A.; Moreno, A.; Sanchez-Verdu, P.
J. Chem. Soc., Perkin Trans. 1 1991, 2589. (j) Marco, J. A.; Carda, M.;
Rodriguez, S.; Castillo, E.; Kneeteman, M. N. Tetrahedron 2003, 59, 4085.
(k) Schmidt, B. J. Chem. Soc., Perkin Trans. 1 1999, 2627. (l) Ojima, I.; Vu,
A. T.; Lee, S.-Y.; McCullagh, J. V.; Moralee, A. C.; Fujiwara, M.; Hoang,
T. H. J. Am. Chem. Soc. 2002, 124, 9164. (m) MoCri, M.; Sakakibara, N.;
Kinoshita, A. J. Org. Chem. 1998, 63, 6082. (n) Kataoka, T.; Yoshimatsu, M.;
Noda, Y.; Sato, T.; Shimizu, H.; Hori, M. J. Chem. Soc., Perkin Trans. 1 1993,
121. (o) F€urstner, A.; Ackermann, L.; Gabor, B.; Lehmann, C. W.; Mynott, R.;
Stelzer, F.; Thiel, O. R. Chem. Eur. J. 2001, 7, 3226. (p) Clavier, H.; Nolan,
S. P.; Mauduit, M. Organometallics 2008, 27, 2287. (q) Schleicher, K. D.;
Jamison, T. F. Org. Lett. 2007, 9, 875. (r) Blackwell, H. E.; O'Leary, D. J.;
Chatterjee, A. K.; Washenfelder, R. A.; Bussmann, D. A.; Grubbs, R. H. J. Am.
Chem. Soc. 2000, 122, 58.
4.3.2.2. Catalyst Loading of 0.1 mol %. To obtain the re-
quired catalyst amount, a solution of the appropriate ruthenium
complex (8 ꢀ 10-3 mmol) in 10 mL of CH2Cl2 was prepared. A
100 μL portion of this solution was transferred to a NMR tube
and evaporated to dryness, and the residue was dried for 1 h
under vacuum. The tube was then closed with a screw-cap
septum top. Separately, in a small vial, substrates 7 and 8
(0.08 mmol, 20.1 and 19.2 mg, respectively) were dissolved in
0.8 mL (0.1 M) of CD2Cl2 and then transferred via syringe to the
respective NMR tube containing the catalyst. The tube was
vigorously stirred for a few seconds (the reaction time was

788 Organometallics, Vol. 29, No. 4, 2010
Vieille-Petit et al.
(ESI): m/z calcd for C12H13NO3Na 226.0844 [M þ Na]þ, found
226.0844.
4.45 (dd, J(H,H) = 6.3 and 1.0 Hz, 2H, CH2-O), 3.79 (s, 3H,
CH3), 3.24 (d, J(H,H) = 6.7 Hz, 2H, CH2-CHdCH), 1.97 (s,
3H, CH3) ppm. 13C{1H} NMR (125 MHz, CDCl3): δ 171.3 (C),
147.0 (C), 144.5 (C), 135.4 (CH), 131.8 (C), 125.4 (CH), 121.6
(CH), 114.8 (CH), 111.6 (CH), 65.4 (CH2), 56.3 (CH3), 38.7
(CH2), 21.4 (CH3) ppm. HRMS (ESI): m/z calcd for
C13H16O4Na 259.0946 [M þ Na]þ, found 259.0948.
4.4.4. (E)-Ethyl 4-(4-Hydroxy-3-methoxyphenyl)but-2-eno-
ate (Table 3, Entry 7). Colorless oil. 1H NMR (300 MHz,
CDCl3): δ 7.00 (dt, J(H,H) = 15.5 and 6.7 Hz, 1H, CH2-
CHdCH), 6.77 (d, J(H,H) = 8.1 Hz, 1H, HPh), 6.60-6.57 (m, 2H,
H
Ph), 5.72 (dt, J(H,H) = 15.5 and 1.7 Hz, 1H, CH2-CHdCH),
5.62 (s, 1H, OH), 4.10 (q, J(H,H) = 7.1 Hz, 2H, CH2-CH3), 3.77
(s, 3H, CH3), 3.36 (dd, J(H,H) = 6.7 and 1.7 Hz, 2H, CH2-
CHdCH), 1.19 (t, J(H,H) = 7.1 Hz, 3H, CH3) ppm. 13C{1H}
NMR (125 MHz, CDCl3): δ 167.1 (C), 148.2 (CH), 147.1 (C),
144.8 (C), 129.9 (C), 122.4 (CH), 121.9 (CH), 115.0 (CH), 111.7
(CH), 60.2 (CH2), 56.3 (CH3), 38.6 (CH2), 14.7 (CH3) ppm.
HRMS (ESI): m/z calcd for C13H16O3Na 259.0946 [M þ Na]þ,
found 259.0943.
Acknowledgment. R.D. thanks the Alfred Werner
Foundation for an Assistant Professorship. L.V.-P.
thanks the Legerlotz Foundation for a research fellow-
ship. For work conducted in St. Andrews, the EC is
gratefully acknowledged for funding of this work through
the FP7 (No. CP-FP 211468-2-EUMET).
4.4.5. (E)-4-(4-Hydroxy-3-methoxyphenyl)but-2-enyl Acetate
(Table 3, Entry 8). Colorless oil. 1H NMR (300 MHz, CDCl3): δ
6.78-6.76 (m, 1H, HPh), 6.60-6.57 (m, 2H, HPh), 5.88-5.77 (m,
1H, CHdCH), 5.58 (s, 1H, OH), 5.58-5.48 (m, 1H, CHdCH),
Supporting Information Available: CIF files giving crystal-
lographic data for 15d,e and 21. This material is available free of
charge via the Internet at http://pubs.acs.org.