New nitrochromenylmethylidene-containing ruthenium metathesis catalyst

Article abstract of DOI:10.1016/j.jorganchem.2011.12.024

New Hoveyda-Grubbs type catalyst containing nitrochromenyl ligand is reported herein. The catalyst was tested in model RCM, CM and enyne reactions. Its activity was compared with that of commercially available complexes and with literature data for Grela catalyst. New catalyst appeared to be fast initiating, but less stable than other catalysts.

Full text of DOI:10.1016/j.jorganchem.2011.12.024

Journal of Organometallic Chemistry 701 (2012) 87e92
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Journal of Organometallic Chemistry
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New nitrochromenylmethylidene-containing ruthenium metathesis catalyst
*
Agnieszka Hryniewicka, Anna Koz1owska, Stanis1aw Witkowski
Institute of Chemistry, University of Białystok, Al. Piłsudskiego 11/4, 15-443 Białystok, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
New Hoveyda-Grubbs type catalyst containing nitrochromenyl ligand is reported herein. The catalyst
was tested in model RCM, CM and enyne reactions. Its activity was compared with that of commercially
available complexes and with literature data for Grela catalyst. New catalyst appeared to be fast initi-
ating, but less stable than other catalysts.
Received 15 July 2011
Received in revised form
8 December 2011
Accepted 22 December 2011
Ó 2012 Elsevier B.V. All rights reserved.
Keywords:
Olefin metathesis
Ruthenium catalyst
Chromene
Methylidene complex
1. Intoduction
stereoelectronic effects were observed [8]. Introduction of this
system may provide a catalyst with some advantageous properties.
Development of metathesis catalysts that combine high activity
with excellent tolerance to a variety of functional groups has been
key to the widespread application of olefin metathesis in organic
synthesis [1]. Much of this success can be attributed to the
discovery of well-defined ruthenium complexes such as Grubbs 1st
generation catalyst (PCy3)2Cl2Ru]CHPh [2], Grubbs 2nd genera-
tion catalyst (1, Fig. 1) [3] and phosphine-free second generation
Hoveyda-Grubbs (2, Fig. 1) [4]. The numerous attempts of
improvement of the ruthenium metathesis catalysts have been
reported. The most popular modifications include variation in N-
heterocyclic carbene fragments [5], chelating alkoxybenzylidene
parts [6] as well as exchange of chloride ligands [7]. Among these
catalysts Hoveyda-Grubbs type complexes have received consid-
erable attention due to very good handling properties. They show
excellent stability to oxygen and moisture. They can be recovered
and chromatographically purified after the reaction for using in
subsequent process [4].
We have described earlier such ruthenium complexes 3e5 (Fig. 1),
which appeared to promote slowly ring-closing metathesis at room
temperature, but they were active at elevated temperature [9].
Ruthenium complex 6 (Fig. 1), containing chromenylmethylidene
part instead of ortho-isopropoxybenzylidene ligand has been
recently synthesized also by our group [10]. In the parent Hoveyda
catalyst 2 the chelating oxygen atom was provided by freely
rotating isopropoxyl substituent. Replacement of this moiety with
conformationally stiffened chromenylmethylidene part, where the
complexing oxygen derived from heterocyclic ring (6, Fig. 1), gave
the catalyst some new attributes. It proved to be quite efficient. It
showed activity comparable to that of commercially available
complexes 1 and 2. The catalyst appeared to be active in ring closing
metathesis (RCM) leading to di-, tri- and even tetrasubstituted
alkenes. It was also very efficient in cross metathesis (CM) of a,b-
unsaturated compounds (e.g. ethyl acrylate). Similarly to Hoveyda-
Grubbs catalysts, the complex 6 was storable and resistant to air
and moisture [10].
Nevertheless, synthesis of tetrasubsituted olefins and efficient
E/Z stereochemistry control in cross metathesis still remain
challenging task. This limitation stimulates further efforts for
construction of new catalysts.
Our earlier experience in vitamin E chemistry prompted us
to synthesize new catalysts bearing chromanylmethylidene ligand.
One of the most interesting modifications of classical Hoveyda-
Grubbs catalyst was introduction of p-nitro group into iso-
propoxystyrene ligand in Grela catalyst (7, Fig. 2), leading to an
increase of reactivity, especially in formation of trisubstituted
double bonds [11]. The success of 7 prompted us to a modification
of chromenyl catalyst 6, where the methyl group at 6 position in
chromene moiety would be replaced with nitro substituent. Strong
electronegative nitro group should change the complexating
properties of the endocyclic ethereal oxygen atom. As a conse-
quence, oxygeneruthenium bond should be weakened and an
In chromanolea-tocopherol model compound, some specific
* Corresponding author. Tel.: þ48 85 7457586; fax: þ48 85 7457581.
E-mail addresses: wit@uwb.edu.pl, staniwit@wp.pl (S. Witkowski).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.12.024

88
A. Hryniewicka et al. / Journal of Organometallic Chemistry 701 (2012) 87e92
N
N
N
N
Cl
Cl
Ru
Ru
O
Cl
Cl
Ph
PCy3
1
N
N
2
Cl
Ru
O
Cl
N
N
N
N
Cl
Cl
Ru
O
Ru
6
Cl
Cl
O
R
O
O
3: R = C16H33
4: R = CH3
5
Fig. 1. Examples of ruthenium olefin metathesis catalysts.
initiation step in metathesis process would be made easier. The
proposed catalyst 8 is displayed in Fig. 2.
(Scheme 2). In the first approach, the reaction was carried out in
refluxing CH2Cl2 in the presence of CuCl. In the alternative pathway
the alkylidene complex 10 was subjected to double exchange: with
NHC liberated from chloroform adduct 11 [14], prepared from
imidazolinium salt [15], followed by nitrochromenyl ligand 9.
Both pathways appeared to be quite efficient, however, the
second one seems to be economically more profitable. The alkyli-
dene complex 10 is commercially available and four times cheaper
than 1. It can be also easy to synthesize from RuCl2(PPh3)3 [13].
Probably due to some termal unstability of 8, the exchange of ligand
runs better at room temperature (up to 70% yield) than at 40 ꢀC
(about 50%). Nevertheless, the complex is stable in chloroform at
2. Results and discussion
2.1. Synthesis of the ligand
The ligand 9 (6-nitro-8-vinyl-2H-chrom-3-ene) was synthesized
in four steps accordingly to the Scheme 1. Double formylation of p-
nitrophenol (Duff method) followed by Wittig methylenation
allowed to afford 4-nitro-2,6-divinylphenol. After etherification
with allyl bromide and metathetic cyclisation in the presence of 1st
Grubbs the nitrochromene 9 was obtained.
0
ꢀC for a few days (in NMR test tube), but at room temperature it
was decomposed within 3 h. The catalyst 8 as solid is air-stable and
storable for few weeks in the fridge. It can be purified by a standard
silica-gel column chromatography using undistilled solvents.
The above approach is similar to that used for the preparation of
chromene ligand incorporated into the catalyst 6 [10]. Double Duff
formylation of the aromatic compounds bearing electron-
withdrawing substituents (e.g. nitro group) usually gives poor
yields. According to Lindoy [12], p-nitrophenol was converted to
the respective dialdehyde with a yield as low as 4% after 7 days. We
have successfully improved the yield up to 60% by heating the
reaction mixture (p-nitrophenol, TFA, hexamethylenetetramine) at
130 ꢀC for 24 h. The 1H NMR spectrum of the crude product showed
an admixture (5%) of monoformylated nitrophenol, which was
difficult to separate by column chromatography. The crude dia-
ldehyde was immediately converted to divinyl compound with
a yield only 30%. The two next steps: eterification and cyclisation
were carried out almost quantitatively.
2.3. Testing of the catalyst 8
The new catalyst 8 was compared with commercially available
complexes in CM reactions of (Z)-4-acetoxy-2-butenyl acetate with
alkenes 12, 14 or 16 (Table 1, entries 1e3). The CM reaction between
12 and 16 was also investigated (entry 4). The catalyst 8 appeared to
be slightly less active than 1 and 2. However it should be noted that
the complex 8 showed good reactivity even at room temperature
and provides CM products in 43e76% yield.
The complex 8 catalyzed CM reaction between 19 and 20 (entry
5) to give poor yield of the desired product 21. Similar results were
observed for commercially available catalysts. In all reactions the
cross metathesis product were accompanied by homometathesis
side-products. The above reaction mixtures are convenient to
chromatographic separation and determination of stereochemical
output (E/Z ratio) by 1H NMR.
2.2. Synthesis of the catalyst 8
The Grubbs 2nd (1) or complex 10 [13] were subjected to
exchange with nitrochromenyl ligand 9 to give the catalyst 8
The new catalyst 8 does not allow to control stereoselectivity
(E/Z) of cross metathesis product, similarly to 1 and 2. However, it is
interesting that complex 8 revealed a higher E-stereocontrol than
other catalysts in reactions where at least one of the substrates was
allylic ether (entries 1, 4 and 5).
The catalyst 8 was tested in model enyne reaction as well as in
standard RCM reactions reported by Grubbs et al. [16] (Table 2). It
appeared to be almost as efficient as the Grela catalyst in enyne
cycloisomerization of 22 [11b]. After 1 h at 0 ꢀC the product 23 was
formed with a yield of 89% (entry 1). The commercially available
N
N
N
N
Cl
Cl
Ru
O
Ru
O
Cl
Cl
NO2
NO2
free rotation
constrained
conformation
of isopropoxyl group
8
7: Grela catalyst
Fig. 2. Chemical structures of Grela and new nitrochromenyl catalysts.

A. Hryniewicka et al. / Journal of Organometallic Chemistry 701 (2012) 87e92
89
CHO
OH
OH
O
O
b, c
O2N
d
a
O2N
O2N
CHO
O2N
9
Scheme 1. Synthesis of the ligand 9. Conditions: (a) hexamethylenetetramine, TFA,130 ꢀC, 24 h (b) Ph3CH3PþBrꢁ, BuLi, THF, (c) allyl bromide, K2CO3, DMF, 80 ꢀC, d) 1st Grubbs 1 mol%,
CH2Cl2, reflux.
N
N
Cl
9, CuCl
CH2Cl2, reflux
Ru
Cl
Ph
PCy3
1
N
N
Cl
Ru
O
MesN
NMes
CCl3
1.
Cl
PCy3
H
NO2
11
Cl
toluene, 65 0C
9, CuCl, rt
Ru
Cl
2.
8
PCy3
10
Scheme 2. Synthesis of the catalyst 8.
complexes were less active under these conditions. It should be
added, that Fürstner et al. [17] reported that analogue of 1 (bearing
unsaturated NHC ring) yielded 23 in 85% after 1 h, but the reaction
was carried out in toluene at 80 ꢀC with 5 mol% loading of the
catalyst.
For estimation of the relative activity of different catalysts in RCM:
diethyl diallylmalonate (24), diethyl 2-allyl-2-methallylmalonate
(26), and diethyl dimethallylmalonate (28) as substrates were
chosen. The respective cyclic products: 25, 27, and 29, bearing di-, tri-
and tetra-substituted double bonds were obtained.
Table 1
Comparative investigation of 8 in CM reactions.
Entry
Substrate(s)
Product
CatalysteYield (E/Z)c
O
O
OAc
1 76% (E/Z 12:1)
2 75% (E/Z 12:1)
8 67% (E/Z 12:1)
1a
12
14
13
OAc
1 81% (E/Z 58:1)
2 80% (E/Z 43:1)
8 76% (E/Z 34:1)
2a
3a
4
15
1 82% (E/Z 5:1)
2 86% (E/Z 5:1)
8 64% (E/Z 3:1)
AcO
AcO
AcO
OAc
16
17
O
O
AcO
1 47% (E/Z 7:1)
2 53% (E/Z 5:1)
8 43% (E/Z 9:1)
+
16
12
18
1 21% (E/Z 6:1)
2 18% (E/Z 8:1)
6d 35% (E/Z 8:1)
8 10% (E/Z 13:1)
O
O
C10H21O
+
C10H21O
5b
21
19
20
All reactions have been performed with 2.5 mol% of the catalyst in CH2Cl2 (0.1 M) at 20 ꢀC for 3 h unless stated otherwise; yield after column chromatography.
a
Reaction with 2 eq of (Z)-4-(acetoxy)-2-butenyl acetate.
b
Reaction at 40 ꢀC (20 ꢀC for catalyst 8), 1 mol% catalyst.
c
Determined by 1H NMR.
Ref. [10].
d

90
A. Hryniewicka et al. / Journal of Organometallic Chemistry 701 (2012) 87e92
Table 2
tetrasubstituted double bonds (entry 4). This reaction demand
a higher temperature (80 ꢀC), and the catalyst 8 can not be used due
to termal unstability.
Comparative investigation of 8 in enyne and RCM reactions.
Entry
Substrate
Product
CatalysteYieldd (time)
O
O
1 1%
3. Conclusion
Ph
Ph
Ph
2 21%
7e 98%
8 89%
1a
We assumed that combination of some merits of the catalysts:
Grela 7 and chromenyl 6 should give an improvement in activity of
the nitrochromenyl catalyst. The new catalyst 8 appeared to be
active but not more than the commercially available complexes. It
displayed good activity in RCM, CM and enyne metathesis trans-
formations. It revealed considerably higher efficiency in enyne
reaction at 0 ꢀC. In general, it showed similar activity to that of
Grubbs and Hoveyda catalysts in selected CM reaction. However, the
commercial complexes are slightly more efficient in RCM reactions.
The new complex 8 appeared to be resistant to air and moisture as
well as it was storable in solution at low temperature, nevertheless,
it was decomposed at elevated temperature. The higher E-stereo-
selectivity of 8 exceeding that of commercial catalysts in CM reac-
tion, when allylic ethers as substrates were used, was observed.
In summary the new catalyst showed in some experiments an
efficiency comparable to that of known complexes. Some further
efforts for construction of better catalysts have been undertaken.
Ph
23
22
EtOOC
COOEt
COOEt
EtOOC
EtOOC
COOEt
COOEt
1 99% (75 min)
2 99% (60 min)
8 67% (90 min)
2b
25
27
29
24
EtOOC
EtOOC
1 63% (90 min)
2 80% (90 min)
8 40% (90 min)
3b
26
1 38% (16 h)
2 15% (16 h)
8 no reaction
EtOOC
COOEt
COOEt
4c
28
4. Experimental section
Reaction conditions:
a
0
ꢀC, CH2Cl2, 0.1 M, 0.5 mol% catalyst, 60 min.
4.1. General remarks
b
c
20 ꢀC, CH2Cl2, 0.1 M, 0.5 mol% catalyst.
80 ꢀC, 0.06 M, toluene, 5 mol% catalyst.
Determined by 1H NMR.
All manipulations of organometallic compounds were per-
formed using standard Schlenk techniques under an atmosphere of
dry argon. CH2Cl2 and DMF were distilled over CaH2, trifluoroacetic
acid (TFAA) e over P2O5, THF e over Na/benzophenone, toluene e
over Na (deoxygenated by bubbling helium for 5 min). 1H and 13C
NMR spectrawere recorded on a Bruker Avance II spectrometer (400
and 100 MHz, respectively). Spectra were referenced relative to the
d
e
Ref. [11b].
The results showed that 8 is active in RCM reactions to give
products bearing di- or tri-substituted double bonds. The RCM rate
for the substrate 24 at room temperature using 8 (0.5 mol%) was
displayed in Fig. 3. The new catalyst initiated reaction very fast (30%
of conversion after 1 min, and 40% after 5 min). Unfortunatelly, the
rate of reaction was significantly decreased in the course of time
(after 90 min only 70%). After prolonged time the yield of 25 was
not increased. The above experiment performed at 0 ꢀC did not give
any better results (30% conversion of 24 after 2 h). The above results
showed that yields of RCM using the reported catalyst are lower if
compare to 1, 2, 6 and 7 (Table 2, entries 2 and 3). According to
literature, Grela catalyst 7 yielded 78% of 25 (8 h, 2.5 mol%, 0 ꢀC) and
95% of 27 (60 min, 1 mol%, 25 ꢀC) [11b]. Our previously reported
catalyst 6 gave 99% conversion of 24 after 45 min and 68%
conversion of 26 after 90 min (catalyst loading and conditions of
the reactions were the same as those for complex 8) [10]. Similarly
chemical shift (d) of TMS. Mass spectra were obtained on AMD-604
spectrometer (70 eV). IR spectra were recorded on a Nicolet series II
Magna-IR 550 FT-IR spectrometer. Flash chromatography (FC) was
performed on silica gel 230e400 mesh (J.T. Baker). Preparative
chromatography was performed on preparative layer of silica gel G
1000 microns (Analtech). Grubbs 1st generation catalyst, 1 and 2
were purchased from Aldrich, 10 [13b], 11 [14], 22 [18] were
synthesized according to literature. Substrates for testing catalysts
were prepared by etherification of proper compounds with allyl
bromide or 2-methyl-3-chloropropene or by esterification with
acetic anhydride. Other chemicals were commercially available.
The numeration of atoms of 8 was displayed in Fig. 4.
to
7
[11b], the catalyst
8
was not active in formation of
4.2. Synthesis of ligand 9
4.2.1. 2-Hydroxy-5-nitro-1,3-benzenedicarboxaldehyde
80
70
60
50
40
30
20
10
0
The solution of p-nitrophenol (1 g, 7.2 mmol, 1 eq) and hexa-
methylenetetramine (2 g, 14.3 mmol, 2 eq) in anhydrous TFAA
(20 mL) was stirred for 24 h at 130 ꢀC. After cooling to the ambient
temperature, the mixture was treated with 1 M HCl for 10 min and
extracted with CH2Cl2. The extract was washed with brine, water,
and dried over Na2SO4. After evaporation to dryness in vacuo
a yellow solid was obtained (910 mg). The crude product was used
in next step without purification. Sample for 1H NMR analysis was
purified by preparative chromatography (hexane: ethyl acetate 1:1)
EtOOC
COOEt
EtOOC
COOEt
0.5 mol% of catalyst 8
mp 124e126 ꢀC, IR (CHCl3)
976 cmꢁ1 1H NMR (400 MHz, CDCl3)
(s, 2H, eCHO), 8.86 (s, 2H, H-4 and 6) ppm; 13C NMR (100 MHz,
CDCl3) 195.6, 166.9, 140.7, 132.1, 123.2 ppm.
n
3451, 3029, 1698, 1674, 1542, 1350,
12.26 (s, 1H, eOH), 10.3
0
10
20
30
40
50
60
70
80
90
;
d
time (minutes)
Fig. 3. RCM of diethyldiallyl malonate (24) with catalyst 8.
d

A. Hryniewicka et al. / Journal of Organometallic Chemistry 701 (2012) 87e92
91
4.3. Synthesis of the catalyst 8
20a
14a
13
20
21
12
14
11
15
4.3.1. Method A
19
To the mixture of catalyst 1 (42 mg, 0.05 mmol, 1 eq) and CuCl
(5 mg, 0.05 mmol,1 eq) in dry CH2Cl2 (2 mL) a solution of 6-nitro-8-
vinyl-2H-chrom-3-ene (9) (10 mg, 0.05 mmol, 1 eq) in CH2Cl2
(2 mL) was added. The solution was stirred at 40 ꢀC for 1 h. The
reaction mixture was concentrated in vacuo. The crude product was
purified by FC (first CH2Cl2, then hexaneeethyl acetate v/v 2:1) to
give 17 mg (50% yield) of green material.
N
22a
16a
N
22
16
10
24
18
Cl
23
17
9
Ru
24a
18a
Cl
8
7
1
8a
O
6
2
NO2
4a
5
3
4.3.2. Method B
4
The catalyst 10 (40 mg, 0.05 mmol, 1 eq) and chloroform adduct
11 (42,5 mg, 0.1 mmol, 2 eq) were heated at 65 ꢀC in dry, deoxy-
genated toluene over 45 min. The reaction was monitored by TLC.
When 10 disappeared completely, the mixture was allowed to
cooled to the room temperature. Next, toluene solution of the
ligand 9 (10 mg, 0.05 mmol, 1 eq) and solid CuCl (5 mg, 0.05 mmol,
1 eq) were added and the reaction mixture was stirred at room
temperature for 1 h. After work-up and chromatographic purifica-
tion (method A) 23 mg (70% yield) of product was obtained.
Fig. 4. Numeration of atoms of catalyst 8.
4.2.2. 4-Nitro-2,6-divinylphenol
Methyltriphenylphosphonium bromide (6.7 g, 18.8 mmol, 4 eq)
and butyllithium (2.7 M solution in heptane; 7 ml, 18.8 mmol, 4 eq)
were stirred in dry THF (50 mL) for 1 h under argon atmosphere. A
solution of 2-hydroxy-5-nitro-1,3-benzenedicarboxyaldehyde
(910 mg, 4.7 mmol, 1 eq) in THF (10 mL) was added dropwise and
the reaction mixture was left at room temperature for 2 h. The
solvent was evaporated to dryness, and the residue was dissolved in
CH2Cl2, washed with water, dried over Na2SO4 and concentrated in
vacuo. The crude product was purified by FC (hexaneeethyl acetate
v/v 9:1) and 270 mg of a yellow solid was isolated (20% after two
IR (CHCl3)
(400 MHz, CDCl3)
n ;
2993, 2921, 1606, 1523, 1338 cmꢁ1 1H NMR
d
16.34 (s, 1H, H-9), 8.02, 7.61 (2d, 2H, J ¼ 2.2 Hz;
2.5 Hz, H-5 and 7), 7.11 (s, 4H, H-15, 17, 21 and 23), 6.4 (dt, 1H,
J ¼ 10.3 and 2.0 Hz, H-4), 5.75 (dt, 1H, J ¼ 10.3 and 3.2 Hz, H-3), 5.04
(t, 2H, J ¼ 2.6 Hz, H-2), 4.19 (s, 4H, H-11 and 12), 2.45 (s, 18H, H-14a,
16a, 18a, 20a, 22a and 24a) ppm; 13C NMR (100 MHz, CDCl3)
d 287.5,
steps). Mp. 110e111 ꢀC, IR (CHCl3)
n
3579, 3028, 1631, 1525,
206.1, 152.2, 143.6, 141.5, 139.3, 138.4, 129.5, 124.4, 122.3, 121.0,
120.1, 116.5, 69.0, 51.6, 21.2 ppm; TOF MS FDþ 1.48 (m/z):667,1;
calculated for C31H33Cl2N3O3Ru: 667.0942, found: 667.1112.
1338 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d 8.18 (s, 2H, H-3 and 5), 6.91
(m, 2H, ¼ CH), 5.88 (dd, 2H, J ¼ 17.7 and 1.3 Hz, ¼ CH2), 5.61 (dd, 2H,
J ¼ 11.2 and 1.3 Hz, ¼ CH2) ppm; 13C NMR (100 MHz, CDCl3)
d 155.0,
141.5, 129.8, 125.8, 122.2, 119.7 ppm.
4.4. Testing of the catalyst 8
4.2.3. 1-Allyloxy-4-nitro-2,6-divinylbenzene
To the mixture of 4-nitro-2,6-divinylphenol (200 mg,1.05 mmol,
1 eq), potassium carbonate (290 mg, 2.1 mmol, 2 eq), and 18-C-6
4.4.1. General CM procedure for alkenes 12, 14 or 16 with (Z)-4-
acetoxy-2-butenyl acetate
To a mixture of the alkene (0.1 mmol) and (Z)-4-acetoxy-2-
butenyl acetate (0.2 mmol) in CH2Cl2 a solution of catalyst 1, 2 or 8
(2.5 mol%) in CH2Cl2 was added. The resulting mixture was stirred
at 20 ꢀC for 3 h and controlled by TLC. The crude product was
purified by FC (hexaneeethyl acetate v/v 20:1) and analyzed by 1H
NMR.
(5 mg) in dry DMF (10 mL) allyl bromide (138 mL, 1.6 mmol, 1.5 eq)
was added. The resulting mixture was stirred at 80 ꢀC for 3 h. Next,
the mixture was filtered through a pad of Celite. Water was added
to the filtrate and the mixture was extracted three times with
diethyl ether. The combined extracts were washed with brine,
water, and dried over Na2SO4. After concentration in vacuo the
residue was purified by FC (hexaneeethyl acetate v/v 20:1) and
4.4.2. General CM procedure for alkenes 12 and 16
237 mg of a colourless oil was obtained (98% yield). IR (CHCl3)
n
To a mixture of the alkenes (0.1 mmol, both) in CH2Cl2 a solution
of catalyst 1, 2 or 8 (2.5 mol%) in CH2Cl2 was added. The resulting
mixture was stirred at 20 ꢀC for 3 h and controlled by TLC. The
crude product was purified by FC (hexaneeethyl acetate v/v 20:1)
and analyzed by 1H NMR.
3028, 1526, 1344, 981, 926 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
8.29
(s, 2H, H-3 and 5), 6.99 (m, 2H,]CHvinyl), 6.06 (m,1H,]CHallyl); 5.91
(d, 2H, J ¼ 17.7 Hz,]CH2 vinyl), 5.49 (d, 2H, J ¼ 11.3 Hz,]CH2 vinyl),
5.43 (d, 1H, J ¼ 17.2 Hz,]CH2 allyl), 5.31 (d, 1H, J ¼ 10.4 Hz,]CH2
allyl), 4.38 (d, 2H, J ¼ 5.6 Hz, OCH2) ppm; 13C NMR (100 MHz, CDCl3)
d
158.5144.5, 133.0, 132.6, 130.0, 120.7, 118.4, 118.0, 75.3 ppm.
4.4.3. General CM procedure for alkenes 19 and 20
To a mixture of the alkenes (0.1 mmol, both) in CH2Cl2 a solution
of catalyst 1, 2 or 8 (1 mol%) in CH2Cl2 was added. The resulting
mixture was stirred at 40 ꢀC (or 20 ꢀC for catalyst 8) for 3 h and
controlled by TLC. The crude product was purified by FC
(hexaneeethyl acetate v/v 20:1) and analyzed by 1H NMR.
4.2.4. 6-Nitro-8-vinyl-2H-chrom-3-ene (9)
To a solution of 1-allyloxy-4-nitro-2,6-divinylbenzene (100 mg,
0.43 mmol) in dry CH2Cl2 (10 mL) in a Schlenk flask, a solution of
1st Grubbs catalyst (3.5 mg, 1 mol%) in CH2Cl2 (2 mL) was added.
The solution was stirred and refluxed for 4 h and concentrated in
vacuo. The residue was purified by FC (hexaneeethyl acetate v/v
9:1) and 83 mg of a yellow solid was obtained (95% yield). Mp.
4.4.4. General enyne procedure for 22
To a solution of the alkene (0.1 mmol) in CH2Cl2 a solution of
catalyst 1, 2 or 8 (0.5 mol%) in CH2Cl2 was added at 0 ꢀC. The
resulting mixture was stirred at 0 ꢀC for 1 h and controlled by TLC.
The crude product was analyzed by 1H NMR.
63e65 ꢀC, IR (CHCl3)
NMR (400 MHz, CDCl3)
n
3087, 2957, 1522, 1339, 1224, 924 cmꢁ1
;
1H
d
8.2, 7.4 (2s, 2H, H-5,7), 6.90 (m, 1H,]CH),
6.43 (dt, 1H, J ¼ 10.0 and 1.9 Hz, H-4), 5.90 (dt, 1H, J ¼ 10.0 and
3.4 Hz, H-3), 5.85 (d, 1H, J ¼ 17.7 Hz,]CH2), 5.41 (d, 1H,
J ¼ 11.1 Hz,]CH2), 5.05 (dd, 2H, J ¼ 3.3 and 2.0 Hz, H-2) ppm; 13C
4.4.5. General RCM procedure for 24 and 26
To a solution of the alkene (0.1 mmol) in CH2Cl2 a solution of
catalyst 1, 2 or 8 (0.5 mol%) in CH2Cl2 was added. The resulting
NMR (100 MHz, CDCl3)
d
156.1, 141.7, 129.2, 125.9, 123.5, 123.2,
122.0, 121.9, 120.8, 117.2, 66.8 ppm; ESI-MS: 226.2 (MþþNa).

92
A. Hryniewicka et al. / Journal of Organometallic Chemistry 701 (2012) 87e92
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mixture was stirred at room temperature for 90 min and controlled
by TLC. The crude product was analyzed by 1H NMR.
4.4.6. General RCM procedure for 28
To a solution of alkene (0.1 mmol) in toluene a solution of
catalyst 1, 2 or 8 (5 mol%) in toluene was added. The resulting
mixture was stirred at 80 ꢀC for 16 h and controlled by TLC. The
crude product was analyzed by 1H NMR.
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Financial support from the Ministry of Science and Higher
Education (Grant Number
acknowledged.
N
N204 154936) is gratefully
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