Full Papers
doi.org/10.1002/ejic.202100078
analysis. HRMS of certain trifluoromethanesulfonate derivatives, the
118.9 (q, J=320.8 Hz, CF3), 18.6 (C-3); 19F NMR (565 MHz, CDCl3)
δ=-75.85 (CF3); MS (EI, 70 eV): m/z (%)=266 (19) [M]+.
GII-p-cresol adduct (19) and GII-p-cresolate derivative (22) could
not be obtained due to decomposition. Caution: Thallium com-
pounds are extremely toxic and should be handled with care.
Electronic and steric influence study
Procedures
Representative Example of Metathesis with GII
(E)-prop-1-en-1-ylbenzene (2b) (0.20 mL, 1.5 mmol, 1 eq.), methyl
acrylate (1b) (0.28 mL, 3.1 mmol, 2 eq.) and GII (6.5 mg,
0.0077 mmol, 0.5 mol%) were refluxed in dry DCM (10 mL) for 2 h
hours (until completion of the reaction, TLC). The reaction mixture
was then filtered and the precipitate washed with cold DCM (3×
Synthesis of (E)-4-(prop-1-en-1-yl)phenyl
trifluoromethanesulfonate (2c)
4-Propionylphenyl trifluoromethanesulfonate (26). Triflic anhy-
°
dride (1.1 eq.) in dry DCM (25 mL) at À 20 C was added dropwise to
30 mL) to yield (E)-stilbene[8] (4b) as colorless platelets (0.27 g,
a solution of 4’-hydroxypropiophenone (27) (2.00 g, 13.3 mmol) and
1
°
°
99%): Rf 0.87 (H/A 8:2); Mp 123.6 C; H NMR (600 MHz, CDCl3) δ=
DMAP (1.79 g, 14.7 mmol) in DCM (50 mL), also at À 20 C, under Ar.
7.55 (br d, J=8.2 Hz, 4H, H-2,6), 7.39 (t, J=7.7 Hz, 4H, H-3,5), 7.29
(m, 2H, H-4), 7.14 (s, 2H, CH=CH); 13C NMR (151 MHz, CDCl3) δ=
137.5 (C-1), 128.8 (C-3,5 and CH=CH), 127.8 (C-4), 126.7 (C-2,6); MS
(EI, 70 eV): m/z (%)=180 (100) [M]+.
The reaction mixture was allowed to warm to rt. and stirred
overnight, after which the solvent was distilled off and EtOAc (ca.
50 mL) and water (ca. 50 mL) added to the reaction mixture. The
water layer was extracted into EtOAc (3×50 mL), after which the
combined organic phases were dried over MgSO4, filtered and the
solvent removed in vacuo. flash column chromatography (DCM)
gave 4-propionylphenyl trifluoromethanesulfonate[46] (26) (3.4 g,
°
Changing the temperature to 10 and 25 C, the solvent to THF,
toluene or neat conditions, and the 2b : 1b ratio (0.2 mL, 1.5 mmol,
1 eq. : 0.69 mL, 7.7 mmol, 5 eq.; 0.2 mL, 1.5 mmol, 1 eq. : 0.13 mL,
1.5 mmol, 1 eq.; 1.0 mL, 7.5 mmol, 5 eq.: 0.13 mL, 1.5 mmol, 1 eq.,
2b : 1b, respectively) all gave (E)-stilbene (4b) in quantitative yield.
1
90%) as a light yellow oil: Rf 0.86 (DCM); H NMR (600 MHz, CDCl3):
δ=8.02 (d, J=8.9 Hz, 2H, H-3’,5’), 7.33 (d, J=8.9 Hz, 2H, H-2’,6 ’),
2.97 (q, J=7.2 Hz, 2H, H-2), 1.18 (t, J=7.2 Hz, 3H, H-3); 13C NMR
(151 MHz, CDCl3): δ 198.9 (C-1), 152.4 (C-1’), 136.8 (C-4 ’), 130.3 (C-
3’,5’), 121.6 (C-2’,6’), 118.7 (q, J=320.7 Hz, CF3), 32.0 (C-2), 7.9 (C-3);
19F NMR (565 MHz, CDCl3): δ=À 75.83 (CF3); IR (neat) 1693 cmÀ 1
(CO).
Representative Example of Metathesis with GII-p-cresol
GII (2.4 mg, 0.0030 mmol, 0.5 mol%) and p-cresol (0.031 g,
0.30 mmol, 0.25 eq.) were heated to reflux in dry DCM (10 mL)
while being stirred. A steady stream of argon was bubbled through
4-(1-Hydroxypropyl)phenyl trifluoromethanesulfonate (28). 4-Pro-
pionylphenyl trifluoromethanesulfonate (26) (2.5 g, 8.9 mmol) was
added to a solution of NaBH4 (0.503 g, 13.3 mmol, 1.5 eq.) in THF/
EtOH (1:1, v/v; 50 mL) and stirred until the reaction was deemed to
be complete by TLC. After completion of the reaction (TLC), the
reaction mixture was concentrated in vacuo, washed with acetone
(3×20 mL) and concentrated again. EtOAc (ca. 50 mL) and water
(ca. 50 mL) were thus added to the reaction mixture. The water
layer was extracted into EtOAc (3×50 mL), after which the
combined organic phases were dried over MgSO4, filtered and the
solvent removed in vacuo. flash column chromatography (H:A 8:2)
gave 4-(1-hydroxypropyl)phenyl trifluoromethanesulfonate (28)
(1.97 g, 78%) as a light yellow oil: Rf 0.47 (H/A 8:2); 1H NMR
(600 MHz, CDCl3): δ 7.41 (d, J=8.7 Hz, 2H, H-2’,6’), 7.24 (d, J=
8.7 Hz, 2H, H-3’,5’), 4.63 (t, J=6.5 Hz, 1H, H-1), 1.81-1.69 (m, 2H, H-
2), 1.16 (d, J=6.2 Hz, 1H, -OH), 0.91 (t, J=7.4 Hz, 3H, H-3); 13C NMR
(151 MHz, CDCl3): δ 148.8(C-4’), 145.3 (C-1’), 127.9 (C-2’,6’), 121.3 (C-
°
the mixture and the vapours condensed at À 20 C. (E)-4-(Prop-1-en-
1-yl)phenyl trifluoromethane-sulfonate (2c) (0.15 g, 0.60 mmol,
1 eq.) and methyl acrylate (1b) (0.10 mL, 1.1 mmol, 2 eq.) were then
added to the mixture. After 2 hours at reflux (completion, TLC), the
solvent was distilled off and EtOAc (50 mL) and water (50 mL)
added to the reaction mixture. The water layer was extracted into
EtOAc (3×50 mL), after which the combined organic phases were
dried over MgSO4, filtered and the solvent removed in vacuo. PLC
(H/A 8:2) gave methyl (E)-3-[4-(trifluoromethylsulfonyloxy)phenyl]-
acrylate[12] (3d) as a light yellow oil (74.5 mg, 43%) and (E)-4,4’-bis
(trifluoromethanesulfonyloxy)stilbene (4c) (9.4 mg, 7%), also as a
light yellow oil:
Methyl (E)-3-[4-(trifluoromethylsulfonyloxy)phenyl]acrylate[12] (3d):
1
Rf 0.49 (H/A 8:2); H NMR (600 MHz, CDCl3,) δ=7.66 (d, J=16.0 Hz,
1H, H-3), 7.59 (d, J=8.7 Hz, 2H, H-2’,6’), 7.29 (d, J=8.7 Hz, 2H, H-
3’,5’), 6.44 (d, J=16.0 Hz, 1H, H-2), 3.81 (s, 3H, H-1’’); 13C NMR
(151 MHz, CDCl3,) δ=166.9 (C-1), 150.5 (C-4’), 142.5 (C-3), 134.9 (C-
1’), 129.9 (C-2’,6’), 122.1(C-3’,5’), 120.0 (C-2), 118.8 (q, J=320.9 Hz,
CF3), 52.0 (C-1’’); 19F NMR (565 MHz, CDCl3) δ=À 75.87 (CF3); IR
(neat, cmÀ 1) 1718 (C=O); MS (EI, 70 eV): m/z (%)=310 (43) [M+].
3’,5’), 118.9 (q, J=320.8 Hz, CF3), 75.0 (C-1), 32.2 (C-2), 10.1 (C-3); 19
NMR (565 MHz, CDCl3) δ À 75.95 (CF3).
F
(E)-4-(prop-1-en-1-yl)phenyl trifluoromethanesulfonate (2c). An-
hydrous CuSO4 (10.84 g, 5.3 mmol) was added to a solution of 4-(1-
hydroxypropyl)phenyl trifluoromethanesulfonate (28) (1.0 g,
3.5 mmol) in dry hexane (40 mL), after which the reaction mixture
was refluxed and stirred under Ar for 4 days. The solvent was then
removed in vacuo, and hexane (ca. 50 mL) added to the reaction
mixture. H2O (ca. 50 mL) was added to this reaction mixture and
the aqueous (aq.) phase extracted into hexane (3×50 mL). The
combined organic phases were dried over MgSO4, filtered and the
(E)-4,4’-bis(trifluoromethanesulfonyloxy)stilbene (4c): Rf 0.58 (H/A
8:2); 1H NMR (600 MHz, CDCl3): δ=7.58 (d, J=8.8 Hz, 4H, H-2,6),
7.29 (d, J=8.8 Hz, 4H, H-3,5), 7.09 (s, 2H, CH=CH); 13C NMR
(151 MHz, CDCl3): δ=149.1 (C-4), 137.2 (C-1), 128.8 (CH=CH), 128.1
(C-2,6), 121.9 (C-3,5), 118.9 (q, J=320.8 Hz, CF3); 19F NMR (565 MHz,
CDCl3) δ=À 75.91 (CF3); MS (EI, 70 eV): m/z (%)=477 (6) [M+].
°
solvent removed in vacuo at ca. 40 C. flash column chromatog-
raphy (H:A 8:2) gave (E)-4-(prop-1-en-1-yl)phenyl trifluoromethane-
sulfonate (2c) (0.56 g, 60%) as a light yellow oil: Rf 0.76 (H/A 8:2); 1H
NMR (600 MHz, CDCl3): δ=7.37 (d, J=8.6 Hz, 2H, H-2’,6’), 7.18 (d,
J=8.6 Hz, 2H, H-3’,5’), 6.39 (br d, J=15.8 Hz, 1H, H-1), 6.29-6.23 (m,
1H, H-2), 1.90 (m, 3H, H-3); 13C NMR (151 MHz, CDCl3): δ=148.3 (C-
4’), 138.5 (C-1’), 129.4 (C-1), 128.3 (C-2), 127.5 (C-2’,6’), 121.5 (C-3’,5’),
NMR investigation
Procedure A: The relevant reagents were dissolved in CDCl3
°
(0.6 mL), stirred at 40 C for 1 hour (unless specified otherwise) and
analyzed by NMR. Diagnostic resonances are indicated.
Eur. J. Inorg. Chem. 2021, 1752–1762
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