Dalton Transactions
Paper
Alkyne synthesis: 3,4,5-trimethoxyphenylacetylene
tert-butyl (4-formyl-3,5-dimethoxyphenoxy)acetate (1.30 g,
4.4 mmol) in anhydrous dichloromethane (15 mL). The result-
ing red solution was stirred for 18 hours. The solvent was
removed under reduced pressure and the residue was stirred
in diethyl ether, filtered and concentrated under reduced
pressure. The crude product was purified by column chromato-
graphy (silica, neat hexane to 5 : 1 v/v hexane–ethyl acetate) to
give the product as a white solid (1.22 g, 62%); m.p. 122–124 °C;
1H NMR (400 MHz, CDCl3) δ 1.50 (9 H, s, H10), 3.79 (6 H, s,
H11), 4.52 (2 H, s, H7), 6.11 (2 H, s, H5), 7.17 (1 H, s, H2); 13C
NMR (101 MHz, CDCl3) δ 28.2, 55.8, 65.9, 82.7, 91.3, 93.1, 107.8,
130.9, 158.1, 160.1, 167.9; LRMS (ESI) m/z 451; (HRMS+) m/z
450.9771 [M + H]+ (C16H21O679Br2) requires 450.9756.
1,1-Dibromo-2-(3,4,5-trimethoxyphenyl)-ethylene
(1.41
g,
4.04 mmol) was dissolved in anhydrous THF (30 mL) and
cooled to −78 °C. n-Butyl lithium (2.5 M in hexane, 6.4 mL,
16.2 mmol) was added slowly and the mixture was stirred at
−78 °C under argon for 30 min. Water (8 mL) was added and
the mixture was extracted with EtOAc (2 × 30 mL). The combined
organic fractions were washed with half-strength brine solution
(30 mL), dried (MgSO4), and the solvent was removed under
reduced pressure. The residue thus obtained was subjected to
column chromatography (silica gel; neat hexane, then hexane–
EtOAc, 9 : 1 v/v) to give 3,4,5-trimethoxyphenylacetylene as a
white solid (0.53 g, 68%); m.p. 71–73 °C (lit.1 m.p. 70–71 °C);
1H NMR (400 MHz, CDCl3) δ 6.72 (2H, s, H4), 3.85 (3H, s, H8),
3.84 (6H, s, H7), 3.03 (1H, s, H1); 13C NMR (151 MHz, CDCl3)
δ 153.1 (C5), 139.3 (C6), 117.0 (C3), 109.4 (C4), 83.7 (C2), 76.2 (C1),
61.0 (C8), 56.2 (C7); (HRMS+) m/z 193.0845 [M + H]+ (C11H13O3
requires 193.0865); Rf = 0.45 (silica; hexane–EtOAc 4 : 1 v/v). The
spectral data were consistent with those reported previously.28
tert-Butyl (4-ethynyl-3,5-dimethoxyphenoxy)acetate
To a solution of tert-butyl [4-(2,2-dibromoethenyl)-3,5-dimethoxy-
phenoxy]acetate (0.797 g, 1.77 mmol) in dry THF (20 mL) under
argon at −78 °C, was added n-butyllithium (1.42 mL of a 2.5 M
solution, 3.54 mmol). The solution was stirred for 30 min when a
further 0.5 eq. of n-butyllithium was added. The mixture was
stirred for a further 15 min before water (20 mL) was added. THF
was removed under reduced pressure and the remaining aqueous
solution was extracted into dichloromethane (3 × 30 mL). The
organic layers were combined, dried over MgSO4, filtered and con-
centrated under reduced pressure. The crude product was puri-
fied by column chromatography (silica, hexane–ethyl acetate
8 : 1 v/v) to give the product as a white solid (0.248 g, 48%); m.
tert-Butyl (4-formyl-3,5-dimethoxyphenoxy)acetate
To a solution of 4-hydroxy-2,6-dimethoxybenzaldehyde (1.00 g,
5.49 mmol) in
a
dichloromethane–dimethylformamide
mixture (5 : 1, 36 mL) under argon was added potassium car-
bonate (1.52 g, 11.0 mmol) and tert-butyl bromoacetate
(1.62 mL, 2.14 g, 11.0 mmol). The mixture was stirred for 24 h
at which point the potassium carbonate was removed by
gravity filtration. The dichloromethane was removed under
reduced pressure and the dimethylformamide was removed by
vacuum distillation to give the product as a white solid (1.35 g,
83%), which was used without further purification; m.p.
130–132 °C; 1H NMR (400 MHz, CDCl3) δ 1.50 (9 H, s, H9),
3.86 (6 H, s, H10), 4.57 (2 H, s, H6), 6.08 (2 H, s, H4), 10.35 (1 H,
s, H1); 13C NMR (101 MHz, CDCl3) δ 28.2, 56.2, 65.7, 83.2, 91.0,
109.5 164.2, 164.4, 167.2, 187.9; LRMS (ESI) m/z 297 [M + H]+;
(HRMS+) m/z 297.1331 [M + H]+ (C15H21O6) requires 297.1338.
1
p. 107–108 °C; H NMR (700 MHz, CDCl3) δ 1.49 (9 H, s, H10),
3.49 (1 H, s, H1), 3.86 (6 H, s, H11), 4.53 (2 H, s, H7), 6.11 (2 H, s,
H5); 13C NMR (176 MHz, CDCl3) δ 28.2 (C9), 56.3 (C11), 65.9 (C7),
76.4 (C2), 82.9 (C9), 84.2 (C1), 91.2 (C5), 94.1 (C3), 160.2 (C6),
163.1 (C4), 167.6 (C8); LRMS (ESI) m/z 293 [M + H]+; (HRMS+)
m/z 293.1390 [M + H]+ (C16H21O6) requires 293.1389.
Ligand and complex synthesis
[Eu·L1]. The synthesis of the tris p-bromo Eu(III) complex
[Eu·L1] has been reported elsewhere.23 1H NMR (400 MHz,
CD3OD) δ 8.60 (1H, s, pyH), 7.97 (1H, s, pyCHN), 7.12 (1H, s, pyH),
4.36 (1H, s, NCHe′q), 0.54 (3H, s, CH3), −0.77 (1H, s, pyCH′N),
−1.37 (1H, s, NCHa′x), −2.23 (1H, s, NCHeq), −5.28 (1H, s, NCHax).
31P NMR (162 MHz, CD3OD) +39.8. m/z (HRMS+) 1020.851 [M +
H]+ (C27H3479Br3N6O6P3151Eu requires 1020.849). Rf = 0.31 (silica;
CH2Cl2–CH3OH–aq. ammonia: 82/15/3: v/v/v).
[Eu·L2]. CAUTION! Care should be taken using azides and
(poly)triazoles, particularly if scaling up the reaction con-
tert-Butyl [4-(2,2-dibromoethenyl)-3,5-dimethoxyphenoxy]acetate
To a solution of triphenylphosphine (4.62 g, 17.6 mmol) and ditions stated here.
tetrabromomethane (2.92 g, 8.8 mmol) in anhydrous dichloro-
To a solution of [Eu·L1] (5.0 mg, 4.9 μmol) in DMF
methane (15 mL) under argon at 0 °C was added a solution of (0.5 mL), NaN3 (3.8 mg, 59 μmol) was added. The reaction was
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 5721–5730 | 5727