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Can. J. Chem. Vol. 88, 2010
an orange solid that was purified using column chromatogra-
phy on basic alumina eluting with 60% CH2Cl2 in hexane to
give the title compound as an orange solid (31 mg, 19%): mp
148–150 8C. UV–vis lmax (nm): 515 (e 45 000 mol/L–1cm–1,
MeOH). dH (500 MHz, CDCl3): 7.44–7.45 (3H, m), 7.34–
7.36 (2H, m), 2.31 (6H, s), 2.28 (4H, q, J = 7.5), 1.19 (6H,
s), 0.97 (6H, t, J = 7.5). dC (125 MHz, CDCl3): 150.3, 139.2,
135.7, 134.9, 131.5, 129.8, 128.6, 128.2, 124.2, 17.8, 15.1,
14.6, 11.9. dN (50.7 MHz, THF-d8): –162.1. m/z HR (MH)+
C23H28N2 calcd.: 332.2252, found: 333.2303. Anal. calcd.
for C23H28N2: C, 83.09; H, 8.49; N, 8.43. Found: C, 83.13;
H, 8.54; N, 8.31.
After 1 h, the reaction mixture was filtered over Celite and
the residue was washed with ether (4 Â 2 mL) to remove
any impurities and the HN(SiMe3)2 byproduct. The product
was dissolved in THF (2 mL) and filtered through Celite.
Slow evaporation of the solvent from the filtrate resulted in
the formation of large red plate crystals. These were isolated
and dried in vacuo to leave the title compound as red crys-
tals (46 mg, 74%). dH (500 MHz, THF-d8): 6.75 (1H, s),
2.35 (4H, q, J = 7.5), 2.16 (6H, s), 2.11 (6H, s), 1.00 (6H,
t, J = 7.5). dC (125 MHz, THF-d8): 153.8, 138.2, 135.3,
128.2, 123.2, 19.4, 16.6, 16.2, 10.5. dN (50.7 MHz, THF-
d8): –225.4. dNa (132.3 MHz, THF-d8): 10.7.
k2-(4,4’-Diethyl-3,3’,5,5’-tetramethyldipyrrinato)
potassium (4c)
k2-(4,4’-Diethyl-3,3’,5,5’-tetramethyl-meso-p-CF3-C6H4-
dipyrrin) (3)
In a glovebox, a THF (2 mL) solution of KCH2Ph27
(25 mg, 0.20 mmol) was added dropwise over 5 min to a
solution of 1 (50 mg, 0.20 mmol) in THF (2 mL). Upon ad-
dition of the base, a bright orange solid precipitated from
the reaction mixture. The reaction vial was sealed and the
contents manually shaken for 30 s then left at room temper-
ature. After 1 h, the solvent was removed in vacuo and the
orange solid was washed with Et2O (2 Â 2 mL) and then
hexanes (3 Â 2 mL) to remove any impurities and byprod-
ucts. Contrary to the sodium complex, the potassium ana-
logue was found to be insoluble in THF. Therefore, the
supernatants were removed in each case by allowing the
solid to settle and then carefully decanting the liquid away.
The resulting orange solid was dried in vacuo to leave the
title compound (37 mg, 66%). dH (500 MHz, DMF-d7): 6.80
(1H, s), 2.34 (4H, q, J = 7.5), 2.18 (6H, s), 2.13 (6H, s),
1.00 (6H, t, J = 7.5). dC (125 MHz, DMF-d7): 153.3, 137.9,
134.6, 132.0, 127.3, 19.3, 16.4, 15.9, 10.7. dN (50.7 MHz,
DMF-d7): –221.4.
To a solution of 3-ethyl-2,4-dimethylpyrrole (0.34 mL,
2.50 mmol) in CH2Cl2 (30 mL), 4-trifluoromethylbenzoyl-
chloride (260 mg, 1.25 mmol) was added, and the reaction
mixture was heated at reflux temperature for 48 h. The re-
sultant pink reaction mixture was extracted with water (2 Â
30 mL), and the organic solution was then dried over
Na2SO4. Removal of the organic solvent in vacuo gave a
crude product that was purified using chromatography on
silica gel. A minor byproduct was eluted with 50% CH2Cl2
in hexane, and it was characterized to be 4-ethyl-3,5-
dimethyl-2-(trifluoromethylphenyl) acetylpyrrole as a pale
yellow solid, mp 165–167 8C. UV–vis lmax (nm): 523 (e
40 000 mol/L–1cm–1, MeOH). dH (500 MHz, CDCl3): 9.20
(1H, bs), 7.65–7.71 (4H, bs), 2.38 (2H, q, J = 7.5), 2.27
(3H, s), 1.85 (3H, s), 1.05 (3H, t, J = 7.5). dC (125 MHz,
CDCl3): 183.7, 143.9, 134.0, 132.4 (q, JC–F = 32.3), 128.9,
128.4, 126.7, 125.8, 125.4, 123.9 (q, JC–F = 270.8), 17.2,
15.1, 11.7, 11.6. dN (50.7 MHz, CDCl3): –228.2. dF
(243 MHz, CDCl3): –63.7. m/z (ESI–): 294.3 (M–). The ma-
jor band was eluted with 10% CH3OH in CH2Cl2. Removal
of the organic solvent in vacuo followed by dissolution of
the solid in CH2Cl2 (30 mL) and then washing with satd.
NaHCO3 solution (2 Â 30 mL) gave 3 as its free-base. Dry-
ing of the solution over Na2SO4 and removal of the organic
solvent in vacuo gave an orange solid that was purified us-
ing column chromatography and basic alumina eluting with
50% CH2Cl2 in hexane to give the title compound as an or-
ange solid (226 mg, 41%), mp (dec.) > 185 8C. dH
(500 MHz, CDCl3): 13.22 (1H, bs), 7.69 (2H, d, J = 10.0),
7.46 (2H, d, J = 10.0), 2.32 (6H, s), 2.27 (4H, q, J = 7.5),
1.15 (6H, s), 0.97 (6H, t, J = 7.5). dC (125 MHz, CDCl3):
k2-(4,4’-Diethyl-3,3’,5,5’-tetramethyl-meso-C6H5-
dipyrrinato) lithium (5a)
In a glovebox, nBuLi (94 mL of a 1.6 mol/L hexanes sol-
ution, 0.15 mmol) was added dropwise over 5 min to a sol-
ution of 2 (50 mg, 0.15 mmol) in THF (3 mL). Upon
addition of the base, the colour of the solution immediately
changed from orange to dark red-brown. The reaction vial
was sealed and the contents were magnetically stirred for
45 min. The solvent was then removed in vacuo and the
red-brown solid was washed with pentane (5 Â 2 mL) to re-
move any impurities and byproducts. The supernatants were
removed in each case by allowing the solid to settle and
carefully decanting the liquid away. The resulting solid was
dried in vacuo to give the title compound as a red solid
(25 mg, 50%). dH (500 MHz, THF-d8): 7.40–7.20 (5H, m),
2.25 (4H, q, J = 7.5), 2.20 (6H, s), 1.08 (6H, s), 0.92 (6H,
t, J = 7.5). dC (125 MHz, THF-d8): 153.3, 145.2, 138.6,
135.8, 131.9, 131.7, 130.7, 128.6, 127.8, 19.1, 16.0, 15.8,
13.3. dN (50.7 MHz, THF-d8): –226.0. dLi (194.4 MHz,
THF-d8): 2.02.
150.7, 142.8, 135.7, 135.4, 134.3, 131.8, 130.4 (q, JC–F
=
32.3), 130.2, 125.4, 124.2 (q, JC–F = 265.0), 17.6, 14.8,
14.4, 12.0. dF (243 MHz, CDCl3): –63.3. dN (50.7 MHz,
CDCl3): –163.6. m/z (MH)+ HR C24H27F3N2 calcd.:
400.2126, found: 401.2187. Anal. calcd. for C24H27F3N2: C,
71.98; H, 6.80; N, 6.99. Found: C, 72.16; H, 6.82; N, 6.85.
k2-(4,4’-Diethyl-3,3’,5,5’-tetramethyldipyrrinato) sodium
(4b)
In a glovebox, an Et2O (2 mL) solution of NaN(SiMe3)2
(40 mg, 0.22 mmol) was added dropwise over 5 min to a
magnetically stirring solution of 1 (57 mg, 0.22 mmol) in
Et2O (2 mL). Upon addition of the base, a bright orange
solid immediately precipitated from the reaction mixture.
k2-(4,4’-Diethyl-3,3’,5,5’-tetramethyl-meso-C6H5-
dipyrrinato) sodium (5b)
In a glovebox, a solution of NaN(SiMe3)2 (28 mg,
0.16 mmol) in Et2O (2 mL) was added dropwise over 5 min
to a magnetically stirring solution of 2 (51 mg, 0.16 mmol)
Published by NRC Research Press