Dogutan et al.
J ) 7.6 Hz, 2H), 5.22-5.24 (m, 1H), 5.29-5.31 (m, 1H), 5.41-
5.44 (m, 1H), 5.48-5.51 (m, 2H), 5.53-5.50 (m, 1H), 5.57-5.60
(m, 1H), 5.62-5.63 (m, 1H), 5.82-5.92 (m, 1H), 6.08-6.14 (m,
1H), 6.68-6.74 (m, 1H), 7.02-7.06 (m, 4H), 7.11-7.14 (m, 5H),
7.19-7.23 (m, 2H), 7.27-7.32 (m, 4H), 7.77 (d, J ) 7.6 Hz, 2H),
9.52-9.58 (br s, 1H), 9.65-9.67 (br s, 1H), 9.92-10.22 (br s, 1H),
10.82-11.2 (br s, 1H); 13C NMR (THF-d8) δ 15.6, 16.0, 21.3, 29.8,
31.9, 32.4, 35.2, 44.8, 45.1, 45.4, 107.6, 107.8, 109.6, 110.6, 117.1,
118.9, 119.6, 125.9, 127.1, 128.4, 128.8, 129.2, 129.4, 129.5, 130.0,
131.9, 132.65, 132.68, 132.7, 133.36, 133.4, 134.4, 134.5, 134.72,
134.75, 134.8, 136.2, 137.62, 137.68, 138.0, 140.8, 141.9, 142.0,
143.2, 143.3, 144.48, 144.5, 148.7, 150.0, 170.7, 183.8; 15N NMR
(THF-d8) δ -215.1, -223.5, -227.2 (two nitrogen atoms) (gHSQC
and gHMBC). The high-resolution exact mass spectrum gave m/z
793.3978, which is assigned to the protonated molecule ion of the
2e-/2H+-oxidized derivative of the title compound, i.e., the pro-
tonated bilene [calcd 793.3940 for (M′ + H)+, M′ ) C53H52N4OS,
where the title compound has C53H54N4OS], owing to oxidation
during the mass spectrometric process. LD-MS (POPOP) obsd
794.0, calcd 794.4018 (C53H54N4OS). Anal. Calcd for C53H54N4-
OS: C, 80.06; H, 6.85; N, 7.05. Anal. Calcd for C53H54N4OS‚H2O:
C, 78.29; H, 6.94; N, 6.89. Found: C, 78.39; H, 6.87; N, 6.84.
20.3, 28.8, 30.9, 34.2, 43.8, 44.1, 44.5, 96.3, 106.6, 106.8, 106.9,
108.8, 109.2, 109.6, 118.5, 125.0, 126.2, 127.5, 127.9, 128.3, 128.4,
128.56, 128.60, 129.0, 130.9, 131.8, 131.83, 132.2, 132.23, 133.5,
133.6, 133.7, 133.8, 133.85, 133.9, 135.3, 135.5, 137.1, 139.9,
141.0, 142.3, 143.3, 147.8, 149.1, 182.8; 15N NMR (THF-d8) δ
-220.7, -223.5, -227.2 (two nitrogen atoms), (gHSQC, gHMBC).
The high-resolution exact mass spectrum gave m/z 811.3035, which
is assigned to the protonated molecule ion of the 2e-/2H+-oxidized
derivative of the title compound, i.e., a protonated bilene [calcd
811.3011 for (M′ + H)+, M′ ) C51H47BrN4O, where the title
compound has C51H49BrN4O]. LD-MS (POPOP) obsd 810.0, 811.1,
812.0, 813.0, 814.1, calcd 812.309 (C51H49BrN4O). Anal. Calcd
for C51H49 BrN4O: C, 75.26; H, 6.07; N, 6.88. Anal. Calcd for
C51H49 BrN4O‚H2O: C, 73.63; H, 6.18; N, 6.73. Found: C, 73.19;
H, 5.90; N, 6.69.
Alternative Synthesis of 7-Br in Dilute Solution (25 mM). A
sample of 6-Br (0.500 g, 1.20 mmol) in dry THF/methanol (100
mL, 3:1) under argon at room temperature was treated with NaBH4
(1.14 g, 30.0 mmol, 25.0 mol equiv) in small portions with rapid
stirring. The progress of the reaction was monitored by TLC [silica,
hexanes/ethyl acetate (3:1)]. The reaction was complete in ∼30
min. The reaction mixture was poured into a mixture of saturated
aqueous NH4Cl and CH2Cl2 (350 mL). The organic phase was
separated, washed with water and brine, dried (K2CO3), and
concentrated under reduced pressure to yield the dipyrrometh-
anecarbinol as a yellow-orange foam. The resulting sample was
dissolved in anhydrous CH2Cl2 (48.0 mL) and treated with 4a
(0.492 g, 1.20 mmol). The reaction mixture was stirred for 10 min
to achieve complete dissolution of 4a. Following the acid catalysis
conditions used in porphyrin syntheses,2 2,6-di-tert-butylpyridine
(345 µL, 1.56 mmol, 32.5 mM) and Sc(OTf)3 (0.0770 g, 0.156
mmol, 3.25 mM) were added. The progress of the reaction was
monitored by TLC [silica, hexanes/ethyl acetate (3:1)]. The reaction
mixture was stirred at room temperature for 1 h. A sample of TEA
(220 µL, 0.0780 mmol, 32.5 mM) was added. The reaction mixture
immediately changed from red to orange-yellow. The reaction
mixture was diluted with CH2Cl2 (∼100 mL) and washed with water
and brine. The organic phase was dried (Na2SO4) and concentrated
to give a brown-yellow paste. Column chromatography [silica,
hexanes/ethyl acetate (3:1)] afforded a brown foam (0.79 g, 80%).
The data (1H NMR, 13C NMR, LD-MS, FAB-MS, and mp) were
consistent with those obtained from samples prepared via earlier
routes.
24-[9-Borabicyclo[3.3.1]non-9-yl]-1-bromo-19-(4-ethylbenzoyl)-
10-(4-methylphenyl)-5-phenyl-15-(4-tert-butylphenyl)bilane (7-
Br-9-BBN). By following the reported procedure for 1-acyldipyr-
romethanes,5 a solution of 7-Br (0.410 g, 0.500 mmol) in toluene
(1 mL) was treated with TEA (170 µL, 1.20 mmol) followed by
9-BBN-OTf (2.00 mL, 1.00 mmol, 0.500 M in hexanes). The
reaction was complete in ∼30 min. The mixture was passed through
an alumina column eluting with CH2Cl2. The product eluted as a
fast-moving yellow band, which upon concentration afforded a
yellow solid (0.380 g, 80%), presumably as a mixture of 8
stereoisomers: mp 103-105 °C; 1H NMR (THF-d8) δ 0.56-0.62
(br s, 1H), 0.72-0.78 (br s, 1H), 1.26 (s, 12H), 1.61-1.96 (m,
12H), 2.26 (s, 3H), 2.69-2.82 (m, 2H), 5.22-5.26 (m, 2H), 5.44-
5.58 (m, 6H), 5.85-5.89 (m, 2H), 6.35-6.38 (m, 1H), 7.01-7.03
(m, 6H), 7.13-7.15 (m, 3H), 7.18-7.21 (m, 2H), 7.25-7.27 (m,
2H), 7.43-7.45 (m, 2H), 8.19-8.21 (m, 2H), 9.58-9.63 (br s, 2H),
10.36-10.46 (br s, 1H); 13C NMR (THF-d8) δ 15.5, 21.3, 24.0,
25.2, 26.1, 26.4, 29.4, 30.3, 31.3, 31.4, 31.6, 34.6, 34.7, 34.8, 43.9,
44.4, 44.5, 97.1, 107.4, 107.5, 107.8, 108.2, 109.3, 110.7, 118.3,
120.8, 125.6, 127.3, 128.1, 128.4, 128.5, 128.6, 128.8, 128.9, 129.4,
129.44, 130.0, 131.4, 131.5, 131.8, 131.9, 132.4, 133.1, 133.2,
134.2, 134.8, 136.67, 136.70, 139.2, 139.4, 141.6, 149.9, 151.2,
152.5, 174.3; 11B NMR (THF-d8) δ 22.5; 15N NMR (THF-d8) δ
-220.9, -227.4 (two nitrogen atoms) (gHSQC), -151.5, -220.9,
-227.4 (two nitrogen atoms) (gHMBC); LD-MS (POPOP) obsd
934.1, 935.1, 936.1, calcd 932.42; FAB-MS obsd 932.4196, calcd
1-Bromo-19-(4-ethylbenzoyl)-10-(4-methylphenyl)-5-phenyl-
15-(4-tert-butylphenyl)bilane (7-Br). The condensation conditions
described below are identical with those of entry 4 in Table 1. A
sample of 6-Br (0.420 g, 1.00 mmol) in dry THF/methanol (80.0
mL, 3:1) under argon at room temperature was treated with NaBH4
(0.946 g, 25.0 mmol, 25.0 mol equiv). The reaction was complete
in 30 min. The reaction mixture was poured into a mixture of
saturated aqueous NH4Cl (50 mL) and diethyl ether (250 mL). The
organic phase was extracted with diethyl ether (∼300 mL), washed
with water and brine, dried (K2CO3), and concentrated under
reduced pressure at ambient temperature. The resulting orange-
yellow paste was transferred to an oven-dried round-bottomed flask
(25 mL) with diethyl ether. The diethyl ether solution of the
dipyrromethanecarbinol was concentrated to give an orange-yellow
paste. For improved stability, the dipyrromethanecarbinol was
handled as a paste containing residual diethyl ether rather than as
a dry solid (see the Supporting Information). A sample of 4a
(0.411 g, 1.00 mmol) was added. A septum was fitted to the flask,
and anhydrous acetonitrile (1.34 mL) was added under a slow argon
flow. The resulting orange-red reaction mixture was stirred for 1
min, whereupon Yb(OTf)3 (0.660 mL of a 10.0 mM stock solution
in anhydrous MeOH) was slowly added. The reaction mixture
immediately turned dark brown. The reaction mixture was stirred
for 20 min. An aliquot was removed from the reaction mixture
and checked by TLC [silica, hexanes/ethyl acetate (3:1)] and LD-
MS. TLC analysis indicated the presence of 4a and bilane 7-Br.
No detectable scrambling was observed by LD-MS analysis. The
reaction mixture was neutralized by the addition of TEA [10 µL,
0.0660 mmol, 10 mol equiv vs Yb(OTf)3]. The reaction mixture
immediately turned light brown. The resulting mixture was diluted
with diethyl ether (∼30 mL), washed with water and brine, dried
(K2CO3), and concentrated to afford a light brown foam. The crude
product was chromatographed [silica (0.530 g), 4 cm diameter ×
15 cm, hexanes/ethyl acetate (3:1), ∼1.5 L solvent]. The bilane-
containing fractions were concentrated to afford the title compound
as a light-brown foam (0.619 g, 76%), presumably as a mixture of
8 stereoisomers. Unreacted 4a was eluted from the column as a
second component, which upon concentration gave an orange foam
(73 mg). A small mixed fraction was obtained as an orange-yellow
paste that contained 7-Br and 4a (15 mg). Data for the title
1
compound: mp 95-97 °C; H NMR (THF-d8) δ 1.29 (m, 12H),
2.27 (s, 3H), 2.69 (q, J ) 7.5 Hz, 2H), 5.21-5.23 (m, 1H), 5.25-
5.27 (m, 1H), 5.41-5.45 (m, 1H), 5.49-5.55 (m, 5H), 5.86-5.89
(m, 2H), 6.76-6.81 (m, 1H), 7.06-7.10 (m, 4H), 7.14-7.18 (m,
5H), 7.19-7.25 (m, 2H), 7.27-7.30 (m, 4H), 7.76 (d, J ) 8.4 Hz,
2H), 9.52-9.62 (br s, 1H), 9.64-9.72 (br s, 1H), 10.24-10.42
(br s, 1H), 10.86-11.04 (br s, 1H); 13C NMR (THF-d8) δ 15.1,
7712 J. Org. Chem., Vol. 72, No. 20, 2007