Synthesis of Boroxifen
J . Org. Chem., Vol. 67, No. 2, 2002 387
evaporated to dryness. The resulting yellow oil was dissolved
in a mixture of freshly distilled pyridine (50 mL) and ether
(50 mL) and cooled to 0 °C under nitrogen. Thionyl chloride
(16 mL) was added dropwise over 5 min. The reaction was
allowed warm to room temperature overnight whereupon
distilled water (100 mL) was added slowly while cooling the
solution over ice. Aqueous HCl (1 M, 100 mL) was added, and
the layers were separated. The dark aqueous layer was
extracted with ether (3 × 200 mL) and combined with the
original organic fraction. The organic solution was further
extracted with 1 M HCl (3 × 100 mL) and dried over sodium
sulfate and the solvent evaporated leaving an orange/red oil.
The product, a yellow oil (27.2 g, 65%), was isolated by column
chromatography (100% hexanes on silica). TLC (70:30 v/v
hexanes-ether): Rf 0.71; IR (NaCl, cm-1): ν 2967(s), 2929-
(m), 2134 (s), 1608(s); 1H NMR (200 MHz, CDCl3): δ 7.14-
6.60 (m, 9H), 4.11 (t, 2H), 3.72 (t, 3J ) 6.0 Hz, 3H), 2.89 (q,
2H), 1.03 (t, 3J ) 7.4 Hz, 3H), 0.24 (s, 9H); 13C NMR (50 MHz,
CDCl3): δ 152.41, 147.77, 136.42, 126.73, 125.82, 124.30,
123.71, 122.53, 115.04, 109.47, 101.49, 94.16, 63.53, 37.49,
27.09, 7.96; MS (EI): m/z calcd for C23H27OSiCl, 382.153, found
382.152.
429.292. Anal. Calcd for C20H29B10OCl: C, 55.81; H, 6.74.
Found: C, 55.78; H, 6.36.
Z-1-(1,2-Dica r b a -closo-d od e ca b or a n yl)-1-(4-(2-iod o-
eth oxy)p h en yl)-2-p h en yl-bu t-1-en e (8). Compound 7 (200
mg, 0.46 mmol) was added to a dry round-bottom flask
containing freshly distilled acetone (20 mL). Sodium iodide
(350 mg, 2.34 mmol) was added and the reaction mixture
brought to reflux for 2 days. The reaction was cooled and the
solvent removed by rotary evaporation leaving a colorless solid,
which was dissolved in methylene chloride and extracted with
distilled water (2 × 25 mL). The organic layer was dried over
sodium sulfate, gravity-filtered, and the solvent removed using
a rotary evaporator. The crude iodide was purified by radial
chromatography with 3% ether in petroleum ether: a colorless
crystalline solid (156 mg, 65%), TLC (5% ether:petroleum
ether): Rf 0.37; IR (CHCl3, cm-1): ν 3020(m), 2971(w), 2579-
(s); 1H NMR (200 MHz, CDCl3): δ 7.01-6.60 (m, 9H), 4.10 (t,
3J ) 6.6 Hz, 2H), 3.32 (t, 2H), 3.13 (s, 1H), 2.92 (q, 3J ) 7.3
Hz, 2H), 0.91 (t, 3H); 13C NMR (50 MHz, CDCl3): δ 156.86,
151.10, 142.38, 131.98,131.73, 128.95, 128.24, 127.39, 125.99,
114.31, 68.42, 62.96, 27.49, 12.59; 11B NMR (160 MHz,
CDCl3): δ -3.50, -8.97, -12.67, -13.96; MS (EI): m/z
observed boron distribution at 521 (20, [M + 1]+); HRMS
(EI): m/z calcd for C18H25B10 (M-OCH2CH2I), 365.2929, found
365.2918.
3-(4-(2-Ch lor oe t h oxy)p h e n yl)-4-p h e n ylh e x-3-e n e -1-
yn e (6). To compound 4 (26.5 g, 69.1 mmol), dissolved in
absolute methanol (200 mL), was added potassium hydroxide
(4.26 g, 76.0 mmol). The reaction was maintained at ambient
temperature overnight under nitrogen. After the addition of
distilled water (100 mL), the mixture was extracted with ether
(3 × 50 mL). The organic fractions were pooled, dried over
sodium sulfate, and gravity-filtered, and the solvent was
removed by rotary evaporation leaving a yellow-colored solid.
The product was initially purified by flash silica gel chroma-
tography (4% ether in petroleum ether) followed by recrystal-
lization from petroleum ether: a colorless solid (15.62 g, 73%),
mp 53-55 °C; TLC (8% ether:hexanes): Rf 0.59; IR (CH2Cl2,
cm-1): ν 3301(m), 3055(m), 2974(m), 2935(w), 2874(w), 1607-
(m), 1508(s); 1H NMR (200 MHz, CDCl3): δ 7.16-6.64 (m, 9H),
Z-1-([3]-1,2-Dica r ba d od eca h yd r ou n d eca r bor a n yl)-1-(4-
(2-d im eth yla m m on iu m -m eth oxy)p h en yl)-2-p h en ylbu t-1-
en e In n er Sa lt (9). The iodide 8 (136 mg, 0.261 mmol) was
added to a dry round-bottom flask containing dimethylamine
(10 mL, 30% solution in EtOH) whereupon gas evolution was
noted. The reaction mixture was stirred at ambient temper-
ature under nitrogen for 3 h. The excess amine was removed
by rotary evaporation leaving a viscous yellow oil. The oil was
triturated with ethereal HCl and allowed to stand at -10 °C
for 48 h. The excess ether was removed by rotary evaporation
leaving a yellow semisolid, which was subsequently dissolved
in a minimal amount of CH2Cl2. The crude product was
purified by radial chromatography (10% methanol in methyl-
ene chloride), yielding a colorless solid (21 mg, 19%): mp 260
°C (decomp); TLC (20% MeOH:CH2Cl2): Rf 0.53; IR (Nujol,
cm-1): ν 3119(m), 2963(m), 2927(m), 2854(w), 2752(w), 2514-
(s), 1603(m); 1H NMR (300 MHz, CD3CN): δ 7.03-6.58 (m,
3
3
4.12 (t, J ) 6.0 Hz, 2H), 3.73 (t, 2H), 3.29 (s, 1H), 2.91 (q, J
) 7.5 Hz, 2H), 1.03 (t, 3H); 13C NMR (50 MHz, CDCl3): δ
156.76, 152.49, 140.37, 131.63, 130.93, 128.96, 128.01, 126.90,
118.24, 113.82, 84.24, 81.38, 67.80, 41.77, 31.16, 12.40; MS
(EI): m/z calcd for C20H19OCl, 310.114, found 310.112. Anal.
Calcd for C20H19OCl: C, 77.29; H, 6.16. Found: C, 77.66; H,
6.34.
3
9H, Ar-H); 4.12 (t, J ) 5.0 Hz, 2H, CH2NMe2); 3.39 (t, 2H,
OCH2); 2.83 (s, 6H, N(CH3)2); 2.55 (q, 2H, CH2CH3); 2.17 (s,
1H, CH); 0.92 (t, 3J ) 7.4 Hz, 3H, CH3); 13C NMR (50 MHz,
CD3CN): δ 154.99, 144.49, 143.58, 141.32, 137.14, 132.03,
129.65, 127.29, 125.36, 117.45, 112.32, 61.08, 57.04, 43.47,
28.84, 12.22; 11B NMR (96 MHz, CD3CN): δ -7.90, -10.47,
-15.37, -18.36, -21.47, -31.58, -35.20; MS (-ES) m/z:
observed boron distributions at 427 (100, [M]); HRMS
(ESMS): m/z calcd for C22H36B9NO, 430.371, found 430.374.
Anal. Calcd for C22H36B9NO: C, 61.92; H, 8.26. Found: C,
61.93; H, 8.96.
Z-1-(1,2-Dica r ba -closo-d od eca bor a n yl)-1-(4-(2-ch lor o-
eth oxy)p h en yl)-2-p h en ylbu t-1-en e (7). Compound 6 (14.43
g, 46.43 mmol) was added as a solid to dry toluene (150 mL)
under nitrogen. 6,9-Bis(acetonitrile)decaborane (10.31 g, 51.07
mmol) was added in one portion. The reaction mixture was
brought to reflux and monitored by TLC and IR spectroscopy.
After 24 h, the solvent was removed by rotary evaporation
leaving a yellow-colored oil. The oil was dissolved in CH2Cl2
(100 mL) and extracted with 0.1 N NaOH (3 × 50 mL). The
aqueous fractions were pooled and further extracted with CH2-
Cl2 (3 × 50 mL). All organic fractions were combined and dried
over sodium sulfate and gravity-filtered. The solvent was
removed by rotary evaporation leaving a yellow solid. The
crude product was purified by silica gel chromatography (4%
ether in petroleum ether) and the resulting solid recrystallized
from petroleum ether resulting in X-ray quality crystals (2.0
g, 10%). The compound showed: mp 55-57 °C; TLC (8% Ether:
Hexanes): Rf 0.50; IR (CH2Cl2, cm-1): ν 3303(m), 3055(m),
2970(m), 2935(m), 2579(s), 1607(s); 1H NMR (500 MHz,
CDCl3): δ 7.16-6.64 (m, Ar-H), 4.09 (t, 3J ) 6.0 Hz, 2H,
OCH2,), 3.71 (t, 2H, CH2Cl), 3.13 (s, 1H, CH), 2.92 (q, 3J ) 7.5
Hz, 2H, CH2CH3,), 0.91 (t, 3H, CH3); 13C NMR (50 MHz,
CDCl3): δ 157.14, 151.13, 142.40, 132.73, 131.73, 128.99,
128.24, 127.39, 126.00, 114.24, 67.82, 62.98, 41.67, 27.49,
12.56; 11B NMR (96 MHz, CDCl3): δ -3.51, -8.99, -12.67,
-13.95; MS (EI): m/z calcd for C20H29B10OCl, 429.290, found
Ack n ow led gm en t. We would like to thank the
National Sciences and Engineering Research Council
(NSERC) of Canada for their financial support of this
work.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR assign-
ments, 1H and 13C NMR spectra of compounds 7 and 9, HPLC
trace of compound 9 and crystallographic data for compound
7 (tables of crystallographic details, non-hydrogen coordinates,
bond-distances and angles, anisotropic displacement param-
eters, hydrogen coordinates and packing diagrams). This
material is available free of charge via the Internet at
http://pubs.acs.org.
J O0158229