The Journal of Organic Chemistry
Article
4-(2,6-Dimethoxyphenyl)-5-phenyl-5H-dibenzophosphole−Bor-
ane (3f). The general procedure was applied starting from (2-
bromophenyl)diphenylphosphine−borane (1a; 4.00 mmol, 1.42 g)
and 1,2-dibromobenzene 2e (4.80 mmol, 1.78 g). Purification of the
crude product by column chromatography (cyclohexane/CH2Cl2 7/3)
provided dibenzophosphole−borane 3f (0.75 g) as a colorless solid.
Yield: 46%. Analytically pure crystals were obtained by crystallization
Calcd for C20H26BO2P (340.20): C, 70.61; H, 7.70. Found: C, 70.68;
H, 7.65.
4-(1-Methoxyhexyl)-5-phenyl-5H-dibenzophosphole−Borane
(3j). The general procedure was applied starting from (2-
bromophenyl)diphenylphosphine−borane (1a; 4.00 mmol, 1.42 g)
and racemic 1,2-dibromobenzene 2g (4.80 mmol, 1.68 g).
Diastereoisomers of the dibenzophosphole−borane 3j (dr = 57/43
according to NMR analysis of the crude product) were separated by
column chromatography (cyclohexane/CH2Cl2 8/2). The main
diastereoisomer (racemic mixture of (R,Rp)-3j and (S,Sp)-3j assuming
configurations similar to 3k−m) was isolated in 26% yield (0.40 g),
whereas the minor diastereoisomer (racemic mixture of (S,Rp)-3j and
(R,Sp)-3j) was recovered in 18% yield (0.28 g).
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from acetonitrile. Mp: 210−212 °C. H NMR (CDCl3, 400 MHz): δ
0.2−1.5 (br 3 H), 2.85 (s, 3 H), 3.78 (s, 3 H), 6.17 (d, 1 H, J = 8.2
Hz), 6.66 (d, 1 H, J = 8.4 Hz), 7.14−7.19 (m, 5 H), 7.29 (t, 1 H, J =
8.3 Hz), 7.30−7.39 (m, 2 H), 7.56−7.60 (m, 2 H), 7.65 (td, 1 H, J =
7.6, 1.2 Hz), 7.92−7.96 (m, 2 H). 13C NMR (CDCl3, 100 MHz): δ
54.5, 55.5, 102.1, 103.5, 116.1 (d, J = 2.8 Hz), 120.4 (d, J = 6.0 Hz),
121.4 (d, J = 6.1 Hz), 127.6 (d, J = 53.6 Hz), 127.9 (d, J = 10.4 Hz),
128.9 (d, J = 10.0 Hz), 129.8, 130.4 (d, J = 11.9 Hz), 130.8 (d, J = 2.1
Hz), 131.2 (d, J = 8.3 Hz), 131.7, 132.1, 132.8 (d, J = 10.4 Hz), 134.2
(d, J = 59.1 Hz), 134.4 (d, J = 62.8 Hz), 139.7 (d, J = 11.2 Hz), 143.8,
143.8 (d, J = 2.7 Hz), 157.1, 158.4. 31P NMR (CDCl3, 162 MHz): δ
24.6 (br). Anal. Calcd for C26H24BO2P (410.25): C, 76.12; H, 5.90.
Found: C, 75.83; H, 5.85.
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Main Diastereoisomer. Mp: 97−99 °C. H NMR (CDCl3, 300
MHz): δ 0.50−2.03 (m, 14 H), 3.24 (s, 3 H), 4.57 (dd, 1 H, J = 9.2,
2.8 Hz), 7.30−7.46 (m, 5 H), 7.52−7.70 (m, 5 H), 7.87−7.98 (m, 2
H). 13C NMR (CDCl3, 75 MHz): δ 14.2, 22.4, 25.7, 31.5, 38.0, 57.1,
81.2 (d, J = 5.2 Hz), 120.8 (d, J = 6.1 Hz), 121.5 (d, J = 6.2 Hz), 126.3
(d, J = 8.3 Hz), 127.6 (d, J = 50.3 Hz), 128.9 (d, J = 10.3 Hz), 129.2
(d, J = 10.3 Hz), 130.3 (d, J = 12.5 Hz), 131.8 (d, J = 56.9 Hz), 131.8
(d, J = 2.4 Hz), 131.9 (d, J = 1.8 Hz), 132.6−132.8 (m), 134.1 (d, J =
63.8 Hz), 143.2 (d, J = 9.8 Hz), 143.7 (d, J = 10.3 Hz), 147.8 (d, J =
10.7 Hz). 31P NMR (CDCl3, 162 MHz): δ 22.3 (br). HRMS (ESI+):
calcd for C25H3010BNaOP+ ([M + Na]+) 410.2056, found 410.2059.
2-Methyl-5-phenyl-4-trimethylsilanyl-5H-dibenzophosphole−
Borane (3g). The general procedure was applied starting from (2-
bromophenyl)diphenylphosphine−borane (1a; 2.00 mmol, 0.71 g)
and 1,2-dibromobenzene 2f (2.40 mmol, 0.77 g). Purification of the
crude product by column chromatography (cyclohexane/CH2Cl2 9/1)
provided dibenzophosphole−borane 3g (0.29 g) as a colorless solid.
Yield: 40%. Mp: 212−214 °C. 1H NMR (CDCl3, 300 MHz): δ 0.16 (s,
9 H), 0.6−2.1 (br, 3 H), 2.52 (s, 3 H), 7.26−7.43 (m, 4 H), 7.48−7.56
(m, 4 H), 7.60 (br t, 1 H, J = 7.6 Hz), 7.80 (br s, 1 H), 7.86 (br d, 1 H,
J = 7.8 Hz). 13C NMR (CDCl3, 100 MHz): δ 0.5, 21.8, 121.1 (d, J =
6.2 Hz), 123.0 (d, J = 6.4 Hz), 128.7 (d, J = 10.0 Hz), 129.0 (d, J =
10.1 Hz), 129.7 (d, J = 48.7 Hz), 129.7(d, J = 11.8 Hz), 131.4 (m),
132.1 (d, J = 9.9 Hz), 134.3 (d, J = 58.6 Hz), 135.8 (d, J = 64.0 Hz),
136.8 (d, J = 13.1 Hz), 141.2 (d, J = 2.2 Hz), 141.8 (d, J = 9.5 Hz),
145.2 (d, J = 1.8 Hz), 145.4 (d, J = 8.9 Hz). 31P NMR (CDCl3, 162
MHz): δ 25.6 (br). Anal. Calcd for C22H26BPSi (360.31): C, 73.34; H,
7.27. Found: C, 73.21; H, 7.36.
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Minor Diastereoisomer. H NMR (CDCl3, 300 MHz): δ 0.71−
1.85 (m, 14 H), 2.48 (s, 3 H), 4.21 (dd, 1 H, J = 8.8, 3.2 Hz), 7.28−
7.50 (m, 5 H), 7.52−7.70 (m, 5 H), 7.84−7.96 (m, 2 H). 31P NMR
(CDCl3, 162 MHz): δ 22.7 (br).
4-(Methoxy(phenyl)methyl)-5-phenyl-5H-dibenzophosphole−
Borane (3k). The general procedure was applied starting from (2-
bromophenyl)diphenylphosphine borane (1a; 4.00 mmol, 1.42 g) and
racemic 1,2-dibromobenzene 2h (4.80 mmol, 1.71 g). Diaster-
eoisomers of the dibenzophosphole−borane 3k (dr = 74/26 according
to NMR analysis of the crude product) were separated by column
chromatography (cyclohexane/CH2Cl2 8/2). The main diaster-
eoisomer (racemic mixture of (R,Rp)-3k and (S,Sp)-3k according to
single-crystal X-ray analysis) was isolated in 30% yield (0.48 g),
whereas the minor diastereoisomer (racemic mixture of (S,Rp)-3k and
(R,Sp)-3k) was recovered in 7% yield (0.11 g).
5-tert-Butyl-2,3-dimethoxy-5H-dibenzophosphole−Borane (3h).
The general procedure was applied starting from (2-bromophenyl)-
tert-butylphenylphosphine−borane (1c; 4.00 mmol, 1.34 g) and 1,2-
dibromobenzene 2c (4.80 mmol, 1.42 g). Purification of the crude
product by column chromatography (cyclohexane/CH2Cl2 4/6)
provided dibenzophosphole−borane 3h (0.34 g) as a colorless solid.
Main Diastereoisomer. An analytically pure sample was obtained
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by crystallization in acetonitrile. Mp: 175−177 °C. H NMR (CDCl3
300 MHz): δ 0.6−2.3 (br 3 H), 3.35 (s, 3 H), 5.65 (s, 1H), 6.75−6.78
(m, 2 H), 6.95−7.08 (m, 3 H), 7.16−7.22 (m, 2 H), 7.32−7.51 (m, 5
H), 7.57 (br t, 1 H, J = 7.6 Hz), 7.64 (br t, 2 H, J = 7.7 Hz), 7.88−7.93
(m, 2 H). 13C NMR (CDCl3, 100 MHz): δ 56.8, 82.4 (d, J = 4.5 Hz),
121.0 (d, J = 6.0 Hz), 121.5 (d, J = 6.2 Hz), 127.1, 127.4, 127.6 (d, J =
51.3 Hz), 127.8 (d, J = 8.1 Hz), 128.1, 128.9 (d, J = 10.5 Hz), 129.3 (d,
J = 10.3 Hz), 130.2 (d, J = 12.2 Hz), 131.5 (d, J = 57.5 Hz), 131.6 (d, J
= 2.1 Hz), 131.9 (d, J = 1.0 Hz), 132.4 (d, J = 10.3 Hz), 132.8, 134.6
(d, J = 62.9 Hz), 140.3, 142.7 (d, J = 9.4 Hz), 144.3 (d, J = 10.3 Hz),
146.2 (d, J = 9.9 Hz). 31P NMR (CDCl3, 162 MHz): δ 23.7 (br). Anal.
Calcd for C26H24BOP (394.25): C, 79.21; H, 6.14. Found: C, 79.08;
H, 6.08.
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Yield: 27%. Mp: 144−146 °C. H NMR (CDCl3, 300 MHz): δ 0.1−
1.8 (br 3 H), 1.12 (d, J = 14.5 Hz, 9 H), 3.98 (s, 3 H), 4.02 (s, 3 H),
7.17 (d, J = 7.2 Hz, 1 H), 7.33−7.41 (m, 2 H), 7.55 (br t, J = 7.6 Hz, 1
H), 7.68−7.80 (m, 2 H). 13C NMR (CDCl3, 75 MHz): δ 25.1 (d, J =
2.8 Hz), 30.7 (d, J = 28.8 Hz), 56.1, 56.3, 104.3 (d, J = 7.7 Hz), 112.2
(d, J = 13.8 Hz), 120.6 (d, J = 5.8 Hz), 122.7 (d, J = 58.1 Hz), 127.3
(d, J = 9.7 Hz), 130.7 (d, J = 11.4 Hz), 131.6 (d, J = 1.8 Hz), 131.7 (d,
J = 54.9 Hz), 137.8 (d, J = 8.1 Hz), 144.2 (d, J = 7.6 Hz), 149.8 (d, J =
12.1 Hz), 152.4 (d, J = 1.8 Hz). 31P NMR (CDCl3, 162 MHz): δ 44.6
(br). Anal. Calcd for C18H24BO2P (314.17): C, 68.81; H, 7.70. Found:
C, 68.78; H, 7.78.
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Minor Diastereoisomer. H NMR (CDCl3, 300 MHz): δ 0.6−2.1
5-Cyclohexyl-2,3-dimethoxy-5H-dibenzophosphole−Borane (3i).
The general procedure was applied starting from (2-bromophenyl)-
cyclohexylphenylphosphine−borane (1d; 4.00 mmol, 1.44 g) and 1,2-
dibromobenzene 2c (4.80 mmol, 1.42 g). Purification of the crude
product by column chromatography (cyclohexane/CH2Cl2 4/6)
provided dibenzophosphole−borane 3i (0.46 g) as a colorless solid.
(br 3 H), 2.72 (s, 3 H), 5.59 (s, 1 H), 7.06 (dd, 1 H, J = 7.7, 4.4 Hz),
7.22−7.63 (m, 11 H), 7.60−7.72 (m, 3 H), 7.86 (br d, 1 H, J = 7.7
Hz), 7.91 (br d, 1 H, J = 7.8 Hz). 13C NMR (CDCl3, 75 MHz): δ 56.2,
82.5 (d, J = 3.9 Hz), 121.0 (d, J = 6.2 Hz), 121.5 (d, J = 6.1 Hz), 127.2,
127.6, 128.4, 128.5 (d, J = 7.9 Hz), 128.7 (d, J = 52.2 Hz), 128.7 (d, J
= 10.5 Hz), 129.2 (d, J = 10.1 Hz), 130.1 (d, J = 12.2 Hz), 131.5 (d, J
= 2.4 Hz), 131.7 (d, J = 1.7 Hz), 131.8 (d, J = 58.7 Hz), 132.4 (d, J =
10.3 Hz), 132.7 (d, J = 1.6 Hz), 135.0 (d, J = 62.2 Hz), 140.3, 142.6 (d,
J = 9.6 Hz), 144.4 (d, J = 10.4 Hz), 146.3 (d, J = 9.8 Hz). 31P NMR
(CDCl3, 162 MHz): δ 24.4 (br).
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Yield: 33%. Mp: 152−154 °C. H NMR (CDCl3, 300 MHz): δ 0.1−
1.4 (br 3 H), 0.95−1.33 (m, 5 H), 1.52−2.06 (m, 6 H), 3.99 (s, 3 H),
4.01 (s, 3 H), 7.15 (d, J = 7.6 Hz, 1 H), 7.32−7.39 (m, 2 H), 7.54 (br t,
J = 7.7 Hz, 1 H), 7.68−7.76 (m, 2 H). 13C NMR (CDCl3, 75 MHz): δ
25.6 (d, J = 1.2 Hz), 26.4−26.5 (m), 26.6 (d, J = 1.5 Hz), 36.4 (d, J =
30.0 Hz), 56.1, 56.3, 104.4 (d, J = 7.8 Hz), 111.9 (d, J = 14.2 Hz),
120.6 (d, J = 6.0 Hz), 122.7 (d, J = 59.9 Hz), 127.4 (d, J = 9.9 Hz),
130.4 (d, J = 11.6 Hz), 131.5 (d, J = 1.7 Hz), 131.6 (d, J = 56.6 Hz),
137.5 (d, J = 8.7 Hz), 143.9 (d, J = 8.3 Hz), 150.0 (d, J = 12.3 Hz),
152.5 (d, J = 2.0 Hz). 31P NMR (CDCl3, 162 MHz): δ 34.6 (br). Anal.
4-(Methoxymethoxy(phenyl)methyl)-5-phenyl-5H-dibenzo-
phosphole−Borane (3l). Synthesis of 3l Starting from a Racemic
Mixture of 1,2-Dibromobenzene 2i. The general procedure was
applied starting from (2-bromophenyl)diphenylphosphine−borane
(1a; 2.52 mmol, 0.89 g) and racemic 1,2-dibromobenzene 2i (3.03
mmol, 1.17 g). Diastereoisomers of dibenzophosphole−borane 3l (dr
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dx.doi.org/10.1021/jo3009098 | J. Org. Chem. 2012, 77, 6117−6127