Palladium-catalyzed synthesis of dibenzophosphole oxides via intramolecular dehydrogenative cyclization

Article abstract of DOI:10.1021/jo201030j

Dibenzophosphole oxides were obtained from secondary hydrophosphine oxides with a biphenyl group by dehydrogenation via phosphine-hydrogen and carbon-hydrogen bond cleavage in the presence of a catalytic amount of palladium(II) acetate, Pd(OAc)₂

Full text of DOI:10.1021/jo201030j

ARTICLE
pubs.acs.org/joc
Palladium-Catalyzed Synthesis of Dibenzophosphole Oxides via
Intramolecular Dehydrogenative Cyclization
Yoichiro Kuninobu,* Takuya Yoshida, and Kazuhiko Takai*
Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushima, Kita-ku,
Okayama 700-8530, Japan
S Supporting Information
b
ABSTRACT: Dibenzophosphole oxides were obtained from secondary hydropho-
sphine oxides with a biphenyl group by dehydrogenation via phosphineꢀhydrogen
and carbonꢀhydrogen bond cleavage in the presence of a catalytic amount of
palladium(II) acetate, Pd(OAc)2. By using this reaction, a ladder-type dibenzo-
phosphole oxide could also be synthesized by double intramolecular dehydrogena-
tive cyclization.
’ INTRODUCTION
Organic π-conjugated oligomers and polymers are useful
compounds as organic materials, such as organic light-emitting
diodes (OLEDs), organic field-effect transisters (OFETs), non-
linear optical (NLO) devices, and organic solar cells. Hetero-
atom(s) are often contained in the π-conjugated systems, and
these heteroatom(s) play an important role in the properties of
the materials. Dibenzophosphole oxides are among the most
useful compounds for organic materials1 and therefore have
received much attention. There are several methods to synthe-
size dibenzophospholes.2,3 The most frequently used method is
the reaction between 2,20-dilithiated biaryls and PhPCl2 followed
by oxidation of the formed dibenzophospholes by air or H2O2.4
The following methods have also been reported: cyclization of
2-biphenylphenylphosphinic acids by intramolecular Friedelꢀ
Crafts reaction,5 treatment of triphenylphosphine oxide with 2
equiv of PhLi and successive oxidation of the formed dibenzo-
phospholes,6 treatment of tetraphenylphosphonium bromide
with lithium diethylamide followed by oxidation,7 thermolysis
of m-terphenyldichlorophosphines,8 and Et3B- and O2-mediated
radical cyclization of secondary phosphine oxides with a biphenyl
group.9 Our new strategy for the synthesis of dibenzophosphole
oxides is shown in Figure 1. In this reaction, dibenzophosphole
oxides will be synthesized from hydrophosphine oxides bearing a
biphenyl group in the presence of a transition-metal catalyst via
the elimination of H2.10ꢀ12 This transformation should contain
successive PꢀH and CꢀH bond cleavage steps.
Figure 1. Retrosynthesis for the formation of dibenzophospholes.
Scheme 1. Synthesis of Dibenzophosphole Oxide 2a from
Phosphine Oxide 1a
We investigated several phosphine oxides with a functional
group, 1 (Table 1). A phosphine oxide with an electron-donating
group, 1b, gave dibenzophosphole oxide 2b in 93% yield
(entry 1). A higher temperature and longer reaction time were
necessary when employing a phosphine oxide with an electron-
withdrawing group, 1c (entry 2).18 In the case of a phosphine
oxide bearing a chlorine atom, 1d, the corresponding dibenzo-
phosphole oxide 2d was provided without loss of the chlorine
atom (entry 3).17 When a phosphine oxide with a substituent at
the 3-position, 1e, was employed as a substrate, a mixture of two
regioisomers, 2e and 2e0, was formed (entry 4). The cyclization
reaction was not inhibited by a substituent at the 2-position, and
the corresponding dibenzophosphole oxide 2f was isolated in
93% yield (entry 5). The corresponding dibenzophosphole oxide
2g was afforded when a phosphine oxide with a phenyl group, 1g,
was employed as a substrate (entry 6). The CꢀP bond formation
’ RESULTS AND DISCUSSION
By heating a secondary hydrophosphine oxide having a biphenyl
group (1a, phosphine oxide) in the presence of a catalytic
amount of palladium(II) acetate in THF at 65 °C for 3 h,
dibenzophosphole oxide 2a was obtained in 94% yield
(Scheme 1).13ꢀ17 Since 1a and 2a are both air stable, they are
easily handled.
Received: May 24, 2011
Published: August 05, 2011
r
2011 American Chemical Society
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Table 1. Synthesis of Dibenzophosphole Oxides 2 from
Several Phosphine Oxides 1
Scheme 2. Deuterium-Labeling Experiment
Scheme 3. Proposed Mechanism for the Formation of
Dibenzophosphole Oxides 2
Scheme 4. Synthesis of Ladder-Type Dibenzophosphole
Oxide
1
a The yield determined by H NMR is reported in parentheses. b 6 h.
c 1,4-Dioxane, 115 °C, 24 h. d Total yield of 2e and 2e0. e 115 °C, 24 h.
f 30 min. g Pd(OAc)2 (10 mol %), 24 h.
occurred regioselectively only at the 1-position of the naphthyl
group of 1h, and dibenzophosphole oxide 2h was isolated in 92%
yield (entry 7). The reaction also proceeded at the thiophene
ring of phenyl[2-(thiophene-3-yl)phenyl]phosphine oxide 1i
and provided a mixture of two regioisomers, 2i and 2i0 (entry 8).
The reaction also proceeded when phosphine oxides with aliphatic
substituents on the phosphorus atom, 1j and 1k, were employed
as substrates, and the corresponding dibenzophosphole oxides 2j
and 2k were obtained in excellent yields (entries 9 and 10).
However, the desired reaction did not proceed using phenyl-
(2-vinylphenyl)phosphine oxide (substrate with an alkene partner)
as a substrate because of the polymerization of the substrate.
Next a deuterium-labeling experiment was carried out to gain
insight into the reaction mechanism (Scheme 2). If the CꢀH
bond activation is the rate-determining step, a kinetic isotope
effect (KIE) should be observed using a mixture of phosphine
oxide 1j and its pentadeuterated substrate 1j-d. By the reaction of
a 1:1 mixture of 1j and 1j-d with a catalytic amount of Pd(OAc)2
in THF at 65 °C for 30 s, dibenzophosphole oxides 2j and 2j-d
were formed in 14% yield (2j:2j-d = 70:30, KIE = 2.3)
(Scheme 2). This result shows that the rate-determining step is
CꢀH bond activation of the aromatic ring.
The proposed mechanism for the formation of dibenzophosp-
hole oxides is as follows (Scheme 3): (1) PꢀH bond activation
via the elimination of acetic acid;19 (2) sequential CꢀH bond
activation via the elimination of another acetic acid unit;20,21 (3)
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reductive elimination to give dibenzophosphole oxide 2 and
Pd(0) species. After step 3, or in the case of using Pd(0) catalysts,
the reaction will proceed via the following pathway: (4) PꢀH
bond activation by oxidative addition; (5) sequential CꢀH bond
activation by σ-bond metathesis; (3) reductive elimination
leading to dibenzophosphole oxide 2. In steps 2 and 5, one of
the most important factors in promoting CꢀH bond activation is
that the phosphoryl moiety of the formed phosphorylpalladium
species works as a directing group, and thus, the palladium center
is brought close to the CꢀH bond. In this mechanism, the
catalytic cycle proceeds between Pd(0) and Pd(II) species.22,23
This method could be applied to the synthesis of ladder-type
dibenzophosphole oxide 4 (Scheme 4). By heating a mixture
of 3, Pd(OAc)2, and THF, ladder-type 5,11-diphenyl-5,11-dihy-
drobenzo[1,2-b:4,5-b0]bis(phosphindole) 5,11-dioxide (4) was
obtained in 87% yield.24ꢀ26 In this reaction, a mixture of two
diastereomers, which are attributable to the orientation of the
column chromatography on silica gel (ethyl acetate) to give 2a (39.0 mg,
94% yield).
Data for biphenylphenylphosphine oxide (1a): 73%; color-
less oil; purification, silica gel column chromatography (AcOEt); TLC
(AcOEt) Rf = 0.38; 1H NMR (400 MHz, CDCl3) δ 7.22ꢀ7.25 (m, 2H),
7.28ꢀ7.37 (m, 8H), 7.39ꢀ7.45 (m, 1H), 7.52 (tt, J = 7.6, 1.6 Hz, 1H),
7.61 (tt, J = 7.6, 1.6 Hz, 1H), 7.88 (d, J = 492.8 Hz, 1H), 7.96 (ddd, J =
13.9, 7.6, 1.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 127.4 (d, J = 12.8
Hz), 127.8, 128.1, 128.3 (d, J = 12.8 Hz), 129.3, 130.3 (d, J = 127.7 Hz),
130.4 (d, J = 12.9 Hz), 130.6 (d, J = 9.1 Hz), 131.4 (d, J = 102.2 Hz),
131.8, 132.2, 132.7 (d, J = 9.1 Hz), 139.1 (d, J = 5.4 Hz), 145.9, (d, J = 9.1
Hz); 31P NMR (162 MHz, CDCl3) δ 20.1; IR (neat, ν/cmꢀ1) 3507,
3448, 3055, 2343, 1589, 1468, 1439, 1196, 1133, 1115, 945, 778, 750,
703, 694, 668; HRMS (EI+) m/z calcd for C18H15OP (M+) 278.0861,
found 278.0852.
Data for (40-chlorobiphenyl)phenylphosphine oxide (1b):
64%; colorless oil; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.55; 1H NMR (400 MHz, CDCl3)
δ 7.16 (d, J = 8.4 Hz, 2H), 7.26 (d, J = 7.2 Hz, 2H), 7.29ꢀ7.35 (m, 5H),
7.42ꢀ7.48 (m, 1H), 7.54 (tt, J = 7.6, 1.6 Hz, 1H), 7.62 (tt, J = 7.6, 1.6 Hz,
1H), 7.88 (d, J = 419.2 Hz, 1H), 7.94 (ddd, J = 14.8, 7.6, 1.2 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ 127.8 (d, J = 12.8 Hz), 128.2, 128.4 (d, J =
12.8 Hz), 130.3 (d, J = 12.8 Hz), 130.4 (d, J = 100.4 Hz), 130.6 (d, J =
9.1 Hz), 130.7, 130.9 (d, J = 102.2 Hz), 132.0, 132.4, 132.9 (d, J =
12.8 Hz), 134.2, 137.6 (d, J = 3.6 Hz), 144.7, (d, J = 9.1 Hz); 31P NMR
(162 MHz, CDCl3) δ 19.1; IR (neat, ν/cmꢀ1) 3509, 3455, 3055, 3015,
2336, 1591, 1570, 1558, 1495, 1464, 1437, 1396, 1198, 1134, 1115, 1088,
1018, 1005, 945, 831, 775, 741, 692; HRMS (EI+) m/z calcd for
C18H14ClOP (M+) 312.0471, found 312.0473.
i
two PdO double bonds (or two Pꢀ Pr bonds), was formed. This
is the first example of the synthesis of this ladder-type dibenzo-
phosphole oxide.
In conclusion, we have succeeded in the synthesis of dibenzo-
phosphole oxides from hydrophosphine oxides using palladium
acetate, Pd(OAc)2, as a catalyst. This reaction proceeds by PꢀH
and CꢀH bond cleavage via dehydrogenation. By using this
method, ladder-type dibenzophosphole oxides were also synthe-
sized. We hope that this reaction will become a useful method to
synthesize dibenzophosphole oxides.
Data for [40-(trifluoromethyl)biphenyl]phenylphosphine
oxide (1c): 68%; colorless oil; purification, silica gel column chroma-
’ EXPERIMENTAL SECTION
1
tography (AcOEt); TLC (AcOEt) Rf = 0.50; H NMR (400 MHz,
General Procedures. All reactions were carried out in a dry
solvent under an argon atmosphere. THF and 1,4-dioxane were
purchased and dried and degassed before use. Pd(OAc)2 was pur-
chased. 2-Bromobiaryls were prepared by SuzukiꢀMiyaura cross-
coupling reaction between aryl iodides (or aryl bromides) and ar-
ylboronic acids.27,28 Proton chemical shifts are reported relative to
Me4Si (CDCl3) at δ 0.00 ppm or residual solvent peak (CDCl3 at δ
7.26 ppm). Carbon chemical shifts are reported relative to CDCl3 at δ
77.00 ppm. Phosphorus chemical shifts are reported relative to external
85% H3PO4 at δ 0.00 ppm.
Typical Procedure for the Synthesis of Biphenylphenyl-
phosphine Oxide (1a). Magnesium turnings (0.267 g, 11.0 mmol)
were suspended in THF (20 mL). A bead of iodine was added to the
above mixture, and the mixture was stirred at room temperature until the
color of iodine faded. To this mixture was added dropwise a solution of
bromobiphenyl (2.33 g, 10.0 mmol) in THF (10 mL) over 5 min. The
reaction mixture was stirred at 80 °C for 1 h and was then cooled to room
temperature. To this Grignard reagent was added dropwise a solution of
dichlorophenylphosphine (2.69 g, 15.0 mmol) in THF (7.5 mL) over 5
min. After the addition was completed, the mixture was stirred at 80 °C
for 3 h and then cooled to 0 °C. To this solution was added ca. 2 mL of
water, and the mixture was stirred at 0 °C for 10 min. To this solution
was added ca. 4 mL of triethylamine, and the mixture was stirred at 0 °C
for 10 min. The mixture was extracted with ethyl acetate (15 mL ꢁ 3),
and the organic layer was dried over anhydrous MgSO4, filtered, and
concentrated under reduced pressure. The product was isolated by
column chromatography on silica gel (ethyl acetate) to give 1a (2.03 g,
73% yield).
CDCl3) δ 7.21ꢀ7.35 (m, 7H), 7.39ꢀ7.45 (m, 1H), 7.52 (d, J = 8.4 Hz,
2H), 7.58 (tt, J = 7.6, 1.2 Hz, 1H), 7.65 (tt, J = 7.6, 1.6 Hz, 1H), 7.88 (d,
J = 500.8 Hz, 1H), 7.98 (ddd, J = 14.8, 7.6, 1.2 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 123.8 (q, J = 271 Hz), 124.8 (q, J = 3.6 Hz), 128.0 (d, J =
12.7 Hz), 128.2 (d, J = 12.8 Hz), 129.5 (q, J = 29.2 Hz), 129.7, 130.0 (d,
J = 3.6 Hz), 130.1 (d, J = 10.9 Hz), 130.4 (d, J = 9.1 Hz), 131.0 (d, J =
10.9 Hz), 131.8 (d, J = 3.7 Hz), 132.4 (d, J = 3.7 Hz), 133.0 (d, J = 10.9
Hz), 142.7 (d, J = 3.6 Hz), 144.3 (d, J = 9.1 Hz); 31P NMR (162 MHz,
CDCl3) δ 19.3; IR (neat, ν/cmꢀ1) 3519, 3449, 3059, 3016, 2994, 2339,
1618, 1590, 1563, 1484, 1471, 1439, 1404, 1322, 1256, 1206, 1106, 1067,
1045, 1021, 1007, 950, 844, 770, 744, 710, 693, 638, 611; HRMS (EI+)
m/z calcd for C19H14F3OP (M+) 346.0734, found 346.0729.
Data for (40-methoxybiphenyl)phenylphosphine oxide
(1d): 70%; colorless oil; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.28; 1H NMR (400 MHz, CDCl3) δ 3.83
(s, 3H), 6.84 (d, J = 8.8 Hz, 2H), 7.18 (d, J = 8.4 Hz, 2H), 7.30ꢀ7.37 (m,
5H), 7.35ꢀ7.45 (m, 1H), 7.49 (td, J = 7.6, 1.6 Hz, 1H), 7.59 (tt, J = 7.4,
1.4 Hz, 1H), 7.91 (ddd, J = 14.0, 7.6, 0.8 Hz, 1H), 7.94 (d, J = 451.6 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 55.1, 113.4, 127.0, 128.1 (d, J =
12.8 Hz), 130.15, 130.19 (d, J = 107.7 Hz), 130.3 (d, J = 12.8 Hz), 130.6,
(d, J = 9.1 Hz), 131.2 (d, J = 102.2 Hz), 131.4 (d, J = 5.4 Hz), 131.6,
132.1, 132.5, 145.6 (d, J = 10.9 Hz), 159.2; 31P NMR (162 MHz,
CDCl3) δ 20.0; IR (neat, ν/cmꢀ1) 3523, 3459, 3055, 3013, 2961, 2937,
2837, 2349, 1609, 1590, 1576, 1516, 1464, 1456, 1436, 1302, 1248, 1934,
1182, 1133, 1115, 1035, 1017, 1000, 944, 835, 805, 768, 748, 707, 694;
HRMS (EI+) m/z calcd for C19H17O2P (M+) 308.0966, found 308.0976.
Data for (30-methylbiphenyl)phenylphosphine oxide (1e):
70%; colorless oil; purification, silica gel column chromatography (AcOEt);
TLC (AcOEt) Rf = 0.28; 1H NMR (400 MHz, CDCl3) δ 2.27 (s, 3H),
6.92 (s, 1H), 7.05 (d, J = 7.6 Hz, 1H), 7.14, (d, J = 7.2 Hz, 1H), 7.21, (t,
J = 7.6 Hz, 1H), 7.29ꢀ7.36 (m, 5H), 7.41ꢀ7.46 (m, 1H), 7.52 (td, J =
7.4, 1.6 Hz, 1H), 7.59 (td, J = 7.4, 1.4 Hz, 1H), 7.87 (d, J = 494.4 Hz, 1H),
Typical Procedure for the Synthesis of Dibenzophosphole
Oxide (2a). A mixture of a secondary hydrophosphine oxide with a
biphenyl group (1a; 41.7 mg, 0.150 mmol), THF (0.15 mL), and
Pd(OAc)2 (1.7 mg, 7.5 μmol) was stirred at 65 °C for 3 h in a sealed
tube. The solvent was removed in vacuo, and the product was isolated by
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7.89 (ddd, J = 13.6, 7.6, 1.0 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 21.3, 126.4, 127.4 (d, J = 12.8 Hz), 128.1, 128.3 (d, J = 12.9 Hz), 128.9,
129.9 (d, J = 104.0 Hz), 130.1, 130.46 (d, J = 10.9 Hz), 130.52, 130.6 (d,
J = 104.0 Hz), 131.8 (d, J = 3.6 Hz), 132.2 (d, J = 3.6 Hz), 132.6 (d, J =
10.9 Hz), 137.9, 139.0 (d, J = 3.6 Hz), 146.0 (d, J = 10.9 Hz); 31P NMR
(162 MHz, CDCl3) δ 18.4; IR (neat, ν/cmꢀ1) 3506, 3455, 3055, 2918,
2860, 2344, 1606, 1560, 1589, 1465, 1438, 1375, 1330, 1255, 1195, 1133,
1115, 1049, 943, 887, 860, 793, 764, 750, 707, 693; HRMS (EI+) m/z
calcd for C19H17OP (M+) 292.1017, found 292.1018.
7.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.9, 15.6, 26.5 (d, J = 67.2
Hz), 124.6 (d, J = 3.7 Hz), 126.2 (d, J = 3.6 Hz), 127.5 (d, J = 10.9 Hz),
128.7, 129.0 (d, J = 91.3 Hz), 130.5 (d, J = 9.1 Hz), 132.0, 132.7 (d, J =
9.1 Hz), 134.3 (d, J = 5.5 Hz), 139.9 (d, J = 5.5 Hz); 31P NMR (162
MHz, CDCl3) δ 42.4; IR (neat, ν/cmꢀ1) 3499, 3445, 3061, 2963, 2930,
2868, 1589, 1564, 1531, 1464, 1435, 1387, 1364, 1260, 1182, 1128, 1096,
1061, 966, 934, 916, 880, 858, 820, 799, 762, 721, 683, 654; HRMS (EI+)
m/z calcd for C13H15OPS (M+) 250.0581, found 250.0591.
Data for biphenylisopropylphosphine oxide (1j): 81%;
white solid; purification, silica gel column chromatography (AcOEt/
Data for (20-methoxybiphenyl)phenylphosphine oxide
(1f, a mixture of two stereoisomers): 70%; colorless oil; purifica-
tion, silica gel column chromatography (AcOEt); TLC (AcOEt) Rf =
0.28; 1H NMR (400 MHz, CDCl3) δ 3.33 (s, 3H), 3.68 (s, 3H), 6.69 (d,
J = 8.0 Hz, 1H), 6.82 (d, J = 4.4 Hz, 2H + 1H), 7.00 (t, J = 7.0 Hz, 1H),
7.11ꢀ7.40 (m, 7H + 7H), 7.41ꢀ7.47 (m, 1H), 7.50ꢀ7.56 (m, 1H +
1H), 7.59 (t, J = 7.4 Hz, 1H + 1H), 7.88 (d, J = 494.4 Hz, 1H), 7.90 (d, J =
494.4 Hz, 1H), 8.02 (dd, J = 12.0, 7.6 Hz, 1H), 8.11 (dd, J = 13.4, 7.4 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 54.7, 55.2, 110.4 (d, J = 18.2 Hz),
120.4 (d, J = 23.6 Hz), 127.6 (d, J = 12.7 Hz), 128.2 (d, J = 12.7 Hz),
129.8 (d, J = 12.7 Hz), 129.96 (d, J = 101.8 Hz), 130.04 (d, J = 10.9 Hz),
130.7 (d, J = 10.9 Hz), 131.1 (d, J = 9.0 Hz), 131.2 (d, J = 11.0 Hz), 131.6,
131.7 (d, J = 12.7 Hz), 131.9, 132.0 (d, J = 9.1 Hz), 132.2, 132.3 (d, J =
9.1 Hz), 132.8, 141.4 (d, J = 10.9 Hz), 141.9 (d, J = 9.1 Hz), 156.0 (d, J =
1
methanol = 95/5); TLC (AcOEt) Rf = 0.10; H NMR (400 MHz,
CDCl3) δ 0.88 (dd, J = 20.2, 7.2 Hz, 3H), 1.02 (dd, J = 17.6, 7.2 Hz, 3H),
1.53ꢀ1.66 (m, 1H), 7.10 (dd, J = 469.6, 3.6 Hz, 1H), 7.35ꢀ7.48 (m,
6H), 7.54 (tt, J = 7.6, 1.6 Hz, 1H), 7.61 (tt, J = 7.6, 1.2 Hz, 1H), 7.97
(ddd, J = 12.8, 8.0, 1.2 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 14.5,
15.4, 26.8 (d, J = 69.4 Hz), 127.4 (d, J = 10.9 Hz), 128.0, 128.3, 128.5 (d,
J = 89.5 Hz), 129.1, 130.4 (d, J = 9.1 Hz), 131.8, 132.4 (d, J = 9.1 Hz),
139.5 (d, J = 3.7 Hz), 145.0 (d, J = 10.9 Hz); 31P NMR (162 MHz,
CDCl3) δ 38.1; IR (neat, ν/cmꢀ1) 3046, 2955, 2922, 2855, 1964, 1881,
1859, 1813, 1755, 1672, 1589, 1562, 1501, 1447, 1433, 1385, 1379, 1366,
1254, 1180, 1128, 1098, 1059, 1018, 976, 966, 935, 912, 893, 870, 783,
754, 745, 702; HRMS (EI+) m/z calcd for C15H17OP (M+) 244.1017,
found 244.1019.
49.1 Hz); 31P NMR (162 MHz, CDCl3) δ 17.4, 20.2; IR (neat, ν/cmꢀ1
)
Data for biphenyl-tert-butylphosphine oxide (1k): 11%;
white solid; purification, silica gel column chromatography (AcOEt/
3503, 3447, 3055, 3011, 2961, 2938, 2835, 2357, 1734, 1601, 1580, 1562,
1497, 1456, 1435, 1296, 1277, 1257, 1180, 1115, 1051, 1024, 1003, 939,
802, 768, 710, 692, 678, 617; HRMS (EI+) m/z calcd for C19H17O2P
(M+) 308.0966, found 308.0976.
1
methanol = 95/5); TLC (AcOEt) Rf = 0.09; H NMR (400 MHz,
CDCl3) δ 0.87 (d, J = 16.8 Hz, 9H), 7.00 (d, J = 471.6 Hz, 1H),
7.25ꢀ7.39 (m, 6H), 7.46 (t, J = 7.6 Hz, 1H), 7.52 (t, J = 7.6 Hz, 1H), 7.92
(dd, J = 11.0 Hz, 7.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 23.6, 32.6
(d, J = 69.4 Hz), 127.2 (d, J = 10.9 Hz), 127.9, 128.2, 129.8, 130.8 (d, J =
9.1 Hz), 131.3 (d, J = 91.3 Hz), 131.8, 132.4 (d, J = 7.3 Hz), 139.8 (d, J =
3.6 Hz), 145.7 (d, J = 9.1 Hz); 31P NMR (162 MHz, CDCl3) δ 40.1; IR
(neat, ν/cmꢀ1) 3055, 2953, 2924, 2853, 1587, 1558, 1462, 1427, 1377,
1366, 1261, 1207, 1165, 1121, 1096, 1047, 1030, 997, 955, 943, 918, 852,
814, 783, 766, 752, 741; HRMS (EI+) m/z calcd for C16H19OP (M+)
258.1174, found 258.1183.
Data for [1,10:40,100-terphenyl]-2-ylphenylphosphine oxide
(1g): 92%; colorless oil; purification, silica gel column chromatography
1
(hexane/AcOEt = 1/1); TLC (hexane/AcOEt = 1/1) Rf = 0.40; H
NMR (400 MHz, CDCl3) δ 7.28ꢀ7.45 (m, 9H), 7.46ꢀ7.56 (m, 5H),
7.58ꢀ7.66 (m, 3H), 8.00 (ddd, J = 14.4, 7.6, 1.2 Hz, 1H), 7.95 (d, J =
494.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 126.9, 127.1, 127.5,
127.57, 127.63, 128.3 (d, J = 12.7 Hz), 129.4 (d, J = 96.4 Hz, 2C), 130.5
(d, J = 12.8 Hz), 130.6 (d, J = 9.1 Hz), 131.9, 132.4, 132.9 (d, J = 10.9
Hz), 138.17, 138.23, 140.5, 140.8, 145.6; 31P NMR (162 MHz, CDCl3)
δ 23.1; IR (neat, ν/cmꢀ1) 1762, 1718, 1670, 1589, 1439, 1190, 1132,
1115, 1076, 1045, 1007, 947, 843, 760, 750, 727, 694, 665; HRMS (EI+)
m/z calcd for C24H19OP (M+) 354.1174, found 354.1177.
Data for biphenylisopropylphosphine oxide-d5 (1j-d): 41%;
white solid; purification, silica gel column chromatography (AcOEt/
methanol = 95/5); TLC (AcOEt/methanol = 95/5) Rf = 0.33; 1H NMR
(400 MHz, CDCl3) δ 0.88 (dd, J = 20.2, 7.2 Hz, 3H), 1.02 (dd, J = 17.6, 7.2
Hz, 3H), 1.53ꢀ1.65 (m, 1H), 7.10 (dd, J = 470.2, 3.4 Hz, 1H), 7.38 (ddd,
J=7.4, 4.6, 0.8Hz, 1H), 7.54(tt,J=7.4, 1.6Hz, 1H), 7.61(tt,J= 7.4, 1.4 Hz,
1H), 7.97 (ddd, J = 12.7, 7.5, 1.2 Hz, 1H); 13C NMR (100 MHz, CDCl3)
δ 14.6, 15.5, 26.9 (d, J = 69.0 Hz), 127.5 (d, J = 10.9 Hz), 127.9 (t, J = 25.5
Hz), 128.0 (t, J = 25.0 Hz), 128.7 (t, J = 23.6 Hz), 130.5 (d, J = 9.1 Hz),
131.9, 132.5 (d, J= 9.1 Hz), 139.4 (d, J= 3.6 Hz), 145.1 (d, J= 10.9 Hz); 31P
NMR (162 MHz, CDCl3) δ 38.8; IR (neat, ν/cmꢀ1) 3046, 2955, 2924,
2855, 1589, 1562, 1321, 1254, 1171, 1128, 1092, 1059, 1016, 976, 934, 872,
835, 781, 760, 692, 650, 606; HRMS (EI+) m/z calcd for C15H12D5OP
(M+) 249.1326, found 249.1328.
Data for [2-(2-naphthalenyl)phenyl]phenylphosphine oxide
(1h): 55%; white solid; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.40; 1H NMR (400 MHz, CDCl3)
δ 7.28ꢀ7.30 (m, 4H), 7.36 (t, J = 7.8 Hz, 2H), 7.44 (t, J = 6.2 Hz, 1H),
7.52 (t, J = 4.0 Hz, 2H), 7.56 (t, J = 7.6 Hz, 1H), 7.65 (t, J = 7.6 Hz, 1H),
7.67 (s, 1H), 7.73 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.4 Hz, 1H), 7.85 (d, J =
6.8 Hz, 1H), 7.89 (d, J = 480.8 Hz, 1H), 8.02 (dd, J = 14.0, 7.6 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ 126.3 (d, J = 3.6 Hz), 126.8, 127.3 (d,
J = 9.1 Hz), 127.7, 128.0, 128.1 (d, J = 12.8 Hz), 128.5 (2C), 130.1 (d, J =
12.8 Hz), 130.2 (d, J = 102.2 Hz), 130.5 (d, J = 3.6 Hz), 130.61, 130.62
(d, J = 12.8 Hz), 131.3 (d, J = 102.2 Hz), 131.6 (d, J = 3.6 Hz), 132.0 (d,
J = 3.6 Hz), 132.4, 132.5 (d, J = 10.9 Hz), 136.3 (d, J = 5.4 Hz), 145.5 (d,
Data for 2,200-bis(phenylphosphine oxide)-p-terphenyl (3,
a mixture of two stereoisomers): 52%; white solid; purification,
silica gel column chromatography (AcOEt/methanol = 5/1); TLC
J = 10.9 Hz); 31P NMR (162 MHz, CDCl3) δ 18.1; IR (neat, ν/cmꢀ1
)
1
3501, 3445, 3053, 3015, 2959, 2926, 2851, 2351, 2335, 1964, 1823, 1587,
1562, 1557, 1504, 1479, 1435, 1362, 1230, 1188, 1130, 1115, 1086, 974,
858, 820, 729, 706, 692; HRMS (EI+) m/z calcd for C22H17OP (M+)
328.1017, found 328.1020.
Data for isopropyl[2-(thiophene-3-yl)phenyl]phosphine
oxide (1i): 51%; colorless oil; purification, silica gel column chroma-
tography (AcOEt/methanol = 95/5); TLC (AcOEt/methanol = 95/5)
Rf = 0.25; 1H NMR (400 MHz, CDCl3) δ 0.87 (dd, J = 20.8, 7.2 Hz, 3H),
1.09 (dd, J = 17.2, 7.2 Hz, 3H), 1.61ꢀ1.72 (m, 1H), 7.11 (dd, J = 468.0,
4.4 Hz, 1H), 7.23 (dd, J = 4.8, 0.8 Hz, 1H), 7.41ꢀ7.46 (m, 2H),
7.48ꢀ7.54 (m, 2H), 7.57ꢀ7.62 (m, 1H), 7.86ꢀ7.93 (dd, J = 13.2,
(AcOEt/methanol = 5/1) Rf = 0.23; H NMR (400 MHz, CDCl3)
δ 0.88 (d, J = 7.2 Hz, 3H), 0.93 (d, J = 7.2 Hz, 3H), 1.07 (dd, J = 7.2, 3.2
Hz, 3H), 1.12 (dd, J = 7.2, 2.8 Hz, 3H), 1.67ꢀ1.82 (m, 2H), 7.01 (dd, J =
466.0, 1.6 Hz, 1H), 7.09 (dd, J = 466.0, 1.6 Hz, 1H), 7.43 (dd, J = 7.6, 4.8
Hz, 2H), 7.55 (s, 4H), 7.57 (t, J = 8.0 Hz, 2H), 7.64 (d, J = 7.2 Hz, 2H),
7.96 (dd, J = 13.2, 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 14.9,
15.6, 27.2 (d, J = 69.4 Hz), 127.8 (d, J = 10.9 Hz), 128.6 (d, J = 91.3 Hz),
129.5, 130.8 (d, J = 9.1 Hz), 132.1 (d, J = 3.6 Hz), 132.6, (d, J = 9.1 Hz),
139.6 (d, J = 3.6 Hz), 144.4 (d, J = 9.1 Hz); 31P NMR (162 MHz,
CDCl3) δ 39.3, 39.5; IR (Nujol, ν/cmꢀ1) 3428, 2727, 2669, 2320, 1589,
1564, 1258, 1186, 1157, 1059, 920, 876, 847, 764, 746, 721, 681, 638;
7373
dx.doi.org/10.1021/jo201030j |J. Org. Chem. 2011, 76, 7370–7376

The Journal of Organic Chemistry
ARTICLE
HRMS (EI+) m/z calcd for C24H28O2P2 (M+) 410.1565, found
410.1555.
J = 7.6, 2.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 19.4, 22.0, 118.5
(d, J = 10.9 Hz), 121.0 (d, J = 10.9 Hz), 121.1 (d, J = 10.9 Hz), 121.9 (d,
J = 10.9 Hz), 127.8, 128.0, 128.7 (d, J = 12.7 Hz, mixture of
regioisomers), 129.3 (d, J = 10.9 Hz), 129.7 (d, J = 9.1 Hz), 129.8 (d,
J = 9.1 Hz), 129.94 (d, J = 9.1 Hz), 129.95 (d, J = 109.0 Hz), 130.1 (d, J =
127.2 Hz), 130.2 (d, J = 10.9 Hz), 130.3 (d, J = 10.9 Hz), 130.9 (d, J =
10.9 Hz), 131.0 (d, J = 10.9 Hz), 131.1, 131.2, 132.0 (d, J = 120.0 Hz),
132.6 (d, J = 120.0 Hz), 133.4, 133.5, 133.6, 133.7, 141.8 (d, J = 21.8 Hz),
141.9 (d, J = 21.8 Hz), 142.0 (d, J = 21.8 Hz), 142.1 (d, J = 21.8 Hz),
144.1 (mixture of regioisomers); 31P NMR (162 MHz, CDCl3) δ 33.6,
34.1; IR (Nujol, ν/cmꢀ1) 1603, 1203, 1186, 1136, 1111, 1090, 1065,
1022, 995, 959, 924, 885, 870, 853, 820, 775, 770, 752, 731, 721; HRMS
(EI+) m/z calcd for C19H15OP (M+) 290.0861, found 290.0847.
Data for 2-methyl-5-phenyl-5H-dibenzophosphole 5-oxide
(2e): purification, recrystallization of a mixture of 2e and 2e0 from 1,2-
dichloromethane/hexane; 1H NMR (400 MHz, CDCl3) δ 2.47 (s, 3H),
7.20 (dd, J = 7.6, 2.8 Hz, 1H), 7.38 (td, J = 7.4, 3.2 Hz, 3H), 7.48 (t, J =
7.2 Hz, 1H), 7.55ꢀ7.73 (m, 6H), 7.81 (dd, J = 7.6, 2.4 Hz, 1H); 13C
NMR (100 MHz, CDCl3) δ 22.0, 121.0 (d, J = 10.9 Hz), 121.9 (d, J = 9.1
Hz), 128.7 (d, J = 10.9 Hz), 129.3 (d, J = 12.8 Hz), 129.8 (d, J = 10.9 Hz),
129.9 (d, J = 10.9 Hz), 130.2 (d, J = 120.0 Hz), 130.3 (d, J = 10.9 Hz),
130.8 (d, J = 9.1 Hz), 131.9 (d, J = 10.9 Hz), 132.1 (d, J = 120.0 Hz),
132.6 (d, J = 120.0 Hz), 133.7 (d, J = 21.8 Hz), 141.8 (d, J = 21.8 Hz),
142.1 (d, J = 21.8 Hz), 144.1; 31P NMR (162 MHz, CDCl3) δ 34.1; IR
(Nujol, ν/cmꢀ1) 1603, 1589, 1568, 1204, 1184, 1109, 1062, 818, 731,
696, 642; HRMS (EI+) m/z calcd for C19H15OP (M+) 290.0861, found
290.0847.
Data for 5-phenyl-5H-dibenzophosphole 5-oxide (2a):
94%; white solid; purification, silica gel column chromatography (AcOEt);
TLC (AcOEt) Rf = 0.35; 1H NMR (400 MHz, CDCl3) δ 7.36ꢀ7.43 (m,
4H), 7.49 (td, J = 7.5, 1.6 Hz, 1H), 7.59 (td, J = 7.6, 1.2 Hz, 2H), 7.65
(dd, J = 12.8, 1.6 Hz, 1H), 7.67 (dd, J = 12.8, 1.2 Hz, 1H), 7.69ꢀ7.75 (m,
2H), 7.83 (dd, J = 7.6, 2.8 Hz, 2H); 13C NMR (100 MHz, CDCl3)
δ 121.2 (d, J = 10.9 Hz), 128.7 (d, J = 12.8 Hz), 129.4 (d, J = 10.9 Hz),
129.9 (d, J = 9.0 Hz), 130.7 (d, J = 104.0 Hz), 131.0 (d, J = 10.9 Hz),
132.2, 132.7 (d, J = 105.8 Hz), 133.4, 141.7 (d, J = 21.9 Hz); 31P NMR
(162 MHz, CDCl3) δ 34.0; IR (Nujol, ν/cmꢀ1) 1589, 1204, 1130, 764,
750, 725, 718, 698; HRMS (EI+) m/z calcd for C18H13OP (M+)
276.0704, found 276.0712.
Data for 3-chloro-5-phenyl-5H-dibenzophosphole 5-oxide
(2b): 90%; white solid; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.48; 1H NMR (400 MHz, CDCl3)
δ 7.38ꢀ7.46 (m, 3H), 7.50ꢀ7.58 (m, 2H), 7.58ꢀ7.68 (m, 4H),
7.68ꢀ7.73 (m, 1H), 7.76 (dd, J = 8.2, 3.4 Hz, 1H), 7.80 (dd, 7.8, 3.0
Hz, 1H) ; 13C NMR (100 MHz, CDCl3) δ 121.1 (d, J = 9.1 Hz), 122.3
(d, J = 10.9 Hz), 128.6 (d, J = 12.8 Hz), 129.4 (d, J = 10.9, 3.6 Hz), 129.6
(d, J = 9.1 Hz), 129.7 (d, J = 104.1 Hz), 130.7 (d, J = 10.9 Hz, 2C), 132.1
(d, J = 107.7 Hz), 132.2 (d, J = 3.6 Hz), 133.1, 133.4, 134.7 (d, J = 105.8
Hz), 135.1 (d, J = 14.6 Hz), 139.7 (d, J = 20.1 Hz), 140.5 (d, J = 21.9 Hz);
31P NMR (162 MHz, CDCl3) δ 33.5; IR (Nujol, ν/cmꢀ1) 1202, 1134,
1098, 885, 829, 772, 762, 727, 696; HRMS (EI+) m/z calcd for
C18H12ClOP (M+) 310.0314, found 310.0304.
Data for 1-methoxy-5-phenyl-5H-dibenzophosphole 5-oxide
(2f): 93%; white solid; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.23; 1H NMR (400 MHz, CDCl3) δ 4.05
(s, 3H), 7.13 (d, J = 8.0 Hz, 1H), 7.30ꢀ7.42 (m, 5H), 7.48 (td, J = 7.2, 1.6
Hz, 1H), 7.57 (tt, J = 7.8, 1.2 Hz, 1H), 7.64ꢀ7.74 (m, 3H), 8.41 (dd, J =
7.8, 3.0 Hz, 1H) ; 13C NMR (100 MHz, CDCl3) δ 55.3, 115.7, 121.3 (d,
J = 9.1 Hz), 126.3 (d, J = 9.1 Hz), 128.1 (d, J = 12.9 Hz), 128.4 (d, J =
12.9 Hz), 128.9 (d, J = 25.5 Hz), 129.1 (d, J = 10.9 Hz), 130.5 (d, J = 12.8
Hz), 130.7 (d, J = 10.9 Hz), 130.8 (d, J = 102.2 Hz), 131.8, 132.0 (d, J =
105.8 Hz), 133.2, 134.6 (d, J = 104.0 Hz), 141.1 (d, J = 21.9 Hz), 156.6
(d, J = 12.8 Hz); 31P NMR (162 MHz, CDCl3) δ 34.5; IR (Nujol, ν/
cmꢀ1) 1582, 1265, 1184, 1132, 1109, 1070, 1040, 997, 866, 789, 762,
748, 723, 708, 665; HRMS (EI+) m/z calcd for C19H15O2P (M+)
306.0810, found 306.0824.
Data for 3-(trifluoromethyl)-5-phenyl-5H-dibenzophosp-
hole 5-oxide (2c): 86%; white solid; purification, silica gel column
chromatography (AcOEt); TLC (AcOEt) Rf = 0.48; H NMR (400
1
MHz, CDCl3) δ 7.43 (td, J = 7.6, 3.2 Hz, 2H), 7.48 (td, J = 7.4, 3.6 Hz,
1H), 7.54 (td, J = 7.6, 1.6 Hz, 1H), 7.62ꢀ7.70 (m, 3H), 7.76 (dd, J = 9.6,
7.6 Hz, 1H), 7.84 (d, J = 8.4 Hz, 1H), 7.90 (dd, J = 7.8, 3.0 Hz, 1H),
7.92ꢀ7.98 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 121.5 (d, J = 9.1
Hz), 121.9 (d, J = 10.9 Hz), 123.5 (q, J = 270.9 Hz), 126.6 (q, J = 3.7 Hz),
126.8 (q, J = 3.7 Hz), 128.9 (d, J = 12.7 Hz), 130.0, 130.1 (d, J = 9.1 Hz),
130.4 (d, J = 3.6 Hz), 130.5 (d, J = 10.9 Hz), 130.9 (d, J = 10.9 Hz, 2C),
131.3 (q, J = 32.8 Hz), 131.4 (d, J = 32.8 Hz), 133.2 (d, J = 114.5 Hz),
134.0 (d, J = 103.7 Hz), 140.3 (d, J = 21.8 Hz), 144.9 (d, J = 21.9 Hz); 31P
NMR (162 MHz, CDCl3) δ 31.5; IR (Nujol, ν/cmꢀ1) 1568, 1335, 1261,
1194, 1132, 1086, 880, 851, 779, 721; HRMS (EI+) m/z calcd for
C19H12F3OP (M+) 344.0578, found 344.0581.
Data for 3-methoxy-5-phenyl-5H-dibenzophosphole
5-oxide (2d): 93%; white solid; purification, silica gel column chro-
matography (AcOEt); TLC (AcOEt) Rf = 0.19; 1H NMR (400 MHz,
CDCl3) δ 3.82 (s, 3H), 7.10 (ddd, J = 8.4, 2.4, 0.8 Hz, 1H), 7.22 (dd, J =
11.0, 2.6 Hz, 1H), 7.31 (tdd, J = 7.6, 3.6, 0.8 Hz, 1H), 7.40 (td, J = 7.4, 3.2
Hz, 2H), 7.50 (td, J = 7.5, 1.6 Hz, 1H), 7.55 (tt, J = 7.6, 1.4 Hz, 1H),
7.63ꢀ7.70 (m, 3H), 7.72 (d, J = 8.0 Hz, 1H), 7.73 (d, J = 8.4, 3.6 Hz, 1H);
13C NMR (100 MHz, CDCl3) δ 55.4, 119.7, 120.3 (d, J = 9.1 Hz), 113.8
(dd, J = 10.9, 3.7 Hz), 122.4 (d, J = 12.8 Hz), 128.1 (d, J = 10.9 Hz), 128.6
(d, J = 12.8 Hz), 129.6 (dd, J = 10.9, 3.6 Hz), 130.7 (d, J = 104.0 Hz),
130.8 (d, J = 10.9 Hz), 132.0 (d, J = 3.7 Hz), 132.1 (d, J = 107.7 Hz),
133.8, 134.2 (d, J = 21.9 Hz), 134.3 (d, J = 105.8 Hz), 141.8 (d, J = 20.1
Hz), 160.6 (d, J = 14.7 Hz); 31P NMR (162 MHz, CDCl3) δ 33.6; IR
(Nujol, ν/cmꢀ1) 1591, 1576, 1569, 1333, 1298, 1275, 1257, 1198, 1132,
1109, 1057, 1036, 1026, 853, 837, 770, 729, 716; HRMS (EI+) m/z calcd
for C19H15O2P (M+) 306.0810, found 306.0820.
Data for 3,5-diphenyl-5H-benzo[b]phosphindole 5-oxide
(2g): 61%; white solid; purification, silica gel column chromatography
1
(hexane/AcOEt = 1/2); TLC (hexane/AcOEt = 1/2) Rf = 0.40; H
NMR (400 MHz, CDCl3) δ 7.36ꢀ7.55 (m, 7H), 7.58ꢀ7.66 (m, 3H),
7.68ꢀ7.76 (m, 3H), 7.81ꢀ7.96 (m, 4H); 13C NMR (100 MHz, CDCl3)
δ 121.2 (d, J = 10.9 Hz), 121.6 (d, J = 10.9 Hz), 126.9, 128.0, 128.5 (d, J =
9.1 Hz), 128.8 (d, J = 12.7 Hz, 2C), 128.9 (d, J = 95 Hz), 129.0, 129.4 (d,
J = 10.9 Hz), 130.0 (d, J = 10.9 Hz), 131.1 (d, J = 11.0 Hz, 2C), 131.6 (d,
J = 109 Hz), 131.7 (d, J = 109 Hz), 132.2 (d, J = 10.9 Hz, 2C), 133.5,
139.6, 142.5 (d, J = 10.9 Hz); 31P NMR (162 MHz, CDCl3) δ 34.4; IR
(Nujol, ν/cmꢀ1) 1560, 1508, 1198, 1134, 1113, 908, 760, 733, 692, 665;
HRMS (EI+) m/z calcd for C24H17OP (M+) 352.1017, found 352.1019.
Data for 11-phenyl-11H-benzo[a]phosphafluorene 11-
oxide (2h): 92%; white solid; purification, silica gel column chroma-
1
tography (AcOEt); TLC (AcOEt) Rf = 0.35; H NMR (400 MHz,
CDCl3) δ 7.36ꢀ7.44 (m, 3H), 7.46ꢀ7.53 (m, 2H), 7.58 (td, J = 7.4, 1.2
Hz, 1H), 7.63ꢀ7.72 (m, 3H), 7.73ꢀ7.79 (m, 1H), 7.83 (d, J = 8.0 Hz,
1H), 7.92 (d, J = 8.0 Hz, 1H), 8.01 (dd, J = 7.8, 3.0 Hz, 1H), 8.22ꢀ8.28
(m, 2H); 13C NMR (100 MHz, CDCl3) δ 119.8 (d, J = 10.9 Hz), 121.3
(d, J = 9.1 Hz), 126.7, 128.2, 128.3, 128.4, 128.7 (d, J = 3.7 Hz), 129.1 (d,
J = 10.9 Hz), 129.3 (d, J = 9.1 Hz), 129.4 (d, J = 9.1 Hz), 130.5 (d, J =
107.3 Hz), 130.7 (d, J = 10.9 Hz), 131.3, 131.7, 131.79 (d, J = 3.6 Hz),
131.80 (d, J= 118.2 Hz), 131.9 (d, J= 118.1 Hz), 135.4, 136.8 (d, J=20.0Hz),
Data for 2-methyl-5-phenyl-5H-dibenzophosphole 5-oxide
(2e) and 4-methyl-5-phenyl-5H-dibenzophosphole 5-oxide
(2e0): 93%; white solid; purification, silica gel column chromatography
(AcOEt); TLC (AcOEt) Rf = 0.19; 1H NMR (400 MHz, CDCl3) δ 2.40
(s, 3H, 2e0), 2.47 (s, 3H, 2e), 7.20 (dd, J = 7.6, 2.8 Hz, 1H), 7.38 (td, J =
7.4, 3.2 Hz, 3H), 7.48 (t, J = 7.2 Hz, 1H), 7.55ꢀ7.73 (m, 6H), 7.81 (dd,
7374
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ARTICLE
141.6 (d, J = 20.0 Hz); 31P NMR (162 MHz, CDCl3) δ 33.3; IR (Nujol,
ν/cmꢀ1) 1589, 1566, 1223, 1196, 1132, 1111, 1055, 968, 889, 771, 723,
691, 635, 604; HRMS (EI+) m/z calcd for C22H15OP (M+) 326.0861,
found 326.0871.
J = 9.1 Hz), 128.4 (td, J = 23.6, 9.0 Hz), 128.9 (d, J = 10.9 Hz), 129.3 (td,
J = 23.6, 9.1 Hz), 129.7 (d, J = 9.1 Hz), 130.4 (d, J = 95.5 Hz), 130.5 (d,
J = 96.4 Hz), 132.6 (t, J = 23.6 Hz), 133.1, 141.6 (d, J = 20.0 Hz), 141.7
(d, J = 20.0 Hz); 31P NMR (162 MHz, CDCl3) δ 51.8; IR (Nujol,
ν/cmꢀ1) 1595, 1564, 1539, 1258, 1182, 1130, 1070, 883, 849, 772, 745,
727, 708, 650; HRMS (EI+) m/z calcd for C15H11D4OP (M+) 246.1108,
found 246.1115.
Data for 6,12-diphenyl-6,12-diphosphaindeno[1,2-b]fluorine
6,12-dioxide (4, a mixture of two stereoisomers): 87%; white
solid; purification, silica gel column chromatography (AcOEt/methanol =
5/1); TLC (AcOEt/methanol = 5/1) Rf = 0.48, 0.23; 1H NMR (400 MHz,
CDCl3) δ 1.06ꢀ1.28 (m, 12H), 2.35ꢀ2.53 (m, 2H), 7.50 (td, J = 7.6, 3.2
Hz, 2H), 7.60 (td, J = 7.4, 1.2 Hz, 2H), 7.86 (t, J = 7.8 Hz, 4H),
8.20ꢀ8.26 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 15.2, 15.3, 15.4,
28.7 (d, J = 69.1 Hz), 28.8 (d, J = 70.9 Hz), 121.4 (d, J = 9.1 Hz), 121.5
(d, J = 10.9 Hz), 122.0 (d, J = 9.1 Hz), 122.1 (d, J = 10.9 Hz), 129.5 (d, J =
9.1 Hz, two stereoisomers), 129.9 (d, J = 9.1 Hz, two stereoisomers),
133.5 (two stereoisomers), 136.0 (d, J = 92.7 Hz), 136.6 (d, J = 92.7 Hz),
140.5 (d, J = 20.0 Hz), 140.6 (d, J = 20.0 Hz), 142.1 (d, J = 11.0 Hz),
142.28 (d, J = 10.9 Hz), 142.34 (d, J = 9.1 Hz), 142.5 (d, J = 9.1 Hz); 31P
NMR (162 MHz, CDCl3) δ 50.8, 51.3; IR (Nujol, ν/cmꢀ1) 1732, 1593,
1298, 1254, 1184, 1157, 1130, 1092, 1074, 1024, 951, 926, 881, 777, 766,
748, 721, 700, 671, 629; HRMS (EI+) m/z calcd for C24H24O2P2 (M+)
406.1252, found 406.1245.
Data for 8-isopropyl-8H-phosphindolo[2,3-b]thiophene
8-oxide (2i): 57%; white solid; purification, silica gel column chroma-
tography (AcOEt/methanol = 95/5); TLC (AcOEt/methanol = 95/5)
Rf = 0.25; 1H NMR (400 MHz, CDCl3) δ 1.10 (dd, J = 18.4, 7.2 Hz, 3H),
1.24 (dd, J = 18.0, 7.2 Hz, 3H), 2.35 (dqq, J = 13.6, 7.2, 7.2 Hz, 1H),
7.30ꢀ7.36 (m, 1H), 7.37 (dd, J = 4.4, 1.2 Hz, 1H), 7.48ꢀ7.52 (m, 2H),
7.70ꢀ7.78 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 15.4, 15.6, 28.8 (d,
J = 74.6 Hz), 120.6 (d, J = 12.7 Hz), 121.3 (d, J = 9.1 Hz), 127.9 (d, J =
10.9 Hz), 129.4 (d, J = 101.8 Hz), 129.9 (d, J = 10.9 Hz), 132.9, 134.5 (d,
J = 101.8 Hz), 137.7 (d, J = 3.7 Hz), 138.6 (d, J = 14.5 Hz), 153.6 (d, J =
21.8 Hz); 31P NMR (162 MHz, CDCl3) δ 46.6; IR (Nujol, ν/cmꢀ1
)
3061, 1595, 1497, 1281, 1190, 1157, 1094, 1072, 1032, 881, 812, 745,
719, 677, 652, 638; HRMS (EI+) m/z calcd for C13H13OPS (M+)
248.0425, found 248.0434.
Data for 4-isopropyl-4H-phosphindolo[2,3-c]thiophene
4-oxide (2i0): 25%; white solid; purification, silica gel column chro-
matography (AcOEt/methanol = 95/5); TLC (AcOEt/methanol = 95/
5) Rf = 0.13; 1H NMR (400 MHz, CDCl3) δ 1.10 (dd, J = 18.0, 7.2 Hz,
3H), 1.24 (dd, J = 18.0, 7.2 Hz, 3H), 2.33 (dqq, J = 14.0, 7.2, 7.2 Hz, 1H),
7.36 (dddd, J = 7.2, 7.2, 3.6, 0.8 Hz, 1H), 7.45 (dd, J = 2.0, 2.0 Hz, 1H),
7.54 (dddd, J = 7.6, 7.6, 1.2, 1.2 Hz, 1H), 7.62 (dd, J = 8.0, 3.2 Hz, 1H),
7.77 (dd, J = 8.4, 8.4 Hz, 1H), 7.83 (dd, J = 4.8, 2.0 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 15.3, 15.5, 29.2 (d, J = 72.7 Hz), 116.5 (d, J = 12.7
Hz), 121.9 (d, J = 9.1 Hz), 128.2 (d, J = 10.9 Hz), 130.2 (d, J = 9.1 Hz),
130.8 (d, J = 11.0 Hz), 132.9, 133.7 (d, J = 99.9 Hz), 135.8 (d, J = 98.1
Hz), 138.6 (d, J = 12.7 Hz), 146.3 (d, J = 25.5 Hz); 31P NMR (162 MHz,
CDCl3) δ 41.2; IR (Nujol, ν/cmꢀ1) 3049, 1595, 1344, 1263, 1258,
1121, 1182, 1126, 1086, 1063, 1032, 939, 885, 841, 777, 748, 718, 681,
662; HRMS (EI+) m/z calcd for C13H13OPS (M+) 248.0425, found
248.0429.
Data for 6,12-diphenyl-6,12-diphosphaindeno[1,2-b]fluorine
6,12-dioxide (4): purification, silica gel column chromatography
1
(AcOEt/methanol = 5/1); H NMR (400 MHz, CDCl3) δ 1.12 (dd,
J = 17.6, 7.2 Hz, 6H), 1.21 (dd, J = 17.6, 7.2 Hz, 6H), 2.46 (dqq, J = 14.8,
7.2, 7.2, 2H), 7.50 (ddd, J = 7.6, 7.6, 3.2 Hz, 2H), 7.65 (dd, J = 7.8, 7.8 Hz,
2H), 7.86 (m, 4H), 8.21 (dd, J = 8.8, 2.4 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 15.4, 15.5, 28.8 (d, J = 69.0 Hz), 121.6 (d, J = 9.1 Hz), 122.2
(dd, J = 10.9, 9.1 Hz), 129.7 (d, J = 10.9 Hz), 130.1 (d, J = 9.1 Hz), 133.7,
136.1 (d, J = 94.6 Hz), 140.7 (d, J = 20.0 Hz), 142.5 (d, J = 10.9 Hz),
142.7 (d, J = 10.9 Hz); 31P NMR (162 MHz, CDCl3) δ 51.4; IR (Nujol,
ν/cmꢀ1) 1593, 1574, 1294, 1192, 1153, 1132, 1093, 1074, 1024, 953,
924, 880, 766, 748, 702, 671, 629; HRMS (EI+) m/z calcd for
C24H24O2P2 (M+) 406.1252, found 406.1245.
Data for 5-isopropyl-5H-dibenzophosphole 5-oxide (2j):
94%; white solid; purification, silica gel column chromatography
1
(AcOEt/methanol = 95/5); TLC (AcOEt) Rf = 0.09; H NMR (400
MHz, CDCl3) δ 1.12 (d, J = 7.2 Hz, 3H), 1.16 (d, J = 7.2 Hz, 3H), 2.35
(sep, J = 7.2 Hz, 1H), 7.43 (td, J = 7.2, 3.6 Hz, 2H), 7.59 (t, J = 7.6 Hz,
2H), 7.79 (dd, J = 7.6, 2.0 Hz, 2H), 7.83 (t, J = 7.6 Hz, 2H); 13C NMR
(100 MHz, CDCl3) δ 15.4, 28.7 (d, J = 71.2 Hz), 121.0 (d, J = 9.1 Hz),
128.8 (d, J = 10.9 Hz), 129.5 (d, J = 7.3 Hz), 130.4 (d, J = 98.6 Hz), 133.0,
141.6 (d, J = 20.1 Hz); 31P NMR (162 MHz, CDCl3) δ 51.4; IR (Nujol,
ν/cmꢀ1) 1597, 1258, 1182, 1080, 1030, 883, 758, 727, 709, 656, 619;
HRMS (EI+) m/z calcd for C15H15OP (M+) 242.0861, found 242.0871.
Data for 5-tert-butyl-5H-dibenzophosphole 5-oxide (2k):
85%; white solid; purification, silica gel column chromatography
(AcOEt/methanol = 95/5); TLC (AcOEt/methanol = 95/5) Rf =
’ ASSOCIATED CONTENT
Supporting Information. 1H and 13C NMR spectra of
S
b
biphenylphenylphosphine oxides 1 and dibenzophosphole oxi-
des 2. This material is available free of charge via the Internet at
http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: kuninobu@cc.okayama-u.ac.jp; ktakai@cc.okayama-u.ac.jp.
1
0.23; H NMR (400 MHz, CDCl3) δ 1.19 (d, J = 15.6 Hz, 9H), 7.42
(tdd, J = 7.6, 3.6, 0.8 Hz, 2H), 7.58 (tt, J = 7.6, 1.2 Hz, 2H), 7.78 (dd, J =
7.6, 2.8 Hz, 2H), 7.84 (tt, J = 7.6, 0.8 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 23.8, 32.8 (d, J = 71.2 Hz), 121.0 (d, J = 9.1 Hz), 128,7 (d, J =
9.1 Hz), 130.1 (d, J = 7.2 Hz), 130.3 (d, J = 96.7 Hz), 133.0, 142.0 (d, J =
’ ACKNOWLEDGMENT
This work was supported by the Ministry of Education,
Culture, Sports, Science, and Technology of Japan and Okayama
University.
18.3 Hz); 31P NMR (162 MHz, CDCl3) δ 54.8; IR (Nujol, ν/cmꢀ1
)
1593, 1572, 1267, 1213, 1180, 1163, 1123, 1082, 1067, 1013, 962, 941,
878, 818, 785, 758, 729, 715, 702; HRMS (EI+) m/z calcd for C16H17OP
(M+) 256.1017, found 256.1010.
Data for 5-isopropyl-5H-dibenzophosphole 5-oxide-d5
(2j-d): 91%; white solid; purification, silica gel column chromatography
(AcOEt/methanol = 95/5); TLC (AcOEt/methanol = 95/5) Rf = 0.23;
1H NMR (400 MHz, CDCl3) δ 1.12 (d, J = 7.2 Hz, 3H), 1.16 (d, J = 7.2
Hz, 3H), 2.35 (dqq, J = 14.4, 7.2, 7.2 Hz, 1H), 7.42 (ddd, J = 7.2, 7.2, 3.2
Hz, 1H), 7.59 (ddd, J = 7.6, 7.6, 0.4 Hz, 1H), 7.77ꢀ7.85 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 15.4, 28.7 (d, J = 69.1 Hz), 120.9, 121.1 (d,
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The Journal of Organic Chemistry
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(23) The third possible pathway is an electrophilic reaction by
palladium catalyst, Pd(OAc)2, which functions as a Lewis acid. However,
this possibility must be low because the reaction did not proceed well
using the following Lewis acids (1,2-dichloroethane, 65 °C, 3 h):
Pd(OAc)2, 92%; Sc(OTf)3, 0%; FeCl3, trace; AlCl3, trace; In(OTf)3,
trace; InCl3, 7%.
(13) Investigation of several catalysts (5.0 mol %, dioxane, 150 °C,
24 h): Pd, 21%; Pd/C, 85%; Pd/CaCO3, 12%; Pd(PPh3)4, 73%; PdBr2,
41%; PdCl2, 64%; PdCl2(PPh3)2, 94%; PdCl2(PhCN)2, 84%; Ni-
(OAc)2 4H2O, 32%; Fe(OAc)2, 40%; Cu(OAc)2 H2O, 50%; Cu-
(OAc)2, 38%; AgOAc, 7%; Cr(CO)6, 6%; Mo(CO)6, trace; W(CO)6,
trace; Re2(CO)10, 9%; [ReBr(CO)3(thf)]2, 5%; RhCl(PPh3)3, 17%;
Ru3(CO)12, 10%.
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(25) The diastereomer ratios of 3 (60:40) and 4 (58:42) were almost
the same.
(26) A blue-purple fluorescence was observed when 254 and 365 nm
UV light was irradiated on a solid sample of 4. In addition, a stronger
blue-purple fluorescence was observed in the case of a chloroform
solution of 4.
3
3
(14) Investigation of catalytic amounts (THF, 65 °C, 3 h): 1.0 mol
%, 47%; 3.0 mol %, 81%.
(15) Investigation of several solvents (50 °C, 4 h): neat, 6%; hexane,
15%; toluene, 28%; CH2ClCH2Cl, 22%; diethyl ether, 20%; THF, 52%;
dioxane, 48%; DME, 48%; ethyl acetate, 29%; acetone, 47%; EtOH,
29%; CH3CN, 40%; DMSO, 24%; DMF, 37%.
(16) At the reviewer’s suggestion, we have added a catalytic amount
of sodium pivalate or mesityl carboxylate to decrease the catalyst loading.
However, the amount of the palladium catalyst could not be decreased
by the addition of the pivalate or carboxylate.
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(17) A blue-purple fluorescence was observed when 254 and 365 nm
UV light was irradiated on a chloroform solution of 2a or a solid sample
of 2a.
(18) In this reaction, a hydrogen acceptor, such as norbornene or
3,3-dimethyl-1-butene, was added to improve the yield of the dibenzo-
phosphole oxide. However, the yield was not increased.
(19) There have been several reports on palladium-catalyzed trans-
formations via PꢀH bond cleavage. See: (a) Han, L.-B.; Choi, N.;
Tanaka, M. Organometallics 1996, 15, 3259–3261. (b) Han, L.-B.; Hua,
R.; Tanaka, M. Angew. Chem., Int. Ed. 1998, 37, 94–96. (c) Han, L.-B.;
7376
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