Synthesis of diarylenynes by olefination of 1-arylpropyne with arylaldehyde and their optical properties

Article abstract of DOI:10.1016/j.tet.2016.06.018

A new synthetic protocol of 1-arylpropyne was developed by taking advantage of 1-(diphenylphosphoryl)propyne as propyne equivalent in Sonogashira coupling: consecutive subjection of phosphorylpropyne to t-BuOK and to aryl halides in the presence of Pd and Cu catalysts afforded the corresponding 1-arylpropynes. The following olefination of the 1-arylpropyne with aldehyde provided the corresponding diarylenyne. When the enynes thus obtained were irradiated with UV light, they showed strong emission in organic solvents and in the solid states. In solution, Ph₂N-substituted enynes exhibited remarkable solvatofluorochromism, and Lippert–Mataga plot analysis demonstrated that they undergo the larger polarization in the excited states than in the ground states.

Full text of DOI:10.1016/j.tet.2016.06.018

Tetrahedron 72 (2016) 4427e4434
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of diarylenynes by olefination of 1-arylpropyne with
arylaldehyde and their optical properties
Kenta Shinohara a, Takanori Nishida a, Ryosuke Wada a, Lifen Peng b, Yuju Minoda a,
,
a
Akihiro Orita a , Junzo Otera
*
a Department of Applied Chemistry and Biotechnology, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 7000005, Japan
b Key Laboratory of Theoretical Organic Chemistry and Functional Molecule of the Ministry of Education, School of Chemistry and Chemical Engineering,
Hunan University of Science and Technology, Xiangtan City, Hunan Province 411201, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 May 2016
Received in revised form 2 June 2016
Accepted 6 June 2016
Available online 7 June 2016
A new synthetic protocol of 1-arylpropyne was developed by taking advantage of 1-(diphenylphos-
phoryl)propyne as propyne equivalent in Sonogashira coupling: consecutive subjection of phosphor-
ylpropyne to t-BuOK and to aryl halides in the presence of Pd and Cu catalysts afforded the
corresponding 1-arylpropynes. The following olefination of the 1-arylpropyne with aldehyde provided
the corresponding diarylenyne. When the enynes thus obtained were irradiated with UV light, they
showed strong emission in organic solvents and in the solid states. In solution, Ph2N-substituted enynes
exhibited remarkable solvatofluorochromism, and LipperteMataga plot analysis demonstrated that they
undergo the larger polarization in the excited states than in the ground states.
Keywords:
1-(Diphenylphosphoryl)propyne
Sonogashira coupling
1.4-Diarylbut-1-en-3-ynes
Photoluminescence
Ó 2016 Elsevier Ltd. All rights reserved.
Solvatofluorochromism
1. Introduction
deprotonation of 1, addition of the propargyl anion to aldehyde,
transformation of the resulting alkoxide to phosphate and t-BuOK-
Great attention is paid to highly expanded
p
-systems because
promoted elimination of phosphoric acid, and all the trans-
formations could be carried out in one-pot manner. Arylpropyne 1,
a starting compound in this olefination, was easily obtained from
ethylsulfone and arylaldehyde by one-pot synthesis (Eq. 5).
For the synthesis of 1-arylpropyne such as 1, Sonogashira cou-
pling of the corresponding aryl halide with propyne would be
straightforward. However, this reaction suffers from inconvenience,
they can be used as organic materials such as light-emitting diodes
(LEDs),1 field-effect transistors (FETs)2 and dye-sensitized solar
cells (DSSCs).3 Although various
p-expanded materials were de-
veloped, only few enyne motifs were explored as organic materials
in spite of the high potentials as sensing fluorophore4 and as
emitter of white light-emitting devices (WOLEDs).5 For syntheses
of the enyne motifs, several synthetic routes were reported; Wit-
tigeHorner olefination of propynal (Eq. 1 in Scheme 1),4 Sonoga-
shira coupling of vinyl halide with terminal ethyne (Eq. 2),6
MizorokieHeck reaction of propynyl halide with olefin (Eq. 3)7
and organolanthanide-catalyzed dimerization of arylethyne (Eq.
4).5 On the other hand, we developed a new protocol of one-pot
olefination between arylaldehyde and arylpropyne and achieved
syntheses of a series of fluorescent arylenyne derivatives (Eq. 6 in
Scheme 2).8 For instance, when naphthylpropyne 1 was treated
successively with BuLi, benzaldehyde, ClP(O)(OEt)2, and t-BuOK,
naphthyl, phenyl-substituted enyne 2 was provided. This olefina-
tion was composed of a number of transformations such as
* Corresponding author. Tel.: þ81 (0)86 256 9533; fax: þ81 (0)86 256 4292;
Scheme 1. Synthetic routes of enyne motif.
e-mail address: orita@dac.ous.ac.jp (A. Orita).
http://dx.doi.org/10.1016/j.tet.2016.06.018
0040-4020/Ó 2016 Elsevier Ltd. All rights reserved.

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K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
Scheme 4. One-pot dephosphorylationeSonogashira coupling.
diarylbut-1-en-3-ynes. We also report optical properties of the
enynes such as UVevis absorption and fluorescence in solution and
in the solid state together with electrochemical data as well.
2. Results and discussion
1-(Phosphoryl)propyne 3 was synthesized by successive treat-
ment of phosphorylethyne 6 with BuLi and Me2SO4 in 88% yield
(Scheme 5). In this methylation route, BuLi served well as a base
while lithium diisopropylamide (LDA) or MeMgBr did not. The
Ph2P(O)-substituted ethynide anion required strong methylating
reagent such as Me2SO4 because of its poor nucleophilicity ascrib-
able to the strong electron-withdrawing effect of Ph2P(O) group.10c
When MeI (10 equiv) was used as a mild methylating reagent,
a chemical yield of 3 decreased to 42%. Alternatively, 3 was syn-
thesized by treatment of 1-propynylmagnesium bromide with
Ph2P(O)Cl.11
Scheme 2. Our synthetic process for enyne 2.
because gaseous propyne (boiling point: ꢀ23 ꢁC) must be manip-
ulated for the coupling.9 In order to avoid this drawback of pro-
pynylation in Sonogashira coupling, we planned to take advantage
of 1-(diphenylphosphoryl)propyne (3) as propyne equivalent
(Scheme 3). We envisioned that 1-phosphorylpropyne 3 would be
transformed to involatile potassium propynide by treatment with t-
BuOK, and the propynide could be used in the following Sonoga-
shira coupling with aryl halides. We already reported that phos-
phoryl(phenyl)ethyne 4 could be used as phenylethyne equivalent
in Sonogashira coupling. In this reaction, potassium phenyl-
ethynide 5 which was in situ prepared by treatment of 4 with t-
BuOK was incorporated to the desired coupling product success-
fully (Scheme 4).10
Scheme 5. Syntheses of phosphorylpropyne 3.
When t-BuOK (1.2 equiv of 3) was added to a THF solution of 3,
the expected dephosphorylation proceeded smoothly, and TLC
analysis showed complete consumption of 3 in 2 h (Scheme 6). By
consecutive addition of Pd and Cu catalysts and 1-iodonaphthalene
in toluene/i-Pr2NH to this reaction mixture, the following Sono-
gashira coupling occured leading to the formation of 7. When 5.0 or
3.0 equiv of 3 was subjected to this reaction in the presence of
1.1 equiv of CuI, 7 was obtained in 82% and 64% yields, respectively.
In contrast, when 2.5 equiv of 3 and 0.05 equiv of CuI were used, the
coupling proceeded somewhat sluggishly, and 7 was obtained in
50% yield. Because of the cost for preparation of 3 and in-
convenience of separation of 7 from t-BuOP(O)Ph2 which was
produced in the dephosphorylation, we employed 3.0 equiv of 3 in
further reactions. In this one-pot reaction, the addition of 1.1 equiv
of CuI enabled the subsequent Sonogashira coupling to proceed
smoothly, and the acceleration effect would be ascribable to the
formation of an equimolar amount of copper propynide and/or the
concomitant formation of KI.
Scheme 3. One-pot propynylation using 3.
We envisioned that when 1-(phosphoryl)propyne 3 was sub-
jected to the one-pot dephosphorylationeSonogashira coupling
technology, the desired propynylation could be achieved without
any tedious operation because involatile potassium propynide
would be in situ formed and supplied to the following Sonogashira
coupling. We disclose herein the usability of 1-(phosphoryl)pro-
pyne 3 which could serve as propyne equivalent in the one-pot
dephosphorylationeSonogashira coupling protocol as well as
one-pot transformation of the resulting 1-arylpropynes to 1,4-
This one-pot propynylation protocol served well for other aryl
halides, and the corresponding propynylarenes were synthesized in
moderate yields (Scheme 7). When bromoiodobenzenes were used,
the propynylation proceeded selectively at iodine moieties, and
bromine remained intact (Entries 1e3). Diiodobenzenes un-
derwent double propynylation by using 6.0 equiv of 3 and 7.2 equiv
of t-BuOK to lead 1,3- and 1,4-di(1-propynyl)benzenes in 65% and

K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
4429
Scheme 6. One-pot synthesis of 7 from 3.
72% yields, respectively (Entries 4 and 5). Iodobenzenes having
functional groups such as H2Ne, PhSO2CH2e and Ph2P(O)eC^Ce
were transformed successfully to the corresponding (1-propynyl)
benzenes in moderate yields (Entries 6e8). Although the one-pot
propynylation worked well in the reaction of Ph2P(O)-protected
ethynylphenyl iodode (Entry 8), Me3Si-protected ethynyl iodide
decomposed in the same reaction conditions, and no formation of
the desired Me3Si-protected ethynylphenylpropyne was observed
(Entry 9). The propynylation could be applied to aryl iodides having
expanded
p-systems (Entries 10 and 11), and Ph2Ne and 1-
naphthyl-substituted arylpropynes were also synthesized in good
yields (Entries 12 and 13). Indol and thiophene derivatives could be
subjected to the propynylation as well (Entries 14 and 15). In the
double propynylation of thienylene diiodide, the reaction pro-
ceeded rather sluggishly, and the formation of a number of un-
identified byproducts was observed (Entries 15).
Next, the arylpropynes 7 and 8 thus obtained were transformed
to enynes 9e12 by the one-pot olefination depicted in Eq. 6 of
Scheme 2. When 1-(1-naphthyl)propyne (7) was treated succes-
sively with BuLi, amino-aldehyde 13, ClP(O)(OEt)2, and t-BuOK, the
expected olefination occurred in one-pot manner, and the desired
enyne 9 was provided in 51% yield (E-isomer) (Scheme 8). When
propyne 7 and aldehyde 14 were subjected to the one-pot olefi-
nation protocol, enediyne 10 was provided in 69% yield. From the
combination of 8 and 13, an amino-substituted enediyne 11 which
was one of regioisomer of 10 was synthesized in 13% yield. In the
synthesis of 11, the final elimination step proceeded rather slug-
gishly to give a number of unidentified byproducts. From the same
one-pot reaction between 7 and 15, dinaphthyl-substituted ene-
diyne 12 was afforded in a moderated yield.
Because a series of enynes 9e12 were synthesized, their UVevis
absorption and fluorescence spectra in CH2Cl2 and in the solid
states were recorded, and all the data were summarized in Table 1.
In Figs. 1e3 were shown the profiles of UVevis absorption and
photoluminescence (PL) spectra of 9e12.
The Ph2N-substituted enyne derivatives 9e11 had strong ab-
sorption bands exhibiting lmax in a range of 380e400 nm, while
enynes 12 did at the shorter wavelength 370 nm (Table 1, Fig. 1).
Enyne derivative 9 indicated rather smaller molar extinction co-
efficient ε than yneeenyne derivatives 10e11: 31,000 versus
>50,000 Lmolꢀ1cmꢀ1
. Also in photoluminescence spectra in
Scheme 7. One-pot synthesis of 1-arylpropynes.
CH2Cl2, Ph2N-substituted enyne derivatives 9e11 indicated emis-
sion at longer wavelengths than di(naphthyl)enyne 16; emission
maxima Emax 470e520 nm for 9e11, 411 nm for 12 (Table 1, Fig. 2).
Enyne 9 exhibited a little smaller fluorescence quantum yield than
When fluorescence spectra of 9 were recorded in various sol-
vents, large solvatochromism was observed; upon changing the
solvents from toluene to acetonitrile, 71 nm of bathochromic shift
was demonstrated (Table 2). Fig. 4 shows the emission profiles of 9
in a series of solvents.
others because of the shorter
p
-system; FF¼0.62 for 9 and >0.74
for 10e12. In emission of the solid states, di(naphthyl)enyne 12
showed emission at 463 nm, and amino-substituted enynes 9e11
did at 500e511 nm (Table 1, Fig. 3).

4430
K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
Fig. 2. Photoluminescence spectra of 9e12 in CH2Cl2 (1.0ꢂ10ꢀ6 M).
Scheme 8. Synthesis of enynes 9e12 by olefination of arylpropynes with
arylaldehydes.
Fig. 3. Photoluminescence spectra of 9e12 in the solid states.
Table 1
Summary of UVevis absorption and PL spectraa
lmax [nm]a/ε [103ꢂL/mol cm]
Emax [nm]c
Emax [nm]c
(powder)/FF
(CH2Cl2)b
(CH2Cl2)d/FF
e
e
Table 2
Summary of emission maxima Emax of 9 in a series of solvents.a
9
390/31.3
385/50.1
397/52.4
370/48.4
472/0.62
516/0.83
506/0.74
411/0.98
501/0.28
511/0.21
500/0.23
463/0.27
10
11
12
Solvb
Tol
442
3282
CHCl3
DCM
DMF
ACN
Emax [nm]
465
4401
473
4765
512
6375
513
6413
Stokes shift [cmꢀ1
]
a
The longest wavelength of absorption bands.
1.0ꢂ10ꢀ4 mol/L.
a
1.0ꢂ10ꢀ6 mol/L.
b
c
b
Tol: toluene, DCM: dichloromethane, DMF: N,N-dimethylformamide, ACN:
The wavelength of the strongest emission band.
1.0ꢂ10ꢀ6 mol/L.
d
e
acetonitrile.
Absolute fluorescence quantum yield.
Fig. 1. UVevis absorption spectra of 9e12 in CH2Cl2 (1.0ꢂ10ꢀ4 M).
Fig. 4. Photoluminescence spectra of 9 in a series of solvents (1.0ꢂ10ꢀ6 M).

K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
4431
The large solvatofluorochromism observed in 9 suggests the
increase of the dipole moment in the excited state S1 (me) compared
to that in the ground state S0 (mg). In order to rationalize the solvent
effects, we invoked LipperteMataga plot.12 LipperteMataga plot
provides quantitative relationship between the solvent orientation
In Fig. 6 were demonstrated HOMO and LUMO of 9 which were
calculated by DFT method (B3LYP/6-31G(d)). The HOMO expands
mainly at triphenylamine moiety, and a lone pair of nitrogen en-
ables the HOMO to expand efficiently among three benzene rings.
In contrast to this, the LUMO is located mainly at naphthyl- and
phenylene-substituted butenyne moiety. TDDFT calculation
revealed that the first excitation in 9 would be ascribable to HOMO-
LUMO transition (f¼1.38). These results also unambiguously sup-
port the fact that 9 would undergo ICT in the photo-excitation
leading to largely charge-separated excited state.16
polarizability
D
f and Stokes shift
D
v as shown in Eq. 7.
ꢀ
ꢁ
2
2
me
ꢀ
mg
D
v ¼
D
f þ Constant
(7)
(8)
4
p
ε0hca3
¼
rDf þ C
ε ꢀ 1
n2 ꢀ 1
D
f ¼
ꢀ
2n2 þ 1
2ε þ 1
v: Stokes shift
D
me: dipole moment in the excited state
mg: dipole moment in the ground state
ε0: vacuum permittivity (8.8542ꢂ10ꢀ12 C2Nꢀ1mꢀ2
h: the Planck constant (6.6262ꢂ10ꢀ34 Js)
)
c: the light velocity (2.9979ꢂ10ꢀ8 msꢀ1
a: the Onsager radius of the solute
ε: solvent dielectric constant
n: refractive index
)
The solvent orientation polarizability
Eq. 8. When v was plotted against f, 2(me
provided as the slope of linear fit in Eq. 7. As presented in Fig. 5, 9
exhibited large slope value
11,100 cmꢀ1 representing that the
D
f is calculated by using
D
D
ꢀ
mg)2/4 ε0hca3 was
p
r
r
amino-substituted enyne 9 underwent intramolecular charge-
transfer (ICT) in photo-excitation to provide highly polarized ex-
cited state.13 The Onsager cavity radius a was estimated from the
optimized distance between the farthest atoms in the direction of
charge separation within 9. Because the DFT calculations (B3LYP/6-
31G(d)) indicated that the optimized molecule lengths of 9 would
Fig. 6. Frontier orbitals of 9 calculated at the B3LYP/6-31G(d) level (a, HOMO; b,
LUMO).
Cyclic voltammetry was recorded for 9e12 in CH2Cl2, and the
results were summarized in Table 3 together with their HOMO and
LUMO levels calculated at the B3LYP/6-31G(d) level. The amino-
substituted enyne derivatives 9e11 underwent smooth oxidation
because of the efficient participation of amino group in HOMO, and
exhibited their first oxidation potentials in a range between 0.28
and 0.37 V. In comparison with these amino-substituted enynes, 12
showed remarkably positive oxidation potentials (>0.89 V), and the
deeper HOMO levels were consistent with the DFT calculation re-
sults; ca. ꢀ4.9 V for 9e11, ꢀ5.2 V for 12. Reduction potential of 12
(>ꢀ2.33 V) was more positive than those of the amino derivatives
9e11 (ꢀ2.38 V to ꢀ2.49 V) diagnostic of the shallower LUMO levels
of 9e11 which were attributable to the electron-donating effect of
amino group.
ꢀ
be 19.1 A, the Onsager cavity radius a of 9 was provided as 7.6 by
multiplying a reduction factor 0.4.14 According to Eq. 7, the change
of dipole moment upon excitation (me mg) in 9 was estimated to be
ꢀ
22.0 D. The change of dipole moments observed in 9 (22.0 D) was
comparable to that of amino-substituted diyne analog 16 (Dm¼24.4
D) presenting the similar polarizabilities of 9 and 16 (Scheme 9).15
Table 3
Summary of cyclic voltammograma and calculated HOMO and LUMO levelsb
Oxidation
HOMO
level [V]
Reduction
LUMO
level [V]
potentials [V]c
potentials [V]c
9
0.37
ꢀ4.82
ꢀ4.87
ꢀ4.84
ꢀ5.15
ꢀ2.49
ꢀ2.46c
ꢀ2.38c
ꢀ2.33c
ꢀ1.71
ꢀ1.98
ꢀ1.92
ꢀ2.10
10
11
12
0.28, 0.43, 1.06c
0.36, 0.53, 1.11
0.89c, 1.23c
a
The reduction and oxidation potentials (vs Fc/Fcþ) were measured under the
following conditions: in CH2Cl2 (1.0ꢂ10ꢀ4 M, 100 mV/s scan rate, 0.1 M Bu4NPF6),
a glassy carbon as the working electrode, a Pt counter electrode, and an Ag/Agþ
reference electrode (0.01M AgNO3 and 0.1 M tetrabutylammonium perchlorate in
acetonitrile) in 0.1 M LiClO4/acetonitrile.
Fig. 5. LipperteMataga plot for 9.
b
Calculated at the B3LYP/6-31G(d) level.
Irreversible oxidation or reduction potentials.
c
3. Conclusion
In conclusion, we developed a new methodology to synthesize 1-
arylpropyne by Sonogashira coupling between the corresponding
Scheme 9. Structure of amino-substituted phenyleneethynylene 16.

4432
K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
aryl halide and potassium propynide which was in situ prepared by
treatment of 1-(phosphoryl)propyne 3 with t-BuOK. The one-pot
dephosphorylation/Sonogashira coupling protocol served well for
syntheses of a series of (1-propynyl)arenes having functional groups
such as amino, sulfonyl and phosphorylethynyl groups. This protocol
exhibited a high haloselectivity between bromine and iodine, and
Sonogashira coupling proceeded preferentially with aryl iodide. 1-
Arylpropynes thus obtained were transformed to 1,4-
diarylbutenynes by successive treatment with BuLi, arylaldehydes,
ClP(O)(OEt)2 and t-BuOK. A series of 1,4-diarylbutenynes emitted
strong fluorescence both in solution and in the solid states when
they were irradiated with UV light. Ph2N-substituted enynes
exhibited remarkably strong emission in solution, and, in polar sol-
vents, large solvatofluorochromism was observed. LipperteMataga
plot analysis demonstrated that in the photo-excitation, Ph2N-
substituted diarylbutenyne underwent an intramolecular charge
transfer (ICT) with a large change of dipole moments.
organic layer was washed with satd NaClaq and dried over MgSO4.
After evaporation, the crude product was subjected to column
chromatography on silica gel (CH2Cl2/hexane 10: 90) to provide 1-
(1-propynyl)naphthalene (7) in a pure form (50.1 mg, 0.301 mmol,
60% yield).
7: colorless oil; 1H NMR (300 MHz, CDCl3):
d 2.22 (s, 3H), 7.37 (t,
J¼7.7 Hz, 1H), 7.47e7.58 (m, 3H), 7.78 (d, J¼8.4 Hz, 1H), 7.83 (d,
J¼7.5 Hz, 1H), 8.35 (d, J¼8.1 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d
4.64, 77.73, 90.78, 121.74, 125.21, 126.20, 126.28, 126.44, 127.90,
128.16, 129.96, 133.17, 133.51; HRMS (EI): 166.0786 (Mþ); calcd for
13H10: 166.0783.
C
4.3.1. 1-Bromo-3-(1-propynyl)benzene (Entry 1 in Scheme
7).8 Colorless oil; 1H NMR (300 MHz, CDCl3):
2.12 (s, 3H), 7.15
d
(dt, J¼1.8, 7.8 Hz, 1H), 7.22 (dt, J¼1.8, 7.8 Hz, 1H), 7.42 (dd, J¼1.5,
7.8 Hz, 1H), 7.55 (dd, J¼1.5, 7.8 Hz, 1H).
4.3.2. 1-Bromo-3-(1-propynyl)benzene (Entry 2 in Scheme
4. Experimental
7).9d Colorless oil; 1H NMR (500 MHz, CDCl3):
d 2.03 (s, 3H), 7.13
(t, J¼7.8 Hz, 1H), 7.29 (d, J¼7.8 Hz, 1H), 7.39 (d, J¼7.8 Hz, 1H), 7.52 (s,
4.1. Materials and methods
1H).
Chemicals were purchased from Aldrich and TCI and used
without further purification. NMR spectra were recorded in parts
per million (ppm) in CDCl3 and CD2Cl2 on JEOL ECP 400 NMR and
LAMBDA 300 and 500 instruments using TMS as an internal stan-
dard. Mass spectra were recorded on JEOL JMS-700 mass spec-
trometer and Bruker MALDI-TOF/TOF MS autoflex speed.
4.3.3. 1-Bromo-4-(1-propynyl)benzene (Entry 3 in Scheme
7).8 Colorless oil; 1H NMR (400 MHz, CDCl3):
(d, J¼8.4 Hz, 2H), 7.41 (d, J¼8.4 Hz, 2H).
d 2.04 (s, 3H), 7.24
4.3.4. 1,3-Di-(1-propynyl)benzene (Entry 4 in Scheme 7).9c Colorless
oil; 1H NMR (400 MHz, CDCl3):
2.04 (s, 6H), 7.18 (t, J¼7.6 Hz, 1H),
7.28 (d, J¼7.6 Hz, 2H), 7.41 (s, 1H).
d
4.2. Synthesis of 311
4.3.5. 1,4-Di-(1-propynyl)benzene (Entry 5 in Scheme 7).17 White
Route 1. To a THF solution (60.0 mL) of ethynyldiphenylphos-
phine oxide (6) (4.53 g, 20.0 mmol) was added a hexane solution
of butyllithium (1.6 M, 15.0 mL, equivalent to 24.0 mmol of BuLi),
and the mixture was stirred at ꢀ78 ꢁC for 30 min. To the mixture
was added dimethyl sulfate (3.80 mL, 40.0 mmol), and the mixture
was stirred at ꢀ78 ꢁC for 3 h, at ꢀ21 ꢁC for 3 h and at rt for 12 h.
After workup with CH2Cl2/satd NH4Claq, the combined organic
layer was washed with satd NaClaq and dried over MgSO4. After
evaporation, the crude product was subjected to column chro-
matography on silica gel (AcOEt/hexane 80: 20) to provide 1-
propynyldiphenylphosphine oxide (3) in a pure form (4.24 g,
17.7 mmol, 88% yield).
powder; mp 160 ꢁC; 1H NMR (500 MHz, CDCl3):
(s, 4H).
d 2.05 (s, 6H), 7.29
4.3.6. 4-(1-Propynyl)aniline (Entry 6 in Scheme 7).18 Yellow oil; 1H
NMR (300 MHz, CDCl3): 1.58 (br, 2H), 2.10 (s, 3H), 7.52 (d,
d
J¼8.6 Hz, 2H), 7.84 (d, J¼8.6 Hz, 2H).
4.3.7. 1-(1-propynyl)-4-phenylsulfonylmethylbenzene (Entry
7 in
Scheme 7). White powder; mp 159e160 ꢁC; 1H NMR (300 MHz,
CDCl3):
d
2.05 (s, 3H), 4.28 (s, 2H), 7.37 (d, J¼8.1 Hz, 2H), 7.27 (d,
J¼8.1 Hz, 2H), 7.45 (t, J¼8.1 Hz, 2H), 7.58e7.62 (m, 3H); 13C NMR
(100 MHz, CDCl3): d 4.33, 62.68, 79.08, 87.32, 124.62, 127.32, 128.63,
3: 1H NMR (300 MHz, CDCl3):
(m, 6H), 7.79e7.87 (m, 4H).
d
2.12 (d, J¼3.6 Hz, 3H), 7.43e7.56
128.92,130.61, 133.77,137.66; HRMS (MALDI): 129.0972 (Mþ); calcd
for C16H14O2S (ePhSO2): 129.0704.
Route 2.11 To
a
THF solution (6.0 mL) of chlor-
odiphenylphosphine oxide (0.473 g, 2.00 mmol) was added a THF
solution of 1-propynylmagnesium bromide (0.5 M, 4.0 mL, equiv-
alent to 2.0 mmol), and the mixture was stirred at ꢀ78 ꢁC for 1.5 h.
After workup with CH2Cl2/satd NH4Claq, the combined organic
layer was washed with satd NaClaq and dried over MgSO4. After
evaporation, the crude product was subjected to column chroma-
tography on silica gel (AcOEt/hexane 80: 20) to provide 1-
propynyldiphenylphosphine oxide (3) in a pure form (0.418 g,
1.74 mmol, 87% yield).
4.3.8. 4-(1-Propynyl)phenylethynyl(diphenyl)phosphine oxide (Entry
8 in Scheme 7). 1H NMR (400 MHz, CDCl3):
d 2.07 (s, 3H), 7.37 (d,
J¼8.0 Hz, 2H), 7.47e7.57 (m, 8H), 7.87 (d, J¼8.0 Hz, 2H), 7.91 (d,
J¼8.0 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d 4.45 79.14, 83.24, 84.91,
89.74, 105.02 (d, J¼118.0 Hz), 118.73 (d, J¼19.2 Hz), 126.69, 128.66
(d, J¼53.2 Hz), 130.97 (d, J¼45.6 Hz), 131.58, 132.29 (d, J¼30.4 Hz),
133.58; HRMS (MALDI): 340.1020 (Mþ); calcd for C23H17OP:
340.1017.
4.3.9. 3-(1-Propynyl)phenylethynlbenzene (Entry 10 in Scheme
4.3. One-pot synthesis of 7 from 3 (representative for
Schemes 6 and 7)
7).8 1H NMR (400 MHz, CDCl3):
d
2.06 (s, 3H), 7.26 (t, J¼7.8 Hz,
1H), 7.34e7.37 (m, 4H), 7.43 (d, J¼7.6 Hz, 1H), 7.51e7.54 (m, 2H),
7.56 (s, 1H).
To a THF solution (4.0 mL) of phosphorylpropyne 3 (0.361 g,
1.50 mmol) was added t-BuOK (0.201 g, 1.79 mmol), and the mix-
ture was stirred at rt for 2 h. To the solution were added 1-
iodonaphthalene (0.09 mL, 0.5 mmol), Pd(PPh3)4 (30.5 mg,
0.025 mmol), CuI (0.105 g, 0.55 mmol), toluene (8.0 mL) and i-
Pr2NH (1.0 mL, 13.7 mmol), and the mixture was stirred at 70 ꢁC for
20 h. After workup with CH2Cl2/satd NH4Claq, the combined
4.3.10. 3-(1-Propynyl)phenylethynlbenzene (Entry 11 in Scheme
7).8 1H NMR (300 MHz, CDCl3):
d 2.07 (s, 3H), 7.34e7.37 (m, 5H),
7.43 (s, 1H), 7.47 (d, J¼5.4 Hz, 1H), 7.51e7.54 (m, 2H).
4.3.11. 4-(4-(1-Propynyl)phenylethynyl)phenyl(diphenyl)amine (En-
try 12 in Scheme 7). Yellow powder; mp 163e164 ꢁC; 1H NMR

K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
4433
(300 MHz, CDCl3)
d
2.07 (s, 3H), 7.00 (d, J¼8.9 Hz, 2H), 7.06 (t,
J¼8.3 Hz, 1H), 7.86 (d, J¼8.0 Hz, 1H), 8.38 (d, J¼8.9 Hz, 1H); 13C NMR
J¼7.3 Hz, 2H), 7.11 (d, J¼8.5 Hz, 4H), 7.26e7.29 (m, 4H), 7.35 (t,
(125 MHz, CD2Cl2): d 88.66, 90.72, 91.33, 93.86, 108.86, 115.86,
J¼8.1 Hz, 4H), 7.41 (d, J¼8.3 Hz, 2H); 13C NMR (125 MHz, CDCl3):
121.01, 122.22, 123.60, 123.83, 125.03, 125.31, 126.21, 126.26, 126.46,
126.80, 128.32, 128.79, 129.41, 130.39, 131.81, 132.56, 133.18, 133.20,
135.83, 140.63, 147.15, 148.04; HRMS (MALDI): 521.2141 (Mþ); calcd
for C40H27N: 521.2144.
d
4.44, 79.58, 87.70, 88.39, 91.09, 115.83, 122.20, 122.70, 123.51,
123.56, 124.99, 129.38, 131.24, 131.39, 132.50, 147.14, 147.98; HRMS
(MALDI): 383.1640 (Mþ); calcd for C29H21N: 383.1644.
11: yellow powder; mp 160 ꢁC; 1H NMR (500 MHz, CDCl3):
4.3.12. 4-(1-Propynyl)phenylethynylnaphthalene (Entry 13 in
d
6.26 (d, J¼16.2 Hz, 1H), 6.99e7.02 (m, 3H), 7.06 (t, J¼7.3 Hz, 2H),
Scheme 7). White powder; mp 97 ꢁC; 1H NMR (400 MHz, CDCl3):
7.12 (d, J¼7.7 Hz, 4H), 7.26e7.30 (m, 6H), 7.45e7.49 (m, 3H), 7.54 (t,
J¼7.3 Hz, 1H), 7.59e7.62 (m, 3H), 7.76 (d, J¼7.0 Hz, 1H), 7.86 (t,
J¼8.9 Hz, 2H), 8.42 (d, J¼8.5 Hz, 1H); 13C NMR (125 MHz, CD2Cl2):
d
2.08 (s, 3H), 7.41 (d, J¼8.4 Hz, 2H), 7.45 (t, J¼7.8 Hz, 1H), 7.51e7.61
(m, 4H), 7.75 (d, J¼7.2 Hz, 1H), 7.85 (t, J¼8.4 Hz, 2H), 8.41 (d,
J¼8.8 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d
4.44, 79.56, 88.00,
d 89.64, 91.28, 92.00, 94.43, 105.72, 120.91, 122.87, 123.18, 123.90,
88.91, 94.06, 120.75, 122.45, 124.08, 125.26, 126.15, 126.44, 126.80,
128.31, 128.87, 130.40, 131.46, 131.51, 133.20; HRMS (MALDI):
266.1109 (Mþ); calcd for C21H14: 266.1096.
124.04, 125.31, 125.71, 126.37, 126.91, 127.30, 127.64, 128.72, 129.37,
129.73, 130.20, 130.87, 131.77, 131.93, 133.49, 141.73, 147.61, 148.93;
HRMS (EI): 521.2149 (Mþ); calcd for C40H27N: 521.2144.
12: yellow powder; mp 192 ꢁC; 1H NMR (500 MHz, CDCl3):
4.3.13. 1-Tosyl-5-(3-(1-propynyl)phenylethynyl)indole (Entry 14 in
d
6.60 (d, J¼16.2 Hz, 1H), 7.17 (d, J¼16.2 Hz, 1H), 7.45 (d, J¼8.6 Hz,
Scheme 7). White powder; mp 119 ꢁC; 1H NMR (500 MHz, CDCl3):
1H), 7.48 (d, J¼8.9 Hz, 1H), 7.51 (d, J¼8.2 Hz, 2H), 7.53e7.56 (m, 2H),
7.59e7.62 (m, 2H), 7.65 (d, J¼8.2 Hz, 2H), 7.72 (d, J¼7.1 Hz, 1H), 7.78
(d, J¼7.3 Hz, 1H), 7.83e7.89 (m, 4H), 8.39 (d, J¼8.3 Hz, 1H), 8.44 (d,
d
2.05 (s, 3H), 2.35 (s, 3H), 6.64 (dd, J¼0.9, 3.8 Hz, 1H), 7.23 (d,
J¼8.6 Hz, 2H), 7.26 (t, J¼3.8 Hz, 1H), 7.33 (td, J¼1.4, 8.0 Hz, 1H), 7.41
(td, J¼1.5, 7.6 Hz, 1H), 7.46 (dd, J¼1.5, 8.6 Hz, 1H), 7.54 (s, 1H), 7.58
(d, J¼3.8 Hz, 1H), 7.70 (d, J¼0.9 Hz, 1H),7.76 (d, J¼8.6 Hz, 2H), 7.96
J¼8.6 Hz, 1H); 13C NMR (125 MHz, CDCl3):
d 89.10, 90.89, 93.80,
94.28, 109.20, 120.78, 120.98, 123.54, 125.31, 125.33, 126.19, 126.20,
126.36, 126.48, 126.49, 126.81, 126.85, 128.33, 128.36, 128.79,
128.85, 128.92, 130.44, 130.47, 136.63, 132.06, 133.19, 133.23, 136.33,
140.54; HRMS (MALDI): 404.1567 (Mþ); calcd for C32H20: 404.1565.
(d, J¼8.6 Hz, 1H); 13C NMR (100 MHz, CDCl3):
d 4.28, 21.49, 78.94,
86.54, 87.89, 89.80, 108.81, 113.53, 118.02, 123.42, 124.30, 124.80,
126.72, 127.23, 128.00, 128.27, 129.90, 130.50, 130.71, 131.12, 134.30,
134.39, 134.99, 145.14; HRMS (MALDI): 409.1137 (Mþ); calcd for
C
26H19NO2S: 409.1139.
Acknowledgements
4.3.14. 2,5-Di-(1-propynyl)thiophene (Entry 15 in Scheme
This work was supported by a Grant-in-Aid for Scientific Re-
search on Innovative Areas ‘Organic Synthesis based on Reaction
Integration. Development of New Methods and Creation of New
Substances’ (No. 2105) and ‘Middle Molecular Strategy: Creation of
Higher Bio-functional Molecules by Integrated Synthesis’ (No.
2707) and Grant-in-Aid for Scientific Research (C) (15K05440) and
Okayama Prefecture Industrial Promotion Foundation. AO deeply
appreciate Professor Hiroshi Ikeda and Mr. Mirai Tanaka (Osaka
Prefecture University) for the discussion of LipperteMataga plot.
AO appreciate Ms. Saori Wada, Mr. Yuki Motoi and Mr. Mikiya Fujii
for supply of starting compounds.
7).19 Colorless oil; 1H NMR (300 MHz, CDCl3):
d
2.06 (s, 6H), 6.91
(s, 2H); 13C NMR (100 MHz, CDCl3):
130.58.
d 4.64, 72.72, 90.41, 124.19,
4.4. Synthesis of 9 by olefination of 8 with 13 (representative
for Scheme 8)
To a THF solution (2.0 mL) of 1-(1-propynyl)naphthalene (8)
(0.083 g, 0.499 mmol) were added DMPU (2.0 mL, 16.5 mmol) and
a hexane solution of butyl lithium (1.6 M, 0.375 mL, equivalent to
0.600 mmol of BuLi), and the mixture was stirred at ꢀ78 ꢁC for
30 min. To the mixture was added a THF solution (2.0 mL) of 4-
formylpheny(diphenyl)amine (13) (0.164 g 0.600 mmol), and the
mixture was stirred at ꢀ78 ꢁC for 30 min. To the mixture was added
diethyl chlorophosphate (0.087 mL, 0.605 mmol), and the mixture
was stirred at rt for 2 h. To the mixture was added t-BuOK (0.337 g,
3.00 mmol), and the mixture was stirred at rt for 12 h. After workup
with CH2Cl2/satd NH4Claq, the combined organic layer was washed
with satd NaClaq and dried over MgSO4. After evaporation, the
crude product was subjected to column chromatography on silica
gel (CH2Cl2/hexane 20: 80) and recrystallization (ethanol) to pro-
vide 4-(1-naphtylethynylethenyl) phenyl(diphenyl)amine (9) in
a pure form (0.106 g, 0.256 mmol, 51% yield).
References and notes
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9: yellow powder; mp 171 ꢁC; 1H NMR (500 MHz, CDCl3):
d 6.40
(d, J¼15.9 Hz, 1H), 7.02e7.08 (m, 5H), 7.13 (d, J¼7.6 Hz, 4H), 7.28 (t,
J¼7.9 Hz, 4H), 7.33 (d, J¼8.6 Hz, 2H), 7.43 (t, J¼7.8 Hz, 1H), 7.52 (t,
J¼7.5 Hz, 1H), 7.58 (t, J¼7.3 Hz, 1H), 7.69 (d, J¼7.4 Hz, 1H), 7.81 (d,
J¼8.3 Hz, 1H), 7.85 (d, J¼8.3 Hz, 1H), 8.40 (d, J¼7.9 Hz, 1H); 13C NMR
€
Volker, S. F.; Delgado, J. L. Angew. Chem., Int. Ed. 2015, 54, 9757; (d) Liu, Z.; Lau,
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Carlo, A.; Bonaccorso, F. Chem. Soc. Rev. 2015, 44, 3244.
(125 MHz, CDCl3):
d 89.45, 94.43, 105.87, 121.27, 122.73, 123.39,
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4. (a) La Clair, J. J. J. Am. Chem. Soc. 1997, 119, 7676; (b) Brummer, O.; La Clair, J. J.;
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129.33, 130.08, 130.10, 133.12, 133.16, 140.87, 147.24, 148.32; HRMS
(MALDI): 421.1822 (Mþ); calcd for C32H23N: 421.1830.
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10: yellow powder; mp 81 ꢁC; 1H NMR (300 MHz, CDCl3):
d 6.56
(d, J¼16.2 Hz, 1H), 7.01 (d, J¼8.9 Hz, 2H), 7.07 (tt, J¼1.8, 7.3 Hz, 2H),
7.11e7.16 (m, 5H), 7.28 (t, J¼8.0 Hz, 4H), 7.38 (td, J¼2.3, 8.9 Hz, 2H),
7.43e7.46 (m, 3H), 7.50 (d, J¼8.3 Hz, 2H), 7.53 (dt, J¼1.3, 7.5 Hz, 1H),
7.60 (dt, J¼1.2, 7.5 Hz, 1H), 7.71 (dd, J¼1.2, 7.2 Hz, 1H), 7.83 (d,
ꢂ
ꢁ

4434
K. Shinohara et al. / Tetrahedron 72 (2016) 4427e4434
10. Upon treatment of phosphorylethynes such as 3 and 4 with t-BuOK, potassium
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ꢀ
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r
. See for the slope value r to the following paper Fang, J.-K.; An, D.-L.; Wa-
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