Synthesis of tetraarylallenes via palladium-catalyzed addition-elimination reactions of 1,1,3-triaryl-2-propyn-1-ols with aryl iodides

Article abstract of DOI:10.1055/s-2005-872228

The palladium-catalyzed reactions of tert-propargylic alcohols with aryl iodides afforded tetraarylallenes in good yields. This reaction involves: (1) oxidative addition of the aryl iodide to Pd(O); (2) arylpalladium intermediate coordination to the carbon-carbon triple bond of the 1,1,3-triaryl-2-propyn-1-ol and subsequent regioselective insertion of the alkynol to form β-hydroxyvinylpalladium species; and (3) β-elimination to produce the tetraarylallenes. Generally, the best results are obtained by employing 5 mol% of Pd(TFA)₂, 10 mol% of PPh₃, two equivalents of aryl iodide and five equivalents of Et₃N in MeCN. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-872228

LETTER
2219
Synthesis of Tetraarylallenes via Palladium-Catalyzed Addition–Elimination
Reactions of 1,1,3-Triaryl-2-propyn-1-ols with Aryl Iodides
Synthesis of
T
et
i
raaryla
-
llenes Mei Wei,a Li-Lan Wei,a,b Wen-Bin Pan,a Ming-Jung Wu*b
a
Fooyin University, 831 Kaohsiung County, Taiwan
b
Faculty of Medicinal and Applied Chemistry, Kaohsiung Medicial University, 807 Kaohsiung, Taiwan
E-mail: mijuwu@.kmu.edu.tw
Received 13 April 2005
enes and triarylethylenes.22 We report herein the first
example for the Pd-catalyzed conversion of propargylic
alcohols with iodoarene to polysubstituted allenes.
Abstract: The palladium-catalyzed reactions of tert-propargylic al-
cohols with aryl iodides afforded tetraarylallenes in good yields.
This reaction involves: (1) oxidative addition of the aryl iodide to
Pd(0); (2) arylpalladium intermediate coordination to the carbon–
carbon triple bond of the 1,1,3-triaryl-2-propyn-1-ol and subsequent
regioselective insertion of the alkynol to form b-hydroxyvinylpalla-
dium species; and (3) b-elimination to produce the tetraarylallenes.
Generally, the best results are obtained by employing 5 mol% of
Pd(TFA)2, 10 mol% of PPh3, two equivalents of aryl iodide and five
equivalents of Et3N in MeCN.
The starting propargylic alcohols were easily prepared by
metal acetylide addition to the appropriate diaryl ketones.
With a wide variety of 1,1,3-triaryl-2-propyn-1-ols in
hand, we first turn our attention to the cascade reaction of
1,1,3-triphenyl-2-propyn-1-ol (1a) and iodobenzene (2a)
as our model system. The reaction of alkynol 1a with two
equivalents of iodobenzene in the presence of 5 mol% of
Pd(OAc)2, 5 mol% of PPh3 and five equivalents of Et3N in
MeCN at 80 °C for 24 hours resulted in the formation of
tetraphenylallene (3aa) in 32% yield (Table 1, entry 1).
The structure of 3aa was unambiguously determined by
X-ray crystallographic analysis (Figure 1).23 When the
catalyst was replaced by the other catalysts, such as
Pd(OCOCF3)2 and Pd(dba)2 under the same reaction con-
ditions, the same product 3aa was obtained in 49% and
30% yields, respectively (Table 1, entries 2 and 3). The
results show that Pd(OCOCF3)2 is the most efficient cata-
lyst for the reaction of triaryl-2-propyn-1-ols with aryl io-
dides. Among the molar ratios of Pd(OCOCF3)2/PPh3
examined, the 1:2 ratio of the 5 mol% of Pd(OCOCF3)2 to
10 mol% of PPh3 was found to be most efficient (Table 1,
entries 4–7). On the other hand, a brief examination of the
influence of base on yield of 3aa revealed that Et3N is the
base of choice. Using K2CO3 or Na2CO3 as the base, no re-
action occurred (Table 1, entries 8 and 9). Thus, the opti-
mal reaction conditions revealed to be as follows:
treatment of 1,1,3-triphenyl-2-propyn-1-ol (1a) with two
equivalents of iodobenzene (2a) in the presence of 5
mol% of Pd(OCOCF3)2, 10 mol% of PPh3 and five equiv-
alents of Et3N as the base in MeCN as the solvent at 80 °C
gave 3aa in 61% yield.
Key words: palladium, tetraarylallenes, addition–elimination,
1,1,3-triaryl-2-propyn-1-ol
Allenes are potential synthetic intermediates for organic
synthesis because of their unique strained structure and in-
teresting reactivity.1 Especially transition metal-catalyzed
reactions of allenes have considerable attention for the
past two decades.2 Examples of transition metal-promoted
allene chemistry include C–C bond formations of allenes
with pronucleophiles and electrophiles,3 carbonylations
of allenes,4 [4+2], [2+2] and [2+2+2] cycloadditions,5 al-
lene cross-coupling reactions6 and polymerizations.7
Therefore, development of efficient methods for the for-
mation of allenes is of great importance.8 The major allene
synthesis is based on the SN2¢-type substitution of propar-
gylic leaving groups with organocopper reagents.9 Other
preparation methods of allenes involve dehydrohalogena-
tion of vinylic halides,10 reductive elimination of haloge-
nated cyclopropanes,11 elimination of enol phosphates,12
and radical b-elimination of vinyl sulfoxides.13 Disubsti-
tuted allenes can be prepared by the Horner–Wadsworth–
Emmons (HWE) reactions of alkenylphosphonates.14 The
palladium-catalyzed reactions for synthesizing the allenes
include hydrogenolysis,15 coupling reactions of allenyl-
stannanes,16 allenylzincs17 and allenylindiums,18 SN2¢ sub-
stitution of 2-bromo-1,3-butadiene derivatives19 and
hydrogen-transfer reactions of propargylic amines.20 Al-
though many methods have been developed for the syn-
thesis of allenes, the synthesis of polysubstituted allenes is
still attractive for a new synthetic method.21 Recently, we
have disclosed a powerful palladium-catalyzed hydroaryl-
ation of aryl iodides with alkynes to give the diarylacetyl-
Various aryl iodides 2a–e bearing electron-donating or
electron-withdrawing groups on the phenyl ring were test-
ed for the reactions of 1a–e under the optimal reaction
conditions, giving the products 3aa–ed in 42–86% yields.
The results are summarized in Table 2. 4-Tolyl iodide
(2b) and 2-methyliodobenzene (2c) were coupled with 1a
to afford the corresponding allenes 3ab and 3ac in 65%
and 68% yields, respectively (Table 2, entries 2 and 3). It
is noteworthy that the ortho substituent of iodoarene 2c
does not affect the product yield of the catalytic reaction.
para-Iodoanisole 2d produced 3ad in 72% yield (Table 2,
entry 4). In a further exploration of the substituent effect
SYNLETT 2005, No. 14, pp 2219–2223
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2
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9
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Advanced online publication: 20.07.2005
DOI: 10.1055/s-2005-872228; Art ID: U10905ST
© Georg Thieme Verlag Stuttgart · New York

2220
L.-M. Wei et al.
LETTER
Table 2 Palladium-Catalyzed Tandem Reactions of tert-Prop-
argylic Alcohols 1 with Aryl Iodides 2
OH
R1
Ar
R1
C
R2
Pd(TFA)2, PPh3
MeCN, Et3N
C
R2
+
ArI
1
2
3
Entry tert-Propargylic
Aryl iodide
Product
alcohol
(yield, %)a
1
1a (R1 = C6H5,
2a (Ar = phenyl)
3aa (61)
R2 = C6H5)
2
3
4
5
1a
2b (Ar = 4-tolyl)
2c (Ar = 2- tolyl)
3ab (65)
3ac (68)
1a
1a
2d (Ar = 4-methoxyphenyl) 3ad (72)
1b (R1 = C6H5,
2a
3ad (74)
Figure 1 X-ray structure of compound 3aa
R2 = 4-CH3OC6H4)
6
7
8
9
1b
1b
1b
1b
2b
2c
2d
3bb (66)
3bc (61)
3bd (58)
Table 1 Palladium-Catalyzed Arylation Reactions of 1,1,3-Tri-
phenyl-2-propyn-1-ol 1a with Iodobenzene 2aa
OH
C
I
Pd(II)
+
C
2e (Ar = 3-methoxyphenyl) 3be (65)
MeCN, base
10 1c (R1 = C6H5,
2b
3cb (42)
R2 = 4-CF3C6H4)
1a
2a
3aa
11 1e (R1 = 4-CH3OC6H4, 2d
3ed (86)
R2 = C6H5)
Entry Catalyst
PPh3
Base
Yield of 3aa
(%)
(%)
a Yields refer to isolated yields. All of the compounds gave satisfac-
tory 1H NMR, 13C NMR and MS data.
1
2
3
4
5
6
7
8
9
Pd(OAc)2
5
Et3N
32
49
30
39
61
20
16
0
Pd(OCOCF3)2
Pd(dba)2
5
Et3N
and 2e with the methoxyl group at the meta position, also
reacted efficiently with 1b to give the adducts 3bd and
3be in 58% and 65% yields (entries 8 and 9). However,
the reaction of 3-(4-trifluoromethylphenyl)-1,1-diphenyl-
2-propyn-1-ol (1c) with 4-iodotoluene (2b) gave a slightly
lower yield (42%) of the addition product 3cb (entry 10).
Moreover, the use of 1,1-diphenyl-2-heptyn-1-ol (1d)
bearing an alkyl group on the alkyne moiety was not ef-
fective for the allene formation. Finally, the alkynol 1e
bearing a methoxyl group at one of the phenyl groups at
C1 was also examined to see whether the reaction might
be affected by the aryl group attached to the a-carbon.
Thus, reaction of 1-(4-methoxyphenyl)-1,3-diphenyl-2-
propyn-1-ol (1e) with 4-iodoanisole (2d) gave allene 3ed
in 86% yield (entry11). This result indicates that the meth-
oxyl group on the phenyl ring at C1 would stabilize the al-
lene 3ed through the resonance effect. Therefore, a higher
yield was obtained.
5
Et3N
Pd(OCOCF3)2
Pd(OCOCF3)2
Pd(OCOCF3)2
Pd(OCOCF3)2
Pd(OCOCF3)2
Pd(OCOCF3)2
–
Et3N
10
15
20
10
10
Et3N
Et3N
Et3N
K2CO3
Na2CO3
0
a Reactions of 1,1,3-triphenylprop-2-yn-1-ol 1a (0.3 mmol) with iodo-
benzene 2a (0.6 mmol) were carried out at 80 °C for 24 h in MeCN
using 5 mol% mmol of Pd catalyst and PPh3.
on the alkyne terminus on compound 1, various tertiary
propargylic alcohol derivatives 1b–d were synthesized by
the addition of a lithium acetylide to diaryl ketones. The
reaction of 3-(4-methoxyphenyl)-1,1-diphenyl-2-propyn-
1-ol (1b) with iodobenzene (2a) under the optimal reac-
tion conditions produces the allene 3ad in 74% yield (en-
try 5). Similarly, para- and ortho-iodotoluene (2b) and
(2c) afforded arylallenes 3bb and 3bc in 66% and 61%
yields, respectively (entries 6 and 7). Aryl iodides 2d with
an electron-donating methoxyl group at the para position
Although the mechanism of the Pd-catalyzed addition–
elimination reactions is not clear at this point, a plausible
mechanism is proposed based on our previous study.24
Possible process consists of the following steps: (1) oxi-
dative addition of the aryl iodides 2 to Pd catalyst; (2) co-
ordination of an arylpalladium intermediate to the
carbon–carbon triple bond of the alkynols 1 with subse-
Synlett 2005, No. 14, 2219–2223 © Thieme Stuttgart · New York

LETTER
Synthesis of Tetraarylallenes
2221
Anal. Calcd for C28H22: C, 93.81; H, 6.19. Found: C, 93.58; H, 6.19.
quent regioselective insertion of the alkynols 1 to form b-
hydroxyvinylpalladium intermediates via carbopallada-
tion; and (3) b-OH group elimination via C–O bond cleav-
age to give the arylated allenes 3 with simultaneous
generation of a HO–Pd(II)–X, which is reduced by tri-
ethylamine to regenerate the Pd(0) species to enable the
next catalytic cycle.
1-(4-Methoxyphenyl)-1,3,3-triphenyl-1,2-propadiene (3ad)
Compound 3ad was obtained in 74% yield as a yellow oil.
1H NMR (400 MHz, C6D6): d = 7.58–7.52 (m, 6 H), 7.43 (dt,
J = 8.8, 2.4 Hz, 2 H), 7.15–7.04 (m, 9 H), 6.71 (dt, J = 8.8, 2.8 Hz,
2 H), 3.27 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 209.8, 160.5, 137.9, 137.9, 130.7,
In conclusion, we have demonstrated a new palladium-
catalyzed addition–elimination reaction of tert-propargyl-
ic alcohols with aryl iodides using triethylamine as the
base to afford good yields of sterically hindered tetraaryl-
allenes. Although the present method is restricted to
preparation of tetraarylallenes, the method might find
wide utility because of experimental ease and the good
product yield of the catalytic reaction. Further application
of these allenes in organic synthesis and detailed mecha-
nistic studies of this novel type reaction are in progress.
129.6, 129.5, 128.5, 115.2, 113.8, 113.8, 55.5.
MS (EI): m/z (%) = 374 (100) [M+], 252 (59), 77 (77).
HRMS (EI): m/z calcd for C28H22O: 374.1671; found: 374.1668.
1-(4-Methoxyphenyl)-1-(4-methylphenyl)-3,3-diphenyl-1,2-
propadiene (3bb)
Compound 3bb was obtained in 66% yield as a yellow oil.
1H NMR (400 MHz, C6D6): d = 7.58–7.55 (m, 4 H), 7.52 (dt,
J = 8.4, 2.0 Hz, 2 H), 7.48 (dd, J = 8.4, 1.6 Hz, 2 H), 7.15–7.03 (m,
6 H), 6.98 (d, J = 8.0, 2 H), 6.72 (dt, J = 8.4, 2.0 Hz, 2 H), 3.27 (s,
3 H), 2.09 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 209.7, 160.5, 138.1, 138.0, 135.0,
130.9, 130.7, 130.4, 129.7, 129.6, 129.5, 128.4, 115.2, 113.7, 113.7,
55.5, 21.8.
Typical Experimental Procedure for the Palladium-Catalyzed
Arylation–Elimination Reactions of tert-Propargylic Alcohols
with Aryl Iodides
MS (EI): m/z (%) = 388 (100) [M+], 252 (67), 77 (87).
A slurry of the alkynol 1 (0.3 mmol), aryl iodides 2 (0.6 mmol),
Pd(OCOCF3)2 (5 mol%), PPh3 (10 mol%) and Et3N (1.5 mmol) in
MeCN (8 mL) at 80 °C was stirred for 24 h. The reaction mixture
was filtered through a short pad of silica gel to remove precipitated
inorganic salts. The silica gel pad was washed three times with a
small amount of EtOAc and the combined solution was evaporated
to dryness under reduced pressure. The residue was chromato-
graphed on silica gel using n-hexane–EtOAc as eluent to give the al-
lenes 3.
HRMS (EI): m/z calcd for C29H24O: 388.1827; found: 388.1824.
1-(4-Methoxyphenyl)-1-(2-methylphenyl)-3,3-diphenyl-1,2-
propadiene (3bc)
Compound 3bc was obtained in 61% yield as a yellow oil.
1H NMR (400 MHz, C6D6): d = 7.54–7.51 (m, 4 H), 7.35 (dt,
J = 8.8, 2.4 Hz, 2 H), 7.15–7.06 (m, 10 H), 6.67 (dt, J = 9.2, 2.8 Hz,
2 H), 3.24 (s, 3 H), 2.22 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 207.8, 160.4, 138.0, 137.9, 137.2,
131.5, 131.3, 130.9, 129.6, 129.5, 129.1, 128.7, 128.4, 127.2, 115.3,
113.6, 111.7, 55.4, 21.1.
1,1,3,3-Tetraphenyl-1,2-propadiene (3aa)
Compound 3aa was obtained in 61% yield as a white solid; mp 165–
166 °C.
1H NMR (200 MHz, CDCl3): d = 7.49–7.27 (m, 20 H).
MS (EI): m/z (%) = 388 (63) [M+], 221 (99), 77 (100).
HRMS (EI): m/z calcd for C29H24O: 388.1827; found: 388.1824.
13C NMR (50 MHz, CDCl3): d = 208.5, 136.3, 128.5, 128.4, 127.5,
112.6.
1,1-Di(4-methoxyphenyl)-3,3-diphenyl-1,2-propadiene (3bd)
Compound 3bd was obtained in 58% yield as a yellow oil.
Anal. Calcd for C27H20: C, 94.14; H, 5.86. Found: C, 94.20; H, 5.81.
1H NMR (400 MHz, C6D6): d = 7.58 (dt, J = 8.0, 2.0 Hz, 4 H), 7.49
(dt, J = 8.8, 2.0 Hz, 4 H), 7.13 (dd, J = 6.0, 1.6 Hz, 4 H), 7.07 (tt,
J = 7.6, 1.2 Hz, 2 H), 6.74 (dt, J = 9.2, 2.8 Hz, 4 H), 3.28 (s, 6H).
13C NMR (100 MHz, C6D6): d = 209.7, 160.5, 138.1, 130.7, 129.9,
129.6, 129.5, 128.4, 115.2, 113.6, 113.5, 55.5.
1-(4-Methylphenyl)-1,3,3-triphenyl-1,2-propadiene (3ab)
Compound 3ab was obtained in 65% yield as a white solid; mp 91–
93 °C.
1H NMR (400 MHz, C6D6): d = 7.57–7.49 (m, 6 H), 7.46 (dt,
J = 8.0, 1.6 Hz, 2 H), 7.13–7.03 (m, 9 H), 6.95 (d, J = 8.4 Hz, 2 H),
2.08 (s, 3 H).
MS (EI): m/z (%) = 404 (100) [M+], 252 (39), 77 (89).
13C NMR (100 MHz, C6D6): d = 209.8, 138.1, 137.8, 137.7, 134.6,
HRMS (EI): m/z calcd for C29H24O2: 404.1776; found: 404.1773.
130.4, 129.6, 129.5, 129.5, 114.0, 113.9, 21.8.
1-(4-Methoxyphenyl)-1-(3-methoxyphenyl)-3,3-diphenyl-1,2-
propadiene (3be)
Anal. Calcd for C28H22: C, 93.81; H, 6.19, Found: C, 93.68; H, 6.04.
Compound 3be was obtained in 65% yield as a yellow oil.
1-(2-Methylphenyl)-1,3,3-triphenyl-1,2-propadiene (3ac)
Compound 3ac was obtained in 68% yield as a white solid; mp 122–
123 °C.
1H NMR (400 MHz, C6D6): d = 7.49 (dt, J = 7.2, 1.6 Hz, 4 H), 7.43
(dt, J = 7.2, 1.2 Hz, 2 H), 7.41–7.39 (m, 1 H), 7.14–7.04 (m, 11 H),
6.99 (tt, J = 7.2, 1.2 Hz, 1 H), 2.16 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 208.2, 138.0, 137.6, 137.4, 136.9,
131.5, 131.3, 129.8, 129.6, 129.5, 128.8, 128.5, 128.2, 127.9, 127.2,
113.8, 112.0, 21.1.
1H NMR (400 MHz, C6D6): d = 7.56–7.56 (m, 4 H), 7.48 (dt,
J = 8.8, 2.0 Hz, 2 H), 7.27–7.25 (m, 2 H), 7.14–7.04 (m, 7 H), 6.77–
6.74 (m, 1 H), 6.71 (dt, J = 8.8, 2.4 Hz, 2 H), 3.26 (s, 3 H), 3.24 (s,
3 H).
13C NMR (100 MHz, C6D6): d = 209.7, 161.2, 160.5, 139.4, 137.8,
130.7, 130.7, 129.6, 129.5, 122.1, 122.1, 115.2, 115.2, 115.0, 114.4,
113.8, 113.8, 55.4, 55.3.
MS (EI): m/z (%) = 404 (100) [M+], 252 (47), 77 (88).
HRMS (EI): m/z calcd for C29H24O2: 404.1776; found: 404.1773.
Synlett 2005, No. 14, 2219–2223 © Thieme Stuttgart · New York

2222
L.-M. Wei et al.
LETTER
1-(4-Trifluoromethylphenyl)-1-(4-methylphenyl)-3,3-diphenyl-
1,2-propadiene (3cb)
Anal. Calcd for C22H15F3O: C, 74.98; H, 4.29. Found: C, 74.68; H,
4.32.
Compound 3cb was obtained in 42% yield as a yellow oil.
1,1-Diphenyl-2-heptyn-1-ol (1d)
Yellow oil.
1H NMR (400 MHz, C6D6): d = 7.64–7.61 (m, 4 H), 7.35–7.24 (m,
6 H), 2.78 (s, 1 H), 2.36 (t, J = 7.2 Hz, 2 H), 1.64–1.56 (m, 2 H),
1.52–1.43 (m, 2 H), 0.95 (t, J = 7.2 Hz, 3 H).
1H NMR (400 MHz, C6D6): d = 7.48 (dt, J = 7.2, 1.6 Hz, 4 H), 7.38–
7.31 (m, 4 H), 7.26 (d, J = 8.0 Hz, 2 H), 7.16–7.05 (m, 6 H), 6.96
(d, J = 8.0 Hz, 2 H), 2.09 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 210.1, 141.5, 138.6, 137.2, 133.8,
130.5, 129.8, 129.7, 129.7, 129.5, 129.3, 128.9, 128.8, 126.5, 114.6,
113.0, 21.8.
13C NMR (100 MHz, C6D6): d = 145.5, 128.1, 127.4, 126.0, 126.1,
88.2, 83.0, 74.4, 30.6, 22.0, 18.6, 13.6.
MS (EI): m/z (%) = 264 (6) [M+], 221 (63), 207 (84), 77 (100).
MS (EI): m/z (%) = 426 (100) [M+], 265 (90), 77 (54).
HRMS (EI): m/z calcd for C29H21F3: 426.1595; found: 426.1592.
HRMS (EI): m/z calcd for C19H20O: 264.1515; found: 264.1515.
1,3-Di(4-methoxyphenyl)-1,3-diphenyl-1,2-propadiene (3ed)
Compound 3ed was obtained in 86% yield as a yellow oil.
1-(4-Methoxyphenyl)-1,3-diphenyl-2-propyn-1-ol (1e)
White solid; mp 83–84 °C.
1H NMR (400 MHz, C6D6): d = 7.58 (d, J = 6.8 Hz, 4 H), 7.49 (dt,
J = 8.8, 2.4 Hz, 4 H), 7.13 (dd, J = 7.6, 1.6 Hz, 4 H), 7.07 (tt,
J = 7.6, 2.0 Hz, 2 H), 6.74 (dt, J = 9.2, 2.4 Hz, 4 H), 3.28 (s, 6 H).
13C NMR (100 MHz, C6D6): d = 209.6, 160.5, 138.2, 130.7, 129.8,
129.6, 129.5, 128.4, 115.2, 113.5, 55.5.
1H NMR (400 MHz, C6D6): d = 7.86 (d, J = 7.8 Hz, 2 H), 7.73 (dt,
J = 8.8, 2.6, Hz, 2 H), 7.40–7.37 (m, 2 H), 7.17 (d, J = 8.0 Hz, 2 H),
7.06 (tt, J = 7.6, 1.6 Hz, 1 H), 6.99–6.96 (m, 3 H), 6.75 (dt, J = 8.8,
2.4 Hz, 2 H), 3.27 (s, 3 H), 3.04 (s, 1 H).
13C NMR (100 MHz, C6D6): d = 160.2, 147.1, 139.0, 132.7, 129.3,
129.2, 129.1, 128.7, 128.4, 127.3, 123.9, 114.6, 94.0, 87.8, 75.4,
55.5.
MS (EI): m/z (%) = 404 (100) [M+], 252 (47), 77 (88).
HRMS (EI): m/z calcd for C29H24O2: 404.1776; found: 404.1773.
Anal. Calcd for C22H18O2: C, 84.04; H, 5.78. Found: C, 84.11; H,
5.82.
General Procedure for the Synthesis of tert-Propargylic Alco-
hols (1)
A three-neck flask was charged with phenylacetylene (24 mmol) in
THF (12 mL). The flask was cooled to –78 °C, and n-BuLi (24
mmol) in hexane (1.6 M) was added dropwise under a nitrogen at-
mosphere. The mixture was stirred for 30 min and then diarylke-
tone (20 mmol) in THF (8 mL) added. The reaction mixture was
stirred for further 2 h, quenched with H2O, and extracted with
EtOAc (3 × 10 mL). The combined extracts were washed with sat.
aq NH4Cl, H2O, brine, dried (MgSO4), and filtered. The solvent was
removed under reduced pressure, and the residue was purified by
flash column chromatography using n-hexane–EtOAc as eluent to
afford the desired products 1.
Acknowledgment
We thank the National Science Council of the Republic of China for
the financial support of this program.
References
(1) (a) Brandsma, L.; Verkruijsse, H. D. Synthesis of Acetylenes,
Allenes, and Cumulenes; Elsevier: Amsterdam, 1981.
(b) The Chemistry of Allenes; Landor, S. R., Ed.; Academic
Press: London, 1982. (c) Schuster, H. F.; Coppola, G. M.
Allenes in Organic Synthesis; Wiley: New York, 1984.
(d) Pasto, D. J. S. Tetrahedron 1984, 40, 2805.
1,1,3-Triphenyl-2-propyn-1-ol (1a)
White solid; mp 81–83 °C.
1H NMR (200 MHz, CDCl3): d = 7.71–7.65 (m, 4 H), 7.55–7.49 (m,
2 H), 7.41–7.28 (m, 9 H), 2.89 (s, 1 H).
(e) Hoffmann-Roder, A.; Krause, N. Angew. Chem. Int. Ed.
2002, 41, 2933.
13C NMR (50 MHz, CDCl3): d = 145.0, 131.8, 128.7, 128.3, 127.7,
127.7, 126.1, 122.4, 91.7, 87.2, 74.8.
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31. (b) Yamamoto, Y.; Radhakrishnanan, U. Chem. Soc.
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Nandanam, E.; Khan, F. A. Chem. Rev. 2000, 100, 3067.
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Soc. 1994, 116, 6019. (b) Trost, B. M.; Gerusz, V. J. J. Am.
Chem. Soc. 1995, 117, 5156. (c) Franzen, J.; Lofstedt, J.;
Dorange, I.; Backvall, J.-E. J. Am. Chem. Soc. 2002, 124,
11246.
(4) (a) Chang, H.-M.; Cheng, C.-H. Org. Lett. 2000, 2, 3439.
(b) Anwar, U.; Grigg, R.; Rasparini, M.; Savic, V.;
Sridharan, V. Chem. Commun. 2000, 645.
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Soc. 1995, 117, 1843. (b) Kimura, M.; Horino, Y.;
Wakamiya, Y.; Okajima, T.; Tamaru, Y. J. Am. Chem. Soc.
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Anal. Calcd for C21H16O: C, 88.69; H, 5.68. Found: C, 88.50; H,
5.66.
3-(4-Methoxyphenyl)-1,1-diphenyl-2-propyn-1-ol (1b)
Yellow solid; mp 66–68 °C.
1H NMR (400 MHz, C6D6): d = 7.84 (d, J = 7.6 Hz, 4 H), 7.34 (dt,
J = 8.8, 2.8 Hz, 2 H), 7.17–7.13 (m, 4 H), 7.04 (tt, J = 7.6, 1.2 Hz,
4 H), 6.59 (dt, J = 8.8, 2.4 Hz, 2 H), 3.16 (s, 3 H), 2.54 (s, 1 H).
13C NMR (100 MHz, C6D6): d = 161.0, 146.9, 134.3, 129.1, 128.4,
127.3, 115.8, 115.0, 92.2, 88.1, 75.7, 55.4.
Anal. Calcd for C22H18O2: C, 84.04; H, 5.78. Found: C, 83.89; H,
5.78.
3-(4-Trifluoromethylphenyl)-1,1-diphenyl-2-propyn-1-ol (1c)
White solid; mp 60–62 °C.
1H NMR (400 MHz, C6D6): d = 7.74 (dt, J = 7.2, 2.0 Hz, 4 H), 7.17–
7.09 (m, 8 H), 7.05 (tt, J = 7.2, 1.6 Hz, 2 H), 2.39 (s, 1 H).
13C NMR (100 MHz, C6D6): d = 146.2, 132.9, 129.2, 128.5, 127.2,
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233. (c) Chaptal, N.; Colovray-Gotteland, V.; Grandjean, C.;
Cazes, B.; Gore, J. Tetrahedron Lett. 1991, 32, 1795.
126.1, 126.1, 126.0, 126.0, 95.8, 86.5, 75.6.
Synlett 2005, No. 14, 2219–2223 © Thieme Stuttgart · New York

LETTER
Synthesis of Tetraarylallenes
2223
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Tetrahedron 2001, 57, 7839.
(23) Crystal data for 3aa: C27H20, M = 344.43 g/mol, crystal size:
0.50 × 0.50 × 0.50 mm, monoclinic, space group P21/c,
l = 0.71073 Å, a = 12.1405 (1) Å, b = 8.4186 (1) Å,
c = 19.2201 (2) Å, a = 90°, b = 101.0624 (5)°, g = 90°,
V = 1927.91 (3) Å3, Z = 4, D = 1.187 mg/m3, m = 0.067
mm–1, T = 295 (2) K, q range: 1.71–27.50°, reflections
collected: 17949, independent reflections: 4403 (Rint
=
0.0313), refinement method: full-matrix least-squares on F2,
final R values [I > 2s(I)]: R1 = 0.0516, wR2 = 0.1300.
Diffractometer: NONIUS KappaCCD. Crystallographic
data (excluding structure factors) for this structure have been
deposited at the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC 260843, and may be
obtained free of charge on application to CCDC, 12 Union
Road, Cambridge CB2 1ED, UK [fax: +44(1223)336033;
e-mail deposit@ccdc.cam.ac.uk].
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2004, 1497. (b) Lin, C.-F.; Lu, W.-D.; Wang, I.-W.; Wu, M.-
J. Synlett 2003, 2057. (c) Wei, L.-M.; Lin, C.-F.; Wu, M.-J.
Tetrahedron Lett. 2000, 41, 1215. (d) Wei, L.-L.; Wei, L.-
M.; Pan, W.-B.; Leou, S.-P.; Wu, M.-J. Tetrahedron Lett.
2003, 44, 1979. (e) Wei, L.-M.; Wei, L.-L.; Pan, W.-B.; Wu,
M.-J. Tetrahedron Lett. 2003, 44, 595.
Synlett 2005, No. 14, 2219–2223 © Thieme Stuttgart · New York