Synthesis of Oxazoles by Tandem Cycloisomerization/Allylic Alkylation of Propargyl Amides with Allylic Alcohols: Zn(OTf)2 as π Acid and σ Acid Catalyst

Article abstract of DOI:10.1021/acs.joc.5b02382

A Zn(OTf)₂-catalyzed tandem cycloisomerization/allylic alkylation of N-(propargyl)arylamides and allylic alcohols to produce oxazole derivatives has been successfully developed. The zinc catalyst served as π acid and also σ acid in this reaction. The target allylic oxazoles have been transformed into multisubstituted diene structures, which are potential aggregation-induced emission active optical materials.

Full text of DOI:10.1021/acs.joc.5b02382

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Note
Synthesis of Oxazoles by Tandem Cycloisomerization/Allylic Alkylation of
Propargyl Amides with Allylic Alcohols: Zn(OTf)2 as # Acid & # Acid Catalyst
Bin Wang, YIng Chen, Ling Zhou, Jianwu Wang, Chen-Ho Tung, and Zhenghu Xu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.5b02382 • Publication Date (Web): 30 Nov 2015
Downloaded from http://pubs.acs.org on December 1, 2015
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Synthesis
of
Oxazoles
by
Tandem
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Cycloisomerization/Allylic Alkylation of Propargyl
Amides with Allylic Alcohols: Zn(OTf)2 as π Acid & σ
Acid Catalyst
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Bin Wang†, Ying Chen†, Ling Zhou§, Jianwu Wang*†, ChenꢀHo Tung† and Zhenghu Xu*†‡
†Key Lab of Colloid and Interface Chemistry of Ministry of Education,
School of Chemistry and Chemical Engineering, Shandong University, No.
27 South Shanda Road, Jinan, Shandong 250100, China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR
China
§Department of Chemistry and Biochemistry, Miami University, Oxford, OH,
45056
xuzh@sdu.edu.cn, jwwang@sdu.edu.cn
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O
Ph
OH
Ph
Ph
O
Zn(OTf)2 (10 mol%)
Ph
N
HN
Ph
Ph
Ph
[Zn]2+
[Zn]2+
up to 94% yield
23 examples
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O
Ph
N
Ph
Abstract: A Zn(OTf)2ꢀcatalyzed tandem cycloisomerization/allylic alkylation of Nꢀ
(propargyl)arylamides and allylic alcohols to produce oxazole derivatives has been
successfully developed. The zinc catalyst served as π acid and also σ acid in this reaction.The
target allylic oxazoles have been transformed into multisubstituted diene structures, which
are potential AIE active optical materials.
Oxazole derivatives are privileged fiveꢀmembered heterocycles widely presented in a
variety of natural products and pharmaceuticals with significant biological activities.1
Oxazoles are useful synthetic intermediates in organic synthesis and also important
ligands for transitionꢀmetal catalysis.2 Thus the development of a practical and useful
method to access this heterocycle is of great importance. Recently, propargylic amides
have been well studied as versatile building blocks to prepare oxazoles.3 Various
transitionꢀmetalꢀcatalysts could catalyze these transformations and significant progress
has been made in this area (Scheme 1). For example, a Pd(0)ꢀcatalyzed
coupling/cyclization of propargylic amide 1 with ArI has been developed to synthesize
disubstituted oxazoles in 2001.4 Later in 2010, Hashmi and coworkers developed a
gold(III)ꢀcatalyzed cyclization of propargylic amide 1 to access methyl oxzaoles.5 Very
recently, Shi and Jiao developed a synergistic gold(I)/Fe(III) dual catalysis from
propargylic amide to oxazole aldehyde.6 In this communication, we report here a cheap
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metal Zn(OTf)2ꢀcatalyzed cyclization/allylic alkylation cascade reaction of propargylic
amides with allylic alcohol 2 to prepare oxazole derivatives. In this transformation,
elimination of one molecule of water is the only byꢀproduct. More importantly, Zn(OTf)2
acted as a π acid to catalyze the cyclization of propargylic amide, but also served as a σ
acid to activate the allylic alcohol, which is the most important feature of this work.
Scheme 1. Transitionꢀmetalꢀcatalyzed cyclization/functionalization of propargylic
amides to synthesize oxazoles.
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O
R
N
M = Au3+ (5 mol%)
or Fe3+ (50 mol%)
O
M = Au+/Fe(acac)3
O
ArI
R
O
[M]
O
O
R
R
HN
tBuOOH
Ar
N
N
R
N
M = Pd
M1
1
OH
Zn(OTf)2 (10 mol%)
Ph
Ph
2a
O
R
Ph
(This work)
N
Ph
3
Previously we combined Au as the π acid and another early transitionꢀmetal as the σ
acid and developed a series of bimetallic relay catalysis to access various biologically
important fused or spiro aminals.7 Following this chemistry, π acids such as gold(I)
catalysts or Zn(II) catalysts could catalyze the cyclization of 1a to form an exocyclic
double bond intermediate M1, which could act as a nucleophile to participate in another
asymmetric allylic alkylation8 in the presence of a palladium catalyst and chiral
phosphine ligands to build chiral oxazole derivatives (Scheme 2). To our great surprise,
whatever chiral ligands such as Trost’s ligand or SEGPHOS were used, the coupled
products 3a were all racemic (eq1). These results indicated that the chiral palladium
catalyst might not participate in this reaction. Then the chiral palladium catalysts were
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removed from the reaction system, the product 3a was isolated in similar yield (eq2).
Herein the zinc catalyst not only served as π acid to catalyze the cyclization of
propargylic amide, but also acted as σ acid to activate the allylic carbonate
Scheme 2. Unexpected Zn(OTf)2ꢀcatalyzed cycloisomerization/allylic alkylation
cascade to synthesize oxazoles
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Allylic alkylation was usually catalyzed by precious metal catalysts such as Pd & Ir, in
comparison zinc salts9 are cheap and readily available, we thereby decided to study this
reaction in detail. Comparing with allylic carbonates or acetates, such reactions of allylic
alcohols10 are more atomꢀeconomic considering water as the only byproduct, and the
whole synthetic process is shorter because allylic carbonates are synthesized from the
corresponding alcohols.11 However because the hydroxyl group is not a good leaving
group, moreover, the in situ formed intermediate M1 is very easy to isomerize into methyl
oxazole 5a in the presence of Brønsted acid or Lewis acid, such a reaction is very
challenging.
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Table 1. Optimization of Reaction Conditionsa
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Entry
Catalyst
Zn(OTf)2
In(OTf)3
1a:2a
2:1
Solvent
DCE
T/oC
60
Yield%b
76
1
2
2:1
DCE
60
56
3
Cu(OTf)2
Ph3PAuNTf2
FeCl3
2:1
DCE
DCE
DCE
DCE
DCE
Toluene
CH3CN
THF
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60
60
60
60
60
60
60
50
70
70
70
70
23
58
<10
<10
21
24
<5
<5
59
93
93
85
0
4c
5
2:1
2:1
6
ZnI2
2:1
7
ZnCl2
2:1
8
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
HOTf
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
1.5:1
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13d
14e
15
DCE
DCE
DCE
DCE
DCE
aReaction conditions: 2a (0.1 mmol), Lewis acid (10 mol%), 4 Å M.S. (50 mg), C2a=0.05 M, 13 h.
bisolated yield. c5 mol% of catalyst. dC2a=0.1 M. e5 mol% of catalyst, C2a=0.1 M.
To test this hypothesis, propargylic amide 1a with allylic alcohol 2a were subjected to
this reaction in the presence of zinc triflate. To our delight, the target product 3a could be
isolated in 76% yield (entry 1, Table 1). Inspired by the observed results, we continued to
optimize the reaction conditions. It turned out that other Lewis acid such as In(OTf)3 and
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Ph3PAuNTf2 could also generate product 3a in less than 60% yields (entries 2ꢀ5). The
reaction of FeCl3 could not produce the coupled product 3a, but only the isomerized
methyl oxazole 5a. Solvent screening showed that DCE is the optimal solvent(entries 8ꢀ
11). The desired product could be isolated in 93% yield by raising the temperature to
70 °C (entry 12). In addition, the use of protic acid HOTf instead of Zn(OTf)2 couldn’t
afford any product.
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With the optimized conditions established, the scope of various propargylic amides
was examined at first. As summarized in Table 2, a large variety of disubstituted or
trisubstituted oxazole derivatives were synthesized in good to excellent yields with very
wide scope. For the paraꢀsubstituted substrates, the reaction afforded the desired products
in good yields (3bꢀg), independent of electronꢀwithdrawing or electronꢀdonating groups.
A series of functional groups such as fluoro, bromo, methoxyl, trifluoromethyl and cyano
were well tolerated under this reaction condition. Substituents at the meta or ortho
position didn’t affect this reaction, giving the corresponding oxazoles in very good yields
(3hꢀj). Substrates bearing a thienyl or styryl group were all suitable substrates for this
transformation and gave the corresponding oxazoles in 75% and 53% yields (3k, 3l). In
addition, adding one more substitutent at the propargylic position could generate fullyꢀ
substituted oxazole derivatives smoothly (3m, 3n).
Next, the scope of allylic alcohols was investigated (Table 3). Various symmetric
diaryl allylic alcohols were suitable substrates for this transformation, giving the
corresponding products in 50ꢀ68% yields (3oꢀq). Gemꢀdiphenyl alcohols 2’ also reacted
smoothly and gave the corresponding functionalized oxazoles in moderate to good yields
(3sꢀ3w). When asymmetric allylic alcohol 2r was used in this reaction, equal amonuts of
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two regioisomers were obtained (3r/3r’= 1/1), which in principle suggested both SN2 and
SN2’ mechanism were involved in this reaction. Unfortunately, other alcohols such as
cinnamyl alcohol and diphenylcarbinol did not react in this transformation. These results
may help to understand the reaction mechanism.
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Table 2. Substrate scope of the propargylic amidesa
aReaction conditions: 1 (0.3 mmol), 2a (0.2 mmol), Zn(OTf)2 (10 mol%), 4 Å M.S. (65 mg), C2a=0.1
M, 70 oC, 13 h, isolated yields were reported.
Table 3. Substrate scope of allylic alcoholsa
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aReaction conditions: 1a (0.3 mmol), 2 (0.2 mmol), Zn(OTf)2 (10 mol%), 4 Å M.S. (65 mg),
C2a=0.1 M, 70 oC, 13 h, isolated yields were reported. bat 60 oC.
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To better understand the reaction process, control experiments were conducted. A
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nonracemicallylic alcohol 2aꢀent (60% ee) was prepared by CBS reduction of chalcone.
When this chiral alcohol 2aꢀent was subjected to the standard reaction, racemic product
3a was obtained (eq3, Scheme 3), which suggested a possible allylcarbenium ion
mechanism. The reaction of 1a in the presence of Zn(OTf)2 could form oxazoline M1 in
70% yield. The isolated M1 was subjected to standard reaction with alcohol 2a, the
product 3a was isolated in 88% yield (eq 4, Scheme 3).
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A plausible mechanism was proposed in Scheme 3. Firstly, Zn(OTf)2 acted as π acid to
activate the triple bond of 1a and subsequent intramolecular 5ꢀexoꢀdig cyclization
forming the oxazoline intermediate M1. At the same time, the zinc catalyst coordinated
with the hydroxyl group and double bond of alcohol 2a to form a relative stable
allylcarbenium ion intermediate M4.12 The intermolecular ene type reaction between
nucelophilic M1 and electrophilic M4 produced the aromatic oxazole derivatives. At the
same time, the released proton and [Zn(OTf)2OH]ꢀ reacted together to regenerate the zinc
catalyst. Thus the SN1 type reaction mechanism led to the racemic product when chiral 2a
was used.
Scheme 3. Control experiments and proposed reaction mechanism
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The obtained allylic oxazoles belong to a unique type of structures, which are difficult
to access by other methods. These compounds could be oxidized to conjugated dienes 4
in the presence of catalytic amounts of Yb(OTf)3 and one equivalent of 2,3ꢀdichloroꢀ5,6ꢀ
dicyanoꢀ1,4ꢀbenzoquinone (DDQ) at room temperature (eq 5).13 Both an electronꢀ
donating group and an electronꢀwithdrawing group were tolerated and gave
functionalized dienes in respectable yields (4c, 4f). The structure of 4f was
unambiguously characterized by single Xꢀray crystallography(for details, see SI).14 These
products all are large conjugated functionalized molecules and might have peculiar
photophysical characters. The UV/Vis absorption and emission spectra of the dienes 4a,
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4c, and 4f in solution were characterized and are shown in Figure 1 (left). They displayed
maximum absorption peak around 370 nm, and exhibited blue emission around 450 nm.
Tetrasubstituted or trisubstituted olefins may have an extraordinary photophysical
phenomenon of aggregationꢀinduced emission (AIE) that is nonꢀemissive or lowꢀ
emissive in solution, but induced to emit efficiently by aggregate formation in the solid
state.15 It is very interesting that the obtained dienes are also AIE active molecules. As
illustrated in Figure 1 (right), when the water fraction increased to 90%, the fluorescence
intensity greatly increased relative to its pure THF solution. As water was a poor solvent
for 4a, increasing the vol% of water in the mix solvent of THF/H2O induced aggregation
of 4a. These functionalized molecules are very promising as blue emissive materials such
as organic lightꢀemitting diodes (OLED).
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Figure 1. UV/Vis absorption and fluorescence spectra of 4a, 4c, 4f in dilute dichloromethane
solution (left). Emission spectra of 4a in THF/H2O solvent mixtures with different volume percents of
H2O (right). Concentration of 10ꢀ5 M.
In conclusion, we have developed a zincꢀcatalyzed cyclization/allylic alkylation
cascade reaction as a convenient synthetic method toward functionalized oxazoles. The
zinc catalyst acted as a π acid to activate Nꢀ(propargyl)arylamides, but also served as σ
acid to facilitate CꢀO bond cleavage of allylic alcohols to form an allylcarbenium ion,
which is the most important feature of this reaction. The allylic oxazoles were easily
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transformed into large πꢀconjugated dienes, which proved to be good AIE luminogens
and will potentially have more applications as the AIE active materials.
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Experimental Section:
General Details. All NMR spectras were recorded on 400 MHz spectrometer. Highꢀ
resolution mass spectrometry (HRMS) were measured in positiveꢀion mode on a QꢀTOF
instrument with an ESI ion source. Routine monitoring of the reaction was performed by
TLC using precoated silica gel plates. All the reagents and solvents used in this reaction
such as DCE were purchased from local company and used directly. Allylic alcohols 2sꢀ
2w were prepared by reported procedure.16
General Procedure for the synthesis of Compounds 3. 2 (0.2 mmol, 0.1 mol/L), 1
(0.30 mmol), Zn(OTf)2(10 mol%) and 4 Å M.S.were mixed in 2 mL DCE. The mixture
was kept stirring at 70oC for 13h. After the reaction was completed (monitored by TLC),
the solution was filtered on celite and then evaporated under reduced pressure.
Purification by flash column chromatography afforded the desired product 3.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3a). Yellow oil (65.3 mg, 93%, pet.
1
ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.98–7.90 (m, 2H), 7.45–7.15 (m,
13H), 6.75 (s, 1H), 6.42 (d, J = 3.1 Hz, 2H), 3.91 (ddd, J = 10.4, 7.2, 2.9 Hz, 1H), 3.30–
13
3.15 (m, 2H); C NMR (100 MHz, CDCl3) δ 160.8, 150.7, 142.8, 137.1, 132.2, 130.7,
130.0, 128.8, 128.7, 128.6, 127.7, 127.6, 127.4, 126.9, 126.309, 126.1, 125.2, 47.7, 32.5;
IR (neat): v (cmꢀ1) 3057, 3025, 1594, 1548, 1489, 1448, 1353, 1264, 1120, 1064, 1025,
962, 826, 773, 734, 709, 688, 547, 525, 491; HRMS exact mass calcd for (C25H21NO+H)
requires m/z 352.1701, found m/z 352.1696.
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(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(pꢀtolyl)oxazole (3b). Yellow oil (62.4 mg, 85%,
5
6
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pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.83 (d, J = 8.0 Hz, 2H), 7.36–
7
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7.13 (m, 12H), 6.72 (s, 1H), 6.41 (d, J = 2.9 Hz, 2H), 3.94–3.83 (m, 1H), 3.27–3.13 (m,
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2H), 2.35 (s, 3H); C NMR (100 MHz, CDCl3) δ 161.1, 150.4, 142.9, 140.2, 137.2,
132.3, 130.7, 129.5, 128.8, 128.6, 127.7, 127.4, 126.9, 126.3, 126.1, 125.12, 125.09, 47.7,
32.5, 21.5; IR (neat): v (cmꢀ1) 3057, 3023, 2918, 1723, 1679, 1599, 1553, 1497, 1451,
1256, 1178, 1113, 1067, 965, 824, 729, 695, 505; HRMS exact mass calcd for
(C26H23NO+H) requires m/z 366.1858, found m/z 366.1864.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(4ꢀmethoxyphenyl)oxazole (3c). Yellow oil (63.6
1
mg, 83%, pet. ether/EtOAc = 10/1). H NMR (400 MHz, CDCl3) δ 7.87 (d, J = 8.8 Hz,
2H), 7.38–7.13 (m, 10H), 6.92 (d, J = 8.8 Hz, 2H), 6.70 (s, 1H), 6.45–6.37 (m, 2H), 3.89
(dd, J = 6.8, 3.3 Hz, 1H), 3.81 (s, 3H), 3.28–3.13 (m, 2H); 13C NMR (100 MHz, CDCl3) δ
161.1, 160.9, 150.1, 142.9, 137.1, 132.3, 130.6, 128.7, 128.6, 127.69, 127.66, 127.4,
126.8, 126.3, 125.0, 120.7, 114.2, 55.4, 47.7, 32.5; IR (neat): v (cmꢀ1) 3059, 3023, 2836,
1611, 1494, 1451, 1358, 1302, 1249, 1169, 1120, 1103, 1025, 962, 833, 739, 692, 610,
522; HRMS exact mass calcd for (C26H23NO2+H) requires m/z 382.1807, found m/z
382.1807.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(4ꢀfluorophenyl)oxazole (3d). Yellow oil (61.4 mg,
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83%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.99–7.78 (m, 2H), 7.37–
7.13 (m, 10H), 7.11–7.01 (m, 2H), 6.73 (s, 1H), 6.42 (d, J = 3.2 Hz, 2H), 3.96–3.79 (m,
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1H), 3.32–3.06 (m, 2H); C NMR (100 MHz, CDCl3) δ 163.8 (d, JCꢀF = 248.0 Hz),
3
160.0, 150.8, 142.8, 137.1, 132.2, 130.7, 128.8, 128.6, 128.1 (d, JCꢀF = 9.0 Hz), 127.6,
127.5, 126.9, 126.3, 125.2, 124.1 (d, 4JCꢀF = 3.0 Hz), 115.9 (d, 2JCꢀF = 22.0 Hz), 47.8, 32.4;
IR (neat): v (cmꢀ1) 3059, 3025, 2916, 1730, 1604, 1558, 1494, 1451, 1412, 1232, 1152,
1123, 1091, 962, 838, 736, 692, 605, 518; HRMS exact mass calcd for (C25H20FNO+H)
requires m/z 370.1607, found m/z 370.1607.
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(E)ꢀ2ꢀ(4ꢀbromophenyl)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)oxazole (3e). Yellow oil (77.0
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mg, 89%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.77 (d, J = 8.4 Hz,
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8
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2H), 7.52 (d, J = 8.4 Hz, 2H), 7.39–7.13 (m, 10H), 6.75 (s, 1H), 6.41 (d, J = 2.6 Hz, 2H),
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3.88 (dd, J = 6.7, 3.5 Hz, 1H), 3.29–3.11 (m, 2H); C NMR (100 MHz, CDCl3) δ 160.0,
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151.1, 142.7, 137.1, 132.1, 132.0, 130.7, 128.8, 128.6, 127.6, 127.53, 127.51, 126.9,
126.6, 126.3, 125.4, 124.4, 47.7, 32.5; IR (neat): v (cmꢀ1) 3057, 3023, 2917, 1724, 1679,
1590, 1553, 1497, 1451, 1256, 1178, 1113, 1067, 965, 827, 729, 695; HRMS exact mass
calcd for (C25H20BrNO+H) requires m/z 430.0807, found m/z 430.0801.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(4ꢀ(trifluoromethyl)phenyl)oxazole (3f). Yellow
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oil (75.7 mg, 90%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 8.02 (d, J =
8.2 Hz, 2H), 7.65 (d, J = 8.3 Hz, 2H), 7.40–7.15 (m, 10H), 6.80 (s, 1H), 6.45–6.39 (m,
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2H), 3.91 (ddd, J = 10.6, 7.2, 3.4 Hz, 1H), 3.32–3.18 (m, 2H); C NMR (100 MHz,
CDCl3) δ 159.4, 151.7, 142.6, 137.0, 132.0, 131.7, 131.4, 130.8, 129.7, 128.8, 128.6,
127.6, 127.5, 127.0, 126.3, 126.2, 126.0, 125.8, 125.8, 125.7, 125.3, 122.6, 47.8, 32.4; IR
(neat): v (cmꢀ1) 3059, 3029, 2921, 1732, 1605, 1558, 1494, 1451, 1418, 1153, 1123, 1091,
972, 838, 737, 692, 609; HRMS exact mass calcd for (C26H20F3NO+H) requires m/z
420.1575, found m/z 420.1578.
(E)ꢀ4ꢀ(5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)oxazolꢀ2ꢀyl)benzonitrile (3g). Yellow solid (37.5
mg, 50%, pet. ether/EtOAc = 10/1): mp 104–106 °C. 1H NMR (400 MHz, CDCl3) δ 8.00
(d, J = 8.4 Hz, 2H), 7.68 (d, J = 8.4 Hz, 2H), 7.41–7.15 (m, 10H), 6.83 (s, 1H), 6.45–6.38
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(m, 2H), 3.90 (ddd, J = 9.5, 7.2, 3.0 Hz, 1H), 3.32–3.18 (m, 2H); C NMR (100 MHz,
CDCl3) δ 158.9, 152.2, 142.5, 136.9, 132.6, 131.9, 131.4, 130.8, 128.8, 128.6, 127.6,
127.0, 126.4, 126.28, 126.27, 126.0, 118.5, 113.2, 47.8, 32.4; IR (neat): v (cmꢀ1) 3059,
3025, 2923, 2221, 1594, 1489, 1448, 984, 972, 836, 756, 741, 690, 651, 549, 486; HRMS
exact mass calcd for (C26H20N2O+H) requires m/z 377.1654, found m/z 377.1652.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(oꢀtolyl)oxazole (3h). Yellow oil (68.6 mg, 94%,
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pet. ether/EtOAc = 20/1). H NMR (400 MHz, CDCl3) δ 7.86 (d, J = 7.7 Hz, 1H), 7.35–
7.15 (m, 13H), 6.80 (s, 1H), 6.44–6.39 (m, 2H), 3.90 (ddd, J = 10.4, 7.1, 3.0 Hz, 1H),
13
3.30–3.17 (m, 2H), 2.60 (s, 3H); C NMR (100 MHz, CDCl3) δ 161.2, 150.2, 142.9,
137.2, 137.1, 132.3, 131.6, 130.7, 129.6, 128.8, 128.7, 128.6, 127.6, 127.4, 126.9, 126.8,
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126.3, 125.9, 125.0, 47.9, 32.4, 22.0; IR (neat): v (cmꢀ1) 3059, 3025, 2923, 1679, 1599,
1492, 1451, 1242, 1108, 962, 729, 695, 525; HRMS exact mass calcd for (C26H23NO+H)
requires m/z 366.1858, found m/z 366.1857.
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(E)ꢀ2ꢀ(2ꢀchlorophenyl)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)oxazole (3i). Yellow oil (62.5 mg,
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60
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81%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.85 (dd, J = 7.3, 2.2 Hz,
1H), 7.48–7.41 (m, 1H), 7.36–7.14 (m, 12H), 6.84 (s, 1H), 6.42 (d, J = 3.1 Hz, 2H), 3.97–
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3.86 (m, 1H), 3.31–3.16 (m, 2H); C NMR (100 MHz, CDCl3) δ 158.7, 151.2, 142.7,
137.1, 132.3, 132.1, 131.2, 130.73, 130.72, 130.67, 128.8, 128.6, 127.6, 127.5, 126.9,
126.8, 126.5, 126.3, 125.3, 47.9, 32.4; IR (neat): v (cmꢀ1) 3057, 3025, 2920, 1599, 1570,
1492, 1451, 1431, 1239, 1130, 1038, 962, 826, 763, 731, 692, 654, 525; HRMS exact
mass calcd for (C25H20ClNO+H) requires m/z 386.1312, found m/z 386.1313.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(mꢀtolyl)oxazole (3j). Yellow oil (65.2 mg, 89%
1
pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.74 (d, J = 9.2 Hz, 2H), 7.40–
6.93 (m, 12H), 6.74 (s, 1H), 6.50–6.12 (m, 2H), 3.91 (dd, J= 6.8, 3.2 Hz, 1H), 3.42–2.88
13
(m, 2H), 2.37 (s, 3H); C NMR (100 MHz, CDCl3) δ 161.0, 150.6, 142.8, 138.5, 137.1,
132.2, 130.8, 130.7, 128.74, 128.65, 128.55, 127.6, 127.4, 126.9, 126.7, 126.3, 125.2,
123.2, 47.8, 32.5, 21.4; IR (neat): v (cmꢀ1) 3057, 3025, 2918, 1599, 1548, 1492, 1451,
1264, 1195, 1118, 1069, 962, 792, 724, 690, 525; HRMS exact mass calcd for
(C26H23NO+H) requires m/z 366.1858, found m/z 366.1860.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ(thiophenꢀ2ꢀyl)oxazole (3k). Yellow oil (53.6 mg,
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75%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.57–7.51 (m, 1H), 7.40–
7.15 (m, 11H), 7.06 (dd, J = 4.8, 3.8 Hz, 1H), 6.69 (s, 1H), 6.44–6.37 (m, 2H), 3.93–3.84
(m, 1H), 3.27–3.13 (m, 2H);13C NMR (100 MHz, CDCl3) δ 157.0, 150.2, 142.7, 137.1,
132.1, 130.7, 130.4, 128.8, 128.6, 127.9, 127.7, 127.6, 127.4, 127.1, 126.9, 126.3, 125.1,
47.6, 32.4; IR (neat): v (cmꢀ1) 3059, 3023, 2906, 1596, 1492, 1448, 1424, 1113, 962, 850,
719, 692, 542, 488; HRMS exact mass calcd for (C23H19NOS+H) requires m/z 358.1266,
found m/z 358.1269.
5ꢀ((E)ꢀ2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀ((E)ꢀstyryl)oxazole (3l). Yellow oil (40.0 mg, 53%,
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pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.48 (d, J = 7.2 Hz, 2H), 7.41–
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7.16 (m, 14H), 6.87 (d, J = 16.4 Hz, 1H), 6.71 (s, 1H), 6.42 (d, J = 3.1 Hz, 2H), 3.90 (ddd,
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J = 10.4, 7.2, 3.0 Hz, 1H), 3.28–3.12 (m, 2H); C NMR (100 MHz, CDCl3) δ 160.7,
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150.4, 142.8, 137.1, 135.7, 135.1, 132.2, 130.7, 129.0, 128.9, 128.8, 128.6, 127.6, 127.5,
127.1, 126.9, 126.3, 125.4, 114.2, 47.7, 32.5; IR (neat): v (cmꢀ1) 3058, 3026, 2921, 1596,
1524, 1494, 1447, 1201, 1111, 1072, 1025, 960, 745, 689, 486; HRMS exact mass calcd
for (C27H23NO+H) requires m/z 378.1858, found m/z 378.1857.
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(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀmethylꢀ4ꢀphenyloxazole (3m). Yellow oil (34.3
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mg, 47%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.54–7.45 (m, 2H),
7.36 (t, J = 7.5 Hz, 2H), 7.32–7.14 (m, 11H), 6.41–6.29 (m, 2H), 3.96 (dd, J = 14.3, 7.1
Hz, 1H), 3.32 (ddd, J = 22.0, 14.9, 7.7 Hz, 2H), 2.41 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 159.6, 145.2, 142.9, 137.2, 135.9, 132.3, 132.0, 130.5, 128.7, 128.6, 128.5,
127.6, 127.4, 127.3, 126.9, 126.8, 126.3, 47.7, 32.7, 13.9; IR (neat): v (cmꢀ1) 3056, 3026,
2924, 1669, 1596, 1492, 1447, 1262, 1072, 962, 745, 693, 530; HRMS exact mass calcd
for (C26H23NO+H) requires m/z 366.1858, found m/z 366.1852.
(E)ꢀ5ꢀ(2,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2,4ꢀdiphenyloxazole (3n). Yellow oil (60.0 mg, 86%,
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pet. ether/EtOAc = 30/1). H NMR (400 MHz, CDCl3) δ 7.99 (dd, J = 6.6, 3.0 Hz, 2H),
7.58 (d, J = 7.3 Hz, 2H), 7.47–7.35 (m, 5H), 7.35–7.12 (m, 11H), 6.49–6.33 (m, 2H),
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4.05 (q, J = 7.3 Hz, 1H), 3.44 (ddd, J = 34.1, 14.9, 7.6 Hz, 2H); C NMR (100 MHz,
CDCl3) δ 159.8, 145.7, 142.8, 137.5, 137.1, 132.3, 132.0, 130.6, 130.1, 128.7, 128.6,
128.5, 127.7, 127.62, 127.61, 127.4, 127.25, 127.24, 126.9, 126.28, 126.25, 47.9, 32.9;
IR (neat): v (cmꢀ1) 3058, 3024, 2921, 1667, 1596, 1555, 1491, 1445, 1069, 1006, 962, 774,
742, 715, 689, 484; HRMS exact mass calcd for (C31H25NO+H) requires m/z 428.2014,
found m/z 428.2018.
(E)ꢀ5ꢀ(2,4ꢀbis(4ꢀfluorophenyl)butꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3o). Yellow oil (52.1
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mg, 68%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.94 (dd, J = 6.5, 3.0
Hz, 2H), 7.47–7.36 (m, 3H), 7.32–7.15 (m, 4H), 7.06–6.90 (m, 4H), 6.75 (s, 1H), 6.31 (dt,
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J = 15.9, 11.3 Hz, 2H), 3.89 (q, J = 7.3 Hz, 1H), 3.20 (qd, J = 15.2, 7.6 Hz, 2H); C
NMR (100 MHz, CDCl3) δ 162.3 (d, 1JCꢀF = 245.0 Hz), 161.7 (d, 1JCꢀF = 243.0 Hz), 160.9,
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150.3, 138.3 (d, JCꢀF = 3.0 Hz), 133.1 (d, JCꢀF = 3.0 Hz), 131.70,131.68, 130.1, 129.6,
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3
129.1 (d, JCꢀF = 8.0 Hz), 128.8, 127.8 (d, JCꢀF = 8.0 Hz), 127.6, 126.0, 125.3, 115.6 (d,
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2JCꢀF = 21.0 Hz), 115.5 (d, JCꢀF = 22.0 Hz), 46.9, 32.5; IR (neat): v (cmꢀ1) 3041, 2921,
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1726, 1599, 1547, 1506, 1447, 1221, 1157, 1120, 1096, 967, 833, 774, 708, 691, 515;
HRMS exact mass calcd for (C25H19F2NO+H) requires m/z 388.1513, found m/z
388.1514.
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(E)ꢀ5ꢀ(2,4ꢀbis(4ꢀchlorophenyl)butꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3p). Yellow oil (41.9
1
mg, 50%, pet. ether/EtOAc = 15/1). H NMR (400 MHz, CDCl3) δ 7.92 (dd, J = 6.6, 3.0
Hz, 2H), 7.46–7.38 (m, 3H), 7.30 (d, J = 8.4 Hz, 2H), 7.24–7.26 (m, 4H), 7.18 (d, J = 8.4
Hz, 2H), 6.75 (s, 1H), 6.35 (d, J = 2.9 Hz, 2H), 3.88 (dt, J = 10.3, 3.6 Hz, 1H), 3.20 (qd, J
13
= 15.2, 7.5 Hz, 2H); C NMR (100 MHz, CDCl3) δ 161.0, 150.1, 140.9, 135.3, 133.2,
132.7, 132.3, 130.1, 129.9, 129.0, 128.9, 128.8, 128.7, 127.6, 127.5, 126.0, 125.3, 47.1,
32.3; IR (neat): v (cmꢀ1) 3026, 2921, 1682, 1594, 1547, 1489, 1447, 1406, 1282, 1120,
1089, 1013, 964, 828, 808, 774, 708, 689, 501; HRMS exact mass calcd for
(C25H19Cl2NO+H) requires m/z 420.0922, found m/z 420.0919.
(E)ꢀ5ꢀ(2,4ꢀdiꢀpꢀtolylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3q). Yellow oil (43.9 mg, 58%,
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pet. ether/EtOAc = 25/1). H NMR (400 MHz, CDCl3) δ 7.97–7.91 (m, 2H), 7.44–7.38
(m, 3H), 7.25–7.18 (m, 2H), 7.17–7.10 (m, 4H), 7.09–7.04 (m, 2H), 6.74 (s, 1H), 6.36 (d,
J = 5.5 Hz, 2H), 3.86 (dd, J = 13.0, 7.4 Hz, 1H), 3.27–3.14 (m, 2H), 2.32 (s, 3H), 2.30 (s,
13
3H); C NMR (100 MHz, CDCl3) δ 160.7, 150.9, 139.9, 137.1, 136.3, 134.4, 131.4,
130.3, 129.9, 129.4, 129.2, 128.7, 127.8, 127.5, 126.2, 126.0, 125.2, 47.2, 32.6, 21.2, 21.0;
IR (neat): v (cmꢀ1) 3019, 2921, 2855, 1594, 1547, 1514, 1484, 1450, 1262, 1118, 1064,
1020, 964, 798, 772, 711, 689, 503; HRMS exact mass calcd for (C27H25NO+H) requires
m/z 380.2014, found m/z 380.2010.
(E)ꢀ2ꢀphenylꢀ5ꢀ(4ꢀphenylꢀ2ꢀ(pꢀtolyl)butꢀ3ꢀenꢀ1ꢀyl)oxazole (E)ꢀ2ꢀphenylꢀ5ꢀ(2ꢀphenylꢀ
4ꢀ(pꢀtolyl)butꢀ3ꢀenꢀ1ꢀyl)oxazole (3r/3r’). Yellow oil (54.9 mg, 75%, pet. ether/EtOAc =
1
15/1). H NMR (400 MHz, CDCl3) δ 7.97–7.91 (m, 2H), 7.45–7.37 (m, 3H), 7.35–7.05
(m, 9H), 6.75 (s, 1H), 6.39 (dd, J = 13.6, 4.2 Hz, 2H), 3.93–3.84 (m, 1H), 3.29–3.15 (m,
2H), 2.32 (s, 1.77H), 2.31 (s, 1.22H); 13C NMR (100 MHz, CDCl3) δ 160.8, 150.8, 142.9,
139.7, 137.2, 136.4, 134.3, 132.4, 131.2, 130.5, 130.4, 129.9, 129.4, 129.2, 128.7, 128.5,
127.8, 127.6, 127.5, 127.4, 126.8, 126.3, 126.2, 126.0, 125.2, 47.7, 47.3, 32.5, 21.2, 21.1;
IR (neat): v (cmꢀ1) 3024, 2921, 1682, 1596, 1547, 1513, 1484, 1447, 1250, 1120, 1064,
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1023, 962, 813, 745, 708, 686, 501; HRMS exact mass calcd for (C26H23NO+H) requires
m/z 366.1858, found m/z 366.1854.
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2ꢀphenylꢀ5ꢀ(2,4,4ꢀtriphenylbutꢀ3ꢀenꢀ1ꢀyl)oxazole (3s). Yellow oil (70.0 mg, 82%, pet.
ether/EtOAc = 20/1). 1H NMR (400 MHz, CDCl3) δ 7.88 (dd, J = 6.6, 2.9 Hz, 2H), 7.44–
7.36 (m, 3H), 7.32 (t, J = 7.5 Hz, 2H), 7.27–7.11 (m, 11H), 6.96–6.87 (m, 2H), 6.78 (s,
1H), 6.27 (d, J = 10.5 Hz, 1H), 3.88 (dt, J = 10.4, 7.4 Hz, 1H), 3.11 (d, J = 7.4 Hz, 2H);
13C NMR (100 MHz, CDCl3) δ 160.9, 150.7, 143.8, 142.9, 142.1, 139.6, 130.6, 130.0,
129.6, 128.8, 128.7, 128.3, 128.1, 127.7, 127.4, 127.32, 127.26, 127.19, 126.7, 126.2,
125.2, 44.4, 33.6; IR (neat): v (cmꢀ1) 3053, 3014, 2919, 1596, 1547, 1489, 1445, 1355,
1262, 1120, 1069, 1023, 977, 830, 759, 688, 630, 574, 532, 464; HRMS exact mass calcd
for (C31H25NO+H) requires m/z 428.2014, found m/z 428.2015.
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5ꢀ(4,4ꢀdiphenylꢀ2ꢀ(pꢀtolyl)butꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3t). Yellow oil (46.9 mg,
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53%, pet. ether/EtOAc = 18/1). H NMR (400 MHz, CDCl3) δ 7.88 (dd, J = 6.4, 3.0 Hz,
2H), 7.44–7.37 (m, 3H), 7.28–7.10 (m, 12H), 6.95–6.88 (m, 2H), 6.78 (s, 1H), 6.25 (d, J
= 10.5 Hz, 1H), 3.85 (dt, J = 10.5, 7.4 Hz, 1H), 3.09 (d, J = 7.4 Hz, 2H), 2.33 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ 160.8, 150.8, 142.6, 142.1, 140.8, 139.6, 136.2, 130.8, 129.9,
129.6, 129.5, 128.6, 128.2, 128.1, 127.7, 127.4, 127.2, 127.11, 127.09, 126.1, 125.1, 43.9,
33.7, 21.1; IR (neat): v (cmꢀ1) 3055, 3021, 2921, 1596, 1545, 1513, 1486, 1443, 1355,
1120, 1072, 1025, 979, 815, 759, 691, 623, 593, 528; HRMS exact mass calcd for
(C32H27NO+H) requires m/z 442.2171, found m/z 442.2158.
5ꢀ(2ꢀ(4ꢀchlorophenyl)ꢀ4,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3u). Yellow oil
(80.4 mg, 87%, pet. ether/EtOAc = 15/1). 1H NMR (400 MHz, CDCl3) δ 7.87 (dd, J = 6.6,
2.9 Hz, 2H), 7.44–7.35 (m, 3H), 7.32–7.10 (m, 12H), 6.94–6.86 (m, 2H), 6.78 (s, 1H),
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6.22 (d, J = 10.4 Hz, 1H), 3.85 (dt, J = 10.2, 7.4 Hz, 1H), 3.08 (d, J = 7.4 Hz, 2H); C
NMR (100 MHz, CDCl3) δ 161.0, 150.3, 143.4, 142.3, 141.9, 139.5, 132.4, 130.0, 129.9,
129.5, 128.9, 128.7, 128.6, 128.3, 128.2, 127.6, 127.5, 127.33, 127.31, 126.1, 125.3, 43.8,
33.6; IR (neat): v (cmꢀ1) 3055, 3021, 2921, 1594, 1547, 1489, 1445, 1357, 1262, 1118,
1089, 1011, 979, 825, 759, 691, 585, 532; HRMS exact mass calcd for (C31H24ClNO+H)
requires m/z 462.1625, found m/z 462.1632.
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5ꢀ(2ꢀ(4ꢀmethoxyphenyl)ꢀ4,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3v). Yellow oil
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(37.2 mg, 41%, pet. ether/EtOAc = 12/1). H NMR (400 MHz, CDCl3) δ 7.91–7.85 (m,
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2H), 7.44–7.37 (m, 3H), 7.27–7.13 (m, 10H), 6.92 (dd, J = 7.6, 1.6 Hz, 2H), 6.87 (d, J =
8.7 Hz, 2H), 6.78 (s, 1H), 6.24 (d, J = 10.5 Hz, 1H), 3.84 (dt, J = 10.6, 7.5 Hz, 1H), 3.79
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(s, 3H), 3.09 (d, J = 7.4 Hz, 2H); C NMR (100 MHz, CDCl3) δ 160.8, 158.3, 150.8,
142.5, 142.1, 139.6, 135.9, 130.9, 129.9, 129.6, 128.6, 128.22, 128.16, 128.10, 127.7,
127.34, 127.25, 127.1, 126.1, 125.1, 114.2, 55.3, 43.5, 33.7; IR (neat): v (cmꢀ1) 3055,
3021, 2924, 2833, 1595, 1547, 1508, 1486, 1443, 1357, 1245, 1174, 1120, 1072, 1030,
977, 828, 762, 691, 625, 593, 542; HRMS exact mass calcd for (C32H27NO2+H) requires
m/z 458.2120, found m/z 458.2119.
5ꢀ(2ꢀ(naphthalenꢀ1ꢀyl)ꢀ4,4ꢀdiphenylbutꢀ3ꢀenꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (3w). Yellow solid
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(50.8 mg, 53%, pet. ether/EtOAc = 15/1): mp 67–69 °C. H NMR (400 MHz, CDCl3) δ
7.88 (dd, J = 11.5, 5.6 Hz, 3H), 7.74 (dd, J = 15.2, 8.3 Hz, 2H), 7.58 (d, J = 7.1 Hz, 1H),
7.51–7.34 (m, 6H), 7.29–7.10 (m, 8H), 6.87 (d, J = 7.2 Hz, 2H), 6.81 (s, 1H), 6.51 (d, J =
13
10.2 Hz, 1H), 4.75 (td, J = 9.6, 5.0 Hz, 1H), 3.22 (ddd, J = 24.5, 15.3, 7.0 Hz, 2H); C
NMR (100 MHz, CDCl3) δ 160.9, 150.8, 143.2, 142.3, 140.3, 139.5, 134.2, 130.8, 130.6,
130.0, 129.7, 129.1, 128.7, 128.22, 128.15, 127.7, 127.6, 127.4, 127.31, 127.26, 126.14,
126.08, 125.7, 125.6, 125.2, 124.3, 123.0, 39.2, 34.0; IR (neat): v (cmꢀ1) 3048, 2953,
2924, 2853, 1596, 1545, 1482, 1445, 1264, 1118, 1069, 1023, 977, 876, 825, 796, 767,
737, 701, 686, 642, 564; HRMS exact mass calcd for (C35H27NO+H) requires m/z
478.2171, found m/z 478.2174.
General Procedure for the synthesis of Compounds 4. To a solution of Yb(OTf)3 (0.02
mmol), 3 (0.2 mmol) in CH2Cl2 (1.5 mL) was slowly added a solution of DDQ (0.2 mmol)
in CH2Cl2 (1.5 mL). The reaction mixture was stirred at room temperature until the
reaction was completed (monitored by TLC). After removal of the solvent under reduced
pressure, the residue was purified through column chromatography.
5ꢀ((1Z,3E)ꢀ2,4ꢀdiphenylbutaꢀ1,3ꢀdienꢀ1ꢀyl)ꢀ2ꢀphenyloxazole (4a). Pale yellow solid
(30.0 mg, 43%, pet. ether/EtOAc = 40/1): mp 105–107 °C. 1H NMR (400 MHz, CDCl3) δ
8.10 (dd, J = 7.3, 2.0 Hz, 2H), 7.95 (d, J= 16.1 Hz, 1H), 7.56–7.28 (m, 14H), 6.63 (d, J =
13
16.1 Hz, 1H), 6.38 (s, 1H); C NMR (100 MHz,CDCl3) δ 161.2, 150.4, 141.2, 141.0,
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137.3, 135.4, 130.5, 129.2, 128.93, 128.88, 128.82, 128.4, 128.2, 128.0, 127.4, 126.9,
126.8, 126.4, 114.5; IR (neat): v (cmꢀ1) 3060, 3021, 2955, 2921, 2850, 1726, 1682, 1472,
1447, 1257, 1130, 1069, 1023, 979, 967, 862, 772, 745, 686, 523,490; HRMS exact mass
calcd for (C25H19NO+H) requires m/z 350.1545, found m/z 350.1564.
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5ꢀ((1Z,3E)ꢀ2,4ꢀdiphenylbutaꢀ1,3ꢀdienꢀ1ꢀyl)ꢀ2ꢀ(4ꢀmethoxyphenyl)oxazole (4c). Pale
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yellow solid (38.1 mg, 51%, pet. ether/EtOAc = 20/1): mp 127–129 °C. H NMR (400
MHz, CDCl3) δ 8.04 (d, J = 8.8 Hz, 2H), 7.94 (d, J = 16.1 Hz, 1H), 7.54–7.24 (m, 11H),
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7.00 (d, J = 8.8 Hz, 2H), 6.62 (d, J = 16.1 Hz, 1H), 6.37 (s, 1H), 3.88 (s, 3H); C NMR
(100 MHz, CDCl3) δ 161.5, 161.4, 149.9, 141.1, 140.6, 137.4, 135.1, 129.2, 128.83,
128.80, 128.4, 128.11, 128.10, 127.9, 126.9, 120.2, 116.4, 114.7, 114.4, 55.4.; IR (neat):
v (cmꢀ1) 3077,2953, 2921, 2850, 1606, 1513, 1482, 1369, 1299, 1248, 1167, 1140, 1106,
1020, 972, 874, 833, 750, 701, 689, 613, 586, 520, 484; HRMS exact mass calcd for
(C26H21NO2+H) requires m/z 380.1651, found m/z 380.1648.
5ꢀ((1Z,3E)ꢀ2,4ꢀdiphenylbutaꢀ1,3ꢀdienꢀ1ꢀyl)ꢀ2ꢀ(4ꢀ(trifluoromethyl)phenyl)oxazole (4f).
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Pale yellow solid (35.1 mg, 42%, pet. ether/EtOAc = 30/1): mp 113–115 °C. H NMR
(400 MHz, CDCl3) δ 8.19 (d, J = 8.2 Hz, 2H), 7.87 (d, J = 16.1 Hz, 1H), 7.73 (d, J = 8.3
13
Hz, 2H), 7.53–7.26 (m, 11H), 6.66 (d, J = 16.1 Hz, 1H), 6.40 (s, 1H); C NMR (100
MHz, CDCl3) δ 159.7, 151.2, 142.3, 140.8, 137.1, 136.1, 130.5, 129.13, 129.11, 128.97,
128.87, 128.85, 128.42, 128.40,128.2, 126.9, 126.5, 125.96, 125.92, 114.1; IR (neat): v
(cmꢀ1) 2960, 2921, 2853, 1689, 1494, 1457, 1374, 1321, 1257, 1164, 1059, 1016, 795,
750, 691,669, 589, 523, 476; HRMS exact mass calcd for (C26H18F3NO+H) requires m/z
418.1419, found m/z 418.1407.
3,3ꢀdiphenylꢀ1ꢀ(pꢀtolyl)propꢀ2ꢀenꢀ1ꢀol (2t). 1H NMR (400 MHz, CDCl3) δ 7.44 – 7.31
(m, 3H), 7.30 – 7.19 (m, 9H), 7.15 (d, J = 7.8 Hz, 2H), 6.29 (d, J = 9.4 Hz, 1H), 5.22 (d, J
13
= 9.4 Hz, 1H), 2.34 (s, 3H), 1.94 (s, 1H); C NMR (100 MHz, CDCl3) δ 143.3, 141.7,
140.6, 139.2, 137.4, 130.3, 129.9, 129.4, 128.4, 128.2, 127.73, 127.68, 127.65, 126.3,
71.6, 21.2; HRMS exact mass calcd for (C22H20OꢀOH) requires m/z 283.1481, found m/z
283.1495.
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1ꢀ(4ꢀmethoxyphenyl)ꢀ3,3ꢀdiphenylpropꢀ2ꢀenꢀ1ꢀol (2v). H NMR (400 MHz, CDCl3) δ
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7.42–7.12 (m, 12H), 6.88 (d, J = 8.6 Hz, 2H), 6.30 (d, J = 9.3 Hz, 1H), 5.21 (d, J = 9.3
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Hz, 1H), 3.79 (s, 3H), 1.94 (s, 1H); C NMR (100 MHz, CDCl3) δ 158.9, 143.0, 141.7,
139.3, 133.9, 129.9, 128.4, 128.11, 128.05, 127.97, 127.6, 127.5, 113.9, 113.7, 74.8, 55.3;
HRMS exact mass calcd for (C22H20O2ꢀOH) requires m/z 299.1430, found m/z 299.1447.
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Supporting Information
1
13
Xꢀray crystal data, H and C NMR spectra and HRMS data.This material is available
free of charge via the Internet at http://pubs.acs.org.
Author Information
Corresponding Author
*Eꢀmail: xuzh@sdu.edu.cn.
*Eꢀmail: jwwang@sdu.edu.cn.
Acknowledgements.
We are grateful for financial support from the Natural Science Foundation of China and
Shandong province (No. 21572118 & JQ201505), China Postdoctoral Science
Foundation, and the fundamental research & subject construction funds of Shandong
University (No 2014JC008, 104.205.2.5).
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