Diversity in Gold-Catalyzed Formal Cycloadditions of Ynamides with Azidoalkenes or 2H-Azirines: [3+2] versus [4+3] Cycloadditions

Article abstract of DOI:10.1002/chem.201500694

Gold-catalyzed cycloadditions of ynamides with azidoalkenes or 2H-azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H-azirine species afford pyrrole products with two regioselectivities when the Cb-substituted 2H-azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron-rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H-benzo[d]azepine products instead.

Full text of DOI:10.1002/chem.201500694

DOI: 10.1002/chem.201500694
Full Paper
&
Reaction Mechanisms
Diversity in Gold-Catalyzed Formal Cycloadditions of Ynamides
with Azidoalkenes or 2H-Azirines: [3+2] versus [4+3]
Cycloadditions
Samir Kundlik Pawar, Rajkumar Lalji Sahani, and Rai-Shung Liu*[a]
Abstract: Gold-catalyzed cycloadditions of ynamides with
azidoalkenes or 2H-azirines give [3+2] or [4+3] formal cyclo-
adducts of three classes. Cycloadditions of ynamides with
2H-azirine species afford pyrrole products with two regio-
selectivities when the Cb-substituted 2H-azirine is replaced
from an alkyl (or hydrogen) with an ester group. For
ynamides substituted with an electron-rich phenyl group,
their reactions with azidoalkenes proceed through novel
[4+3] cycloadditions to deliver 1H-benzo[d]azepine products
instead.
Introduction
Notably, pyrroles and 1H-benzo[d]azepines in Equations (4) and
(5) involve cleavage of the Ca=N bond of 2H-azirine, whereas
the pyrrole products in Equation (3) arise from cleavage of the
CbÀN bond of 2H-azirine. The occurrence of these diverse
products enables precise elucidation of the reaction mecha-
nism, which excludes the intermediacy of gold carbenes (III)
because of improper rationalization of the resulting products
in Equations (4) and (5).[9,10]
Metal-catalyzed cycloadditions are powerful tools to construct
carbo- or heterocyclic frameworks.[1] Organic azides are valu-
able precursors to generate nitrenes in catalytic cycloadditions
to access azacyclic compounds.[2] Related azidoalkenes com-
monly serve as three-atom motifs for several catalytic [3+2] cy-
cloaddition reactions.[3] At elevated temperatures, azidoalkenes
(I) undergo a loss of N2 to form stable 2H-azirines (II).[4,5] Azi-
doalkenes and 2H-azirines, accordingly, are likely to give the
same products under thermal activation. Chiba et al. reported
rhodium-/copper-catalyzed [4+2] formal cycloadditions of 1-
azidostyrene with internal alkynes to form isoquinoline deriva-
tives [Eq (1)].[6] Xiao et al. reported metal-free, light-induced
[3+2] formal cycloadditions of 2H-azirines with alkynes to yield
functionalized pyrrole products through the cleavage of a CÀC
bond of the 2H-azirines [Eq. (2); EWG=electron-withdrawing
group).[7] Immediately prior to completion of this work, Huang
and co-workers reported gold-catalyzed [3+2] formal cycload-
ditions of 2H-azirines with ynamides to form pyrrole derivatives
[Eq. (3)];[8] gold carbenes (III) were postulated as reaction inter-
mediates. The work of Huang and co-workers does not reflect
the diversity of reactions that can generate products of three
types, as depicted in Equations (3)–(5). With the use of azidoal-
kenes, the reactions produce the same compounds as those
described in Huang’s work [Eq. (3)], but the reaction regiose-
lectivity is completely different for those 2H-azirines with a
Cb-substituted ester [Eq. (4)]. Particularly notable are the novel
[4+3] formal cycloadditions between azidoalkenes and
arenynamides with an electron-rich aryl group [Eq. (5)].
Results and Discussion
[a] S. K. Pawar,+ R. L. Sahani,+ Prof. Dr. R.-S. Liu
Department of Chemistry, National Tsing-Hua University
Hsinchu 30013 (Taiwan)
E-mail: rsliu@mx.nthu.edu.tw
[+] These authors contributed equally to this work.
We first examined the reactions of cyclopropyl-substituted
ynamide 1a with 1-azidostyrene 2a over LAuCl/AgNTf2
(L=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) or
(tBu)2(o-biphenyl)P) in CH2Cl2 or nitromethane at 288C, but no
desired pyrrole product 3a formed in a detectable amount.
Table 1, entry 1, depicts the reaction conditions with P(tBu)2(o-
Supporting information for this article is available on the WWW under
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yield (Table 2, entry 12). We also
tested the reaction on 1,2-disub-
stituted azidovinyl species 2e,
resulting in pyrrole species 3n in
63% yield (Table 2, entry 13).
Among these products, we per-
formed XRD on representative
species 3c to elucidate its struc-
ture.[12]
Table 1. Optimized conditions for [3+2] formal cycloadditions.
Entry
Catalyst[a]
Solvent
t
Yield [%][c]
4’[d]
[h]
1a
3a
4’’[d]
[b]
1
2
3
4
5
6
7
LAuCl/AgNTf2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
DCE[e]
11
11
10
12
12
12
12
–
15
–
–
–
65
60
52
84
75
72
–
12
11
33
5
5
8
–
–
–
–
–
–
60
PPh3AuCl/AgNTf2
AuCl3
IPrAuCl/AgNTf2
IPrAuCl/AgSbF6
IPrAuCl/AgNTf2
AgNTf2
We tested the reaction on (E)-
ethyl 3-azidobut-2-enoate (5a),
which gave products in a compli-
cated mixture in hot DCE or
MeNO2 for either IPrAuCl/AgNTf2
or PPh3AuCl/AgNTf2 [Eq. (6)] be-
cause azide species 5a did not
convert into 2H-azirine 5a’ at
–
95
CH3NO2
–
[a] [1a]=0.24m, 4 Š molecular sieves (4 Š MS; 20 mg). Tf=triflyl, Ms=mesyl. [b] L=P(tBu)2(o-biphenyl) or IPr.
[c] Product yields are reported after separation on a column of silica gel. [d] The yields of compound 4’ are
reported based on starting 2a. [e] DCE=1,2-dichloroethane.
biphenyl)AuCl/AgNTf2 in MeNO2 at 808C (11 h); desired cyclo-
Table 2. Scope of [3+2] formal cycloadditions.
adduct 3a and 2,5-diphenylpyrazine 4’[11] were obtained in 65
and 12% yield, respectively. Compound 4’ arose from a dehy-
drogenative dimerization of species 2a under the reaction con-
ditions. The use of PPh3AuCl/AgNTf2 and AuCl3 afforded the
desired cycloadduct 3a in diminished yields, that is, 60 and
52%, respectively (Table 1, entries 2 and 3). To our delight, the
use of IPrAuCl/AgNTf2 in hot nitromethane increased the yield
of desired 3a to 84% (Table 1, entry 4). Changing the silver
source to IPrAuCl/AgSbF6 slightly decreased the yield of cyclo-
adduct 3a to 75% (Table 1, entry 5). Commonly used DCE
appeared to be less efficient than nitromethane, giving 3a in
72% yield (Table 1, entry 6). AgNTf2 alone was catalytically inac-
tive, instead 1-azidostyrene 2a was transformed into 2H-azirine
4’’, whereas ynamide 1a remained intact (Table 1, entry 7).
We expanded the scope of the reaction by using diverse
ynamides 1 with various azidoalkenes 2 to access pyrrole
compounds 3 (Table 2). The reactions of phenyl-substituted
ynamides 1b–d (X=H, Me, and Cl) with (1-azidovinyl)benzene
(2a) and IPrAuCl/AgNTf2 (5 mol%) in hot nitromethane (808C,
11–13 h) gave desired cycloadducts 3b–d in 62–68% yield
(Table 2, entries 1–3). The reaction was extended to thienyl-
substituted ynamide 1e to afford desired 3e in 62% yield
(Table 2, entry 4). The reaction was compatible with 2-en-1-yna-
mide 1 f, yielding pyrrole derivative 3 f in 62% (Table 2,
entry 5). For unsubstituted and alkyl-substituted ynamides 1g
and 1h, their gold-catalyzed cycloadditions with 2a produced
desired products 3g and 3h in 67 and 39% yield, respectively
(Table 2, entries 6 and 7). Such [3+2] formal cycloadditions
were extended to ynamides 1i and 1j, with different sulfona-
mides, giving desired 3i and 3j in 66 and 67% yield, respec-
tively (Table 2, entries 8 and 9). The results in Table 2, entries 10
and 11, show the compatibility of this reaction with various
vinylazides 2b and 2c, which have different 4-phenyl substitu-
ents (4-XC6H4, X=OMe and Cl), giving expected pyrrole
products 3k and 3l in 52 and 56% yield, respectively. For
n-butyl-substituted vinyl azide 2d, its reaction with 2-cyclo-
propyl-1-ynamide 1a afforded pyrrole species 3m in 66%
[a] L=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, [1]=0.24m, 4 Š
MS (20 mg). [b] Product yields are reported after separation on a column
of silica gel.
elevated temperatures. In contrast, the use of 2H-azirine 5a’
with these two catalysts enabled the efficient production of cy-
cloadducts 6a in 82 and 90% yield with IPrAuCl/AgNTf2 or
PPh3AuCl/AgNTf2, respectively [Eq. (7)]. Herein, the regioselec-
tivity of this cycloaddition involves cleavage of the Ca=N bond
of 2H-azirine, which is distinct from those instances in Table 2
and Equation (3), which involve the cleavage of a single CbÀN
bond.
The results in Table 3 show the substrate scope of the reac-
tion. Herein, ynamides 1 were treated with ethyl 2H-azirine-2-
carboxylates 5 (1.2 equiv) and AuClPPh3/AgNTf2 (5 mol%) in
DCE (288C) for 3–11 h, producing cycloadducts 6b–i in
reasonable yields (74–86%). We first tested the reactions on
phenyl-substituted ynamides 1b, 1k, and 1l (X=H, OMe, and
CF3), affording desired 6b–d in 75–86% yield. These cyclo-
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Table 4. Scope of gold-catalyzed [4+3] formal cycloadditions.
Table 3. Distinct regioselectivity of ethyl 2H-azirine-2-carboxylates.
[a] [7]=0.24m, 4 Š MS (20 mg). [b] Product yields are reported after
separation on a column of silica gel.
cycloadduct 8i in 42% yield, together with pyrrole species 9i
in 29% yield (Table 4, entry 9). For 3-thienyl-substituted
ynamide 7g, its reaction with 2a gave [4+3] cycloadduct 8j
efficiently (72%; Table 4, entry 10). Among these [4+3] cyclo-
adducts, we undertook XRD analysis of compounds 8a and 8j
to confirm their 3H-azepine frameworks.[12]
[a] [1]=0.23m, 4 Š MS (20 mg). [b] Product yields are reported after
separation on a column of silica gel.
additions were applicable to thienyl-substituted ynamide 1e,
which yielded pyrrole derivative 6e in 82% (Table 3, entry 4).
These cycloadditions proceeded well with alkenyl- and alkyl-
substituted ynamides 1 f and 1m; the corresponding products
6 f and 6g were obtained in 74 and 82% yield, respectively
(Table 3, entries 5 and 6). The results in Table 3, entries 7 and 8,
show the compatibility of such cycloadditions with ethyl
2H-azirine-2-carboxylates 5b and 5c, which gave the corre-
sponding products 6h and 6i in satisfactory yields (Table 3,
entries 7 and 8). XRD of cycloadduct 6b was undertaken to
verify its proposed structure.[12]
We conducted experiments to confirm that 2H-azirine 4’’
was produced in 91% yield by heating 2a in hot nitromethane
(808C, 8 h); species 4’’ thereby underwent dimerization to
form 2,5-diphenylpyrazine 4’ selectively [Eq. (8)].[11] We ob-
served such a pyrazine derivative 4’ during catalyst screening
experiments (see Table 1). Particularly notable was the use of
2H-azirine 4’’, which reacted with cyclopropyl- and 3-thienyl-
substituted ynamides 1a and 7g to yield desired [3+2] and
[4+3] cycloadducts 3a and 8j selectively [Eqs. (9) and (10)].
We postulate that these cycloadditions might proceed through
an initial transformation of 2a into 4’’, which is an active inter-
mediate in this catalytic system.
Surprisingly, new [4+3] formal cycloadditions occur with
those ynamides with R1 =Me or OMe at their meta-phenyl po-
sitions, as exemplified by species 7a–f (Table 4); the conditions
are the same as those outlined in Table 2. We tested the cata-
lytic reactions of 2a with arenynamides 7a and 7b (R1 =Me),
which contained two distinct sulfonamides, yielding 1H-ben-
zo[d]azepine derivatives 8a and 8b in 47 and 48%, respective-
ly; competing pyrrole species 9a and 9b were produced in 23
and 24% yield, respectively. The [4+3] formal cycloadducts 8c
and 8d were produced in satisfactory yields (74 and 60%, re-
spectively) from 2a and arenynamides 7c and 7d, which con-
tained 3,5- and 3,4-dimethylphenyl groups (Table 4, entries 3
and 4). Such cycloaddition reactions were compatible with var-
ious 1-azidostyrenes 2a–c (Ar=4-XC6H4; X=H, Cl, and OMe)
that reacted with arenynamide 7e (R1 =OMe) to form [4+3]
formal cycloadducts 8e–g in 59–72% yields (Table 4, entries 5–
7). This [4+3] cycloaddition can be extended to arenynamide
7 f, which contains a 3,4-dimethoxyphenyl group, giving the
expected cycloadduct 8h in 78% yield (Table 4, entry 8). The
formal cycloaddition of 7e with 2e afforded the corresponding
We postulate the reaction mechanism in Scheme 1 to ration-
alize the resulting three types of cycloadducts. These products
begin with the addition of 2H-aziridines on gold p-alkyne A to
yield common intermediates B. Because the 2H-aziridine ring
of species B also has an iminium character, we accordingly
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afforded [3+2] pyrrole products with two distinct regio-
selectivities, depending on the substituents of the 2H-azirines.
For ynamides substituted with an electron-rich phenyl group,
their reactions with azidoalkenes proceeded through novel
[4+3] cycloadditions[14] to deliver 1H-beno[d]azepine products
instead. The presence of such diverse cycloadducts provides
precise information on the mechanism of cycloaddition; thus
excluding gold carbenes as reaction intermediates.
Experimental Section
General
Scheme 1. Proposed mechanisms for diverse products.
Unless otherwise noted, all reactions were carried out under a nitro-
gen atmosphere in oven-dried glassware by using standard
syringe, cannula, and septa apparatus. THF and hexane were dried
with sodium benzophenone and distilled before use. CH2Cl2, DCE,
and toluene were dried over CaH2 and distilled before use. Nitro-
methane was dried over activated 4 Š MS. Et3N and CH3NO2 were
stored over 4 Š MS prior to use. Reagents were purchased from
commercial sources and used without purification, unless other-
wise stated. 1H and 13C NMR spectra were recorded on Varian
400 MHz, Varian 500 MHz, Bruker 400 MHz, and Bruker 600 MHz
spectrometers by using CDCl3, CD2Cl2, and C6D6 as internal
standards.
postulate phenyl attack of those ynamides with an electron-
rich group (R1 =3-XC6H4) at their azirine rings, ultimately giving
desired product 8e (X=OMe). For other ynamides and 2H-
aziridines (X=H, CO2Et), their corresponding intermediates B
undergo a 1,2-hydrogen shift to form new intermediates C. In
the case of 2H-aziridines with X=H, species D undergoes intra-
molecular cyclization through alkene attack at the less
hindered CH= carbon of the aziridine ring, yielding pyrrole
product 3a. For 2H-aziridines with an ester moiety, the corre-
sponding intermediate E prefers a Michael-type reaction, in
which the =CHPh carbon is attacked by this tethered alkene,
further yielding pyrrole products 6h.
Our mechanism opposes the intermediacy of gold carbenes
that are postulated by Huang et al.[8] because they cannot
rationalize products 6h and 8e. As depicted in Equation (11),
gold-driven ring opening of an azirinium ring of species B is
expected to give gold carbene F, which undergoes an aza-
Nazarov cyclization[13] to give pyrrole products with different
structures from our resulting product 6h (R1 =cyclopropyl).
Similarly, although the electron-rich benzene group of gold
carbenes G can attack at the CH2=CPh carbon, the resulting
seven-membered product is expected to have a structure
distinct from our observed product 8e [X=OMe; Eq. (12)].
Accordingly, the intermediacy of gold carbenes is unlikely to
occur here.
Standard procedure for synthesis of 3a
A solution of 1a (100 mg, 0.58 mmol) and 2a (109 mg, 0.75 mmol)
in nitromethane (1.5 mL) at 288C was added to a solution of
[1,3-bis(diisopropylphenyl)imidazol-2-ylidene]AuCl
(17.9 mg,
0.03 mmol), silver bis(trifluoromethanesulfonyl)imide (11.2 mg,
0.03 mmol), and powdered 4 Š MS (20 mg) in nitromethane
(0.5 mL). The resulting solution was stirred at 808C for 12 h before
it was filtered through a short Celite pad, concentrated, and eluted
through a column of silica gel (10% ethyl acetate/hexane, Rf =0.3
in 25% ethyl acetate/hexane system) to afford compound 3a
(141 mg, 0.48 mmol, 84%) as a pale yellow solid.
Standard procedure for synthesis of 6a
A solution of 1a (100 mg, 0.58 mmol) and 5a’ (88 mg, 0.69 mmol)
in DCE (2.0 mL) at 288C was added to a solution of PPh3AuCl
(14.3 mg, 5 mol%), silver bis(trifluoromethanesulfonyl)imide
(11.2 mg, 5 mol%), and powdered 4 Š MS (20 mg) in DCE (0.5 mL).
The resulting solution was stirred at RT for 8 h before it was filtered
through a short Celite pad, concentrated, and eluted through
a column of silica gel (20% ethyl acetate/hexane system) to afford
compound 6a (156 mg, 0.52 mmol, 90%) as a white solid.
Standard procedure for synthesis of 8a
A solution of 7a (100 mg, 0.45 mmol) and 2a (85 mg, 0.58 mmol)
in nitromethane (1.5 mL) at 288C was added to a solution of [1,3-
bis(diisopropylphenyl)imidazol-2-ylidene]AuCl (13.9 mg, 5 mol%),
silver bis(trifluoromethanesulfonyl)imide (8.7 mg, 5 mol%), and
powdered 4 Š MS (20 mg) in nitromethane (0.5 mL). The resulting
solution was stirred at 808C for 16 h before it was filtered through
a short Celite pad, concentrated, and eluted through a column of
silica gel (8% ethyl acetate/hexane, Rf =0.3 in 20% ethyl acetate/
hexane system) to afford compound 8a (72 mg, 0.21 mmol, 47%)
as a white solid and 9a (35 mg, 0.10 mmol, 23%) as a colorless
viscous liquid.
Conclusion
Diverse chemoselectivity of gold-catalyzed cycloadditions of
ynamides with azidoalkenes or 2H-azirines was described. Our
control experiments indicated that the initial azidoalkenes
were thermally converted into 2H-azirines to activate the reac-
tions. Formal cycloadditions of ynamides with 2H-aziridines
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Compound 3a: Pale yellow solid (141 mg, 84%); m.p. 195–1968C;
1H NMR (600 MHz, CDCl3): d=8.51 (s, 1H), 7.39–7.38 (m, 2H), 7.32–
7.29 (m, 2H), 7.19–7.17 (m, 1H), 6.97 (d, J=3.0 Hz, 1H), 3.38 (s,
3H), 3.02 (s, 3H), 1.65–1.61 (m, 1H), 0.91–0.88 (m, 2H), 0.66–
0.63 ppm (m, 2H); 13C NMR (150 MHz, CDCl3): d=131.9, 130.0,
128.8, 126.6, 125.2, 123.8, 122.6, 101.9, 38.4, 37.6, 7.7, 6.8 ppm;
HRMS: m/z calcd for C15H18N2O2S: 290.1089; found: 290.1100.
2H), 7.27–7.17 (m, 6H), 6.42 (d, J=3.0 Hz, 1H), 3.10 (s, 3H), 2.95 (t,
J=7.5 Hz, 2H), 2.83 (s, 3H), 2.74 ppm (t, J=7.5 Hz, 2H); 13C NMR
(150 MHz, CD2Cl2): d=142.5, 132.5, 130.5, 129.3, 128.9, 128.8, 127.0,
126.4, 125.6, 124.1, 120.9, 106.1, 38.8, 38.0, 37.1, 28.1 ppm; HRMS:
m/z calcd for C20H22N2O2S: 354.1402; found: 354.1404.
Compound 3i: White solid (94.5 mg, 66%); m.p. 152–1538C;
1H NMR (600 MHz, CDCl3): d=8.98 (s, 1H), 7.54–7.52 (m, 2H), 7.39–
7.16 (m, 13H), 6.66 (d, J=3.1 Hz, 1H), 2.89 ppm (s, 3H); 13C NMR
(150 MHz, CDCl3): d=141.6, 134.1, 131.6, 131.5, 129.4, 128.9, 128.5,
127.4, 127.1, 126.8, 125.8, 124.1, 123.4, 123.1, 122.3, 105.9,
40.6 ppm; HRMS: m/z calcd for C23H20N2O2S: 388.1245; found:
388.1250.
Compound 3b: Pale yellow solid (106 mg, 68%); m.p. 178–1798C;
1H NMR (600 MHz, CDCl3): d=8.89 (s, 1H), 7.52–7.51 (m, 2H), 7.48–
7.47 (m, 2H), 7.40–7.38 (m, 2H), 7.37–7.34 (m, 2H), 7.28–7.22 (m,
2H), 6.61 (d, J=3.1 Hz, 1H), 3.34 (s, 3H), 2.74 ppm (s, 3H); 13C NMR
(150 MHz, CDCl3): d=134.4, 131.6, 130.9, 128.9, 128.7, 127.0, 126.9,
126.7, 124.0, 121.4, 105.2, 38.8, 38.6 ppm (one aromatic quaternary
carbon merged); HRMS: m/z calcd for C18H18N2O2S: 326.1089;
found: 326.1090.
Compound 3j: Pale yellow solid (77.6 mg, 67%); m.p. 157–1588C;
1H NMR (600 MHz, CDCl3): d=8.71 (s, 1H), 7.57 (d, J=8.1 Hz, 2H),
7.48 (d, J=8.2 Hz, 2H), 7.38 (t, J=7.5 Hz, 2H), 7.25–7.24 (m, 1H),
7.19 (d, J=8.1 Hz, 2H), 7.11–7.07 (m, 3H), 6.82–6.81 (m, 2H), 6.50
(d, J=3.2 Hz, 1H), 3.16 (s, 3H), 2.38 ppm (s, 3H); 13C NMR
(150 MHz, CDCl3): d=144.0, 134.9, 134.3, 131.8, 129.8, 129.6, 128.9,
128.0, 127.6, 127.2, 126.8, 126.2, 124.3, 123.8, 120.9, 105.6, 38.3,
21.5 ppm; HRMS: m/z calcd for C24H22N2O2S: 402.1402; found:
402.1410.
Compound 3c: White solid (99 mg, 65%); m.p. 186–1878C;
1H NMR (600 MHz, CDCl3): d=8.75 (s, 1H), 7.48–7.47 (m, 2H), 7.41–
7.40 (m, 2H), 7.37–7.35 (m, 2H), 7.25–7.23 (m, 1H), 7.22–7.19 (m,
2H), 6.59 (d, J=3.1 Hz, 1H), 3.33 (s, 3H), 2.75 (s, 3H), 2.36 ppm (s,
3H); 13C NMR (150 MHz, CDCl3): d=136.4, 131.7, 131.4, 130.8,
129.4, 128.9, 127.0, 126.9, 124.0, 123.9, 121.4, 105.3, 38.7, 38.6,
21.1 ppm; HRMS: m/z calcd for C19H20N2O2S: 340.1245; found:
340.1251.
Compound 3k: White solid (96.2 mg, 52%); m.p. 135–1368C;
1H NMR (600 MHz, CDCl3): d=8.29 (s, 1H), 7.32–7.31 (m, 2H), 6.87–
6.85 (m, 2H), 5.85 (d, J=3.0 Hz, 1H), 3.79 (s, 3H), 3.36 (s, 3H), 3.01
(s, 3H), 1.61–1.59 (m, 1H merged with water signal from CDCl3),
0.89–0.87 (m, 2H), 0.64–0.62 ppm (m, 2H); 13C NMR (150 MHz,
CDCl3): d=158.6, 130.1, 125.2, 124.9, 124.6, 122.5, 114.3, 100.9,
55.3, 38.4, 37.6, 7.7, 6.9 ppm; HRMS: m/z calcd for C16H20N2O3S:
320.1195; found: 320.1197.
Compound 3d: Pale yellow solid (91.8 mg, 62%); m.p. 203–2048C;
1H NMR (600 MHz, CDCl3): d=8.88 (s, 1H), 7.47–7.44 (m, 4H), 7.37–
7.35 (m, 4H), 7.26–7.23 (m, 1H), 6.57 (d, J=3.1 Hz, 1H), 3.33 (s,
3H), 2.77 ppm (s, 3H); 13C NMR (150 MHz, CDCl3): d=132.8, 132.4,
131.4, 131.2, 128.9, 128.1, 127.2, 124.1, 124.0, 120.2, 104.9, 38.9,
38.5 ppm (two aromatic CH merged); HRMS: m/z calcd for
C18H17ClN2O2S: 360.0699; found: 360.0695.
Compound 3l: Pale yellow solid (105 mg, 56%); m.p. 170–1718C;
1H NMR (600 MHz, CD2Cl2): d=8.48 (s, 1H), 7.37–7.35 (m, 2H), 7.33–
7.31 (m, 2H), 6.02 (d, J=3.1 Hz, 1H), 3.37 (s, 3H), 3.04 (s, 3H), 1.65–
1.56 (m, 1H), 0.93–0.90 (m, 2H), 0.66–0.63 ppm (m, 2H); 13C NMR
(150 MHz, CD2Cl2): d=132.4, 131.0, 129.4, 128.9, 126.4, 125.3, 123.4,
103.0, 38.7, 38.1, 7.9, 7.1 ppm; HRMS: m/z calcd for C15H17ClN2O2S:
324.0699; found: 324.0693.
Compound 3e: Pale yellow solid (95.7 mg, 62%); m.p. 155–1568C;
1H NMR (600 MHz, CDCl3): d=9.04 (s, 1H), 7.48–7.46 (m, 2H), 7.36–
7.33 (m, 2H), 7.25–7.21 (m, 2H), 7.17–7.16 (dd, J=1.1, 3.5 Hz, 1H),
7.06–7.05 (m, 1H), 6.61 (d, J=3.1 Hz, 1H), 3.36 (s, 3H), 2.91 ppm (s,
3H); 13C NMR (150 MHz, CDCl3): d=135.9, 131.4, 131.2, 128.8,
127.3, 127.1, 124.1, 123.6, 123.5, 123.3, 115.7, 104.5, 39.0, 38.3 ppm;
HRMS: m/z calcd for C16H16N2O2S2: 332.0653; found: 332.0650.
Compound 3m: Brown viscous liquid (103 mg, 66%); 1H NMR
(600 MHz, CDCl3): d=7.87 (s, 1H), 5.36 (d, J=3.0 Hz, 1H), 3.30 (s,
3H), 2.96 (s, 3H), 2.43 (t, J=7.7 Hz, 2H), 1.56–1.49 (m, 3H), 1.34–
1.30 (m, 2H), 0.88 (t, J=7.4 Hz, 3H), 0.82–0.80 (m, 2H), 0.55–
0.53 ppm (m, 2H); 13C NMR (150 MHz, CDCl3): d=131.3, 122.3,
120.8, 101.1, 38.4, 37.4, 31.3, 27.5, 22.4, 13.8, 7.6, 6.8 ppm; HRMS:
m/z calcd for C13H22N2O2S: 270.1402; found: 270.1403.
Compound 3 f: Pale yellow solid (85.3 mg, 62%); m.p. 196–1978C;
1H NMR (600 MHz, CDCl3): d=8.69 (s, 1H), 7.68 (d, J=8.3 Hz, 2H),
7.50–7.48 (m, 2H), 7.36 (t, J=7.5 Hz, 2H), 7.25–7.22 (m, 5H), 7.16–
7.14 (m, 1H), 7.01–7.00 (m, 2H), 6.59 (d, J=2.9 Hz, 1H), 6.55 (d, J=
16.1 Hz, 1H), 5.78 (d, J=16.1 Hz, 1H), 3.34 (s, 3H), 2.20 ppm (s,
3H); 13C NMR (150 MHz, CDCl3): d=144.3, 137.5, 134.6, 131.6,
131.0, 129.7, 128.9, 128.4, 127.8, 126.9, 126.8, 126.7, 125.9, 125.7,
123.9, 119.1, 118.7, 102.0, 39.6, 21.3 ppm; HRMS: m/z calcd for
C26H24N2O2S: 428.1558; found: 428.1555.
Compound 3n: White solid (110 mg, 63%); m.p. 156–1578C;
1H NMR (600 MHz, CDCl3): d=8.11 (s, 1H), 7.38–7.35 (m, 4H), 7.24–
7.22 (m, 1H), 3.30 (s, 3H), 3.00 (s, 3H), 2.19 (s, 3H), 1.55–1.51 (m,
1H), 0.86–0.83 (m, 2H), 0.63–0.61 ppm (m, 2H); 13C NMR (150 MHz,
CDCl3): d=132.9, 128.6, 126.8, 126.6, 126.4, 124.8, 119.7, 116.3,
38.6, 38.5, 10.7, 6.1, 5.2 ppm; HRMS: m/z calcd for C16H20N2O2S:
304.1245; found: 304.1246.
Compound 3g: Pale yellow solid (96 mg, 67%); m.p. 182–1838C;
1H NMR (600 MHz, C3D6O): d=10.52 (s, 1H), 7.60 (d, J=8.4 Hz, 2H),
7.47–7.45 (m, 2H), 7.41–7.40 (m, 2H), 7.36–7.34 (m, 4H), 7.28–7.25
(m, 3H), 7.12–7.10 (m, 2H), 6.25–6.24 (m, 1H), 2.45 ppm (s, 3H);
13C NMR (150 MHz, C3D6O): d=144.9, 142.4, 137.4, 136.7, 130.3,
129.9, 129.8, 129.3, 128.9, 128.5, 128.1, 126.1, 125.4, 124.9, 114.2,
104.5, 21.5 ppm; HRMS: m/z calcd for C23H20N2O2S: 388.1245;
found: 388.1247.
Compound 6a: White solid (156 mg, 90%); m.p. 133–1368C;
1H NMR (400 MHz, CDCl3): d=8.62 (brs, 1H), 4.25 (q, J=7.1 Hz,
2H), 3.18 (s, 3H), 3.01 (s, 3H), 2.36 (s, 3H), 1.84–1.80 (m, 1H), 1.31
(t, J=7.1 Hz, 3H), 0.84–0.80 (m, 2H), 0.61–0.57 ppm (m, 2H);
13C NMR (100 MHz, CDCl3): d=165.4, 134.2, 122.7, 121.6, 111.5, 59.3,
Compound 3h: Colorless viscous oil (58.3 mg, 39%); 1H NMR
(600 MHz, CD2Cl2): d=8.42 (s, 1H), 7.48–7.46 (m, 2H), 7.39–7.36 (m,
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38.9, 38.5, 14.4, 13.7, 7.4, 6.4 ppm; HRMS: m/z calcd for
C13H20N2O4S: 300.1144; found: 300.1140.
Compound 6i: White solid (178 mg, 85%); m.p. 180–1848C;
1H NMR (400 MHz, CDCl3): d=8.65 (s, 1H), 7.39 (q, J=7.8 Hz, 2H),
7.32 (d, J=7.1 Hz, 3H), 4.15 (q, J=7.1 Hz, 2H), 3.24 (s, 3H), 2.98 (s,
3H), 1.89–1.82 (m, 1H), 1.14 (t, J=7.1 Hz, 3H), 0.88–0.84 (m, 2H),
0.66–0.62 ppm (q, J=5.5 Hz, 2H); 13C NMR (150 MHz, CDCl3): d=
165.2, 134.5, 131.8, 128.7, 128.2, 128.0, 125.2, 121.9, 112.5, 59.7,
38.7, 38.5, 13.9, 7.1, 6.3 ppm; HRMS: m/z calcd for C18H22N2O4S:
362.1300; found: 362.1300.
Compound 6b: White solid (135 mg, 84%); m.p. 199–2038C;
1H NMR (600 MHz, CDCl3): d=9.09 (s, 1H), 7.40 (t, J=7.5 Hz, 2H),
7.33 (d, J=7.3 Hz, 1H), 7.24 (d, J=6.5 Hz, 2H), 4.32 (q, J=7.1 Hz,
2H), 3.14 (s, 3H), 2.57 (s, 3H), 2.21 (s, 3H), 1.35 ppm (t, J=7.1 Hz,
3H); 13C NMR (150 MHz, CDCl3): d=161.0, 133.3, 129.9, 128.6,
127.5, 127.4, 126.2, 122.5, 117.2, 60.3, 38.9, 38.2, 14.5, 11.0 ppm;
HRMS: m/z calcd for C16H20N2O4S: 336.1144; found: 336.1137.
Compound 8a: Pale yellow solid (71.7 mg, 47%); m.p. 161–1638C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.38–7.34 (m, 5H), 7.27 (s,
1H), 7.19 (s, 1H), 7.06 (s, 2H), 4.63 (d, J=12.7 Hz, 1H), 3.22 (s, 3H),
3.11 (s, 3H), 2.79 (d, J=12.7 Hz, 1H), 2.38 ppm (s, 3H); 13C NMR
(150 MHz, CDCl3 at À508C): d=147.9, 140.9, 139.6, 133.6, 132.9,
131.8, 131.1, 129.5, 128.9, 128.3, 127.9, 127.7, 127.3, 39.4, 37.9, 35.8,
21.3 ppm; HRMS: m/z calcd for C19H20N2O2S: 340.1245; found:
340.1250.
Compound 6c: White solid (115 mg, 75%); m.p. 187–1908C;
1H NMR (600 MHz, CDCl3): d=8.94 (s, 1H), 7.15 (d, J=8.4 Hz, 2H),
6.94 (d, J=9.0 Hz, 2H), 4.31 (q, J=7.2 Hz, 2H), 3.82 (s, 3H), 3.13 (s,
3H), 2.61 (s, 3H), 2.19 (s, 3H), 1.35 ppm (t, J=7.2 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d=160.9, 159.0, 131.1, 127.4, 126.4, 125.4, 122.1,
117.0, 114.0, 60.2, 55.2, 38.8, 38.3, 14.5, 11.0 ppm; HRMS: m/z calcd
for C17H22N2O5S: 366.1249; found: 366.1247.
Compound 9a: Colorless viscous liquid (35 mg, 23%); 1H NMR
(600 MHz, CDCl3): d=8.67 (s, 1H), 7.49–7.48 (m, 2H), 7.36 (t, J=
7.7 Hz, 2H), 7.32–7.30 (m, 2H), 7.27 (t, J=7.5 Hz, 1H), 7.25–7.22 (m,
1H), 7.08 (d, J=7.4 Hz, 1H), 6.60 (d, J=3.1 Hz, 1H), 3.34 (s, 3H),
2.74 (s, 3H), 2.38 ppm (s, 3H); 13C NMR (150 MHz, CDCl3): d=138.3,
134.3, 131.7, 130.8, 128.9, 128.6, 127.9, 127.5, 126.9, 124.1, 124.0,
121.5, 105.4, 38.8, 38.6, 21.6 ppm (one aromatic quaternary carbon
merged); HRMS: m/z calcd for C19H20N2O2S: 340.1245; found:
340.1248.
Compound 6d: White solid (125 mg, 86%); m.p. 204–2078C;
1H NMR (600 MHz, CDCl3): d=9.26 (brs, 1H), 7.67 (d, J=8.0 Hz,
2H), 7.39 (d, J=8.0 Hz, 2H), 4.34 (q, J=7.1 Hz, 2H), 3.13 (s, 3H),
2.66 (s, 3H), 2.22 (s, 3H), 1.36 ppm (t, J=7.1 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d=160.9, 137.2, 130.1, 129.6 (q, J(C,F)=30.0 Hz),
127.5, 125.8, 125.5 (d, J(C,CF3)=3.3 Hz), 124.0 (d, J(C,CF3)=
271.0 Hz), 121.3, 117.7, 60.5, 38.8, 38.6, 14.4, 11.1 ppm; HRMS: m/z
calcd for C17H19F3N2O4S: 404.1018; found: 404.1022.
Compound 8b: Pale yellow solid (67 mg, 48%); m.p. 164–1658C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.67 (d, J=8.3 Hz, 2H),
7.35–7.31 (m, 7H), 7.18 (s, 1H), 7.00 (s, 2H), 6.67 (s, 1H), 4.79 (d, J=
12.7 Hz, 1H), 3.09 (s, 3H), 2.72 (d, J=12.7 Hz, 1H), 2.44 (s, 3H),
2.29 ppm (s, 3H); 13C NMR (150 MHz, CDCl3 at À508C): d=148.4,
144.6, 140.9, 139.3, 134.8, 133.6, 132.9, 131.8, 130.5, 129.9, 129.4,
128.5, 128.2, 128.1, 127.5, 127.2, 127.1, 38.5, 36.5, 21.7, 21.2; HRMS:
m/z calcd for C25H24N2O2S: 416.1558; found: 416.1553.
Compound 6e: White solid (130 mg, 82%); m.p. 148–1508C;
1H NMR (400 MHz, CDCl3): d=9.01 (s, 1H), 7.29 (dd, J=4.96, 1.2 Hz,
1H), 7.02–6.98 (m, 2H), 4.10 (q, J=7.1 Hz, 2H), 3.18 (s, 3H), 2.64 (s,
3H), 2.44 (s, 3H), 1.10 ppm (t, J=7.1 Hz, 3H); 13C NMR (150 MHz,
CDCl3): d=164.6, 134.3, 134.2, 128.0, 126.6, 125.3, 124.5, 113.8,
111.2, 59.3, 39.5, 38.0, 13.9, 13.5 ppm; HRMS: m/z calcd for
C14H18N2O4S2: 342.0708; found: 342.0703.
Compound 6 f: White solid (114 mg, 74%); m.p. 172–1748C;
1H NMR (600 MHz, CDCl3): d=8.94 (s, 1H), 7.57 (d, J=16.7 Hz, 1H),
7.45 (d, J=7.3 Hz, 2H), 7.31 (t, J=7.2 Hz, 2H), 7.23 (d, J=7.0 Hz,
1H), 6.86 (d, J=16.8 Hz, 1H), 4.30 (q, J=6.8 Hz, 2H), 3.32 (s, 3H),
2.95 (s, 3H), 2.43 (s, 3H), 1.36 ppm (t, J=7.0 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d=165.3, 137.8, 134.8, 129.7, 128.6, 127.4, 126.0,
122.4, 120.6, 118.4, 110.0, 59.6, 39.3, 38.0, 14.4, 13.9 ppm; HRMS:
m/z calcd for C18H22N2O4S: 362.1300; found: 362.1304.
1
Compound 9b: Pale yellow viscous liquid (33 mg, 24%); H NMR
(600 MHz, CDCl3): d=8.92 (s, 1H), 7.59 (d, J=8.1 Hz, 2H), 7.51 (d,
J=8.1 Hz, 2H), 7.39 (t, J=7.6 Hz, 2H), 7.26–7.24 (m, 3H), 7.00 (t,
J=7.6 Hz, 1H), 6.92 (d, J=7.5 Hz, 1H), 6.63 (d, J=7.6 Hz, 1H), 6.50
(d, J=3.2 Hz, 1H), 6.30 (s, 1H),3.34 (s, 3H), 2.74 ppm (s, 3H), 2.38
(s, 3H); 13C NMR (150 MHz, CDCl3): d=144.1, 137.4, 133.9, 131.4,
129.8, 129.3, 128.8, 127.9, 127.6, 127.3, 126.8, 126.6, 124.2, 123.8,
123.6, 120.0, 105.5, 37.9, 21.6, 21.3 ppm (one aromatic quaternary
carbon merged); HRMS: m/z calcd for C25H24N2O2S: 416.1558;
found: 416.1551.
Compound 6g: Colorless viscous liquid (137 mg, 82%); 1H NMR
(600 MHz, CDCl3): d=8.77 (s, 1H), 4.28 (q, J=7.2 Hz, 2H), 3.24 (s,
3H), 2.93 (s, 3H), 2.36 (t, J=7.8 Hz, 2H), 2.25 (s, 3H), 1.47–1.42 (m,
2H), 1.37–1.31 (m, 5H), 0.92 ppm (t, J=7.2 Hz, 3H); 13C NMR
(150 MHz, CDCl3): d=161.0, 127.1, 126.5, 121.5, 117.3, 60.1, 38.5,
38.0, 32.3, 23.7, 22.9, 14.5, 13.8, 10.7 ppm; HRMS: m/z calcd for
C14H24N2O4S: 316.1457; found: 316.1460.
Compound 8c: Pale yellow solid (84 mg, 74%); m.p. 192–1948C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.24 (s, 1H), 7.21–7.19 (m,
2H), 7.16–7.13 (m, 3H), 6.96 (s, 1H), 6.81 (s, 1H), 4.43 (d, J=
12.7 Hz, 1H), 3.12 (s, 3H), 3.92 (s, 3H), 2.85 (d, J=12.7 Hz, 1H), 2.25
(s, 3H), 1.64 (s, 3H); 13C NMR (150 MHz, CDCl3 at À508C): d=151.5,
142.4, 138.7, 137.3, 136.7, 136.0, 131.6, 131.4, 131.3, 128.5, 127.5,
126.7, 125.7, 39.5, 38.1, 35.5, 22.5, 20.9 ppm; HRMS: m/z calcd for
C20H22N2O2S: 354.1402; found: 354.1404.
Compound 6h: Colorless viscous liquid (155 mg, 82%); 1H NMR
(400 MHz, CDCl3): d=8.31 (s, 1H), 4.26 (q, J=7.1 Hz, 2H), 3.21 (s,
3H), 2.98 (s, 3H), 2.78 (t, J=7.6 Hz, 2H), 1.87–1.80 (m, 1H), 1.65–
1.55 (m, 2H), 1.32 (t, J=7.2 Hz, 3H), 0.92 (t, J=7.3 Hz, 3H), 0.86–
0.81 (m, 2H), 0.62–0.59 ppm (m, 2H); 13C NMR (150 MHz, CDCl3):
d=165.2, 138.3, 122.9, 121.3, 111.2, 59.3, 38.7, 38.5, 29.7, 22.5, 14.4,
13.8, 7.4, 6.4 ppm; HRMS: m/z calcd for C15H24N2O4S: 328.1457;
found: 328.1457.
Compound 8d: Colorless viscous liquid (89.6 mg, 60%); 1H NMR
(600 MHz, CD2Cl2 at À508C): d=7.37–7.36 (m, 4H), 7.34–7.31 (m,
1H), 7.23 (s, 1H), 7.13 (s, 1H), 6.90 (s, 1H), 4.46 (d, J=12.7 Hz, 1H),
3.23 (s, 3H), 3.16 (s, 3H), 2.72 (d, J=12.7 Hz, 1H), 2.27 (s, 3H),
2.12 ppm (s, 3H); 13C NMR (150 MHz, CD2Cl2 at À508C): d=147.6,
141.0, 138.6, 135.3, 133.6, 133.0, 130.5, 129.5, 129.4, 129.2, 128.2,
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128.1, 127.1, 39.9, 37.2, 35.3, 19.6, 19.5 ppm; HRMS: m/z calcd for
C20H22N2O2S: 354.1402; found: 354.1403.
6.88–6.85 (m, 2H), 3.82 (s, 3H), 3.42 (s, 3H), 2.59 (s, 3H), 2.12 ppm
(s, 3H); 13C NMR (150 MHz, CDCl3): d=159.6, 135.9, 132.7, 129.5,
128.7, 127.1, 126.8, 126.7, 124.1, 122.3, 115.7, 114.7, 112.2, 55.2,
39.5, 38.1, 11.2 ppm (one aromatic quaternary carbon merged);
HRMS: m/z calcd for C20H22N2O3S: 370.1351; found: 370.1354.
Compound 9d: Colorless viscous liquid (18 mg, 12%); 1H NMR
(600 MHz, CDCl3): d=8.65 (s, 1H), 7.49–7.48 (m, 2H), 7.37 (t, J=
7.6 Hz, 2H), 7.28–7.23 (m, 3H, merged with CDCl3 solvent signal),
7.13 (d, J=7.8 Hz, 1H), 6.60 (d, J=3.0 Hz, 1H), 3.33 (s, 3H), 2.76 (s,
3H), 2.29 (s, 3H), 2.27 ppm (s, 3H); 13C NMR (150 MHz, CDCl3): d=
136.8, 135.1, 131.8, 131.7, 130.6, 129.9, 128.9, 128.4, 126.9, 124.3,
123.9, 121.4, 105.4, 38.7, 38.6, 19.9, 19.4 ppm (one aromatic quater-
nary carbon merged); HRMS: m/z calcd for C20H22N2O2S: 354.1402;
found: 354.1402.
Compound 8j: Pale yellow solid (111 mg, 72%); m.p. 176–1778C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.59–7.58 (m, 2H), 7.46 (d,
J=5.1 Hz, 1H), 7.43–7.39 (m, 3H), 7.24 (s, 1H), 6.97 (d, J=5.1 Hz,
1H), 4.88 (d, J=13.2 Hz, 1H), 3.21 (s, 3H), 3.09 (s, 3H), 2.49 ppm (d,
J=13.2 Hz, 1H); 13C NMR (150 MHz, CDCl3 at À508C): d=142.7,
139.7, 137.6, 131.7, 128.9, 128.6, 128.4, 128.2, 128.1, 126.2, 124.6,
39.0, 36.1, 33.9 ppm; HRMS: m/z calcd for C16H16N2O2S2: 332.0653;
found: 332.0656.
Compound 8e: White solid (97 mg, 65%); m.p. 131–1328C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.37–7.34 (m, 5H), 7.22 (s,
1H), 7.08 (d, J=8.8 Hz, 1H), 6.88 (d, J=2.3 Hz, 1H), 6.80 (dd, J=
8.8, 2.3 Hz, 1H), 4.64 (d, J=12.6 Hz, 1H), 3.83 (s, 3H), 3.21 (s, 3H),
3.07 (s, 3H), 2.81 ppm (d, J=12.6 Hz, 1H); 13C NMR (150 MHz,
CDCl3 at À508C): d=160.5, 147.6, 140.9, 133.1, 132.6, 130.9, 130.4,
129.5, 128.7, 128.3, 127.3, 113.6, 111.0, 55.4, 38.9, 38.4, 35.9 ppm;
HRMS: m/z calcd for C19H20N2O3S: 356.1195; found: 356.1191.
Acknowledgements
We thank the National Science Council, Taiwan for financial
support of this work.
Keywords: cycloaddition · gold · homogeneous catalysis ·
reaction mechanisms · structure elucidation
Compound 8 f: Pale yellow solid (96 mg, 59%); m.p. 167–1688C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.33–7.28 (m, 4H), 7.18 (s,
1H), 7.04 (d, J=8.8 Hz, 1H), 6.87 (d, J=2.5 Hz, 1H), 6.80 (dd, J=
2.6, 8.8, Hz, 1H), 4.64 (d, J=12.6 Hz, 1H), 3.83 (s, 3H), 3.21 (s, 3H),
3.08 (s, 3H), 2.78 ppm (d, J=12.6 Hz, 1H); 13C NMR (150 MHz,
CDCl3 at À508C): d=160.6, 147.7, 139.4, 133.2, 133.0, 132.7, 130.7,
130.2, 129.8, 128.4, 128.3, 113.7, 111.2, 55.4, 39.1, 38.3, 35.8 ppm;
HRMS: m/z calcd for C19H19ClN2O3S: 390.0805; found: 390.0806.
[1] For metal-catalyzed cycloaddition reactions, see selected reviews:
a) P. A. Wender, V. A. Verma, T. H. Paxton, Acc. Chem. Res. 2008, 41, 40–
49; b) M. Lautens, W. Klute, W. Tam, Chem. Rev. 1996, 96, 49–92; c) P. A.
Inglesby, P. A. Evans, Chem. Soc. Rev. 2010, 39, 2791–2805; d) S. M. A.
Sohel, R.-S. Liu, Chem. Soc. Rev. 2009, 38, 2269–2281; e) A. S. K. Hashmi,
Chem. Rev. 2007, 107, 3180–3211; f) F. López, J. L. MascareÇas, Beilstein
J. Org. Chem. 2011, 7, 1075–1094; g) C. Aissa in Comprehensive Organic
Synthesis, 2nd ed. (Eds.: P. Knochel, G. A. Molander), Elsevier, Amster-
Compound 8g: White solid (116 mg, 72%); m.p. 171–1728C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.29 (d, J=8.5 Hz, 2H),
7.18 (s, 1H), 7.08 (d, J=8.8 Hz, 1H), 6.91–6.88 (m, 3H), 6.81–6.79
(dd, J=2.6, 8.8, Hz, 1H), 4.63 (d, J=12.6 Hz, 1H), 3.83 (s, 6H), 3.19
(s, 3H), 3.04 (s, 3H), 2.79 ppm (d, J=12.6 Hz, 1H); 13C NMR
(150 MHz, CDCl3 at À508C): d=160.6, 158.8, 147.4, 133.5, 133.1,
131.9, 130.6, 130.5, 128.9, 113.6, 113.5, 111.2, 55.4, 55.3, 38.9, 38.5,
35.9 ppm (one aromatic quaternary carbon merged); HRMS: m/z
calcd for C20H22N2O4S: 386.1300; found: 386.1299.
´
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Compound 8h: White solid (112 mg, 78%); m.p. 178–1808C;
1H NMR (600 MHz, CDCl3 at À508C): d=7.42–7.37 (m, 5H), 7.27 (s,
1H), 6.89 (s, 1H), 6.62 (s, 1H), 4.66 (d, J=12.7 Hz, 1H), 3.96 (s, 3H),
3.67 (s, 3H), 3.22 (s, 3H), 3.06 (s, 3H), 2.73 ppm (d, J=12.7 Hz, 1H);
13C NMR (150 MHz, CDCl3 at À508C): d=149.9, 147.3, 147.1, 140.6,
133.0, 130.9, 129.3, 128.3, 128.1, 127.4, 124.4, 110.0, 109.1, 55.9,
55.7, 38.6, 37.7, 35.9 ppm; HRMS: m/z calcd for C20H22N2O4S:
386.1300; found: 386.1294.
Compound 8i: Colorless viscous liquid (65 mg, 42%); 1H NMR
(600 MHz, CDCl3 at À508C): d=7.36 (t, J=7.5 Hz, 2H), 7.30–7.29
(m, 1H), 7.22 (s, 2H), 6.84 (d, J=2.6 Hz, 1H), 6.76 (d, J=8.8 Hz, 1H),
6.69–6.67 (dd, J=2.7, 8.8 Hz, 1H),), 4.55 (d, J=12.4 Hz 1H), 3.78 (s,
3H), 3.17 (s, 3H), 2.99 (s, 3H), 2.89 (d, J=12.7 Hz, 1H), 2.00 ppm (s,
3H); 13C NMR (150 MHz, CDCl3 at À508C): d=159.7, 146.3, 142.1,
140.1, 132.8, 131.2, 130.9, 130.4, 128.2, 126.7, 126.2, 113.4, 111.2,
55.4, 38.7, 38.5, 35.9, 22.5 ppm; HRMS: m/z calcd for C20H22N2O3S:
370.1351; found: 370.1350.
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(600 MHz, CDCl3): d=8.39 (s, 1H), 7.44–7.43 (m, 2H), 7.41–7.38 (m,
2H), 7.32 (t, J=7.9 Hz, 1H), 7.27–7.25 (m, 1H), 6.92–6.89 (m, 1H),
Chem. Eur. J. 2015, 21, 10843 – 10850
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Full Paper
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[12] CCDC-1042641 (3c), 1044445 (6b), 1042642 (8a), and 1042643 (8j) con-
tain the supplementary crystallographic data for this paper. These data
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Received: February 17, 2015
Published online on June 11, 2015
Chem. Eur. J. 2015, 21, 10843 – 10850
www.chemeurj.org
10850
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim