Regioselectivity switch: Gold(I)-catalyzed oxidative rearrangement of propargyl alcohols to 1,3-diketones

Article abstract of DOI:10.1021/jo301381z

The gold(I)-catalyzed oxidative rearrangement of propargyl alcohols provides an efficient and selective route to 1,3-diketones under mild conditions. Pyridine-N-oxides were used as external oxidants with, different from related substrates, no alkylidenecycloalkanones or oxetan-3-ones formed as side-products.

Full text of DOI:10.1021/jo301381z

Note
pubs.acs.org/joc
Regioselectivity Switch: Gold(I)-Catalyzed Oxidative Rearrangement
of Propargyl Alcohols to 1,3-Diketones
A. Stephen K. Hashmi,* Tao Wang, Shuai Shi, and Matthias Rudolph
Ruprecht-Karls-Universitat Heidelberg, Organisch-Chemisches Institut, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: The gold(I)-catalyzed oxidative rearrangement of propargyl
alcohols provides an efficient and selective route to 1,3-diketones under
mild conditions. Pyridine-N-oxides were used as external oxidants with,
different from related substrates, no alkylidenecycloalkanones or oxetan-3-
ones formed as side-products.
n the recent past, gold-catalyzed oxidative rearrangements
Scheme 2. Known Reactivity Pattern (eq 1) and Initial
Hypothesis for a Switch in Chemoselectivity by Introducing
the R Group (eq 2)
I
have significantly enriched the arsenal of gold-catalyzed
methodology for organic synthesis.1 Diphenylsulfoxide, pyr-
idine-N-oxides and nitrones are often used as O-donors in the
oxidative rearrangements of alkyne-containing substrates, such
as 1,6-enynes,2 1,5-enynes,3 propargyl esters,2a alkynylcyclo-
propanes,4 homopropargylic alcohols5 and propargyl alcohols.6
α-Carbonyl carbenoids are proposed as common key
intermediates in these reactions (Scheme 1) undergoing an
Scheme 1. Generation of α-Carbonyl Carbenoids
are important intermediates for various heterocyclic com-
pounds9 and key structural units in many chelating ligands for
lanthanide and transition metals.10
We began our study by examining 1-(phenylethynyl)-
cyclobutanol (1a) and 3,5-dichloropyridine-1-oxide (2a) in
presence of various gold(I) catalysts (Table 1, entries 1−5). To
our delight, the desired product 2-benzoylcyclopentanone (3a)
was obtained in moderate yields, and no formation of oxetan-3-
one was observed. Among the gold catalysts, IPrAuNTf2 gave
the best result (entry 3, 65%) and was chosen for the screening
of a series of different pyridine-N-oxides. But no improvement
of the yield was possible (entries 6−8). When relatively
electron-rich pyridine N-oxides were added, the consumption
of the starting material was incomplete. It was assumed that the
basic pyridine derivative formed during the reaction was
inhibiting the gold catalyst;5 thus, acid was added to retain the
catalytic activity. Indeed, the reaction proceeded well when
triflimide (HNTf2) was added as additive in combination with
4-picoline-N-oxide (2b), 2-benzoylcyclopentanone (3a) was
array of versatile transformations. In this process, terminal
alkynes (Y = H) favor the oxidation at the C2 alkynyl carbon
atom but internal alkynes (Y ≠ H) show little selectivity.7
In 2010, Liming Zhang et al. reported the gold-catalyzed
synthesis of oxetan-3-ones from propargyl alcohols and
pyridine-N-oxides via the C2 carbonylated α-carbonyl carbe-
noids (Scheme 2, eq 1).6c In their work, terminal alkynes
showed high selectivity in the transformation of secondary
propargyl alcohols and a primary alcohol, but for the
transformation of tertiary alcohols, electron withdrawing groups
were required at the alkyne terminus. We envisioned that by
changing the groups at the alkyne terminus, 1,3-diketones
should be obtained via the C1 carbonylated α-carbonyl
carbenoids (Scheme 2, eq 2). As part of our efforts to develop
gold-catalyzed reactions and mechanistic aspects,8 we herein
report a different regio-selectivity for the gold(I)-catalyzed
oxidative rearrangement of propargyl alcohols to 1,3-diketones,
by using pyridine-N-oxides as external oxidants. 1,3-Diketones
Received: July 19, 2012
Published: August 10, 2012
© 2012 American Chemical Society
7761
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
a
a
Table 1. Optimization of the Reaction Conditions
Table 2. Scope of the Reaction of Propargyl Alcohols
N-
solvent/time
(h)
yield
b
entry
1
catalyst
oxide
acid
(%)
Ph3PAuCl/
AgNTf2
2a
DCM/19
40 (45)
2
3
4
5
6
7
8
9
Ph3PAuCl/AgSbF6
IPrAuCl/AgNTf2
IPrAuCl/AgSbF6
IPrAuCl/AgOTf
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
Ph3PAuCl/AgSbF6
2a
2a
2a
2a
2b
2c
2d
2b
2b
2a
2b
2b
2b
2b
2b
2b
2b
DCM/10
DCM/19
DCM/5
60
65
56
DCM/19
DCM/19
DCM/19
DCM/19
DCM/16
DCM/16
DCM/16
DCE/16
35 (51)
46 (50)
43 (50)
38 (48)
83
HNTf2
HNTf2
HNTf2
HNTf2
HNTf2
HNTf2
HNTf2
PTSA
10 IPrAuCl/AgNTf2
85
11
12
13
14
15
16
17
18
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
IPrAuCl/AgNTf2
69
80
CH3CN/16
THF/16
51 (40)
61 (32)
49
Toluene/16
DCM/26
DCM/20
DCM/24
76
MsOH
TFA
80
77
a
Reaction conditions: 1a (400 μmol), 2 (800 μmol), [Au/Ag] (5.0
mol %), acid (480 μmol, if added in the reaction), solvent (4 mL),
b
room temperature. Percentage of 1a recovered after column is in
parentheses.
obtained in 85% yield after 16 h (entry 10), and the same
reaction with the PPh3 ligand on gold gave a slightly lower yield
(entry 9). The yield was slightly improved when triflimide was
added with 3,5-dichloropyridine-1-oxide (2a) (entry 11).
Different solvents were examined but failed to improve the
reaction (entries 12−15). A comparative study with PTSA
(entry 16), MsOH (entry 17) and TFA (entry 18) gave no
superior results. Thus, 5 mol % of IPrAuNTf2, 2 equivalents of
4-picoline-N-oxide (2b) and 1.2 equivalents of triflimide in
dichloromethane at room temperature were chosen as the
optimal conditions for the transformation of propargyl alcohols
to 1,3-diketones. The role of the acid might simply be to
protonate the pryidine that is set free in the course of the
reactionit is only important that the acid forms a weakly
coordinating conjugated base in order to avoid deactivation of
the catalyst. With less than 1 equivalent of acid, no efficient
conversion is observed.
Under these optimized reaction conditions, a wide variety of
propargyl alcohols 1 were examined and the results are
summarized in Table 2. First, cyclobutanols bearing various
ethynyl groups were examined (entries 1−11). The reaction of
this type of substrate proceeded smoothly to deliver the
oxidation/ring-expansion products in moderate to excellent
yields, no matter if the substituents at the acetylenic terminus
were aromatic groups (entries 1−8) or alkyl groups (entries 9−
11). To expand the substrate scope, different cycloalkanols
were then tested (entries 12−16). Cyclopropanol derivative
(1m) gave the expected product 2-benzoylcyclobutanone (3m)
a
Reaction conditions: 1 (400 μmol), 2b (800 μmol), IPrAuNTf2 (5.0
b
mol %), HNTf2 (480 μmol), DCM (4 mL). 2d was used as oxidant
and no HNTf2 was added. NMR yield, CH2Br2 was added as an
c
internal standard, and the product is not stable upon column
chromatography.12 No reaction. 3t/3t′ = 10:1.
d
e
7762
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
in 82% NMR yield. Unfortunately, cyclopentanol (1n) and
cyclohexanol derivative (1o) could not undergo the reaction
under the reaction conditions. The ring strain of cyclobutanol
and cyclopropanol, which usually is the driving force for the
ring expansion of these small ring compounds, might explain
these results. The larger steric hindrance of cyclopentanol and
cyclohexanol if compared to cyclobutanol and cyclopropanol
might play a role, too.11 To further investigate the reaction,
more flexible cycloalcohol substrates were examined under the
same reaction conditions. To our delight, they were converted
with good yields to the corresponding diketone products
(entries 15 and 16). This indicates that, in addition to angular
strain, steric hindrance of the substrates is also a crucial factor
in the reaction. Noncyclic alcohols were examined last. 2-
Methyl-4-phenylbut-3-yn-2-ol (1r) gave the 1,2-methyl shift
product (3r) in 78% yield (entry 17). Hydride migration was
favored in the reaction of 4-phenylbut-3-yn-2-ol (1s) (entry 18)
but was less favored in 1,3-diphenylprop-2-yn-1-ol (1t) (entry
19). The phenyl group showed stronger migration ability than
the methyl group in 2,4-diphenylbut-3-yn-2-ol (1u) (entry 20)
as well. The migration ability inferred from the results of entries
18 and 19 (Ph > H > CH3) was not corroborated by the results
of entries 19 and 20, where methyl migration is slightly favored
over hydride.
Scheme 4. Plausible Mechanisms for the Conversion of 1 to
3
In pathway B, pyridine-N-oxide coordinates to cationic gold(I)
to form gold complex IIA. Syn addition of this moiety to the
alkyne gives vinyl-gold intermediate IIB, which undergoes
fragmentation to gold carbenoid IIIA and, finally, to 1,3-
diketone (3).
In 2005, Toste et al. reported a gold(I)-catalyzed ring
expansion of cyclopropanols and cyclobutanols to alkylidene-
cycloalkanones,13 but such products were not observed in the
oxidative rearrangement process described here. It is note-
worthy that some of the substrates are prone to undergo ring
expansion in the absence of the oxidant to give alkylidenecy-
cloalkanones. For example 1-(phenylethynyl)cyclopropanol
(1m) was rapidly converted to (4a) in presence of IPrAuNTf2
(Scheme 3, eq 1), while in the presence of the oxidant 2 the
Generally in this type of gold-catalyzed alkyne oxidation, an
α-carbonyl carbenoid is proposed to be generated from
nucleophilic attack of N-oxide on alkyne which is activated by
cationic gold catalyst (pathway A). However, coordination of
the gold complex to the alkyne moiety is liable to undergo
intramolecular reaction leading to alkylidenecycloalkanone (4),
which was not observed in the reaction. Calculations predicted
that coordination of gold to the N-oxide was favored over
coordination to the alkyne in an intramolecular oxidative
rearrangement of acetylenic amine N-oxide.14 Thus, pathway B
is considered as a reasonable mechanism for this reaction.
Efforts to grow single crystals of N-oxide complex of gold
failed; but the coordination of N-oxide to the gold complex was
indeed revealed by a series of NMR experiments15 (Supporting
Information).
Scheme 3. Product 4a from the Gold-catalyzed
Rearrangement of 1m Does Not Provide 3m with the Gold
Catalyst and 2
CONCLUSION
■
We have developed an efficient gold(I)-catalyzed oxidative
rearrangement of propargyl alcohols to 1,3-diketones under
mild conditions. Pyridine-N-oxides were used as external
oxidants. The reaction shows high selectivity to 1,3-diketones
and no alkylidenecycloalkanones13 or oxetan-3-ones6c were
observed. NMR experiments indicated a coordination of the
gold catalyst to pyridine-N-oxide.
a
NMR yield, CH2Br2 was added as an internal standard.
EXPERIMENTAL SECTION
■
Propargyl Alcohols Were Prepared According to Literature
Procedures.16 To a solution of terminal alkyne (6 mmol) in
tetrahydrofuran (30 mL), n-butyllithium (2.5 M in hexane, 2.4 mL, 6
mmol) was added dropwise by syringe at −78 °C. After stirring for 30
min, a solution of ketone (5 mmol) in THF (5 mL) was added
dropwise and the mixture stirred at the same temperature for 1 h. The
solution was allowed to warm to room temperature and was quenched
with saturated aqueous NH4Cl and was extracted with diethyl ether.
The combined organic extracts were washed with brine, dried over
magnesium sulfate and concentrated under vaccuo. The crude residue
was purified by flash chromatography on silica gel (petrol ether/
EtOAc) to give the expected propargyl alcohol.
dicarbonyl compound 3m is formed (Scheme 3, eq 2). The
conversion of 4a to 3m under these oxidative conditions (2,
IPrAuNTf2) is not possible.
Two plausible pathways that account for the oxidative
rearrangement of propargyl alcohols are depicted in Scheme 4.
In pathway A, coordination of the cationic gold(I) to the alkyne
moiety induces the nucleophilic attack of pyridine-N-oxide on
the triple bond to give vinyl-gold intermediate IA, which
undergoes fragmentation to gold carbenoid IIIA. Rearrange-
ment of gold carbenoid IIIA finally affords the 1,3-diketone (3).
7763
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
1-(Phenylethynyl)cyclobutanol (1a). Yield: 732 mg, 85%; 1H
NMR (300 MHz, CDCl3): δ = 7.46−7.42 (m, 2 H); 7.33−7.28 (m, 3
H); 2.58−2.30 (m, 5 H); 1.93−1.82 (m, 2 H). 1a is known.17
1-(p-Tolylethynyl)cyclobutanol (1b). Yield: 810 mg, 87%; 1H
NMR (300 MHz, CDCl3): δ = 7.33 (d, 2 H, J = 8.1 Hz); 7.10 (d, 2 H,
J = 7.9 Hz); 2.57−2.48 (m, 3 H), 2.40−2.29 (m, 5 H), 1.92−1.81 (m,
2 H). 1b is known.16
1-((4-Methoxyphenyl)ethynyl)cyclobutanol (1c). Yield: 800 mg,
colorless oil, 79%; 1H NMR (300 MHz, CDCl3): δ = 7.39−7.34 (m, 2
H); 6.85−6.80 (m, 2 H); 3.80 (s, 3 H), 2.56−2.46 (m, 2 H); 2.42 (br,
1 H), 2.38−2.28 (m, 2 H); 1.91−1.80 (m, 2 H). 13C NMR (75 MHz,
CDCl3): δ = 159.6, 133.1, 114.8, 113.9, 91.1, 83.3, 68.4, 55.2, 38.7,
971, 961, 942, 889, 859, 813, 755, 702, 666, 539, 476, 424 cm−1;
HRMS (EI+): C17H16O2 calcd 252.1150; found 252.1156.
1-(Hex-1-yn-1-yl)cyclobutanol (1i). Yield: 518 mg, colorless oil,
1
68%; H NMR (300 MHz, CDCl3): δ = 2.41−2.31 (m, 2 H); 2.27−
2.17 (m, 5 H); 1.82−1.71 (m, 2 H), 1.54−1.34 (m, 4 H), 0.91 (t, 3 H,
J = 7.1 Hz). 1j is known.18
1-(Cyclohexylethynyl)cyclobutanol (1k). Yield: 606 mg, colorless
1
oil, 68%; H NMR (300 MHz, CDCl3): δ = 2.44−2.31 (m, 3 H);
2.28−2.17 (m, 3 H); 1.82−1.64 (m, 6 H); 1.55−1.22 (m, 6 H). 13C
NMR (75 MHz, CDCl3): δ = 88.1, 83.8, 68.1, 38.9, 32.7, 29.0, 25.9,
24.8, 12.8 ppm, IR (film): v = 3323, 2989, 2932, 2854, 2664, 2232,
̃
1448, 1422, 1363, 1318, 1299, 1246, 1175, 1125, 1065, 1012, 979, 955,
933, 891, 850, 823, 778, 738, 641, 515, 480, 422 cm−1; HRMS (EI+):
C12H18O calcd 178.1358; found 178.1359.
12.9 ppm, IR (film): v = 3373, 2992, 2941, 2838, 2228, 1607, 1572,
̃
1510, 1462, 1442, 1419, 1286, 1249, 1175, 1155, 1107, 1031, 961, 914,
833, 807, 596, 542, 470 cm−1; HRMS (EI+): C13H14O2 calcd
202.0994; found 202.0998.
1-(3-Phenoxyprop-1-yn-1-yl)cyclobutanol (1l). Yield: 708 mg,
1
colorless oil, 70%; H NMR (300 MHz, CDCl3): δ = 7.34−7.26 (m,
1-((4-Fluorophenyl)ethynyl)cyclobutanol (1d). Yield: 856 mg,
2 H); 7.02−6.97 (m, 3 H); 4.74 (s, 2 H), 2.45−2.19 (m, 5 H); 1.88−
1
1.75 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 157.7, 129.4, 121.4,
colorless oil, 90%; H NMR (300 MHz, CDCl3): δ = 7.45−7.38 (m,
2 H); 7.04−6.96 (m, 2 H); 2.57−2.47 (m, 2 H); 2.39−2.28 (m, 3 H);
115.0, 90.8, 78.4, 67.8, 56.2, 38.2, 12.8 ppm, IR (film): v = 3346, 3064,
̃
1.92−1.81 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 162.5 (d, JFC
=
2992, 2945, 2871, 2243, 1937, 1598, 1495, 1456, 1422, 1375, 1337,
1304, 1265, 1216, 1175, 1125, 1080, 1046, 1008, 990, 957, 886, 811,
778, 754, 691, 645, 507 cm−1; HRMS (EI+): C13H14O2 calcd
202.0994; found 202.1016.
247.5 Hz), 133.6 (d, JFC = 8.3 Hz), 118.8 (d, JFC = 3.8 Hz), 115.5 (d,
JFC = 21.8 Hz), 92.2 (d, JFC = 1.5 Hz), 82.4, 68.3, 38.6, 12.9 ppm, IR
(film): v = 3344, 2992, 2944, 2875, 2366, 1893, 1601, 1507, 1422,
̃
1294, 1231, 1155, 1109, 1013, 962, 915, 836, 817, 591, 538, 453 cm−1;
HRMS (EI+): C12H11FO calcd 190.0794; found 190.0755.
1-(Phenylethynyl)cyclopropanol (1m). Yield: 475 mg, colorless oil,
1
60%; H NMR (300 MHz, CDCl3): δ = 7.44−7.38 (m, 2 H); 7.33−
1-((3-Chlorophenyl)ethynyl)cyclobutanol (1e). Yield: 753 mg,
7.27 (m, 3 H); 2.61 (br, 1 H), 1.21−1.07 (m, 4 H). 1m is known.19
1-(Phenylethynyl)cyclopentanol (1n). Yield: 829 mg, colorless oil,
1
colorless oil, 75%; H NMR (300 MHz, CDCl3): δ = 7.49−7.48 (m,
1 H); 7.34−7.28 (m, 3 H); 2.63−2.52 (m, 3 H); 2.46−2.35 (m, 2 H);
1.99−1.93 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ = 134.1, 131.5,
129.7, 129.5, 128.5, 124.4, 93.7, 82.1 68.2, 38.5, 12.9 ppm, IR (film): v
= 3322, 3068, 2993, 2944, 2873, 2849, 1593, 1562, 1475, 1207, 1302,
1288, 1245, 1213, 1158, 1112, 1091, 1079, 998, 963, 929, 881, 808,
784, 708, 682, 477 cm−1; HRMS (EI+): C12H11ClO calcd 206.0498;
found 206.0520.
1
89%; H NMR (300 MHz, CDCl3): δ = 7.54−7.39 (m, 2 H); 7.32−
7.27 (m, 3 H); 2.11−1.98 (m, 5 H); 1.94−1.72 (m, 4 H). 1n is
̃
known.20
1-(Phenylethynyl)cyclohexanol (1o). Yield: 851 mg, colorless oil,
1
85%; H NMR (300 MHz, CDCl3): δ = 7.45−7.40 (m, 2 H); 7.32−
7.27 (m, 3 H); 2.17 (br, 1 H), 2.04−1.95 (m, 2 H); 1.77−1.56 (m, 7
H); 1.32−1.26 (m, 2 H). 1o is known.17
1-((3,5-Dimethoxyphenyl)ethynyl)cyclobutanol (1f). Yield: 894
mg, colorless oil, 77%; 1H NMR (300 MHz, CDCl3): δ = 6.58 (d, 2 H,
J = 2.4 Hz); 6.42 (t, 1 H, J = 2.4 Hz); 3.76 (s, 6 H), 2.76 (br, 1 H),
2.56−2.46 (m, 2 H); 2.39−2.28 (m, 2 H); 1.91−1.80 (m, 2 H). 13C
NMR (75 MHz, CDCl3): δ = 160.4 124.0, 109.4, 101.7, 92.1, 83.3,
1-(Phenylethynyl)cyclododecanol (1p). Yield: 1.04 g, 73%; 1H
NMR (300 MHz, CDCl3): δ = 7.45−7.38 (m, 2 H); 7.32- 7.27 (m, 3
H); 1.99−1.89 (m, 2 H); 1.83−1.72 (m, 3 H); 1.61−1.56 (m, 2 H),
1.38 (s, 16 H). 1p is known.20
1-(Phenylethynyl)cyclopentadecanol (1q). Yield: 1.14 g, white
crystalline solid, 70%; mp 52−53 °C; 1H NMR (300 MHz, CDCl3): δ
= 7.45−7.39 (m, 2 H); 7.32−7.27 (m, 3 H); 1.94 (s, 1 H), 1.88−1.79
(m, 4 H); 1.46−1.35 (m, 24 H). 13C NMR (75 MHz, CDCl3): δ =
131.7, 128.2, 128.1, 122.9, 93.5, 83.5, 71.3, 39.7, 27.4, 26.9, 26.7, 26.7,
68.2, 55.3, 38.5, 12.9 ppm, IR (film): v = 3386, 2994, 2940, 2839,
̃
1597, 1457, 1421, 1352, 1301, 1261, 1206, 1178, 1157, 1107, 1065,
992, 954, 928, 895, 834, 703, 682, 654, 540 cm−1; HRMS (EI+):
C14H16O3 calcd 232.1099; found 232.1078.
1-((3,5-Bis(trifluoromethyl)phenyl)ethynyl)cyclobutanol (1g).
1
26.4, 22.2 ppm, IR (film): v = 3382, 3057, 2930, 2856, 1741, 1599,
̃
Yield: 1.16 g, white crystalline solid, 75%; mp 36−37 °C; H NMR
1573, 1490, 1459, 1445, 1373, 1351, 1253, 1154, 1070, 1045, 1001,
940, 914, 756, 691, 591, 525 cm−1; HRMS (EI+): C23H34O calcd
326.2610; found 326.2602.
(300 MHz, CDCl3): δ = 7.87 (s, 2 H); 7.80 (s, 1 H); 2.60−2.50 (m, 2
H); 2.42−2.31 (m, 3 H); 1.96−1.85 (m, 2 H). 13C NMR (75 MHz,
CDCl3): δ = 131.9 (q, JFC = 33.5 Hz), 131.6 (d, JFC = 3.0 Hz), 125.1,
122.9 (q, JFC = 271.0 Hz), 121.8−121.6 (m, 1 C), 96.1, 80.7, 68.2,
2-Methyl-4-phenylbut-3-yn-2-ol (1r). Yield: 609 mg, 76%; 1H
NMR (300 MHz, CDCl3): δ = 7.43−7.39 (m, 2 H); 7.32−7.27 (m, 3
H); 2.03 (s, 1 H), 1.62 (s, 6 H). 1r is known.17
38.4, 13.0 ppm, IR (KBr): v = 3556, 3399, 2999, 2947, 1616, 1464,
̃
1384, 1281, 1247, 1176, 1135, 1107, 969, 898, 848, 700, 684, 424
cm−1; HRMS (EI+): C14H10F6O calcd 308.0636; found 308.0630.
1-((2,4,5-Trimethylphenyl)ethynyl)cyclobutanol (1h). Yield: 868
1
4-Phenylbut-3-yn-2-ol (1s). Yield: 446 mg, 61%; H NMR (300
MHz, CDCl3): δ = 7.45−7.41 (m, 2 H); 7.33−7.28 (m, 3 H); 4.76 (q,
1 H, J = 6.6 Hz), 2.01 (br, 1 H); 1.55 (d, 3 H, J = 6.6 Hz). 1s is
known.21
1
mg, colorless oil, 81%; H NMR (300 MHz, CDCl3): δ = 7.19 (s, 1
H); 6.97 (s, 1 H); 2.57−2.49 (m, 2 H); 2.42−2.31 (m, 6 H); 2.23 (s, 3
H); 2.19 (s, 3 H); 1.93−1.82 (m, 2 H). 13C NMR (75 MHz, CDCl3):
δ = 137.4, 137.1, 133.6, 132.8, 130.8, 119.6, 95.5, 82.5, 68.5, 38.9, 19.9,
1
1,3-Diphenylprop-2-yn-1-ol (1t). Yield: 833 mg, 80%; H NMR
(300 MHz, CDCl3): δ = 7.65−7.61 (m, 2 H); 7.51−7.30 (m, 8 H);
5.70 (d, 1 H, J = 6.3 Hz), 2.36 (d, 1 H, J = 6.3 Hz). 1t is known.17
2,4-Diphenylbut-3-yn-2-ol (1u). Yield: 834 mg, 75%; 1H NMR
(300 MHz, CDCl3): δ = 7.77−7.73 (m, 2 H); 7.53−7.46 (m, 2 H);
7.43−7.29 (m, 6 H); 2.55 (s, 1 H); 1.89 (s, 3 H). 1u is known.22
Typical Procedure for Gold(I)-Catalyzed Oxidative Rear-
rangement of Propargyl Alcohols. 4-Picoline-N-oxide (0.8 mmol)
was added to a stirring suspension of IPrAuCl (0.02 mmol) and
AgNTf2 (0.02 mmol) in dichloromethane (4 mL) and stirred for 5 min
at room temperature. After that, HNTf2 (0.48 mmol) was added and
the mixture was allowed to stir for additional 5 min. To the resulting
solution propargyl alcohol (0.4 mmol) was added and the combined
solution was then stirred at rt until the reaction was completed
(monitored by TLC). After evaporation, the residue was purified by
19.6, 19.0, 12.9 ppm, IR (film): v = 3326, 2989, 2941, 2869, 2222,
̃
1617, 1504, 1455, 1422, 1381, 1297, 1246, 1161, 1116, 1070, 1000,
960, 910, 877, 795, 710, 528, 503, 457 cm−1; HRMS (EI+): C15H18O
calcd 214.1358; found 214.1345.
1-((6-Methoxynaphthalen-2-yl)ethynyl)cyclobutanol (1i). Yield:
883 mg, white crystalline solid, 70%; mp 103−104 °C; 1H NMR (300
MHz, CDCl3): δ = 7.89 (s, 1 H); 7.69−7.64 (m, 2 H); 7.45 (dd, 1 H, J
= 1.8 Hz, 8.5 Hz); 7.17−7.09 (m, 2 H); 3.92 (s, 3 H); 2.62−2.53 (m, 2
H); 2.43−2.32 (m, 3 H); 1.96−1.85 (m, 2 H). 13C NMR (75 MHz,
CDCl3): δ = 158.3, 134.1, 131.4, 129.3, 129.0, 128.4, 126.7, 119.4,
117.6, 105.8, 92.1, 83.9, 68.4, 55.3, 38.7, 13.0 ppm, IR (KBr): v = 3368,
̃
2993, 2942, 2846, 1628, 1601, 1499, 1483, 1464, 1410, 1387, 1370,
1330, 1292, 1259, 1227, 1197, 1184, 1164, 1151, 1122, 1112, 1025,
7764
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
column chromatography on silica gel (petrol ether/EtOAc = 10:1)
afforded the desired product.
1080, 1024, 904, 846, 766, 742, 700, 682, 637, 515, 447 cm−1; HRMS
(EI+): C14H10F6O2 calcd 324.0585; found 324.0586.
2-Benzoylcyclopentanone (3a). Yield: 64 mg as a mixture of a keto
2-(2,4,5-Trimethylbenzoyl)cyclopentanone (3h). Yield: 65 mg as a
mixture of a keto and an enol forms (keto/enol = 20:80 by 1H NMR),
red solid, 70%; mp 77−79 °C; 1H NMR (300 MHz, CDCl3, keto/enol
= 20:80) δ = 13.86 (br, 1 H, enol), 7.52 (s, 1 H, keto), 7.06 (s, 1 H,
enol), 7.02 (s, 1 H, keto and enol), 4.17 (t, 1 H, J = 8.1 Hz, keto),
2.52−1.85 (m, 15 H, keto and enol). 13C NMR (75 MHz, CDCl3, keto
and enol): δ = 214. Two (keto), 209.5 (enol), 199.3 (keto), 171.9
(enol), 141.0, 138.5, 136.6, 134.8, 133.7, 133.6, 133.5, 133.4, 132.1,
131.5, 131.5, 129.0, 110.6, 59.3, 38.9, 37.9, 27.8, 27.1, 21.1, 21.0, 21.0,
1
1
and an enol forms (keto/enol = 22:78 by H NMR), 85%; H NMR
(300 MHz, CDCl3, keto/enol = 22:78) δ = 14.49 (s, 1 H, enol), 8.02−
7.41 (m, 5 H, keto and enol), 4.27 (t, 1 H, J = 7.8 Hz, keto), 2.90−
1.94 (m, 6 H, keto and enol). 3a is known.23
2-(4-Methylbenzoyl)cyclopentanone (3b). Yield: 67 mg as a
mixture of a keto and an enol forms (keto/enol = 38:62 by 1H
1
NMR), red solid, 83%; mp 37−38 °C; H NMR (300 MHz, CDCl3,
keto/enol = 38:62) δ = 14.60 (s, 1 H, enol), 7.94−7.26 (m, 4 H, keto
and enol), 4.26 (t, 1 H, J = 7.8 Hz, keto), 2.92−1.93 (m, 9 H, keto and
enol). 13C NMR (75 MHz, CDCl3, keto and enol): δ = 213.5 (keto),
210.0 (enol), 195.1 (keto), 169.0 (enol), 144.3, 141.5, 134.0, 131.7,
129.5, 129.2, 129.0, 128.1, 108.7, 57.0, 38.9, 37.5, 28.4, 27.2, 21.6, 21.5,
19.7, 19.5, 19.3, 19.2, 19.1 ppm, IR (film): v = 3451, 2948, 2920, 2862,
̃
2361, 1634, 1498, 1448, 1399, 1370, 1312, 1295, 1270, 1225, 1184,
1163, 1024, 912, 886, 871, 819, 781, 675, 634, 611, 527, 506, 444
cm−1; HRMS (EI+): C15H18O2 calcd 230.1307; found 230.1316.
2-(6-Methoxy-2-naphthoyl)cyclopentanone (3i). Yield: 101 mg as
21.2, 21.1 ppm. IR (film): v = 3462, 2961, 1741, 1670, 1611, 1565,
̃
1
a mixture of a keto and an enol forms (keto/enol = 38:62 by H
1508, 1449, 1409, 1379, 1310, 1279, 1253, 1184, 1151, 1117, 1068,
900, 827, 785, 730, 680, 632, 600, 556, 501, 469 cm−1; HRMS (EI+):
C13H14O2 calcd 202.0994; found 202.0973. 3b is known but not fully
characterized.24
NMR), yellow solid, 94%; 122−124 °C; 1H NMR (300 MHz, CDCl3,
keto/enol = 38:62) δ = 14.72 (s, 1 H, enol), 8.45−7.15 (m, 6 H, keto
and enol), 4.39 (t, 1 H, J = 8.0 Hz, keto), 3.94 (s, 3 H, keto and enol),
3.00−1.95 (m, 6 H, keto and enol). 13C NMR (75 MHz, CDCl3, keto
and enol): δ = 213.7 (keto), 209.9 (enol), 195.2 (keto), 169.2 (enol),
159.9, 159.2, 137.5, 135.9, 132.0, 131.7, 131.4, 130.6, 129.7, 128.9,
128.0, 127.8, 127.0, 126.8, 125.2, 125.0, 119.7, 119.6, 109.0, 105.7,
105.6, 57.0, 55.4, 55.4, 39.0, 37.5, 28.6, 27.3, 21.3, 21.1 ppm, IR (film):
2-(4-Methoxybenzoyl)cyclopentanone (3c). Yield: 69 mg as a
mixture of a keto and an enol forms (keto/enol = 53:47 by 1H NMR),
79%; 1H NMR (300 MHz, CDCl3, keto/enol = 53:47) δ = 14.74 (s, 1
H, enol), 7.98 (d, 1 H, J = 8.7 Hz, keto and enol), 7.77 (d, 1 H, J = 8.7
Hz, keto and enol), 6.95 (d, 2 H, J = 8.7 Hz, keto and enol),4.20 (t, 1
H, J = 7.8 Hz, keto), 3.87 (s, 3 H, keto), 3.86 (s, 3 H, enol), 2.90−1.88
(m, 6 H, keto and enol). 3c is known.25
v = 3428, 2966, 2863, 1813, 1741, 1625, 1590, 1481, 1457, 1440, 1411,
̃
1362, 1326, 1308, 1272, 1248, 1210, 1167, 1136, 1069, 1026, 961, 941,
908, 855, 847, 817, 779, 764, 717, 639, 511, 476, 462 cm−1; HRMS (EI
+): C17H16O3 calcd 268.1099; found 268.1098.
2-(4-Fluorobenzoyl)cyclopentanone (3d). Yield: 66 mg as a
mixture of a keto and an enol forms (keto/enol = 20:80 by 1H
1
2-Pentanoylcyclopentanone (3j). Yield: 48 mg as a mixture of a
keto and an enol forms (keto/enol = 41:59 by 1H NMR), red oil, 71%;
1H NMR (300 MHz, CDCl3, keto/enol = 41:59) δ = 13.63 (s, 1 H,
enol), 3.37 (t, 1 H, J = 7.8 Hz, keto), 2.83−0.87 (m, 15 H, keto and
enol). 13C NMR (75 MHz, CDCl3, keto and enol): δ = 213.2 (keto),
205.0 (keto), 204.8 (enol), 179.4 (enol), 109.4 (enol), 61.8, 42.8, 38.8,
36.9, 34.2, 27.6, 25.7, 25.4, 25.3, 22.4, 22.2, 20.8, 20.3, 13.8, 13.8 ppm,
NMR), 80%; H NMR (300 MHz, CDCl3, keto/enol = 20:80) δ =
14.54 (s, 1 H, enol), 8.06−8.01 (m, 1 H, keto), 7.81−7.75 (m, 1 H,
enol), 7.19−7.08 (m, 2 H, keto and enol), 4.21 (t, 1 H, J = 7.8 Hz,
keto), 2.88−1.92 (m, 6 H, keto and enol). 3d is known.26
2-(3-Chlorobenzoyl)cyclopentanone (3e). Yield: 75 mg as a
mixture of a keto and an enol forms (keto/enol = 5:95 by 1H
NMR), white solid, 84%; mp 54−56 °C; 1H NMR (300 MHz, CDCl3,
keto/enol = 5:95) δ = 14.37 (s, 1 H, enol), 7.98−7.35 (m, 5 H, keto
and enol), 4.21 (t, 1 H, J = 7.8 Hz, keto), 2.86 (t, 2 H, J = 7.1 Hz,
enol), 2.50 (t, 2 H, J = 7.8 Hz, enol), 2.04−1.93 (m, 2 H, enol). 13C
NMR (75 MHz, CDCl3, enol): δ = 210.8, 166.6, 136.3, 134.5, 130.9,
IR (film): v = 2960, 2934, 2873, 1743, 1710, 1656, 1612, 1465, 1408,
̃
1378, 1282, 1234, 1201, 1122, 1029, 1003, 909, 883, 829, 757, 478
cm−1; HRMS (EI+): C10H16O2 calcd 168.1150; found 168.1152. 3j is
known but not fully characterized.28
129.6, 128.1, 126.1, 109.7, 37.6, 28.2, 21.2 ppm, IR (film): v = 3425,
̃
2-(Cyclohexanecarbonyl)cyclopentanone (3k). Yield: 51 mg as a
mixture of a keto and an enol forms (keto/enol = 33:67 by 1H NMR),
3064, 2974, 2904, 2855, 1741, 1638, 1606, 1562, 1480, 1468, 1449,
1413, 1365, 1315, 1282, 1269, 1240, 1223, 1184, 1154, 1130, 1098,
1071, 1024, 916, 895, 876, 831, 795, 741, 715, 686, 675, 514 cm−1;
HRMS (EI+): C12H11ClO2 calcd 222.0448; found 222.0452.
1
red oil, 66%; H NMR (300 MHz, CDCl3, keto/enol = 33:67) δ =
13.84 (s, 1 H, enol), 3.55 (t, 1 H, J = 7.8 Hz, keto), 2.79 - 1.15 (m, 17
H, keto and enol). 13C NMR (75 MHz, CDCl3, keto and enol): δ =
213.6 (keto), 208.3 (keto), 205.2 (enol), 183.0 (enol), 108.1 (enol),
59.8, 50.4, 43.2, 38.8, 36.8, 30.9, 28.9, 28.5, 27.2, 26.0, 25.9, 25.8, 25.8,
2-(3,5-Dimethoxybenzoyl)cyclopentanone (3f). Yield: 81 mg as a
mixture of a keto and an enol forms (keto/enol = 35:65 by 1H NMR),
1
white solid, 81%; mp 75−77 °C; H NMR (300 MHz, CDCl3, keto/
25.7, 25.5, 25.1, 20.9, 20.4 ppm, IR (film): v = 3458, 2933, 2855, 1810,
̃
enol = 35:65) δ = 14.50 (s, 1 H, enol), 7.13−6.55 (m, 3 H, keto and
enol), 4.18 (t, 1 H, J = 8.1 Hz, keto), 3.83 (s, 6 H, keto), 3.82 (s, 6 H,
enol), 2.89−1.91 (m, 6 H, keto and enol). 13C NMR (75 MHz,
CDCl3, keto and enol): δ = 213.2 (keto), 210.3 (enol), 195.5 (keto),
168.5 (enol), 160.8, 160.6, 138.5, 136.4, 109.3, 107.1, 106.1, 105.8,
103.2, 57.3, 55.5, 55.4, 38.9, 37.5, 28.4, 27.5, 21.2, 21.0 ppm, IR (film):
1744, 1704, 1647, 1613, 1450, 1378, 1351, 1310, 1269, 1236, 1140,
1084, 1026, 1001, 945, 910, 893, 849, 831, 760, 668, 630, 556, 520,
477 cm−1; HRMS (EI+): C12H18O2 calcd 194.1307; found 194.1298.
3k is known but not fully characterized.29
2-(2-Phenoxyacetyl)cyclopentanone (3l). Yield: 53 mg as a
mixture of a keto and an enol forms (keto/enol = 35:65 by 1H
NMR), red oil, 61%; 1H NMR (300 MHz, CDCl3, keto/enol = 35:65)
δ = 13.40 (br, 1H, enol), 7.25−6.80 (m, 5 H, keto and enol), 4.91−
4.57 (m, 2 H, keto and enol), 3.55 (t, 1 H, J = 8.6 Hz, keto), 2.60−
1.73 (m, 6 H, keto and enol). 13C NMR (75 MHz, CDCl3, keto and
enol): δ = 212.5 (keto), 205.1 (enol), 200.8 (keto), 173.7 (enol),
158.0, 157.6, 129.6, 121.7, 121.5, 114.6, 114.4, 109.8, 72.6, 67.4, 58.8,
v = 3422, 3101, 3007, 2965, 2941, 2842, 1741, 1626, 1567, 1471, 1450,
̃
1431, 1410, 1361, 1319, 1283, 1217, 1203, 1186, 1165, 1082, 1062,
1051, 945, 929, 919, 892, 875, 847, 838, 731, 677, 511 cm−1; HRMS
(EI+): C14H16O4 calcd 248.1049; found 248.1042. 3f is known but not
fully characterized.27
2-(3,5-Bis(trifluoromethyl)benzoyl)cyclopentanone (3g). Yield: 77
mg as a mixture of a keto and an enol forms (keto/enol = 20:80 by 1H
NMR), red oil, 59%; 1H NMR (300 MHz, CDCl3, keto/enol = 20:80)
δ = 14.29 (br, 1 H, enol), 8.52−7.96 (m, 3 H, keto and enol), 4.28 (t,
1 H, J = 8.1 Hz, keto), 2.93−1.99 (m, 6 H, keto and enol). 13C NMR
(75 MHz, CDCl3, keto and enol): δ = 211.8 (keto), 211.4 (enol),
192.5 (keto), 164.0 (enol), 137.9, 136.7, 132.7, 132.2, 131.8, 129.6,
128.0, 128.0, 124.8, 124.1, 124.1, 121.2, 110.6, 57.7, 39.0, 37.6, 28.0,
38.6, 36.3, 25.3, 25.0, 20.9, 20.5 ppm, IR (film): v = 3448, 3063, 2969,
̃
2916, 1746, 1721, 1667, 1599, 1495, 1455, 1430, 1404, 1365, 1328,
1292, 1268, 1223, 1173, 1132, 1083, 1012, 909, 886, 822, 786, 755,
692, 613, 569, 508 cm−1; HRMS (EI+): C13H14O3 calcd 218.0943;
found 218.0937. 3l is known.30
2-Benzoylcyclobutanone (3m). Yield: 25 mg, 35%; 1H NMR (300
MHz, CD2Cl2, keto/enol >99:1) δ = 8.06−8.02 (m, 2 H), 7.64−7.58
(m, 1 H), 7.55−7.48 (m, 2 H), 5.25−5.19 (m, 1 H), 3.22−3.14 (m, 2
H), 2.84−2.76 (m, 1 H), 2.26−2.16 (m, 1 H). 3m is known.12,31
26.4, 21.2, 20.9 ppm, IR (film): v = 3474, 3099, 2970, 2361, 1745,
̃
1690, 1653, 1626, 1601, 1453, 1385, 1340, 1280, 1240, 1179, 1136,
7765
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
2-Benzoylcyclotridecanone (3p). Yield: 78 mg, white solid, 65%;
mp 102−103 °C; 1H NMR (300 MHz, CDCl3, keto/enol > 99:1) δ =
7.97−7.93 (m, 2H), 7.60−7.54 (m, 1 H), 7.49−7.44 (m, 2 H), 4.46
(dd, 1 H, J = 3.0 Hz, 10.2 Hz), 2.70−2.60 (m, 1 H), 2.37−2.27 (m, 1
H), 2.19−2.15 (m, 1 H), 1.86−1.24 (m, 19 H). 13C NMR (75 MHz,
CDCl3): δ = 207.1, 196.3, 136.3, 133.5, 128.8, 128.5, 63.0, 39.7, 27.9,
AUTHOR INFORMATION
■
Corresponding Author
*hashmi@hashmi.de
Notes
The authors declare no competing financial interest.
26.9, 26.2, 26.1, 25.5, 25.1, 24.9, 24.9, 24.3, 22.4 ppm, IR (film): v =
̃
3422, 2923, 2862, 1708, 1679, 1596, 1580, 1461, 1448, 1410, 1363,
1327, 1294, 1280, 1264, 1250, 1206, 1175, 1104, 1066, 1021, 1003,
980, 965, 936, 795, 764, 739, 706, 694, 660, 603, 567, 494 cm−1;
HRMS (EI+): C20H28O2 calcd 300.2089; found 300.2081.
ACKNOWLEDGMENTS
■
T. Wang and S. Shi are grateful for the fellowships from China
Scholarship Council (CSC).
2-Benzoylcyclohexadecanone (3q). Yield: 96 mg, white solid, 70%;
1
mp 71−73 °C; H NMR (300 MHz, CDCl3, keto/enol > 99:1) δ =
REFERENCES
■
7.97−7.94 (m, 2 H), 7.59−7.53 (m, 1 H), 7.48−7.42 (m, 2 H), 4.45
(q, 1 H, J = 4.8 Hz), 2.67−2.56 (m, 1 H), 2.32−2.09 (m, 2 H), 1.89−
1.79 (m, 1 H), 1.64−1.53 (m, 2 H), 1.30 (s, 22 H). 13C NMR (75
MHz, CDCl3): δ = 206.9, 196.1, 136.3, 133.5, 128.8, 128.6, 63.2, 39.6,
28.8, 27.5, 27.4, 27.1, 27.0, 26.7, 26.5, 26.5, 26.4, 26.4, 26.2, 26.1, 22.4
(1) (a) Rudolph, M.; Hashmi, A. S. K. Chem. Soc. Rev. 2012, 41,
2448. (b) Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180.
́
(2) (a) Witham, C. A.; Mauleοn, P.; Shapiro, N. D.; Sherry, B. D.;
Toste, F. D. J. Am. Chem. Soc. 2007, 129, 5838. (b) Qian, D.; Zhang, J.
Chem. Commun. 2011, 47, 11152.
ppm, IR (film): v = 3439, 2929, 2856, 1713, 1679, 1596, 1581, 1449,
̃
(3) Vasu, D.; Hung, H.-H.; Bhunia, S.; Gawade, S. A.; Das, A.; Liu,
R.-S. Angew. Chem., Int. Ed. 2011, 50, 6911.
(4) (a) Li, C.-W.; Pati, K.; Lin, G.-Y.; Sohel, S. M. A.; Hung, H.-H.;
Liu, R.-S. Angew. Chem., Int. Ed. 2010, 49, 9891. (b) Xu, C. F.; Xu, M.;
Jia, Y. X.; Li, C.-Y. Org. Lett. 2011, 13, 1556.
(5) (a) Ye, L.; Cui, L.; Zhang, G.; Zhang, L. J. Am. Chem. Soc. 2010,
132, 3258. For excellent reviews, see: (b) Alcaide, B.; Almendros, P.;
Alonso, J. M. Org. Biomol. Chem. 2011, 9, 4405.
(6) (a) Li, G.; Zhang, L. Angew. Chem., Int. Ed. 2007, 46, 5156.
(b) Yeom, H.-S.; Lee, Y.; Jeong, J.; So, E.; Hwang, S.; Lee, J.-E.; Lee,
Shim, S.; Shin, S. Angew. Chem., Int. Ed. 2010, 49, 1611. (c) Ye, L.; He,
W.; Zhang, L. J. Am. Chem. Soc. 2010, 132, 8550.
(7) (a) Lu, B.; Li, C.; Zhang, L. J. Am. Chem. Soc. 2010, 132, 14070.
(b) Cui, L.; Zhang, G.; Peng, Y.; Zhang, L. Org. Lett. 2009, 11, 1225.
(c) Davies, P. W.; Cremonesi, A.; Martin, N. Chem. Commun. 2011,
47, 379. (d) Gronnier, C.; Kramer, S.; Odabachian, Y.; Gagosz, F. J.
Am. Chem. Soc. 2012, 134, 828. (e) Cuenca, A. B.; Montserrat, S.;
Hossain, K. M.; Mancha, G.; Lledos, A.; Medio-Simon, M.; Ujaque, G.;
Asensio, G. Org. Lett. 2009, 11, 4906. (f) Chen, D.; Song, G.; Jia, A.;
Li, X. J. Org. Chem. 2011, 76, 8488.
1400, 1351, 1234, 1114, 1078, 1048, 1001, 953, 765, 699, 690, 598
cm−1; HRMS (EI+): C23H34O2 calcd 342.2559; found 342.2536.
2-Methyl-1-phenylbutane-1,3-dione (3r). Yield: 55 mg as a
mixture of a keto and an enol forms (keto/enol = 87:13 by 1H
1
NMR), 78%; H NMR (300 MHz, CDCl3, keto/enol = 87:13) δ =
16.60 (s, 1 H, enol), 7.98−7.36 (m, 5 H, keto and enol), 4.48 (q, 1 H,
J = 7.2 Hz, keto), 2.25 (s, 3 H, enol), 2.14 (s, 3 H, keto), 1.92 (s, 3 H,
enol), 1.44 (d, 3 H, J = 7.2 Hz, keto). 3r is known.32
1-Phenylbutane-1,3-dione (3s). Yield: 33 mg as a mixture of a keto
1
1
and an enol forms (keto/enol = 8:92 by H NMR), 50%; H NMR
(300 MHz, CDCl3, keto/enol = 8:92) δ = 16.16 (s, 1 H, enol), 7.95
−7.41 (m, 5 H, keto and enol), 6.18 (s, 1 H, enol), 4.10 (s, 2 H, keto),
2.30 (s, 3 H, keto), 2.20 (s, 3 H, enol). 3s is known.33
2-Methyl-3-oxo-3-phenylpropanal (3s′). Yield: 26 mg as a mixture
1
of a keto and an enol forms (keto/enol = 30:70 by H NMR), 26%;
1H NMR (300 MHz, CDCl3, keto/enol = 30:70) δ = 15.39 (d, 1 H,
enol), 9.76 (d, 1 H, J = 2.3 Hz, keto), 8.60 (d, 1 H, J = 4.8 Hz, enol),
7.99−7.41 (m, 5 H, keto and enol), 4.40 (qd, 1 H, J = 2.3 Hz, 6.9 Hz,
keto), 1.99 (s, 3 H, enol), 1.48 (d, 3 H, J = 6.9 Hz, keto). 3s′ is
known.34
(8) (a) Hashmi, A. S. K.; Braun, I.; Nosel, P.; Schadlich, J.; Wieteck,
̈
̈
M.; Rudolph, M.; Rominger, F. Angew. Chem., Int. Ed. 2012, 51, 4456.
(b) Hashmi, A. S. K.; Yang, W.; Rominger, F. Angew. Chem., Int. Ed.
2011, 50, 5762. (c) Hashmi, A. S. K.; Schuster, A. M.; Rominger, F.
Angew. Chem., Int. Ed. 2009, 48, 8247. (d) Hashmi, A. S. K.; Rudolph,
3-Oxo-2,3-diphenylpropanal (3t). Yield: 65 mg as a mixture of a
1
1
keto and an enol forms (keto/enol = 3:97 by H NMR), 73%; H
NMR (300 MHz, CDCl3, keto/enol = 3:97) δ = 15.91 (d, 1 H, J = 5.4
Hz, enol), 9.98 (d, 1 H, J = 3.6 Hz, keto), 8.63 (d, 1 H, J = 5.4 Hz,
enol), 8.01−7.07 (m, 10 H, keto and enol), 5.39 (d, 1 H, J = 3.6 Hz,
keto). 3t is known.35
́
M.; Huck, J.; Frey, W.; Bats, J.; Hamzic, M. Angew. Chem., Int. Ed.
2009, 48, 5848. For a review on mechanisms in homogeneous gold
catalysis, see: (e) Hashmi, A. S. K. Angew. Chem., Int. Ed. 2010, 49,
5232.
1,2-Diphenylbutane-1,3-dione (3u). Yield: 54 mg as a mixture of a
1
1
keto and an enol forms (keto/enol = 27:73 by H NMR), 57%; H
NMR (300 MHz, CDCl3, keto/enol = 27:73) δ = 17.48 (s, 1 H, enol),
8.09−7.19 (m, 10 H, keto and enol), 5.78 (s, 1 H, keto), 2.36 (s, 3 H,
keto), 2.15 (s, 3 H, enol). 3u is known.36
(9) Kel’in, A. V.; Maioli, A. Curr. Org. Chem. 2003, 7, 1855.
(10) Garnovskii, A. D.; Kharisov, B. I.; Blanco, L. M.; Garnovskii, D.
A.; Burlov, A. S.; Vasilchenko, I. S.; Bondarenko, G. I. J. Coord. Chem.
1999, 46, 365.
(11) Alcaide, B.; Almendros, P.; Luna, A.; Gom
Torres, M. R. J. Org. Chem. 2012, 77, 3549.
2-Methyl-1,3-diphenylpropane-1,3-dione (3u′). Yield: 15 mg,
́
ez-Campillos, G.;
1
16%; H NMR (300 MHz, CDCl3, keto/enol > 99:1) δ = 7.97−
7.94 (m, 4 H), 7.60−7.54 (m, 2 H), 7.48−7.42 (m, 4 H), 5.26 (q, 1 H,
J = 6.9 Hz), 1.61 (d, 3 H, J = 6.9 Hz). 3u′ is known.33
(E)-2-Benzylidenecyclobutanone (4a). Yield: 60 mg, 95%; 1H
NMR (300 MHz, CDCl3) δ = 7.54−7.49 (m, 2 H), 7.44−7.37 (m, 3
H), 7.05−7.02 (m, 1 H), 3.18−3.09 (m, 2 H), 3.04−2.96 (m, 2 H). 4a
is known.13
(12) Huet, F.; Lechevallier, A.; Conia, J.-E. Chem. Lett. 1981, 10,
1515.
(13) Markham, J. P.; Staben, S. T.; Toste, F. D. J. Am. Chem. Soc.
2005, 127, 9708.
(14) Noey, E. L.; Luo, Y.; Zhang, L.; Houk, K. N. J. Am. Chem. Soc.
2012, 134, 1078.
(15) Ph3PAuNTf2 (100 μmol) and pyridine-N-oxide (the number of
equivalents given on each line of the spectrum) were stirred for 20 min
in CDCl3 at rt.
(16) Wei, L.-M.; Wei, L.-L.; Pan, W.-B.; Wu, M.-J. Tetrahedron Lett.
2003, 44, 595.
(17) Zhu, H.-T.; Ji, K.-G.; Yang, F.; Wang, L.-J.; Zhao, S.-C.; Ali, S.;
Liu, X.-Y.; Liang, Y.-M. Org. Lett. 2011, 13, 684.
(18) Zora, M.; Herndon, J. W.; Li, Y.; Rossi, J. Tetrahedron 2011, 57,
5097.
ASSOCIATED CONTENT
■
S
* Supporting Information
1
Spectra for compounds 1a−u, 3a−u, 3u′, 4a as well as H and
31P NMR spectra of Ph3PAuNTf2 and different ratios of
pyridine-N-oxide and Ph3PAuNTf2. This material is available
free of charge via the Internet at http://pubs.acs.org.
7766
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767

The Journal of Organic Chemistry
Note
(19) Trost, B. M.; Xie, J.; Maulide, N. J. Am. Chem. Soc. 2008, 130,
17258.
(20) Potkin, V. I.; Dikusar, E. A.; Kozlov, N. G. Russ. J. Org. Chem.
2002, 38, 1260.
(21) Panteleev, J.; Huang, R. Y.; Lui, E. K. J.; Lautens, M. Org. Lett.
2011, 13, 5314.
(22) Ishikawa, T.; Mizuta, T.; Hagiwara, K.; Aikawa, T.; Kudo, T.;
Saito, S. J. Org. Chem. 2003, 68, 3702.
(23) Wei, L.-M.; Wei, L.-L.; Pan, W.-B.; Wu, M.-J. Tetrahedron Lett.
2007, 48, 3155.
(24) Campbell, R. D.; Harmer, W. L. J. Org. Chem. 1963, 28, 379.
(25) Fos, E.; Borras
Heterocyclic Chem. 1992, 29, 203.
̀ ́
, L.; Gasull, M.; Mauleon, D.; Carganico, G. J.
(26) He, H.-Y.; Qu, Y.-L.; Zhao, C.-X. Chin. J. Chem. 1998, 16, 549.
(27) Cirigottis, K. A.; Cleaver, L.; Corrie, J. E. T.; Grasby, R. G.;
Green, G. H.; Mock, J.; Nimgirawath, S.; Read, R. W.; Ritchie, E.;
Taylor, W. C.; et al. Aust. J. Chem. 1974, 27, 345.
(28) Doering, W. v. E.; Finkelstein, M. J. Org. Chem. 1958, 23, 141.
(29) Yu, J. W.; Kim, H. H.; Jahng, Y. Pharmazie 2002, 57, 301.
(30) British Patent, 1980, GB 1568855.
(31) Lechevallier, A.; Huet, F.; Conia, J. M. Tetrahedron 1983, 39,
3329.
(32) Matsukawa, Y.; Isobe, M.; Kotsuki, H; Ichikawa, Y. J. Org. Chem.
2005, 70, 5339.
(33) Bartlett, S. L.; Beaudry, C. M. J. Org. Chem. 2011, 76, 9852.
(34) Nesmeyanov, A. N.; Rybinskaya, M. I.; Kelekhsaeva, T. G.
Zhurnal Organicheskoi Khimii 1968, 4, 921.
(35) Li, S.; Lundquist, K.; Stomberg, R. Acta. Chem. Scan. 1993, 47,
867.
(36) Padwa, A.; Brookhart, T. J. Org. Chem. 1979, 44, 4021.
7767
dx.doi.org/10.1021/jo301381z | J. Org. Chem. 2012, 77, 7761−7767