Gold catalysis: Products and intermediates obtained from N-propargylcarboxamides bearing additional substituents on nitrogen

Article abstract of DOI:10.1002/ejoc.201100179

The reaction of several propargylamide substrates with additional substituents on the nitrogen atom was investigated. Under aqueous conditions acyloxy-substituted allylammonium salts could selectively be obtained. Monitoring of the reactions by ¹H NMR spectroscopy indicated the presence of an intermediate. Then switching to anhydrous reaction conditions allowed the isolation and characterization of these intermediates, oxazoliniminium species. Workup of the allylammonium salts under basic conditions led to an acyl transfer from the oxygen atom to the nitrogen atom, which proves that these products are not formed by a direct gold-catalysed hydration of the triple bond only, and at the same time nicely explains the selective monohydration of only one out of two triple bonds. A careful control of the conditions allows the synthesis of either oxazolinum salts oracyloxy-substituted enynes with an ammonium unit in the tether. The latter compounds are stable in the presence of the gold catalyst; they do not undergo a gold-catalysed enyne cycloisomerization. Copyright

Full text of DOI:10.1002/ejoc.201100179

FULL PAPER
DOI: 10.1002/ejoc.201100179
Gold Catalysis: Products and Intermediates Obtained from
N-Propargylcarboxamides Bearing Additional Substituents on Nitrogen
A. Stephen K. Hashmi,*[a] Lise Molinari,[a] Frank Rominger,[a] and Thomas Oeser[a]
Keywords: Alkynes / Allylammonium salts / Amides / Gold / Iminium salts
The reaction of several propargylamide substrates with ad-
ditional substituents on the nitrogen atom was investigated.
Under aqueous conditions acyloxy-substituted allylammo-
nium salts could selectively be obtained. Monitoring of the
reactions by 1H NMR spectroscopy indicated the presence of
an intermediate. Then switching to anhydrous reaction con-
ditions allowed the isolation and characterization of these in-
termediates, oxazoliniminium species. Workup of the allyl-
ammonium salts under basic conditions led to an acyl trans-
fer from the oxygen atom to the nitrogen atom, which proves
that these products are not formed by a direct gold-catalysed
hydration of the triple bond only, and at the same time nicely
explains the selective monohydration of only one out of two
triple bonds.
Whereas N-propargylcarboxamides 1 derived from pri-
mary amines delivered the corresponding N,O-heterocycles
2, 3 or 4, substrates 1 derived from secondary amines af-
forded the allylamines 5 (Scheme 1). For an efficient cata-
lytic transformation to 5 some acid had to be added in or-
der to facilitate the proto-deauration step; thus the ammo-
nium salts 6 were isolated. Only three examples of this
transformation have been reported, in only one case the
product had been isolated und fully characterized.[5]
Here we report our detailed study on the reaction to the
unusual acyloxy-substituted allylamonium salts 6.
Introduction
Homogeneous gold catalysis is now an established syn-
thetic tool,[1] which – apart from creative methodology de-
velopment and detailed mechanistic studies[2] – has now
also entered the field of total synthesis.[3] The gold-cata-
lysed synthesis of heterocycles is a highly useful tool.[4] In
this area we have developed a simple synthesis of oxazoles[5]
and alkylideneoxazolines[6] from N-propargylcarbox-
amides.[7] The same class of substrates then also allowed the
isolation of vinylgold intermediates,[8] a technique which
subsequently proved to be of broad scope.[9]
Results and Discussion
While the mechanism has not been studied in detail, the
reaction was assumed to proceed similarly to the synthesis
of the alkylideneoxazolines. After initial coordination of the
triple bond (soft, alkynophilic transition metal fragment, π-
acid),[1b,1g] the carbonyl oxygen atom attacks in a 5-exo-dig
mode. Since there is no hydrogen atom on the nitrogen
atom, which could be eliminated as a proton and sub-
sequently initiate the proto-deauration step,[10] the external
–
acid H+X– delivers the proton (X– = BF4 or OTs) for the
formation of the alkylideneoxazolininium salt intermediate
7. Being significantly more electrophilic than the alkylid-
eneoxazolines 2, the intermediate 7 now undergoes nucleo-
philic attack by the water molecules being present (in most
gold-catalyzed reactions it is not necessary to exclude
water) and re-protonation at the nitrogen atom, leading to
intermediate A. The addition of water seemingly is faster
than a possible aromatization of 7 by isomerization of the
exocyclic double bond. The ring-opening of A by fragmen-
tation of the C–N and O–H bonds and re-protonation at
Scheme 1. Different reaction pathways of N-propargylcarbox-
amides 1 with gold catalysts.
[a] Organisch-Chemisches Institut, Ruprecht-Karls-Universität
Heidelberg,
Im Neuenheimer Feld 270, 69120 Heidelberg, Germany
Fax: +49-6221-54-4205
E-mail hashmi@hashmi.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201100179.
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Gold Catalysis
the nitrogen atom finally leads to the observed product 6. 1af (Entry 10, as expected[12] the acceptor-substituted furan
None of these intermediates had been detected so far moiety does not undergo a furan-yne cyclisation[13]) and the
(Scheme 2).
acrylamide 1ag (Entry 11). A remarkable chemoselectivity
was observed with the 1,6-enyne-type substrate 1c (En-
try 12). The oxazol formation still dominates over the enyne
cycloisomerisation – no side products were observed. The
N-methyl-N-propargyl substrate 1c and the N-benzyl-N-
propargyl substrate 1d also gave the expected products 6c
and 6d (Entries 13 and 14). We also conducted control ex-
periments with Bronsted acids and silver salts[14] as cata-
lysts; however, no conversion of 1 was observed.
An X-ray crystal structure analysis of single crystals
clearly proved the connectivities in the product 6ac (Fig-
ure 1).[15]
Scheme 2. Proposed mechanism for the formation of 6.
On the basis of the overall transformation, we speculated
whether the dipropargyl derivative 1a could deliver the
products 6a, which still bear a propargyl group on the nitro-
gen atom and thus contain an enyne substructure. Such en-
yes are known to undergo gold-catalyzed enyne cycloisom-
erizations.[11] Therefore, we were hoping for a domino se-
quence to deliver one or several of the products 8–10 as
shown in Scheme 3.
Figure 1. Molecular structure of 6ac in the crystal.
In addition, we monitored the reactions by 1H NMR
spectroscopy during the conversion; a representative set of
spectra is shown in Figure 2. From these spectra it became
clear that not only the signals of the starting material are
disappearing (pink, propargylic methylene groups, broaden-
ing by slow amid rotation) and the product signals (red,
ammonium protons) are evolving in the course of the reac-
tion, but also a set of transient peaks is visible (the methyl-
ene protons and the alkynyl proton of the oxazolium inter-
mediate in green, compare Figure 3, and the hydroxy pro-
ton of the orthoester species in blue). This suggested that
Scheme 3. Is a domino allylamine formation/enyne cycloisomeriza-
tion possible?
We prepared a series of N,N-dipropargylcarboxamides we should be able to investigate this intermediate by choos-
1aa–1ag as well as the N-allyl- (1b), N-methyl- (1c) and N- ing the proper conditions.
benzyl- (1d) -N-propargylcarboxamides and then investi-
Thus, we conducted the catalysis in the absence of water,
gated their reactions with the gold catalyst/acid reagent and this indeed allowed the synthesis of the oxazolinium
(Table 1). As detected by 1H NMR spectroscopy, all conver- salt intermediate (Table 2). For the phenyl- (Entry 1), 4-bro-
sions were quantitative, no side products had formed. For mophenyl- (Entry 2) and 3,4-dimethoxyphenyl-substituted
1ac it was exemplified that a simple filtration of the crude substrates bearing a second propargyl group on the nitro-
product through a pad of aluminium oxide (in order to re- gen atom a selective conversion to 7aa–7ad was observed.
move the gold catalyst) delivers the pure product, in this The substrates 1c bearing a phenyl substituent and a methyl
case 89%. With 1aa different catalysts were tested. While group on the nitrogen atom as well as the substrate 1d with
Ph3PAu+ (Entry 2) and even Ph3PAuCl (Entry 3, much a phenyl substituent and a benzyl group on the nitrogen
slower conversion) gave the product, the most simple condi- atom reacted similarly. A representative 1H NMR spectrum
tions, which still gave a fast conversion, use AuCl3 in MeCN of crude 7aa is shown in Figure 3; again, the products form
(Entry 1). Thus, AuCl3 and Ph3PAu+ were used in the reac- in an essentially quantitative yield as judged by the 1H
tions with the aryl bromide 1ab (Entries 4, 5), the dimeth- NMR spectra – the reaction is highly selective. All the
oxyarene 1ac (Entries 6, 7), the nitroarene 1ad (Entry 8), major signals could be assigned to the different hydrogen
the cinnamyl derivative 1ae (Entry 9), the furyl derivative atoms of the product as shown there; the diethyl ether origi-
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A. S. K. Hashmi, L. Molinari, F. Rominger, T. Oeser
FULL PAPER
Table 1. Synthesis and gold-catalyzed conversion of the substrates 1aa–1af and 1b.
[a] All conversions were quantitative, no side products had formed. [b] HBF4 instead of HOTs was used as additive.
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Gold Catalysis
1
Figure 2. H NMR in situ study of the reaction of 1aa with AuCl3/PTSA in CD3CN (Table 1, Entry 1).
1
Figure 3. In situ H NMR spectrum of 7aa in MeCN (the Et2O signal originates from the acid HBF4·Et2O).
nates from one of the reagents (the integrals are shown as ously identified by a crystal structure analysis (Figure 4).[15]
numbers under the signals, the signals of H1Ј and H2/ In the case of 6ab, even a basic aluminium oxide filtration
H2Ј overlap).
was sufficient to induce this rearrangement. This excludes
Finally, we were interested in the behavior of the sub- that a subsequent gold-catalysed hydration of the C–C tri-
strates 6 under basic conditions. After deprotonation to 11, ple bond is occurring, as then a twofold reaction (con-
we observed an immediate acyl group migration for 6aa, verting both propargyl groups) should be expected, but not
6ab and 6ac, and the compounds 12aa, 12ab and 12ac were the observed selective monohydration of only one single
obtained (Scheme 4). Compound 12ab could be unambigu- alkynyl group.
Scheme 4. Acyl migration after deprotonation of 6.
Figure 4. Molecular structure of 12ab in the crystal.
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A. S. K. Hashmi, L. Molinari, F. Rominger, T. Oeser
FULL PAPER
(0.02 equiv.). This solution was stirred at room temp. for 15 min
and then cooled down to 0 °C. Acyl chloride (1.0 equiv.) was added
slowly. After stirring at 0 °C for 30 min, the reaction mixture was
warmed to room temp. and stirred for 3 h. The reaction was
quenched by the addition of water. The aqueous layer was extracted
twice with dichloromethane. The combined organic phases were
washed with brine, dried with Na2SO4, filtered, and the solvent was
removed in vacuo. The product was purified by flash chromatog-
raphy.
Table 2. Formation of the oxazolinium salt intermediate 7.
General Procedure 2a (GP 2a). Preparation of Aminium Salts 6: To
a stirred solution of a carboxamide (1.0 equiv.) in acetonitrile (ca.
0.5 m) at room temp. were added AuCl3 (0.05 equiv.) and p-tolu-
enesulfonic acid (1.0 equiv.). This solution was stirred at room
temp. for 30 min and then filtered through a pad of Celite. The
filtrate was concentrated in vacuo.
General Procedure 2b (GP 2b). Preparation of Aminium Salts 6: To
a stirred solution of a carboxamide (1.0 equiv.) in acetonitrile (ca.
0.5 m) at room temp. were added AuCl3 (0.05 equiv.) and tetrafluo-
roboric acid (1.0 equiv.). This solution was stirred at room temp.
for 5 min, and then water (1.0 equiv.) was added. The reaction mix-
ture was stirred at room temp. for 1 h and concentrated in vacuo.
General Procedure 2c (GP 2c). Preparation of Aminium Salts 6: The
gold complex Ph3PAuCl (0.05 equiv.) was activated with AgOTs
(0.05 equiv.) in dichloromethane at room temp. for 30 min. To a
stirred solution of a carboxamide (1.0 equiv.) in dichloromethane
(ca. 1 m) at room temp. were added the activated gold complex and
p-toluenesulfonic acid (1.0 equiv.). This solution was stirred at
room temp. for 20 min and then filtered through a pad of Celite.
The filtrate was concentrated in vacuo.
General Procedure 2d (GP 2d). Preparation of Aminium Salts 6: To
a stirred solution of a carboxamide (1.0 equiv.) in dichloromethane
(ca. 0.5 m) at room temp. were added Ph3PAuCl (0.05 equiv.) and
p-toluenesulfonic acid (1.0 equiv.). This solution was stirred at
room temp. for 1 h and then filtered through a pad of Celite. The
filtrate was concentrated in vacuo.
General Procedure 3 (GP 3). Preparation of Oxazolium Salts 7: To
a stirred solution of a carboxamide (1.0 equiv.) in dichloromethane
(ca. 0.5 m) at room temp. were added Ph3PAuCl (0.05 equiv.) and
tetrafluoroboric acid (1.0 equiv.). This solution was stirred at room
temp. for 5 min and then concentrated in vacuo.
Conclusions
The gold-catalysed isomerisation of the substrates 1 is of
general scope, and the corresponding allylammonium salts
6 can be obtained in good yields and even be isolated. An-
other intermediate of the reaction, the oxazoliniminium
salts 7, could also be identified under anhydrous conditions,
which confirms the mechanistic proposal for the formation
of 6.
An overall monohydration of the substrates 1 by the for-
mation and subsequent deprotonation of 6 is possible; this
selective monohydration excludes a competing direct gold-
catalysed hydration.
N,N-Bis(prop-2-yn-1-yl)benzamide (1aa): Preparation according to
GP1 on a 12.7 mmol scale. Flash chromatography on SiO2 (PE/
EtOAc, 9:1) afforded 1aa as a yellow oil (2.40 g, 12.18 mmol, 96%).
IR (neat): ν = 3292, 3062, 2976, 2915, 2120, 1640, 1450, 1411, 1357,
˜
1255, 1178, 1148, 999, 954, 790, 671 cm–1. 1H NMR (300 MHz,
CDCl3, 20 °C): δ = 2.32 (br. s, 2 H), 4.33 (br. s, 4 H), 7.39–7.47 (m,
3 H), 7.52–7.58 (m, 2 H) ppm. 1H NMR (500 MHz, CDCl3,
–40 °C): δ = 2.31 (s, 1 H), 2.43 (s, 1 H), 4.15 (d, J = 2.0 Hz, 2 H),
4.46 (d, J = 2.2 Hz, 2 H), 7.39–7.48 (m, 3 H), 7.54–7.59 (m, 2 H)
ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 33.6, 38.5, 73.7,
72.5, 77.9, 77.9, 127.3 (2 C), 128.7 (2 C), 130.8, 133.7, 171.0 ppm.
MS [EI(+), 70 eV]: m/z (%) = 197 (29) [M]+, 158 (59), 105 (100),
77 (16). HRMS [EI(+)]: calcd. for [C13H11NO]+ 197.0841; found
197.0837.
The use of the building blocks 6 in organic synthesis will
be reported in due course.
4-Bromo-N,N-bis(prop-2-yn-1-yl)benzamide (1ab): Prepared accord-
ing to GP1 on a 5.23 mmol scale. Flash chromatography on SiO2
(PE/EtOAc, 9:1) afforded 1ab as yellow crystals (1.33 g, 4.81 mmol,
Experimental Section
General Procedure 1 (GP 1). Preparation of N,N-Dipropargyl- 92%). IR (KBr): ν = 3442, 3257, 3218, 2927, 2111, 1644, 1590,
˜
carboxamides 1: To a stirred solution of N,N-dipropargylamine hy-
drochloride (1.0 equiv.) in dichloromethane (ca. 0.2 m) under nitro-
gen at room temp. were added Et3N (2.0 equiv.) and DMAP
1450, 1424, 1285, 1260, 1172, 1073, 999, 954, 844, 753 cm–1. 1H
NMR (250 MHz, CDCl3, 20 °C): δ = 2.33 (br. s, 2 H), 4.26 (br. s,
4 H), 7.41–7.48 (m, 2 H), 7.54–7.61 (m, 2 H) ppm. 1H NMR
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Gold Catalysis
(500 MHz, CDCl3, –40 °C): δ = 2.32 (s, 1 H), 2.43 (s, 1 H), 4.13 (s,
2 H), 4.44 (s, 2 H), 7.49 (d, J = 8.3 Hz, 2 H), 7.58 (d, J = 8.2 Hz,
37.5, 72.5, 73.4, 77.9, 78.2, 111.7, 117.4, 145.2, 145.7, 159.4 ppm.
MS [EI(+), 70 eV]: m/z (%) = 187 (10) [M]+, 95 (100). HRMS
2 H) ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 33.9, 38.5, [EI(+)]: calcd. for [C11H9NO2]+ 187.0633; found 187.0610.
72.7, 74.0, 77.7, 77.8, 125.2 (2 C), 129.1 (2 C), 131.9, 132.0, 132.7,
3-Methyl-N,N-bis(prop-2-yn-1-yl)but-2-enamide (1ag): Prepared ac-
170.0 ppm. MS [EI(+), 70 eV]: m/z (%) = 277 (25) [M]+, 275 (25),
cording to GP1 on a 4.31 mmol scale. Flash chromatography on
238 (60), 236 (60), 185 (95), 183 (100), 157 (35), 155 (35). HRMS
SiO2 (PE/EtOAc, 7:3) afforded 1ag as yellow crystals (967 mg,
[EI(+)]: calcd. for [C13H10BrNO]+ 276.9925; found 276.9937.
3.99 mmol, 93%). IR (neat): ν = 3305, 2979, 2916, 2249, 1628,
˜
3,4-Dimethoxy-N,N-bis(prop-2-yn-1-yl)benzamide (1ac): Prepared 1454, 1414, 1234, 1184, 911, 733, 648 cm–1. 1H NMR (500 MHz,
according to GP1 on a 3.99 mmol scale. Flash chromatography on
SiO2 (PE/EtOAc, 6:4) afforded 1ac as white crystals (990 mg,
CDCl3, –40 °C): δ = 1.85 (s, 3 H), 1.92 (s, 3 H), 2.25 (s, 1 H), 2.33
(s, 1 H), 4.22 (s, 2 H), 4.33 (s, 2 H), 5.82 (s, 1 H) ppm. 13C NMR
3.87 mmol, 97%). IR (KBr): ν = 3440, 3302, 3254, 3226, 3007, (126 MHz, CDCl3, –40 °C): δ = 20.6, 26.7, 33.0, 36.8, 72.2, 73.1,
˜
2959, 2837, 2116, 1639, 1518, 1441, 1266, 1224, 1178, 1136, 1025,
77.9, 78.4, 116.5, 150.1, 167.7 ppm. MS [EI(+), 70 eV]: m/z (%) =
755, 721 cm–1. 1H NMR (300 MHz, CDCl3, 20 °C): δ = 2.32 (br. s,
176 (8) [M + H]+, 136 (10), 83 (100), 55 (45). HRMS [EI(+)]: calcd.
2 H), 3.90 (s, 3 H), 3.91 (s, 3 H), 4.33 (br. s, 4 H), 6.89 (d, J = for [C11H13NO]+ 175.0997; found 175.0932.
8.3 Hz, 1 H), 7.14–7.25 (m, 2 H) ppm. 1H NMR (500 MHz, CDCl3,
N-(Prop-2-en-1-yl)-N-(prop-2-yn-1-yl)benzamide (1b): To a stirred
–40 °C): δ = 2.30 (s, 1 H), 2.44 (s, 1 H), 3.91 (s, 3 H), 3.93 (s, 3 H),
4.21 (s, 2 H), 4.41 (s, 2 H), 6.90 (d, J = 8.3 Hz, 1 H), 7.20 (s, 1 H),
7.26 (s, 1 H) ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 34.2,
38.9, 56.0, 56.1, 72.3, 73.6, 78.2, 78.5, 110.0, 110.5, 120.9, 125.8,
148.1, 150.5, 170.9 ppm. MS [EI(+), 70 eV]: m/z (%) = 257 (35)
[M]+, 218 (24), 165 (100), 137 (10), 77 (16). HRMS [EI(+)]: calcd.
for [C15H15NO3]+ 257.1052; found 257.1053.
solution of N-(prop-2-ynyl)benzamide (2.50 g, 15.70 mmol) in THF
(60 mL) under nitrogen at 0 °C was added NaH (95%, 660 mg,
21.98 mmol, 1.4 equiv.) in two portions. The reaction mixture was
warmed to room temp. and stirred for 1 h. Then allyl bromide
(1.6 mL, 18.84 mmol, 1.2 equiv.) was added slowly at 0 °C, after
which the reaction mixture was warmed to room temp. and stirred
overnight. The reaction mixture was diluted with EtOAc (50 mL)
4-Nitro-N,N-bis(prop-2-yn-1-yl)benzamide (1ad): Prepared accord- and then quenched with saturated ammonium chloride solution
ing to GP1 on a 4.31 mmol scale. Flash chromatography on SiO2
(PE/EtOAc, 7:3) afforded 1ad as yellow crystals (967 mg,
(50 mL). The aqueous phase was extracted with EtOAc
(3ϫ20 mL). The combined organic layers were washed with water
(2ϫ20 mL) and brine (20 mL), dried with Na2SO4, filtered, and
concentrated in vacuo. The crude product was purified by flash
chromatography on SiO2 (PE/EtOAc, 9:1) to afford 1b as yellow
3.99 mmol, 93%). IR (KBr): ν = 3441, 3289, 3103, 2987, 2913,
˜
2859, 2118, 1642, 1601, 1524, 1449, 1350, 1271, 1185, 1001, 865,
727, 678 cm–1. 1H NMR (250 MHz, CDCl3, 20 °C): δ = 2.36 (br. s,
2 H), 4.12 (br. s, 2 H), 4.49 (br. s, 2 H), 7.74 (d, J = 8.8 Hz, 2 H), oil (2.55 g, 12.80 mmol, 82%). IR (neat): ν = 3291, 3242, 3062,
˜
8.31 (d, J = 8.8 Hz, 2 H) ppm. 1H NMR (500 MHz, CDCl3, 3027, 2919, 2117, 1645, 1452, 1411, 1351, 1258, 1151, 1112, 991,
1
–40 °C): δ = 2.35 (s, 1 H), 2.47 (s, 1 H), 4.09 (d, J = 1.3 Hz, 2 H),
929, 790, 701, 671 cm–1. H NMR (300 MHz, CDCl3, 20 °C): δ =
4.47 (d, J = 1.3 Hz, 2 H), 7.79 (d, J = 8.4 Hz, 2 H), 8.33 (d, J = 2.29 (s, 1 H), 3.79–4.47 (m, 4 H), 5.17–5.36 (m, 2 H), 5.81 (s, 1 H),
1
8.4 Hz, 2 H) ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 33.8, 7.33–7.55 (m, 5 H) ppm. H NMR (500 MHz, CDCl3, –40 °C): δ
38.3, 73.1, 74.4, 77.3, 124.1 (2 C), 128.4 (2 C), 140.1, 148.4, = 2.28 (s, 1 H), 2.43 (s, 1 H), 3.91–4.04 (m, 4 H), 4.20–4.32 (m, 4
168.7 ppm. MS [EI(+), 70 eV]: m/z (%) = 243 (17) [M]+, 203 (100),
150 (83), 104 (40). HRMS [EI(+)]: calcd. for [C13H10N2O3]+
242.0691; found 242.0720.
H), 5.21–5.38 (m, 4 H), 5.69–5.91 (m, 2 H), 7.33–7.63 (m, 10 H)
ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 33.6, 38.1, 46.9,
50.8, 71.8, 73.1, 78.6, 78.7, 118.1, 118.9, 126.8 (2 C), 126.9 (2 C),
128.5 (2 C), 128.6 (2 C), 130.4, 130.4, 131.5, 132.1, 134.5, 134.7,
171.1, 172.0 ppm. MS [EI(+), 70 eV]: m/z (%) = 199 (10) [M]+,
160 (16), 158 (14), 105 (100), 77 (45). HRMS [EI(+)]: calcd. for
[C13H13NO]+ 199.0997; found 199.1011.
(2E)-3-Phenyl-N,N-bis(prop-2-yn-1-yl)prop-2-enamide (1ae): Pre-
pared according to GP1 on a 4.37 mmol scale. Flash chromatog-
raphy on SiO2 (PE/EtOAc, 9:1) afforded 1ae as a yellow oil
(868 mg, 3.89 mmol, 89%). IR (neat): ν = 3292, 1651, 1610, 1454,
˜
1416, 1346, 1206, 978, 764, 684 cm–1. 1H NMR (300 MHz, CDCl3,
N-Methyl-N-(prop-2-yn-1-yl)benzamide (1c): To a stirred solution
of N-methyl-N-propargylamine (890 mL, 10.70 mmol, 1.0 equiv.) in
20 °C): δ = 2.34 (br. s, 2 H), 4.39 (br. s, 4 H), 6.88 (d, J = 15.4 Hz,
1 H), 7.30–7.46 (m, 3 H), 7.52–7.56 (m, 2 H), 7.74 (d, J = 15.4 Hz, dichloromethane (50 mL) under nitrogen at room temp. were added
1
1 H) ppm. H NMR (500 MHz, CDCl3, –40 °C): δ = 2.30 (s, 1 H), Et3N (1.65 mL, 11.77 mmol, 1.1 equiv.) and DMAP (26 mg,
2.40 (s, 1 H), 4.34 (s, 2 H), 4.42 (s, 2 H), 6.89 (d, J = 15.4 Hz, 1
0.21 mmol, 0.02 equiv.). This solution was stirred at room temp. for
H), 7.41 (d, J = 4.8 Hz, 3 H), 7.53–7.71 (m, 2 H), 7.76 (d, J = 15 min and then cooled down to 0 °C. Benzoyl chloride (1.24 mL,
15.4 Hz, 1 H) ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 34.7, 10.70 mmol, 1.0 equiv.) was added slowly. After stirring at 0 °C for
36.5, 72.5, 73.6, 77.9, 78.2, 115.8, 128.1 (2 C), 128.9 (2 C), 130.3,
134.4, 144.6, 166.2 ppm. MS [EI(+), 70 eV]: m/z (%) = 223 (10)
[M]+, 184 (8), 142 (95), 131 (100), 77 (27). HRMS [EI(+)]: calcd.
for [C15H13NO]+ 223.0997; found 223.0986.
30 min, the reaction mixture was warmed to room temp. and stirred
for 3 h. The reaction was quenched by addition of water (30 mL).
The aqueous layer was extracted with dichloromethane
(2ϫ20 mL). The combined organic phases were washed with brine
(20 mL), dried with Na2SO4, filtered, and the solvent was removed
in vacuo. The crude product was purified by flash chromatography
on SiO2 (PE/EtOAc, 7:3) to afford 1c as a yellow oil (1.72 g,
9.94 mmol, 93%). 1H NMR (300 MHz, [D6]DMSO): δ = 2.98 (s, 3
H), 3.06 (t, J = 2.5 Hz, 1 H), 4.16–4.18 (br. s, 2 H), 7.40–7.45 (m,
N,N-Bis(prop-2-yn-1-yl)furan-2-carboxamide (1af): Prepared ac-
cording to GP1 on a 4.31 mmol scale. Flash chromatography on
SiO2 (PE/EtOAc, 7:3) afforded 1af as yellow crystals (967 mg,
3.99 mmol, 93%). IR (neat): ν = 3288, 3235, 2961, 1635, 1483,
˜
1
1415, 1355, 1265, 1182, 1020, 923, 759 cm–1. H NMR (500 MHz,
1
5 H) ppm. The H NMR data corresponds to that reported in the
CDCl3, 20 °C): δ = 2.30 (s, 2 H), 4.50 (s, 4 H), 6.47–6.54 (m, 1 H),
7.18 (d, J = 3.5 Hz, 1 H), 7.51–7.57 (m, 1 H) ppm. 1H NMR
(500 MHz, CDCl3, –40 °C): δ = 2.29 (s, 2 H), 2.42 (s, 2 H), 4.40 (s,
4 H), 4.51 (s, 4 H), 6.50–6.55 (m, 2 H), 7.21 (d, J = 3.0 Hz, 2 H),
7.59 (s, 2 H) ppm. 13C NMR (126 MHz, CDCl3, –40 °C): δ = 34.7,
literature.[6a]
N-Benzyl-N-(prop-2-yn-1-yl)benzamide (1d): To a stirred solution of
N-(prop-2-ynyl)benzamide (2.50 g, 15.70 mmol) in THF (60 mL)
under nitrogen at 0 °C was added NaH (95%, 660 mg, 21.98 mmol,
Eur. J. Org. Chem. 2011, 2256–2264
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2261

A. S. K. Hashmi, L. Molinari, F. Rominger, T. Oeser
FULL PAPER
1.4 equiv.) in two portions. The reaction mixture was warmed to
room temp. and stirred for 1 h. Then benzyl bromide (2.24 mL,
18.84 mmol, 1.2 equiv.) was added slowly at 0 °C, after which the
reaction mixture was warmed to room temp. and stirred overnight.
The reaction mixture was diluted with EtOAc (50 mL) and then
quenched with saturated ammonium chloride solution (50 mL).
The aqueous phase was extracted with EtOAc (3ϫ20 mL). The
combined organic layers were washed with water (2ϫ20 mL) and
brine (20 mL), dried with Na2SO4, filtered, and concentrated in
vacuo. The crude product was purified by flash chromatography
on SiO2 (PE/EtOAc, 9:1) to afford 1d as yellow oil (3.26 g,
CD3CN): δ = 21.3, 36.9, 48.8, 56.5, 56.6, 74.3, 79.4, 111.8, 112.1,
113.4, 121.8, 125.5, 126.7 (2 C), 129.6 (2 C), 140.9, 143.9, 147.0,
149.8, 155.0, 165.6 ppm. MS (ESI): m/z (%) = 276 (100) [M]+.
HRMS (ESI): calcd. for [C15H18NO4]+ 276.1230; found 276.1232.
6ac was also prepared according to GP2c on a 0.15 mmol scale.
2-[(4-Nitrobenzoyl)oxy]-N-(prop-2-yn-1-yl)prop-2-en-1-aminium
Tetrafluoroborate (6ad): Prepared according to GP2b on a
0.10 mmol scale. IR (KBr): ν = 3478, 3273, 2921, 2723, 2590, 2412,
˜
2125, 1741, 1568, 1519, 1541, 1347, 1279, 1198, 1083, 923, 852, 717,
1
579 cm–1. H NMR (500 MHz, CD2Cl2): δ = 2.75 (t, J = 2.5 Hz, 1
H), 4.07–4.13 (m, 4 H), 5.55 (d, J = 2.8 Hz, 1 H), 5.59 (d, J =
2.8 Hz, 1 H), 7.79 (s, 2 H), 8.27 (s, 4 H) ppm. 13C NMR (126 MHz,
CD2Cl2): δ = 37.3, 48.9, 72.2, 79.8, 114.2, 124.1 (2 C), 132.0 (2 C),
134.0, 144.9, 151.6, 164.5 ppm. MS (ESI): m/z (%) = 261 (100)
[M]+. HRMS (ESI): calcd. for [C13H13N2O4]+ 261.0875; found
261.0873.
13.06 mmol, 83%). IR (neat): ν = 3286, 3242, 3061, 3030, 2922,
˜
2928, 2118, 1639, 1495, 1450, 1417, 1362, 1255, 1145, 1077, 1000,
789, 699 cm–1. 1H NMR (500 MHz, CDCl3, –40 °C): δ = 2.35 (s, 1
H), 2.46 (s, 1 H), 3.88 (s, 2 H), 4.30 (s, 2 H), 4.72 (s, 2 H), 4.91 (s,
2 H), 7.22–7.71 (m, 20 H) ppm. 13C NMR (126 MHz, CDCl3,
–40 °C): δ = 33.4, 38.0, 47.1, 51.7, 72.3, 73.5, 78.2, 78.3, 126.8 (2
C), 126.9 (2 C), 127.0 (2 C), 127.8 (2 C), 127.9 (2 C), 128.6 (2 C),
128.7 (2 C), 128.8 (2 C), 129.0 (2 C), 130.4 (2 C), 134.6, 134.7,
135.4, 136.0, 171.4, 172.1 ppm. MS [EI(+), 70 eV]: m/z (%) = 249
(20) [M]+, 210 (80), 158 (10), 105 (100), 77 (35). HRMS [EI(+)]:
calcd. for [C17H15NO]+ 249.1154; found 249.1160.
2-{[(2E)-3-Phenylprop-2-enoyl]oxy}-N-(prop-2-yn-1-yl)prop-2-en-
1-aminium Tosylate (6ae): Prepared according to GP2a on a
0.12 mmol scale. IR (neat): ν = 3433, 3027, 2131, 1731, 1634, 1451,
˜
1206, 1124, 1034, 1009, 685, 568 cm–1 1H NMR (500 MHz,
.
CD3CN): δ = 2.33 (s, 3 H), 2.92 (s, 1 H), 3.96 (s, 2 H), 4.01 (s, 2
H), 5.35 (d, J = 1.8 Hz, 1 H), 5.39 (d, J = 1.8 Hz, 1 H), 6.56 (d, J
= 16.0 Hz, 1 H), 7.19 (d, J = 7.8 Hz, 2 H), 7.38–7.49 (m, 3 H), 7.59
(d, J = 6.9 Hz, 2 H), 7.67 (d, J = 7.8 Hz, 2 H), 7.78 (d, J = 16.0 Hz,
1 H), 8.94 (br. s, 2 H) ppm. 13C NMR (75 MHz, CD3CN): δ =
21.4, 37.0, 48.9, 74.1, 79.5, 111.6, 117.8, 126.9 (2 C), 129.5 (2 C),
129.9 (2 C), 130.0 (2 C), 131.9, 135.0, 141.9, 146.5, 147.8,
165.9 ppm. MS [FAB(+)]: m/z (%) = 242 (74) [M]+, 131 (100).
HRMS [FAB(+)]: calcd. for [C15H16NO2]+ 242.1181; found
242.1177.
2-(Benzoyloxy)-N-(prop-2-yn-1-yl)prop-2-en-1-aminium
Tosylate
(6aa): Prepared according to GP2a on a 0.10 mmol scale. IR (neat):
ν = 3234, 2990, 2790, 2120, 1733, 1600, 1451, 1188, 1123, 1033,
˜
1
1009, 815, 708, 683, 567 cm–1. H NMR (500 MHz, CD3CN): δ =
2.34 (s, 3 H), 2.91 (s, 1 H), 4.03 (s, 4 H), 5.38 (d, J = 2.3 Hz, 1 H),
5.46 (d, J = 2.3 Hz, 1 H), 7.16 (d, J = 7.9 Hz, 2 H), 7.47 (t, J =
7.6 Hz, 2 H), 7.60 (d, J = 8.0 Hz, 2 H), 7.65 (t, J = 7.5 Hz, 1 H),
8.05 (d, J = 8.0 Hz, 2 H), 9.04 (br. s, 2 H) ppm. 13C NMR (75 MHz,
CD3CN): δ = 21.4, 36.9, 48.6, 74.2, 79.5, 112.3, 126.8 (2 C), 129.6
(2 C), 129.8 (2 C), 131.1 (2 C), 141.7, 142.5, 146.8, 165.8 ppm. MS
(ESI): m/z (%) = 216 (100) [M]+, 234 (13) [M + H2O]+, 252 (41)
[M + HCl]+, 296 (6) [M + HBr]+, 298 (6) [M + HBr]+. HRMS
(ESI): calcd. for [C13H14NO2]+ 216.1019; found 216.1021.
2-[(Furan-2-ylcarbonyl)oxy]-N-(prop-2-yn-1-yl)prop-2-en-1-aminium
Tosylate (6af): Prepared according to GP2a on a 0.15 mmol scale.
IR (neat): ν = 3434, 3011, 2798, 1737, 1471, 1395, 1303, 1174, 1035,
˜
1
1010, 685, 569 cm–1. H NMR (300 MHz, CD3CN): δ = 2.37 (s, 3
6aa was also prepared according to GP2c on a 0.10 mmol scale
and according to GP2d on a 0.10 mmol scale.
H), 2.93 (t, J = 2.6 Hz, 1 H), 4.00 (br. s, 4 H), 5.40 (d, J = 2.5 Hz,
1 H), 5.46 (d, J = 2.5 Hz, 1 H), 6.60 (dd, J = 3.6, 1.7 Hz, 1 H),
7.22 (d, J = 8.0 Hz, 2 H), 7.39 (dd, J = 3.6, 0.8 Hz, 1 H), 7.64 (d,
J = 8.1 Hz, 2 H), 7.77 (dd, J = 1.7, 0.8 Hz, 1 H), 8.95 (br. s, 2 H)
ppm. 13C NMR (75 MHz, CD3CN): δ = 21.4, 37.0, 48.7, 74.1, 79.6,
112.3, 113.4, 121.5, 126.9 (2 C), 129.9 (2 C), 141.9, 142.4, 144.2,
146.0, 149.3, 157.3 ppm. MS [FAB(+)]: m/z (%) = 206 (100) [M]+.
HRMS [FAB(+)]: calcd. for [C11H12NO3]+ 206.0817; found
206.0788.
2-[(4-Bromobenzoyl)oxy]-N-(prop-2-yn-1-yl)prop-2-en-1-aminium
Tosylate (6ab): Prepared according to GP2a on a 0.72 mmol scale.
IR (KBr): ν = 3405, 2961, 2928, 2117, 1728, 1654, 1447, 1426, 1253,
˜
1
1174, 1015, 838 cm–1. H NMR (300 MHz, CDCl3): δ = 2.35 (s, 3
H), 2.44 (s, 1 H), 4.02 (s, 2 H), 4.08 (s, 2 H), 5.34 (d, J = 2.4 Hz,
1 H), 5.41 (d, J = 2.4 Hz, 1 H), 7.06 (d, J = 7.9 Hz, 2 H), 7.33 (d,
J = 8.5 Hz, 2 H), 7.54 (d, J = 8.0 Hz, 2 H), 7.81 (d, J = 8.6 Hz, 2
H), 9.69 (br. s, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 21.5,
35.6, 47.5, 73.3, 78.2, 111.9, 126.0 (2 C), 127.6, 128.8 (2 C), 129.0,
131.7 (2 C), 131.9 (2 C), 140.5, 141.2, 145.2, 164.2 ppm. MS (ESI):
m/z (%) = 294 (95) [M]+, 296 (100) [M]+. HRMS (ESI): calcd. for
[C13H13BrNO2]+ 294.0124; found 294.0126.
2-[(3-Methylbut-2-enoyl)oxy]-N-(prop-2-yn-1-yl)prop-2-en-1-
aminium Tosylate (6ag): Prepared according to GP2a on a
0.15 mmol scale. IR (neat): ν = 3022, 2979, 2131, 1733, 1647, 1445,
˜
1
1380, 1209, 1181, 1124, 1071, 1034, 817, 683, 567 cm–1. H NMR
(500 MHz, CD3CN): δ = 1.92 (s, 3 H), 2.15 (s, 3 H), 2.37 (s, 3 H),
2.93 (t, J = 2.3 Hz, 1 H), 3.87 (s, 2 H), 3.95 (s, 2 H), 5.23 (d, J =
1.9 Hz, 1 H), 5.33 (d, J = 1.7 Hz, 1 H), 5.77 (d, J = 1.0 Hz, 1 H),
7.23 (d, J = 8.0 Hz, 2 H), 7.66 (d, J = 8.1 Hz, 2 H), 9.05 (br. s, 2
H) ppm. 13C NMR (126 MHz, CD3CN): δ = 20.7, 21.4, 27.6, 36.8,
48.8, 74.2, 79.4, 111.1, 115.3, 126.8 (2 C), 129.8 (2 C), 141.4, 143.5,
146.5, 162.5, 165.3 ppm. MS (ESI): m/z (%) = 194 (100) [M]+.
HRMS (ESI): calcd. for [C11H16NO2]+ 194.1176; found 194.1178.
6ab was also prepared according to GP2c on a 0.10 mmol scale.
2-[(3,4-Dimethoxybenzoyl)oxy]-N-(prop-2-yn-1-yl)prop-2-en-1-amin-
ium Tosylate (6ac): Prepared according to GP2a on a 1.94 mmol
scale. The crude product was purified by flash chromatography on
Alox (PE/EtOAc, 6:4) to afford 6ac as white crystals (773 mg,
1.73 mmol, 89%). IR (KBr): ν = 3435, 2985, 2842, 2118, 1724,
˜
1599, 1516, 1455, 1348, 1274, 1217, 1174, 1135, 1034, 1007, 758,
682, 570 cm–1. 1H NMR (300 MHz, CD3CN): δ = 2.32 (s, 3 H), 2-(Benzoyloxy)-N-(prop-2-en-1-yl)prop-2-en-1-aminium Tosylate
2.88 (t, J = 2.3 Hz, 1 H), 3.81 (s, 3 H), 3.86 (s, 3 H), 3.98 (s, 2 H),
(6b): Prepared according to GP2a on a 0.12 mmol scale. IR (neat):
4.00 (d, J = 2.3 Hz, 2 H), 5.34 (d, J = 2.2 Hz, 1 H), 5.43 (d, J = ν = 3477, 3010, 2819, 1734, 1601, 1452, 1269, 1213, 1123, 1089,
˜
2.2 Hz, 1 H), 6.93 (d, J = 8.5 Hz, 1 H), 7.13 (d, J = 7.9 Hz, 2 H), 1034, 1010, 850, 709, 685, 569 cm–1. 1H NMR (300 MHz, CD3CN):
7.52 (d, J = 1.9 Hz, 1 H), 7.56 (d, J = 8.0 Hz, 2 H), 7.69 (dd, J =
δ = 2.35 (s, 3 H), 3.74 (q, J = 5.7 Hz, 2 H), 3.87 (t, J = 5.7 Hz, 2
8.5, 2.0 Hz, 1 H), 8.87 (br. s, 2 H) ppm. 13C NMR (75 MHz, H), 5.36 (d, J = 2.4 Hz, 1 H), 5.41 (dd, J = 10.3, 1.2 Hz, 1 H), 5.45
2262
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 2256–2264

Gold Catalysis
(d, J = 2.4 Hz, 1 H), 5.51 (q, J = 1.2 Hz, 1 H), 5.99 (ddt, J = 17.1,
10.3, 2.5 Hz, 1 H), 7.18 (dd, J = 8.4, 0.5 Hz, 2 H), 7.46–7.54 (m, 2
H), 8.19 (d, J = 9.0 Hz, 2 H), 8.46 (d, J = 9.0 Hz, 2 H) ppm. 13C
NMR (126 MHz, CD2Cl2): δ = 40.3, 54.4, 72.4, 79.0, 95.4, 124.6,
H), 7.58–7.63 (m, 2 H), 7.64–7.71 (m, 1 H), 8.09 (dt, J = 8.5, 125.1 (2 C), 132.5 (2 C), 150.9, 152.4, 171.7 ppm.
1.6 Hz, 2 H), 8.69 (br. s, 2 H) ppm. 13C NMR (75 MHz, CD3CN):
3-Methyl-5-methylidene-2-phenyl-4,5-dihydro-1,3-oxazol-3-ium
δ = 21.4, 48.9, 50.1, 111.6, 124.6, 126.7 (2 C), 128.9, 129.7 (2 C),
129.8 (2 C), 129.9, 131.1 (2 C), 134.9, 141.4, 143.3, 147.3,
165.8 ppm. MS [FAB(+)]: m/z (%) = 218 (100) [M]+, 105 (28).
HRMS [FAB(+)]: calcd. for [C13H16NO2]+ 218.1181; found
218.1181.
Tetrafluoroborate (7c): Prepared according to GP3 on a 0.15 mmol
1
scale. H NMR (500 MHz, CD3CN): δ = 3.55 (s, 3 H), 5.01 (s, 2
H), 5.02–5.08 (m, 1 H), 5.31 (dd, J = 7.5, 3.1 Hz, 1 H), 7.74 (t, J
= 7.8 Hz, 2 H), 7.91 (t, J = 7.5 Hz, 1 H), 7.96 (d, J = 7.6 Hz, 2 H)
ppm. 13C NMR (126 MHz, CD3CN): δ = 37.2, 57.1, 93.4, 120.31,
130.7 (2 C), 131.4 (2 C), 137.2, 152.1, 171.3 ppm.
2-(Benzoyloxy)-N-methylprop-2-en-1-aminium Tosylate (6c): Pre-
pared according to GP2d on a 0.2 mmol scale. 1H NMR
(500 MHz, CD2Cl2): δ = 2.31 (s, 3 H), 2.70 (t, J = 5.4 Hz, 3 H),
3.84 (t, J = 5.4 Hz, 2 H), 5.32 (d, J = 2.5 Hz, 1 H), 5.42 (d, J =
2.5 Hz, 1 H), 7.13 (d, J = 8.3 Hz, 2 H), 7.39–7.48 (m, 2 H), 7.55–
7.66 (m, 3 H), 8.05 (d, J = 8.3 Hz, 2 H), 8.33 (br. s, 2 H) ppm.
4-Bromo-N-(2-oxopropyl)-N-(prop-2-yn-1-yl)benzamide (12ab): Pre-
pared according to GP2a on a 2.08 mmol scale. The crude product
was purified by flash chromatography on Alox (PE/EtOAc, 7:3) to
afford 12ab as white crystals (407 mg, 1.39 mmol, 67%). IR (neat):
ν = 3287, 3258, 2921, 2120, 1730, 1647, 1592, 1456, 1426, 1361,
˜
1255, 1171, 1070, 1013, 839, 753 cm–1. 1H NMR (500 MHz,
CDCl3): δ = 2.25 (s, 3 H), 2.36 (s, 1 H), 4.07 (s, 2 H), 4.41 (s, 2 H),
7.46 (d, J = 7.5 Hz, 2 H), 7.58 (d, J = 7.6 Hz, 2 H) ppm. 13C NMR
(126 MHz, CDCl3): δ = 27.4, 40.4, 54.1, 73.7, 78.0, 124.9, 128.9,
131.9, 133.3, 170.4, 202.4 ppm. MS [EI(+), 70 eV]: m/z (%) = 295
(10) [M]+, 293 (9), 252 (34), 250 (34), 185 (100), 183 (100), 157
(19), 155 (19). HRMS [EI(+)]: calcd. for [C13H12BrNO2]+ 293.0051;
found 293.0041.
The 1H NMR data corresponds to that reported in the literature.[6a]
2-(Benzoyloxy)-N-benzylprop-2-en-1-aminium Tosylate (6d): Pre-
pared according to GP2a on a 0.15 mmol scale. IR (neat): ν = 3433,
˜
3038, 2789, 1734, 1601, 1453, 1233, 1124, 1034, 1010, 851, 704,
684, 569 cm–1. 1H NMR (300 MHz, CD3CN): δ = 2.36 (s, 3 H),
3.89 (t, J = 5.5 Hz, 2 H), 4.28 (t, J = 5.6 Hz, 2 H), 5.37 (d, J =
2.3 Hz, 1 H), 5.46 (d, J = 2.2 Hz, 1 H), 7.19 (d, J = 7.9 Hz, 2 H),
7.33–7.41 (m, 3 H), 7.47–7.56 (m, 4 H), 7.59 (d, J = 8.0 Hz, 2 H),
7.68 (t, J = 7.4 Hz, 1 H), 8.07 (d, J = 7.2 Hz, 2 H), 8.79 (s, 2 H)
ppm. 13C NMR (75 MHz, CD3CN): δ = 21.3, 49.3, 51.3, 112.1,
126.8 (2 C), 129.6 (2 C), 129.7 (2 C), 129.9 (2 C), 130.4, 131.1 (2
C), 131.2 (2 C), 131.8, 134.9, 141.4, 143.3, 147.2, 165.9 ppm. MS
(ESI): m/z (%) = 268 (100) [M]+. HRMS (ESI): calcd. for
[C17H18NO2]+ 268.1338; found 268.1340.
Supporting Information (see footnote on the first page of this arti-
cle): Detailed insets (Figure S2) and integrals (Figure S1) of the
NMR spectra used in Figure 2, which are the basis for the assign-
ment.
Acknowledgments
5-Methylidene-2-phenyl-3-(prop-2-yn-1-yl)-4,5-dihydro-1,3-oxazol-
3-ium Tetrafluoroborate (7aa): Prepared according to GP3 on a
0.11 mmol scale. 1H NMR (250 MHz, CD3CN): δ = 3.11 (t, J =
2.4 Hz, 1 H), 4.76 (d, J = 2.4 Hz, 2 H), 5.11 (d, J = 3.5 Hz, 3 H),
5.38 (dd, J = 7.5, 3.4 Hz, 1 H), 7.78 (t, J = 7.5 Hz, 2 H), 7.95 (m,
3 H) ppm. 13C NMR (75 MHz, CD3CN): δ = 40.6, 54.7, 73.5, 79.1,
94.3, 119.9, 130.9 (2 C), 131.4 (2 C), 137.8, 151.9, 172.5 ppm. MS
[FAB(+)]: m/z (%) = 198 (100) [M]+, 154 (21), 136 (24), 105 (29).
HRMS [FAB(+)]: calcd. for [C13H12NO]+ 198.0913; found
198.0920.
This work was supported by Umicore AG & Co. KG and by the
Deutsche Forschungsgemeinschaft (SFB 623).
[1] a) G. Dyker, Angew. Chem. 2000, 112, 4407–4409; Angew.
Chem. Int. Ed. 2000, 39, 4237–4239; b) A. S. K. Hashmi, Gold
Bull. 2003, 36, 3–9; c) A. S. K. Hashmi, Gold Bull. 2004, 37,
51–65; d) N. Krause, A. Hoffmann-Röder, Org. Biomol. Chem.
2005, 3, 387–391; e) A. S. K. Hashmi, G. Hutchings, Angew.
Chem. 2006, 118, 8064–8105; Angew. Chem. Int. Ed. 2006, 45,
7896–7936; f) A. S. K. Hashmi, Chem. Rev. 2007, 107, 3180–
3211; g) A. Fürstner, P. W. Davies, Angew. Chem. 2007, 119,
3478–3519; Angew. Chem. Int. Ed. 2007, 46, 3410–3449; h) D. J.
Gorin, B. D. Sherry, F. D. Toste, Chem. Rev. 2008, 108, 3351–
3378; i) E. Jiménez-Núnez, A. M. Echavarren, Chem. Rev.
2008, 108, 3326–3350; j) Z. G. Li, C. Brouwer, C. He, Chem.
Rev. 2008, 108, 3239–3265.
2-(4-Bromophenyl)-5-methylidene-3-(prop-2-yn-1-yl)-4,5-dihydro-
1,3-oxazol-3-ium Tetrafluoroborate (7ab): Prepared according to
GP3 on a 0.10 mmol scale. 1H NMR (500 MHz, CD2Cl2): δ = 2.83
(t, J = 2.5 Hz, 1 H), 4.76 (d, J = 2.5 Hz, 2 H), 5.09 (dt, J = 5.0,
2.7 Hz, 1 H), 5.18 (t, J = 2.8 Hz, 2 H), 5.39 (dt, J = 4.9, 3.0 Hz, 1
H), 7.84–7.89 (m, 4 H) ppm. 13C NMR (126 MHz, CD2Cl2): δ =
40.2, 54.2, 72.8, 78.7, 94.8, 117.9, 132.2 (2 C), 133.1, 133.8 (2 C),
150.7, 170.6 ppm.
[2] A. S. K. Hashmi, Angew. Chem. 2010, 122, 5360–5369; Angew.
Chem. Int. Ed. 2010, 49, 5232–5241.
[3] A. S. K. Hashmi, M. Rudolph, Chem. Soc. Rev. 2008, 37, 1766–
1775.
2-(3,4-Dimethoxyphenyl)-5-methylidene-3-(prop-2-yn-1-yl)-4,5-dihy-
[4] A. S. K. Hashmi, M. Bührle, Aldrichim. Acta 2010, 43, 27–33.
[5] a) A. S. K. Hashmi, J. P. Weyrauch, W. Frey, J. W. Bats, Org.
Lett. 2004, 6, 4391–4394; b) D. Dorsch, L. T. Burgdorf, R. Ger-
icke, N. Beier, W. Mederski, WO 2005123688 A2, 2005; Chem.
Abstr. 2005, 144, 69837; c) D. Dorsch, O. Schadt, A. Blaukat,
F. Stieber, WO 2008/017361 A2; Chem. Abstr. 2008, 148,
190536.
[6] a) J. P. Weyrauch, A. S. K. Hashmi, A. Schuster, T. Hengst, S.
Schetter, A. Littmann, M. Rudolph, M. Hamzic, J. Visus, F.
Rominger, W. Frey, J. W. Bats, Chem. Eur. J. 2010, 16, 956–963;
b) A. S. K. Hashmi, M. Rudolph, S. Schymura, J. Visus, W.
Frey, Eur. J. Org. Chem. 2006, 4905–4909; compare also an-
other example observed in: c) C. Ferrer, A. M. Echavarren, An-
gew. Chem. 2006, 118, 1123–1127; Angew. Chem. Int. Ed. 2006,
45, 1105–1109.
dro-1,3-oxazol-3-ium Tetrafluoroborate (7ac): Prepared according
to GP3 on a 0.10 mmol scale. H NMR (500 MHz, CD3CN): δ =
1
3.11 (t, J = 2.4 Hz, 1 H), 3.92 (s, 3 H), 3.98 (s, 3 H), 4.77 (d, J =
2.3 Hz, 2 H), 5.05 (d, J = 3.6 Hz, 3 H), 5.32 (dd, J = 7.2, 3.6 Hz,
1 H), 7.26 (d, J = 8.6 Hz, 1 H), 7.46 (d, J = 1.9 Hz, 1 H), 7.68 (dd,
J = 8.6, 2.0 Hz, 1 H) ppm. 13C NMR (126 MHz, CD3CN): δ =
40.7, 55.0, 57.0, 74.3, 57.3, 78.9, 93.7, 111.2, 113.3, 113.5, 127.5,
150.8, 151.8, 157.8, 171.6 ppm.
5-Methylidene-2-(4-nitrophenyl)-3-(prop-2-yn-1-yl)-4,5-dihydro-
1,3-oxazol-3-ium Tetrafluoroborate (7ad): Prepared according to
GP3 on a 0.10 mmol scale. 1H NMR (500 MHz, CD2Cl2): δ = 2.83
(t, J = 2.6 Hz, 1 H), 4.76 (d, J = 2.6 Hz, 2 H), 5.14 (dt, J = 5.3,
2.9 Hz, 1 H), 5.23 (t, J = 2.9 Hz, 2 H), 5.43 (dt, J = 5.2, 3.0 Hz, 1
Eur. J. Org. Chem. 2011, 2256–2264
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. S. K. Hashmi, L. Molinari, F. Rominger, T. Oeser
FULL PAPER
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[15] CCDC-797255 (6ac) and -797256 (12ab) contain the supple-
mentary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Received: February 8, 2011
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B. Miehlich, W. Frey, J. W. Bats, Chem. Eur. J. 2006, 12, 5806–
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Published Online: March 9, 2011
2264
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Eur. J. Org. Chem. 2011, 2256–2264