Regioselective synthesis of enones via a titanium-promoted coupling of unsymmetrical alkynes with Weinreb amides

Article abstract of DOI:10.1021/jo5014417

A modular titanium-promoted coupling of unsymmetrical internal alkynes with Weinreb amides is described. The coupling reaction takes place at room temperature and affords E-trisubstituted enones in moderate to good yields with high levels of regioselectivity. The system shows moderate chemoselectivity.

Full text of DOI:10.1021/jo5014417

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Note
Regioselective Synthesis of Enones via a Titanium Promoted
Coupling of Unsymmetrical Alkynes with Weinreb Amides
Sajan Silwal, and Ronald James Rahaim
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo5014417 • Publication Date (Web): 13 Aug 2014
Downloaded from http://pubs.acs.org on August 15, 2014
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The Journal of Organic Chemistry
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Regioselective Synthesis of Enones via a Titanium Promoted Cou-
pling of Unsymmetrical Alkynes with Weinreb Amides
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Sajan Silwal and Ronald J. Rahaim*
107 Physical Sciences 1, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
*E-mail: rahaim@okstate.edu
ABSTRACT: A modular titanium promoted coupling of unsymmetrical internal alkynes with Weinreb amides is described. The
coupling reaction takes place at room temperature affording (E)-trisubstituted enones in moderate to good yields with high levels of
regioselectivity. The system showed moderate chemoselectivity.
α,β-Unsaturated ketones (enones) are an important building block that have found widespread use in the synthesis of natural
products1 and biologically active small molecules.2 The utility of enones is in the diverse array of structures that can be accessed
from this motif. As such, numerous methods have been developed for the preparation of enones3 such as, dehydrative Aldol’s,4
oxidations,5 olefination reactions with α-ketophosphonates,6 palladium dehydrogenation,7 transition metal catalyzed isomerization
of propargylic alcohols,8 hydroacylation of alkynes,9 and acylation of organometallic reagents.10 While all of these methods com-
plement each other there is still a need for a method that can prepare tri- and tetra-substituted enones in a modular manner from
readily available and easily modifiable substrates.
As part of our endeavors in developing methodology for applications in natural product mimic libraries, we speculated that a tita-
nium promoted coupling11 of an alkyne and an acyl electrophile could afford enones in a modular manner with high selectivity.
Stemming from the seminal work of Kulinkovich on the cyclopropanation of esters,12 Sato demonstrated that diisopropoxytitanacy-
clopropenes undergo intramolecular nucleophilic acyl substitution with carbonates (Scheme 1a).13 This work was expanded upon
by Six for the formation of α,β-unsaturated carboxylic acids and esters via an intermolecular titanium reductive coupling of alkynes
with carbon dioxide14 and carbonates (Scheme 1b).15 Complementarily, zirconocene mediated couplings of alkynes with chloro-
formates16 and carbon dioxide17 have also been reported. The use of group IV metallacycles to form enones from alkynes, surpris-
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ingly, has not been reported. For applications in library preparation a vast pool of readily available acyl electrophiles are needed to
facilitate diversification of the library. Based on this requirement, we chose to investigate Weinreb amides, which are bench stable
reactive acyl electrophiles that can easily and efficiently be prepared from ubiquitous carboxylic acids.18 Weinreb amides have
been utilized in enone synthesis with vinyl lithium19 and Grignard20 reagents, but not with titana- or zircona-cyclopropenes.
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Scheme 1. Titanium mediated synthesis of conjugated carbonyls from alkynes
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Evaluation of the titanacycle literature indicated the optimal starting point was generation of the titanacyclopropene via Sato’s
methods, where Ti(OiPr)4 is reduced with i-PrMgCl followed by ligand exchange with an alkyne.21 A limitation of this method for
application in small molecule library synthesis is that diisopropoxytitanacyclopropenes are thermally unstable and typically cannot
be warmed above -30 °C. It was speculated that the rate of reaction of the titanacyclopropene with a Weinreb amide would be
faster than the decomposition pathways and side reactions at room temperature, in addition the coupling would generate a stabilized
intermediate that would be thermally stable through coordination of the methoxy group to the titanium.
While the ultimate goal was development of a simple mix and stir procedure that would operate at room temperature, the reaction
was first investigated under cryogenic reaction conditions. A room temperature procedure would require the titanacyclopropene to
be generated in the presence of the Weinreb amide and it was not clear if the Grignard reagent would preferentially react with the
Ti(OiPr)4 over the Weinreb amide. Thus, for the initial optimization reactions the titanacyclopropene of alkyne 10 was generated
under prototypical cryogenic conditions (-78 to -40 °C for 3 hours) followed by addition of the Weinreb amide (11) at -78 °C and
warming to room temperature. Under these conditions the desired enone was formed (Table 1, entry 1), establishing that a titanacy-
clopropene can undergo coupling with a Weinreb amide and with high regioselectivity, favoring enone 12a. Increasing the concen-
tration of Weinreb amide 11 to 2 equivalents increased the yield of the enone (entry 2) but further increases had no effect (entry
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3).22 Attempts to further increase the yield through adjustment of the solvent (entries 4-6) established Et2O as the optimal choice.
The choice of reducing agent was critical as a negative effect was seen with EtMgBr (entry 7) and cyclopentylmagnesium chloride
(entry 8). It has been demonstrated that the use of n-BuLi produces thermally stable titanacycles.23 Surprisingly, under this reac-
tion manifold the use of n-BuLi to generate the titanacyclopropene afforded the enone in moderate yield but with a complete rever-
sal in regioselectivity, favoring enone 12b (entry 9). Simplification of the procedure by generating the titanacyclopropene in the
presence of the Weinreb amide was explored next. It was found that addition of n-BuLi to the reaction mixture last did not result in
titanacycle formation, instead the n-BuLi selectively reacted with only the Weinreb amide affording 1-phenylpentanone (entry 10).
Conversely, addition of i-PrMgCl to the reaction mixture last (entry 11) at -78 °C followed by warming to room temperature af-
forded the desired enone in the same yield and regioselectivity as the stepwise process (entry 2). The yield was increased further to
67% by running this sequential addition of reagents at room temperature (entry 12).
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Table 1. Optimization of Titanium Coupling Conditionsa
%yieldb
entry
solvent
equiv 12 reducing agent
(13a/13b)c
1
2
3
4
5
6
7
8
Et2O
Et2O
Et2O
1
2
5
2
2
2
2
1
2
2
2
2
i-PrMgCl
i-PrMgCl
i-PrMgCl
i-PrMgCl
i-PrMgCl
i-PrMgCl
EtMgBr
c-C5H9MgCl
nBuLi
nBuLi
i-PrMgCl
i-PrMgCl
32 (>99/1)
59 (97/3)
52 (97/3)
THF
34
0
0
0
20
MTBE
Toluene
Et2O
Et2O
THF
THF
Et2O
Et2O
9d
10e,f
11g
12h
37 (14/86)
0
58 (97/3)
67 (97/3)
aConditions: alkyne 10 (1 mmol), Ti(OiPr)4 (1.5 mmol), reducing agent (3 mmol), and Et2O (10 mL) at -78 °C, warmed to -40 °C for 3
hours, cooled to -78 °C then addition of Weinreb amide 11, and warm to room temperature. bisolated yield after flash chromatography.
cratio of regioisomers determined by GCMS of the crude reaction mixture. dnBuLi added at -78 °C, warm to room temperature then addi-
tion of Weinreb amide 11. enBuLi added last at room temperature. f1-phenylpentanone was isolated in 84%. gi-PrMgCl added last at -78
°C then warm to room temperature. hi-PrMgCl added last at room temperature
Having established the optimal conditions to be the operationally simple procedure of combining all of the reagents and adding
the i-PrMgCl last at room temperature followed by stirring for 4 hours, substrate screening was initiated to determine the scope of
this coupling reaction (Table 2). Initial efforts focused on varying the Weinreb amide while keeping the alkyne static with the un-
symmetrical alkyne 1-phenyl-1-propyne (10). In all of the cases examined (entries 1-22) the regioselectivity of the coupling reac-
tion was greater than 97/3. Formation of the carbon-carbon bond favored the alkyne carbon that contained the sterically smaller
substituent, regardless of the Weinreb amide employed. Aliphatic Weinreb amides (entries 12-16) were higher yielding than the
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aromatic Weinreb amides (entries 1-11), except for the sterically large N-methoxy-N-methylpivalamide which afforded the enone in
moderate yield (entry 17) comparable to its aromatic counterparts. The system tolerated aromatic and aliphatic halogens (entries 2-
6 and 13), of note is that an aromatic bromide did not undergo magnesium halogen exchange with the Grignard reagent.24 The sys-
tem tolerated meta and para substituted aromatic Weinreb amides, whereas ortho25 substituted aromatics (I, OMe, Me) would not
react with the in situ formed titanacycle (entries 7 and 10), with the exception of a naphthalene (entry 11). Methoxy groups (entry
8) inhibited coupling, presumably due to coordination with the titanium complex. To establish that coordination was the issue and
not deactivation of the Weinreb amide carbonyl from electron donation, a Weinreb amide with a TBS protected phenol was pre-
pared, which reacted without incident (entry 9). Additional functional groups on the aromatic Weinreb amide that were found to be
incompatible with the system were a –NO2, –CN, –OAc, and –C(O)CH3. Furan (entry 18) and thiophene (entry 19) heteroaromat-
ics were tolerated, but a pyridine (entry 20) inhibited coupling.26 Conjugated Weinreb amides underwent coupling producing the
1,4-dien-3-one’s (entries 21 and 22) in modest yield. These products have the potential to undergo a Nazarov cyclization,27 but
under these reaction conditions less than 3% of the Nazarov product was observed.
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A near quantitative yield was obtained with 4-octyne (entry 23) whereas the sterically more congested diphenylacetylene (entry
24) afforded the enone in moderate yield. As already demonstrated with 1-phenyl-1-propyne, an alkyne with a clear steric differ-
ence between the groups attached to the alkyne, undergoes coupling with high regioselectivity. To test the limits of the regioselec-
tivity unsymmetrical alkynes of varying steric bulk were examined. The coupling reaction afforded a near one to one mixture of
regioisomers when the steric differentiating group was distal to the alkyne (entry 25) or when the two groups were similarly sized
(entry 27). A single isomer was obtained with 3-benzyloxy-1-propynylbenzene (entry 26), albeit in low yield, presumably due to
formation of a dimeric titanacycle that inhibited reaction with the Weinreb amide. High regioselectivity was seen with silyl pro-
tected terminal alkynes (entries 29-31). The sterically congested phenyl-tert-butylacetylene participated in the coupling affording
the enone in moderate yield but with high selectivity (entry 32).
trimethylsilylacetylene completely inhibited the reaction.28
Increasing the sterics further with tert-butyl-
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Table 2. Substrate Screening of Titanium Mediated Coupling of Alkynes and Weinreb Amidesa,b
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8
entry
1
product
%yieldc
67
entry
15
product
%yieldc
95
entry
24
product(s)
%yieldc
48
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75
16
17
92
52
25
26
(53/47)
2
3
R = 4-F
R = 4-Cl
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0
13
4
R = 3-Br
5
R = 4-CF3
R = 3-CF3
R = 2-CF3
R = 4-OMe
R = 4-OTBS
R = 2,6-Me
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18
53
27
6
(50/50)
7
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0
64
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20
52
0
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29
9
53
trace
(23/77)
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11
12
20
(91/9)
46
87
21
31d
30
(86/14)
53
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74
80
22
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27e
95
31
32
(86/14)
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aConditions: alkyne (1 mmol), Weinreb amide (2 mmol), Ti(OiPr)4 (1.5 mmol), Et2O (10 mL), added last i-PrMgCl (3 mmol), room
temperature, 4 hours. bUnless otherwise stated ratio of regioisomers was ≥ 97/3 as determined by GCMS of the crude reaction mixture,
major isomer shown. cIsolated yield by flash chromatography. d41% alkyne recovered. e52% alkyne recovered.
Our earlier findings demonstrated when n-BuLi was used as the reducing agent (Table 1, entry 9) the enone was formed favoring
the opposite regioisomer. Based on this result, we became interested in the possibility to selectively access either regioisomer by
simply changing the reducing agent. Unfortunately, when n-BuLi was employed in the coupling reaction the yields were consid-
erably lower and with a number of the substrates screened there was no reaction. Control reactions were run to help determine
which element was causing the reversal in regioselectivity. First, we explored the possibility of a solvent effect. Since the solution
of i-PrMgCl used was in ether and the n-BuLi was in hexanes we ran the coupling reaction with the Grignard reagent in the pres-
ence of added hexanes. This only resulted in a lower yield of enone with no erosion in the selectivity, consistent with the solvent
screening data where the reaction did not take place in toluene (Table 1, entry 6). Next we examined the role of the metal cations.
To examine if the lithium cation was interacting with the titanium complex and thereby affecting the regiocontrol, 10 equivalents of
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LiCl was added to the reaction with i-PrMgCl, which was found to have no effect. In theory, reduction of the Ti(OiPr)4 with the
reducing agent produces two equivalents of a metal alkoxide, which could be affecting the aggregate structure of the titanacycle
and/or coordinating to the titanium and forming an ate complex. Thus, we ran the coupling reaction using i-PrMgCl with 2 equiva-
lents of lithium tert-butoxide added, which lowered the yield of the enone to 66% from 92% and slightly eroded the regiocontrol to
96/4. The root cause of the regioselectivity difference with n-BuLi and i-PrMgCl remains unclear.
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Titanacycles are carbanion reagents, as such, we examined subsequent reactions of the stabilized titanacycle intermediate. As
shown in Scheme 2, the in situ formed titanacycle 14 could be quenched with deuterium oxide to afford the deuterated enone in
82% yield with greater than 95% deuterium incorporation, and titanium halogen exchange of 14 with iodine afforded the conju-
gated vinyl iodide in moderate yield. Attempts to transmetallate the chelated and stabilized titanium-carbon bond in titanacycle 14
with copper(I) salts would only occur with CuOtBu, albeit in low yield, but could be used to couple with allyl bromide to form the
skipped diene-one 17. Reaction of titanacycle 14 with benzaldehyde did not occur due to the decreased reactivity of the stabilized
titanacycle, however, precomplexation of the aldehyde with BF3•OEt2 facilitated addition and a subsequent cyclization to yield the
tetrasubstituted furan 18 in 66% yield.29 A more detailed examination of this approach to furan and heterocycle synthesis is under-
way and will be reported in due course.
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Scheme 2. Subsequent Reactions of Stabilized Intermediate Titanacycle 14
In summary, this report describes a titanium mediated coupling of internal alkynes with Weinreb amides to yield (E)-
trisubstituted enones in moderate to good yields. The regioselectivity of the reaction is due to the steric difference between the
groups attached to the alkyne, with levels as high >99/1 being obtained. Additionally, this is the first demonstration that organoti-
tanium reagents react with Weinreb amides, thereby expanding the arsenal of nucleophiles that can react with this important acyl
electrophile.
EXPERIMENTAL SECTION
Methods: All reactions were carried out in oven dried or flame dried glassware under an atmosphere of argon, with magnetic
stirring. Reactions were monitored either by thin-layer chromatography with 0.25mm precoated silica gel plates, or Gas Chroma-
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tography. Visualization of all TLCs were performed by UV and/or staining with phosphomolybdic acid, KMnO4, or Seebach’s
stain. Purifications were performed by flash chromatography with silica gel (60 Å, 230-400 mesh) packed in glass columns and
eluted with hexanes/Et2O, unless otherwise noted.
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Materials: Diethyl ether, dichloromethane, chloroform, and tetrahydrofuran were purified and dried using a solvent-purification
system that contained activated alumina. 1,2-Dichloroethane and pyridine were freshly distilled from calcium hydride under argon.
All Weinreb amides were prepared following literature procedures30 from purchased carboxylic acids.
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Instrumentation: H NMR and 13C NMR spectra were obtained on a 400 MHz NMR Spectrometer (400 MHz for H and 101
MHz for 13C) with chemical shifts reported relative to residual chloroform solvent peaks (δ = 7.26ppm for 1H and δ = 77.0ppm for
13C). Data for H NMR were recorded as follows: chemical shift (δ, ppm), multiplicity (s = singlet, d = doublet, t = triplet, q =
1
quartet, quin = quintet, sex = sextet, sept = septet, m = multiplet or unresolved), coupling constant(s) in Hz, integration. Melting
points reported are uncorrected. Low Resolution Mass Spectra was performed by GC-MS and High Resolution Mass Spectra
(HRMS) were determined using an Orbitrap operated in FT mode to provide a nominal resolution of 100,000.
General procedure: A round bottom flask was sealed with a septa followed by placing the system under an atmosphere of argon
by performing a vacuum-purge cycle three times, then attaching a balloon of argon. The round bottom flask was charged with the
alkyne (1 mmol), Weinreb amide (2 mmol), dry diethyl ether (10 mL), and titanium isopropoxide (1.5 mmol, 0.44 mL). To this
stirring mixture was injected a solution of isopropyl magnesium chloride (2M in ether, 3 mmol, 1.5 mL) dropwise over 5 minutes.
The reaction was stirred at room temperature for 4 hours, followed by opening the system to the air and quenching with 1 mL of
water. The mixture was dried over magnesium sulfate, filtered, and concentrated. The crude material was subjected to flash chro-
matography eluting with hexanes/EtOAc (98/2), unless otherwise noted. Note 1: any solid reagents were added to the flask prior to
the vacuum-purge cycle. Note 2: a small aliquot of the quenched reaction mixture was used to determine the regioisomer ratio by
GCMS.
(E)-2-Methyl-1,3-diphynylprop-2-en-1-one (Table 2, entry 1): subjection of 1-phenyl-1-propyne (1 mmol, 0.125 mL) and N-
methoxy-N-methylbenzamide (2.0 mmol, 0.304 mL) to the general procedure afforded 0.149 g (67%) of the enone as a yellow oil
after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.81 – 7.75 (m, 3H), 7.59 – 7.52 (m, 1H), 7.51 – 7.32 (m, 7H), 7.21 (q, J
= 1.2 Hz, 1H), 2.30 (d, J = 1.2 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 199.3, 142.1, 138.4, 136.7, 135.6, 131.5, 129.6, 129.4,
128.5, 128.4, 128.1, 14.3. Physical and spectral data were consistent with those reported in literature.31
(E)-2-Methyl-3-phenyl-1-(4-fluoro-phenyl)prop-2-en-1-one (Table 2, entry 2): subjection of 1-phenyl-1-propyne (1.0 mmol,
0.125 mL) and 4-fluoro-N-methoxy-N-methyl benzamide (2.0 mmol, 0.311 mL) to the general procedure afforded 0.145 g (60%)
1
of the enone as yellowish liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.80 (dd, J = 8.6, 5.5 Hz, 2H), 7.42
(m, 5H), 7.14 (m, 3H), 2.27 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 197.9, 164. 9, 163.6, 141.7, 136.6, 135.5, 134.4, 132.0, 131.9,
129.6, 128.6, 128.4, 115.4, 115.3, 14.5; IR (neat) 3055, 2923, 1644, 1594, 1258, 1225, 1154, 1010, 691. 637 cm-1. HRMS (ESI)
m/z: [M+H]+ Calcd for C16H13FO: 241.1024, Found 241.1020.
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(E)-1-(4-Chlorophenyl)-2-methyl-3-phenylprop-2-en-1-one (Table 2, entry 3): subjection of 1-phenyl-1-propyne (1.0 mmol,
0.125 mL) and 4-Chloro-N-methoxy-N-methyl benzamide (2.0 mmol, 0.326 mL) to the general procedure afforded 0.145 g (57%)
of the enone as yellow oil after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.70 (m, 2H), 7.42 (m, 7H), 7.14 (m, 1H),
2.26 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 198.0, 142.2, 137.9, 136.7, 136.5, 135.4, 130.8, 129.6, 128.7, 128.4, 128.4, 14.4;
Physical and spectral data were consistent with those reported in literature.32
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(E)-1-(3-Bromophenyl)-2-methyl-3-phenylprop-2-en-1-one (Table 2, entry 4): subjection of 1-phenyl-1-propyne (1.0 mmol,
0.125 mL) and 3-Bromo-N-methoxy-N-methyl benzamide (2.0 mmol, 0.334 mL) to the general procedure afforded 0.171 g (57%)
1
of the enone as a brownish liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.87 (m, 1H), 7.66 (d, J = 8.4 Hz,
2H), 7.45 – 7.30 (m, 6H), 7.18 (s, 1H), 2.27 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 197.6, 142.9, 140.4, 136.4, 135.3, 134.4,
132.1, 129.7, 128.8, 128.4, 128.2, 127.8, 122.4, 14.2; IR (neat): 3058, 2923, 1645, 1562, 1248, 1018, 728, 695 cm-1. HRMS (ESI)
m/z: [M+H]+ Calcd for C16H13BrO: 301.0223, Found 301.0221.
(E)-2-Methyl-3-phenyl-1-(4-(trifluoromethyl)phenyl) prop-2-en-1-one (Table 2, entry 5): subjection of 1-phenyl-1-propyne (1.0
mmol, 0.125 mL) and 4-trifluoromethyl-N-methoxy-N-methylbenzamide (2.0 mmol, 0.369 mL) to the general procedure afforded
0.159 g (55%) of the enone as a yellow liquid after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.82 (d, J = 8.0 Hz, 2H),
7.73 (d, J = 8.4 Hz, 2H), 7.42 (m, 5H), 7.17 (s, 1H), 2.28 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 198.1, 143.7, 141.9, 136.5,
135.3, 133.1, 132.7, 129.8, 129.5, 128.9, 128.5, 125.2, 125.2, 125.2, 125.1, 14.0; IR (neat) 3055, 2962, 1649, 1616, 1321, 1107,
1064, 1022, 693 cm-1. HRMS (ESI) m/z: [M+H]+ Calcd for C17H13F3O: 291.0992, Found 291.0992.
(E)-2-Methyl-3-phenyl-1-(3-trifluoromethyl)phenyl) prop-2-en-1-one (Table 2, entry 6): subjection of 1-phenyl-1-propyne (1.0
mmol, 0.125 mL) and 3-trifluoromethyl-N-methoxy-N-methylbenzamide (2.0 mmol, 0.369 mL) to the general procedure afforded
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0.161 g (56%) of the enone as a yellow oil after flash chromatography; H NMR (400 MHz, CDCl3) δ 8.01 (s, 1H), 7.92 (d, J =
7.6 Hz, 1H), 7.80 (d, J = 8.4 Hz, 1H), 7.60 (t, J = 7.6 Hz, 1H), 7.43 (m, 5H), 7.17 (s,1H), 2.30 (s, 3H); 13C NMR (101 MHz,
CDCl3) δ 197.8, 143.2, 139.2, 136.5, 135.3, 132.5, 130.9, 130.6, 129.7, 128.9, 128.8, 128.5, 128.07, 128.03, 128.00, 127.9, 126.17,
126.13, 126.09, 126.05, 14.2; IR (neat) 2926, 1647, 1611, 1575, 1331, 1244, 1093, 1071, 695 cm-1. HRMS (ESI) m/z: [M+H]+
Calcd for C17H13F3O: 291.0992, Found 291.0994.
(E)-1-(4-((tert-Butyldimethylsilyl)oxy)phenyl)-2-methyl-3-phenylprop-2-en-1-one (Table 2, entry 9): subjection of 1-phenyl-1-
propyne (1.0 mmol, 0.125 mL) and TBS protected-4 hydroxy-N-methoxy-N-methylbenzamide (2.0 mmol, 0.529 mL) to the general
1
procedure afforded 0.189 g (54%) of the enone as a yellowish oil after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.77
(d, J = 8.8 Hz, 2H), 7.42 (m, 5H), 7.14 (s, 1H), 6.91 (d, J = 8.8 Hz, 2H), 2.27 (s, 3H), 1.02 (s, 9H), 0.27 (s, 6H); 13C NMR
(101 MHz, CDCl3) δ 198.2, 159.3, 140.0, 136.8, 135.8, 131.8, 131.2, 129.5, 128.2, 119.5, 29.8, 25.5, 18.1, 14.8, -4.4; IR (neat):
2955, 2928, 2857, 1643, 1595, 1505, 1253, 906, 837, 805, 736, 691 cm-1. HRMS (ESI) m/z: [M+H]+ Calcd for C22H28O2Si:
353.1932, Found 353.1936.
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(E)-2-Methyl-1-(naphthalen-1-yl)-3-phenylprop-2-en-1-one (Table 2, entry 11): subjection of 1-phenyl-1-propyne (1.0 mmol,
0.125 mL) and N-methoxy-N-methyl-1-naphthamide (2.0 mmol, 0.430 g) to the general procedure afforded 0.055 g (20%) of the
enone as a yellow oil after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 8.01 (d, J = 8.0 Hz, 1H), 7.98 (d, J = 8.0 Hz, 1
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H), 7.93 m, 1H), 7.53(m, 4H), 7.40 – 7.29 (m, 5H), 7.22 (s,1H), 2.37 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 200.8, 144.9,
138.5, 137.4, 135.6, 133.6, 131.0, 130.2, 129.8, 128.8, 128.4, 128.3, 126.9, 126.4, 126.3, 125.6, 124.4, 13.4; IR (neat): 3054, 2922,
1643, 1574, 1245, 1197, 777, 692 cm-1. HRMS (ESI) m/z: [M+H]+ Calcd for C20H16O: 273.1274, Found 273.1270.
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(E)-2-Methyl-1,5-diphenylpent-1-en-3-one (Table 2, entry 12): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL) and N-
methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded 0.217 g (87%) of the enone as
yellow oil after flash chromatography;. 1H NMR (400 MHz, CDCl3) δ 7.50 (s, 1H), 7.44 – 7.19 (m, 10H), 3.15 (t, J = 8.0 Hz, 2H),
3.02 (t, J = 8.0 Hz, 2H), 2.08 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 201.3, 141.5, 138.7, 137.2, 135.8, 129.7, 128.47, 128.42,
128.40, 126.1, 39.6, 30.8, 13.2. Physical and spectral data were consistent with those reported in literature.33
(E)-5-Chloro-2-methyl-1-phenylpent-1-en-3-one (Table 2, entry 13): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL)
and 3-chloro-N-methoxy-N-methylpropanamide (2.0 mmol, 0.266 mL) to the general procedure afforded 0.153 g, (74%) of the
enone as a yellow oil after flash chromatography (r.r. = 97:3); 1H NMR (400 MHz, CDCl3) δ 7.51 (s, 1H), 7.43 (m, 5H), 3.87 (t, J =
6.4 Hz, 2H), 3.31 (t, J = 6.9, 2H), 2.08 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 198.4, 139.4, 136.9, 135.4, 129.6, 128.7, 128.4, 40.2,
39.2, 12.9; IR (neat): 2962, 2919, 1661, 1575, 1195, 1065, 727, 694, 657 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C12H13ClO:
209.0728, Found 209.0729.
(E)-4-Ethyl-2-methyl-1-phenyloct-1-en-3-one (Table 2, entry 14): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL) and
2-ethyl-N-methoxy-N-methylhexanamide (2.0 mmol, 0.410 mL) to the general procedure afforded 0.196 g (80%) of the enone as a
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yellow liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.51 (s, 1H), 7.43 (m, 4H), 7.33 (m, 1H), 3.26 (quin, J =
6.8 Hz, 1H), 2.08 (s, 3H), 1.70 (m, 2H), 1.58 – 1.41 (m, 2H), 1.35 – 1.18 (m, 4H), 0.88 (m, 6H); 13C NMR (101 MHz, CDCl3) δ
206.9, 138.5, 137.9, 136.1, 129.6, 128.3, 128.3, 46.5, 32.4, 29.8, 26.0, 22.9, 13.9, 13.4, 12.0; IR (neat): 2958, 2928, 2858, 1658,
1047, 694 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C17H24O: 245.1900, Found 245.1900.
(E)-1-Cyclohexyl-2-methyl-3-phenylprop-2-en-1-one (Table 2, entry 15): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125
mL) and N-methoxy-N-methyl-1-cyclohexanamide (2.0 mmol, 0.335 mL) to the general procedure afforded 0.217 g (95%) of the
enone as a yellow liquid after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.49 (s, 1H), 7.40 (m, 5H), 3.16 (t, J = 11.7 Hz,
1H), 2.04 (s, 3H), 1.82 (d, J = 10.8 Hz, 4H), 1.53 – 1.19 (m, 6H); 13C NMR (101 MHz, CDCl3) δ 205.8, 137.6, 136.4, 136.0, 129.5,
128.2, 128.2, 44.5, 29.8, 25.83, 25.80, 13.4; IR (neat): 2927, 2852, 1658, 1448, 1590, 1005, 753, 696 cm-1. HRMS (ESI) m/z:
[M+H]+ Calcd for C16H20O: 229.1587, Found 229.1587.
(E)-2,5,5-Trimethyl-1-phenylhex-1-en-3-one(Table 2, entry 16): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL) and N-
methoxy-N,3,3-trimethylbutanamide (2.0 mmol, 0.340 mL) to the general procedure afforded 0.198 g (92%) of the enone as a yel-
low liquid after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.47 (s, 1H), 7.37 (m, 5H), 2.71 (s, 2H), 2.04 (s, 3H), 1.06 (s,
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9H); 13C NMR (101 MHz, CDCl3) δ 202.6, 139.0, 138.6, 136.1, 129.57, 128.4, 128.3, 49.2, 31.4, 30.1, 13.2; IR (neat): 2953, 2866,
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1655, 1362, 764, 698 cm-1; HRMS (ESI) Calculated for C15H20O [M+H]+: 217.1587, observed: 217.1585.
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(E)-2,4,4-Trimethyl-1-phenylpent-1-en-3-one (Table 2, entry 17): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL) and
N-methoxy-N-methylpivalamide (2.0 mmol, 0.310 mL) to the general procedure afforded 0.106 g (52%) of the enone as a yellowish
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liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.37 (m, 5H), 6.93 (s, 1H), 2.09 (s, 3H), 1.36 (s, 9H); 13C NMR
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(101 MHz, CDCl3) δ 211.9, 137.6, 135.9, 131.8, 129.1, 128.2, 127.5, 44.1, 27.9, 16.0; IR (neat): 2966, 2869, 1683, 1659, 1477,
1047, 765, 694 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C14H18O: 203.1431, Found 203.1429.
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(E)-1-(Furan-2-yl)-2-methyl-3-phenylprop-2-en-1-one (Table 2, entry 18): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125
mL) and N-methoxy-N-methylfuran-2-carboxamide (2.0 mmol, 0.268 mL) to the general procedure afforded 0.111g (53%) of the
enone as yellow oil after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.66 (s, 1H), 7.50 (s,1H), 7.46 – 7.30 (m, 5H), 7.17
(d, J = 3.2 Hz, 1H), 6.55 (d, J = 3.6 Hz, 1H), 2.23 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 185.1, 151.8, 146.7, 139.3, 136.3, 135.7,
129.6, 128.4, 128.3, 119.5, 111.7, 14.5; IR (neat): 2916, 2848, 1630, 1575, 1558, 1463, 1389, 1273, 1024, 1011, 889, 761, 706, 692
cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C14H12O2: 213.0911, Found 213.0910.
(E)-2-Methyl-3-phenyl-1-(thiophen-2-yl)prop-2-en-1-one (Table 2, entry 19): subjection of 1-phenyl-1-propyne (1.0 mmol,
0.125 mL) and N-methoxy-N-methylthiophene-2-carboxamide (2.0 mmol, 0.281 mL) to the general procedure afforded 0.117 g
(52%) of the enone as yellow oil after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.69 (d, J = 3.6 Hz, 1H), 7.67 (d, J =
4.8 Hz, 1H), 7.48 – 7.32 (m, 6H), 7.14 (t, J = 4.4 Hz, 1H), 2.26 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 190.5, 143.4, 139.0,
136.9, 135.6, 133.5, 133.4, 129.5, 128.4, 128.3, 127.6, 14.8; IR (neat): 2917, 1618, 1512, 1411, 1263, 1002, 847, 723, 693 cm-1;
HRMS (ESI) m/z: [M+H]+ Calcd for C14H12OS: 229.0682, Found 229.0679.
(E,E)-2-Methyl-1-phenylhexa-1,4-dien-3-one (Table 2, entry 21): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL) and
(E)-N-methoxy-N-methylbut-2-enamide (2.0 mmol, 0.264 mL) to the general procedure afforded 0.056 mg (31%) of the enone as
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yellowish liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.46 (m, 1H), 7.44 – 7.30 (m, 5H), 6.95 (dq, J = 15.2,
6.8 Hz, 1H), 6.79 (dq, J = 15.2, 1.49 Hz, 1H), 2.11 (s, 3H), 1.95 (d, J = 6.8 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 192.8, 143.0,
138.4, 137.9, 135.9, 129.6, 128.3, 128.2, 126.9, 18.3, 13.5; IR (neat): 3024, 2913, 1659, 1612, 1575, 1491, 1441, 1287, 1206, 1063,
964, 915, 753, 694 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C13H14O: 187.1118, Found 187.1116.
(E,E)-2-Methyl-1,5-diphenylpenta-1,4-dien-3-one (Table 2, entry 22): subjection of 1-phenyl-1-propyne (1.0 mmol, 0.125 mL)
and N-methoxy-N-methylcinnamamide (2.0 mmol, 0. 382 g) to the general procedure afforded 0.066 g (27%) of the enone as yel-
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low oil after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.72 (d, J = 15.6 Hz, 1H), 7.62 (m, 3H), 7.50 – 7.33 (m, 9H),
2.20 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 192.6, 143.4, 138.6, 138.5, 135.9, 135.1, 130.1, 129.7, 128.8, 128.5, 128.4, 128.2,
121.9, 13.8; IR (neat): 3025, 2920, 1650, 1593, 1494, 1448, 1328, 1200, 1061, 762, 698 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for
C18H16O: 249.1274, Found 249.1272.
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(E)-1-Phenyl-4-propyloct-4-en-3-one (Table 2, entry 23): subjection of 4-octyne (1.0 mmol, 0.147 mL) and N-methoxy-N-
methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded 0.232 g (95%) of the enone as yellow oil
after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.28 (m, 2H), 7.21 (m, 3H), 6.57 (t, J = 7.3 Hz, 1H), 2.97 (m, 4H), 2.27
(m, 2H), 2.21 (q, J = 7.4 Hz, 2H), 1.47 (sex, J = 7.2 Hz, 2H), 1.33 (sex, J = 7.2 Hz, 2H), 0.95 (t, J = 7.2 Hz, 3H), 0.89 (t, J = 7.2 Hz,
3H); 13C NMR (101 MHz, CDCl3) δ 200.7, 142.8, 141.8, 141.6, 128.39, 128.38, 125.9, 39.2, 30.9, 30.8, 27.7, 22.5, 22.2, 14.2, 13.9.
Physical and spectral data were consistent with those reported in literature.34
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(E)-1,2,5-Triphenylpent-1-en-3-one (Table 2, entry 24): subjection of diphenyl acetylene (1.0 mmol, 0.178 g) and N-methoxy-
N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded 0.149 g (48%) of the enone as colorless
o
solid after flash chromatography; m.p. = 88 C; 1H NMR (400 MHz, CDCl3) δ 7.69 (s, 1H), 7.44 (m, 3H), 7.36 – 7.13 (m, 10H),
7.06 (m, 2H), 3.00 (t, J = 7.2 Hz, 2H), 2.93 (t, J = 6.8 Hz, 2H); 13C NMR (101 MHz, CDCl3) δ 200.4, 141.3, 140.4, 138.2, 136.8,
134.6, 130.8, 129.5, 129.1, 129.0, 128.39, 128.38, 128.2, 127.9, 125.9, 41.8, 30.4; IR (neat): 3027, 2922, 1676, 1568, 1353, 1281,
1190, 738, 696 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C23H20O: 313.1587, Found 313.1584.
(E)-7-((tert-Butyldimethylsilyl)oxy)-4-ethyl-1-phenylhept-4-en-3-one (Table 2, entry 25): subjection of tert-butyl(hex-3-yn-1-
yloxy)dimethylsilane (1.0 mmol, 0.252 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general
procedure afforded 0.259 g (75%) of the enone as colorless liquid after flash chromatography that was an inseparable mixture of
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regioisomers (r.r. = 53:47); H NMR (400 MHz, CDCl3) δ 7.21 (m, 2H), 7.13 (m, 3H), 6.59 (t, J = 7.2 Hz, 1H, measured 0.43H),
3.51 (t, J = 6.8 Hz, 2H, measured 0.89H), 2.89 (m, 4H), 2.49 (t, J = 6.8 Hz, 2H, measured 0.87H), 2.27 (m, 2H), 0.99 (t, J = 7.6 Hz,
3H, measured 1.37H), 0.82 (s, 9H, measured 3.64H), -0.03 (s, 6H, measured 2.40H); 13C NMR (101 MHz, CDCl3) δ 200.4, 146.4,
141.54, 137.6, 128.38, 128.33, 125.94, 62.2, 39.13, 32.3, 30.6, 29.4, 25.9, 18.3, 13.4, -5.4; (E)-4-(2-((tert-
butyldimethylsilyl)oxy)ethyl)-1-phenylhept-4-en-3-one: 1H NMR (400 MHz, CDCl3) δ 7.21 (m, 2H), 7.13 (m, 3H), 6.54 (t, J = 7.2
Hz, 1H, measured 0.49H), 3.65 (t, J = 6.4 Hz, 2H, measured 1.04H), 2.89 (m, 4H), 2.40 (q, J = 6.8 Hz, 2H, measured 1.09H), 2.24
(m, 2H), 0.88 (t, J = 7.6 Hz, 3H, measured 1.96H), 0.83 (s, 9H, measured 5.04H), 0.00 (s, 6H, measured 3.29H); 13C NMR (101
MHz, CDCl3) δ 200.3, 144.4, 141.49, 138.7, 128.35, 128.32, 125.91, 61.8, 39.10, 30.7, 25.8, 22.4, 19.0, 18.2, 13.8, -5.4; IR (neat):
2955, 2928, 2856, 1668, 1496, 1471, 1251, 1094, 833, 774, 697 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C21H34O2Si: 347.2401,
Found 347.2391.
(E)-2-((Benzyloxy)methyl)-1,5-diphenylpent-1-en-3-one (Table 2, entry 26): subjection of (3-(benzyloxy)prop-1-yn-1-
yl)benzene (1.0 mmol, 0.206 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure
afforded 0.045 g (13%) of the enone as yellow oil after flash chromatography; 1H NMR (400 MHz, CDCl3) δ 7.69 (s, 1H), 7.48 (m,
2H), 7.39 – 7.19 (m, 13H), 4.59 (s, 2H), 4.35 (s, 2H), 3.12 (t, J = 8.0 Hz, 2H), 3.01 (t, J = 8.0 Hz, 2H); 13C NMR (101 MHz,
CDCl3) δ 200.2, 143.4, 141.4, 137.9, 136.8, 134.7, 129.8, 129.4, 128.5, 128.48, 128.43, 128.3, 128.2, 127.7, 126.1, 73.1, 63.6, 40.0,
30.4; IR (neat): 3026, 2924, 1668, 1494, 1452, 1069, 1027, 733 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C25H24O2: 357.1850,
Found 357.1837.
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(E)-2-(Cyclohex-1-en-1-yl)-1,5-diphenylpent-1-en-3-one (Table 2, entry 27): subjection of (cyclohex-1-en-1-ylethynyl)benzene
(1.0 mmol, 0.189 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded
0.191 g (60%) of the enone as yellow oil after flash chromatography that was an inseparable mixture of regioisomers (r.r. = 50:50);
1H NMR (400 MHz, CDCl3) δ 7.62 (m, 2H), 7.42 – 7.15 (m, 9H), 5.66 (m, 1H), 3.05 (m, 4H), 2.19 (m, 2H), 1.75 (m, 4H), 1.51 (m,
2H); 13C NMR (101 MHz, CDCl3) δ 201.10, 142.40, 141.48, 137.6, 136.3, 135.7, 135.2, 130.2, 128.6, 128.3, 128.2, 127.8, 125.9,
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40.6, 30.6, 28.3, 25.4, 22.3, 21.7; (E)-1-(cyclohex-1-en-1-yl)-2,5-diphenylpent-1-en-3-one: H NMR (400 MHz, CDCl3) δ 7.42 –
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7.15 (m, 11H), 6.22 (m, 1H), 2.92 (m, 2H), 2.84 (m, 2H), 2.11 (m, 4H), 1.65 (q, J = 7.6 Hz, 2H), 1.41 (m, 2H); 13C NMR (101
MHz, CDCl3) δ 200.6, 142.8, 141.5, 140.8, 136.6, 134.1, 130.1, 129.0, 128.5, 128.4, 128.3, 127.4, 125.8, 41.6, 30.5, 27.2, 26.8,
22.5, 21.5; IR: 3025, 2929, 1668, 1571, 1494, 1446, 1179, 1071, 908, 729 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C23H24O:
317.1900, Found 317.1890.
(E)-4-(Cyclohex-1-en-1-ylmethylene)-1-phenyldecan-3-one (Table 2, entry 28): Subjection of 1-(oct-1-yn-1-yl)cyclohex-1-ene
(1.0 mmol, 0.219 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded
0.208 g (64%) of the enone as yellowish liquid after flash chromatography that was an inseparable mixture of regioisomers (r.r. =
77:23); 1H NMR (400 MHz, CDCl3) δ 7.27 – 7.05 (m, 5H), 6.75 (s, 1H, measured 0.58H), 5.85 (m, 1H, measured 0.56H), 2.89 (m,
4H), 2.35 (t, J = 7.2 Hz, 2H, measured 1.74H), 2.10 (m, 4H, measured 3.69H), 1.57 (m, 4H), 1.21 (m, 8H), 0.81 (t, J = 6.8 Hz, 3H);
(E)-4-(cyclohex-1-en-1-yl)-1-phenylundec-4-en-3-one: 1H NMR (400 MHz, CDCl3) δ 7.27 – 7.05 (m, 5H), 6.57 (t, J = 7.6 Hz, 1H,
measured 0.19H), 6.53 (s, 1H, measured 0.22H), 2.83 (m, 2H), 2.69 (m, 2H, measured 0.41H), 2.35 (m, 2H, measured 1.74H), 1.86
(m, 4H, measure 0.75H), 1.57 (m, 4H), 1.21 (m, 8H), 0.81 (t, J = 6.8 Hz, 3H).; combined 13C NMR (101 MHz, CDCl3) δ 201.5,
141.9, 141.6, 139.3, 135.0, 133.6, 128.3, 127.1, 125.9, 39.5, 31.5, 30.9, 30.2, 29.5, 28.2, 26.6, 26.1, 22.6, 22.5, 21.7, 14.0; IR (neat):
3026, 2924, 2855, 1663, 1495, 1452, 1105, 921, 747, 697 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C23H32O: 325.2526, Found
325.2517.
(E)-1,7-Diphenyl-4-((trimethylsilyl)methylene)heptan-3-one (Table 2, entry 29): subjection of trimethyl(5-phenylpent-1-yn-1-
yl)silane (1.0 mmol, 0.240 mL) and N-methoxy-N-methyl-3-phenyl propanamide (2.0 mmol, 0.365 mL) to the general procedure
afforded 0.180 g (51%) of the enone as yellowish liquid after flash chromatography; (r.r. = 91:9, only a single isomer was isolated);
1H NMR (400 MHz, CDCl3) δ 7.16 (m, 4H), 7.07 (m, 6H), 6.42 (s, 1H), 2.88 (t, J = 8.0 Hz, 2H), 2.80 (t, J = 7.6 Hz, 2H), 2.52 (t, J
= 7.6 Hz, 2H), 2.28 (t, J = 8.0 Hz,2H), 1.52 (quin, J = 7.6 Hz, 2H), 0.00 (s, 9H); 13C NMR (101 MHz, CDCl3) δ 201.3, 156.1,
142.0, 141.4, 139.9, 128.4, 128.39, 128.37, 128.2, 126.0, 125.7, 39.4, 36.3, 31.9, 31.0, 30.6, -0.4; IR (neat): 3025, 2951, 1672,
1602, 1495, 1452, 1248, 836, 745, 696 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C23H30OSi: 351.2139, Found 351.2137.
(E)-2-(Cyclohex-1-en-1-yl)-5-phenyl-1-(trimethylsilyl) pent-1-en-3-one (Table 2, entry 30): subjection of (cyclohex-1-en-1-
ylethynyl)trimethylsilane (1.0 mmol, 0.207 mL) and N-methoxy-N-methyl-3-phenyl propanamide (2.0 mmol, 0.365 mL) to the
general procedure afforded 0.143 g (46%) of the enone as yellow oil after flash chromatography that was an inseparable mixture of
regioisomers (r.r. = 86:14); 1H NMR (400 MHz, CDCl3) δ 7.32 (m, 2H), 7.24 (m, 3H), 6.57 (bs, 1H, measured 0.02H), 6.52 (bs, 1H,
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measured 0.75H), 5.62 (m, 1H, measured 0.18H), 5.53 (tt, J = 3.6, 1.7 Hz, 1H, measured 0.77H), 2.97 (m, 4H), 2.15 (m, 2H), 2.03
(m, 2H), 1.69 (m, 4H), 0.12 (s, 9H, measured 7.69H), -0.04 (s, 9H, measured 1.29H); 13C NMR (101 MHz, CDCl3) δ 201.4, 158.8,
141.5, 139.5, 137.4, 128.4, 127.4, 126.0, 40.4, 30.5, 29.0, 25.1, 22.4, 21.7, -0.2; IR (neat): 3027, 2928, 1674, 1496, 1245, 836, 748,
697 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C20H28OSi: 313.1983, Found 313.1978.
1
2
3
4
5
6
7
8
9
(E)-2,5-Diphenyl-1-(trimethylsilyl)pent-1-en-3-one (Table 2, entry 31): subjection of 1-phenyl-2-trimethylsilylacetylene (1.0
mmol, 0.197 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded 0.149 g
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
(53%) as yellow liquid after flash chromatography that was an inseparable mixture of regioisomers; (r.r. = 86:14); H NMR (400
MHz, CDCl3) δ 7.50 – 7.15 (m, 10H), 7.11 (m, 1H, measured 0.92H), 3.04 (m, 4H, measured 3.18H), 3.00 – 2.75 (m, 4H, measured
0.89H), 0.00 (bs, 9H, measured 6.96H), -0.37 (bs, 9H, measured 1.37H); 13C NMR (101 MHz, CDCl3) δ 200.1, 155.4, 142.3, 141.3,
138.7, 129.3, 128.4, 128.4, 127.9, 127.7, 125.9, 41.1, 30.4, -0.7; IR (neat): 3027, 2952, 1679, 1578, 1247, 1099, 856, 834, 747, 697
cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C20H24OSi: 309.1670, Found 309.1667.
(E)-6,6-Dimethyl-1,4-diphenylhept-4-en-3-one (Table 2, entry 32): Subjection of (3,3-dimethylbut-1-yn-1-yl)benzene (1.0
mmol, 0.180 mL) and N-methoxy-N-methyl-3-phenylpropanamide (2.0 mmol, 0.365 mL) to the general procedure afforded 0.104 g
1
(35%) of the enone as colorless liquid after flash chromatography; H NMR (400 MHz, CDCl3) δ 7.35 (m, 3H), 7.30 – 7.18 (m,
4H), 7.13 (m, 3H), 6.89 (s, 1H), 2.89 (t, J = 8.0 Hz, 2H), 2.75 (t, J = 8.0 Hz, 2H), 0.94 (s, 9H); 13C NMR (101 MHz, CDCl3) δ
200.8, 151.1, 141.4, 139.5, 137.0, 130.0, 128.3, 128.2, 127.8, 127.3, 125.8, 44.8, 41.5, 34.1, 30.4; IR (neat): 3026, 2959, 1688,
1593, 1495, 1475, 1359, 1215, 1111, 1072, 1030, 747 cm-1; HRMS (ESI) m/z: [M+H]+ Calcd for C21H24O: 293.1900, Found
293.1890.
ASSOCIATED CONTENT
Notes
The authors declare no competing financial interest
ACKNOWLEDGMENT
We thank Oklahoma State University for support of this project. Mass spectrometry analyses were performed in the DNA/Protein Re-
source Facility at Oklahoma State University, using resources supported by the NSF MRI and EPSCoR programs (DBI/0722494).
Supporting Information
1H and 13C NMR spectra for all products. This material is available free of charge via the Internet at http://pubs.acs.org.
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