Copper-Catalyzed Carbenoid Insertion Reactions of α-Diazoesters and α-Diazoketones into Si-H and S-H Bonds

Article abstract of DOI:10.1021/acs.joc.6b02998

An efficient copper-catalyzed carbenoid insertion reaction of α-diazo carbonyl compounds into Si-H and S-H bonds was developed. A wide range of α-silylesters and α-thioesters was obtained in high yields (up to 98%) from α-diazoesters using 5 mol% of a simple copper(I) salt as catalyst. Using 0.05 mol% of the same catalyst, α-diazoketones led to α-silylketones in low to good yields (up to 70%).

Full text of DOI:10.1021/acs.joc.6b02998

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Article
Copper-Catalyzed Carbenoid Insertion Reactions of #-
Diazoesters and #-Diazoketones into Si–H and S–H Bonds
Hoda Keipour, Angela Jalba, Léo Delage-Laurin, and Thierry Ollevier
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b02998 • Publication Date (Web): 28 Jan 2017
Downloaded from http://pubs.acs.org on January 28, 2017
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Copper-Catalyzed Carbenoid Insertion Reactions of α-Diazoesters
and α-Diazoketones into Si–H and S–H Bonds
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Hoda Keipour, Angela Jalba, Léo Delage-Laurin, Thierry Ollevier*
Département de chimie, Université Laval, 1045 avenue de la Médecine, Québec, QC, G1V 0A6,
Canada
ABSTRACT: An efficient copper-catalyzed carbenoid insertion reaction of α-diazo carbonyl
compounds into Si–H and S–H bonds was developed. A wide range of α-silylesters and α-
thioesters was obtained in high yields (up to 98%) from α-diazoesters using 5 mol % of a simple
copper(I) salt as catalyst. Using 0.05 mol % of the same catalyst, α-diazoketones led to α-
silylketones in low to good yields (up to 70%).
INTRODUCTION
Metal-catalyzed reactions of diazo compounds have been commonly used in organic synthesis.1
The resulting metal-carbenoid intermediates are capable of undergoing a broad range of reac-
tions, sometimes ideal for initiating cascade sequences leading to the rapid generation of struc-
tural complexity.2 Diazo compounds, which are commonly used as carbene precursors, have
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been extensively employed as versatile cross-coupling partners in various transition metal-
catalyzed reactions.3 Diazo compounds can be converted into highly reactive free carbene inter-
mediates under thermolytic or photolytic conditions.4 Because of the limited synthetic applica-
tions of the latter due to their lack of selectivity for most chemical transformations, there has
been a significant interest for the transition metal-catalyzed decomposition of diazo compounds.4
Metal carbene species can undergo diverse transformations, such as X–H insertion reactions (X =
C, Si, N, O, S, etc).5 Formation of diazocarbonyl compounds via diazo transfer is applicable to a
wide range of active methylene compounds, typically ketones and carboxylic acid derivatives,
and their subsequent derivatization allows to reach a wide molecular variety. Watanabe was the
first to develop the reaction of various silanes with methyl α-diazoacetate in the presence of cop-
per powder as catalyst.6 The efficient use of Rh2(OAc)2 in the formation of α-silyl carbonyl com-
pounds was also demonstrated.7 Various asymmetric insertion reactions of α-diazoesters into Si–
H and S–H bonds involving chiral rhodium and iridium catalysts and only a few examples in-
volving copper ones have been disclosed, but in the presence of expensive and complicated lig-
ands. Doyle and Moody investigated chiral dirhodium(II) complexes as efficient catalysts for Si–
H insertion.8 High enantioselectivities in the Si–H bond insertion of α-vinyldiazoacetates and α-
diazophenylacetates, catalyzed by rhodium(II) prolinate complexes, have been reported by Da-
vies.9 Hashimoto demonstrated the effective use of Rh2(S-PTPA)4 and Rh2(S-PTPG)4 as catalysts
for the enantioselective Si–H insertion reaction.10 Ball developed a strategy to use natural poly-
peptide ligands in the development of chiral dirhodium catalysts.11 In 2013, Lacour used Rh(II)
complexes derived from enantiopure binaphtyl ligand.12 Katsuki developed a Si–H carbenoid
insertion reaction using an iridium complex as catalyst.13 Rhodium(I)-catalyzed asymmetric
Si−H insertion reactions have been developed by Xu.14 Che demonstrated that chiral iridium
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porphyrin displays excellent reactivity and stereoselectivity towards carbene insertion.15 Asym-
metric copper-catalyzed Si–H insertion reaction was reported by Panek using [Cu(OTf)]2·PhH
and [(CH3CN)4Cu]PF6 in the presence of a chiral diimine ligand.16 In 2008, Zhou also developed
an asymmetric Si−H insertion reaction using Cu(OTf)2 with spiro diimine ligands.17 Pérez also
reported a chiral silver complex as efficient catalyst for insertion reactions.18 Moreover, Gouver-
neur reported X–H (X = Si, B, P, S, N) insertion reactions on other types of substrates than es-
ters, such as 1-aryl 2,2,2-trifluoro-1-diazoalkanes, using [(CH3CN)4Cu]PF6 as catalyst.19 Regard-
ing the S–H insertion reaction, in recent years, a number of methods have been proven useful,
involving bis(NHC)ruthenium(II)-porphyrins,20 Cu(I)-zeolites,21 urea and phosphates,22 biocata-
lysts,23 and chiral Rh(II) and Cu(I) catalysts.24 An enantioselective version of the S–H insertion
reaction was also achieved using copper(I) spiro diimine complexes.25
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Because most of the asymmetric versions of the insertion reactions of α-diazoesters into Si–H
and S–H bonds involve expensive and complicated ligands, a general and practical method for
Si–H and S–H bond insertion reactions of silanes and thiols with α-diazoesters and α-
diazoketones would thus represent a valuable addition to the toolbox of synthetic chemistry. The
challenge also resides in developing the reaction with α-diazoketones that have never been used
for the insertion reaction into Si–H or S–H using a copper catalyst. In this article, we report Si–H
and S–H insertion reactions of α-diazoesters and α-diazoketones and demonstrate the scope and
applicability of the reaction using practical conditions (Scheme 1). α-Diazoesters and α-
diazoketones were easily prepared from commercially available esters and ketones according to
known procedures.17,26 Given that most of the catalyzed X–H insertion reactions with α-
diazoesters involve rhodium complexes, we focused here on an efficient and green metal catalyt-
ic system to probe the reactivity of α-diazoesters and α-diazoketones into Si–H and S–H bonds.
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Scheme 1. General scheme for Si–H and S–H insertion reactions using α-diazoesters and α-
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diazoketones
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RESULTS AND DISCUSSION
The reaction of α-diazophenylacetate 1a and triethylsilane in dichloromethane was first exam-
ined at room temperature with [(CH3CN)4Cu]PF6 as catalyst. The reaction was complete within
0.1 h at 25 ºC and the Si–H insertion product was obtained in 68% yield (Table 1, entry 1). By
using a slow addition protocol, the yield was improved to 85% within 0.5 h at 25 ºC (Table 1,
entry 2). Using the same reaction conditions, different copper sources such as Cu(OTf)
,
2
[Cu(OTf)]2·PhMe and CuCl were tested but none of them afforded the same reactivity as
[(CH3CN)4Cu]PF6 (Table 1, entries 3–5). No conversion was obtained using Cu(OAc)2 (Table 1,
entry 6). We checked the solubility of all copper catalysts used in this study. All copper salts have
shown high solubility in dichloromethane, except Cu(OAc)2, which is scarcely used in diazo
decomposition reactions anyway. [Cu(OTf)]2·PhH led to a decreased yield but because of in-
creased dimerization pathway. Consequently, the observed reactivity is not thought to be influ-
enced by any solubility issue. By decreasing the temperature to 0 ºC, –10 and –20 ºC, the yield
was improved by using slow addition of α-diazophenylacetate, with the compromise of a longer
reaction time (Table 1, entries 7–9). A catalyst loading of 5 mol % was effective, whereas the
product was formed in lower yield when the catalytic loading was decreased to 2 mol % (Table
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1, entries 10–13). Once the slow addition protocol had been established, [(CH3CN)4Cu]PF6 (5
mol %) was selected for further studies, because it appeared superior to other copper catalysts.
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Table 1. Screening of copper sources for Si–H insertion of methyl α-diazophenylacetate
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(1a)a
Entry [Cu] (mol %)
T (ºC) Time (h)
Yield (%)
1b
2
[(CH3CN)4Cu]PF6 (5)
[(CH3CN)4Cu]PF6 (5)
Cu(OTf)
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0.1
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0.5
3
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85
70
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2 (5)
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[Cu(OTf)]2·PhMe (5)
CuCl (5)
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Cu(OAc)2 (5)
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[(CH3CN)4Cu]PF6 (5)
[(CH3CN)4Cu]PF6 (5)
[(CH3CN)4Cu]PF6 (5)
[(CH3CN)4Cu]PF6 (2)
[(CH3CN)4Cu]PF6 (2)
[(CH3CN)4Cu]PF6 (2)
[(CH3CN)4Cu]PF6 (2)
–
–10
–20
25
0
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1.5
2
–10
–20
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aReaction conditions: copper salt (2–5 mol %), silane (1 mmol), methyl α-diazophenylacetate
b
1a (0.5 mmol), CH2Cl2 (1 mL), slow addition (1 h) of methyl α-diazophenylacetate (1a). With-
out slow addition of methyl α-diazophenylacetate (1a)
Next, the effects of various solvents were studied on the efficiency of the insertion reaction.
Chloroform, 1,2-dichloroethane and toluene were all suitable solvents and moderate to very good
yields were obtained (Table 2, entries 1–3). When the reaction was run in polar, coordinating
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solvents, such as THF, the conversion was lower and the reaction time was extended, whereas
acetonitrile led to a good yield (Table 2, entries 4 and 5). Diethyl ether and hexane afforded low
yields (Table 2, entries 6 and 7); dimethylcarbonate led to more diazo dimerization into the
tetrasubstituted olefin after subsequent irreversible extrusion of nitrogen and coupling (Table 2,
entry 8). However, none of these solvents gave results superior to dichloromethane, which was
consequently chosen in further studies.
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Table 2. Screening of solvents for Si–H insertion reaction of methyl α-diazophenylacetate
(1a)a
Entry Solvent Silane
T (h)
0.5
0.5
5
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12
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1
Yield (%)
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CHCl3
DCE
Et3SiH
Et3SiH
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Toluene Et3SiH
CH3CN Et3SiH
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THF
Et2O
Et3SiH
Et3SiH
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Hexane Et3SiH
DMC Et3SiH
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CH2Cl2 PhMe2SiH
CH2Cl2 Ph3SiH
CH2Cl2 Ph2MeSiH
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aReaction conditions: [(CH3CN)4Cu]PF6 (5 mol %), silane (1 mmol), methyl α-
diazophenylacetate (1a) (0.5 mmol), solvent (1 mL), 25 °C.
Other silanes, such as phenyldimethylsilane, triphenylsilane and diphenylmethylsilane were also
successfully used in this transformation, affording the desired α-silylesters in moderate to high
yields (Table 2, entries 9–11).
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A variety of α-diazoesters were examined to expand the scope of the substrates used for the Si–H
insertion reaction with triethylsilane, run under the optimal reaction conditions. All substrates
reacted to produce the corresponding α-silylesters in very good to excellent yields (Scheme 2,
2b–m; 85–98%), regardless of the nature and position of the substituents on the phenyl ring of
the α-diazoesters (Scheme 2, 2b–m). However, the reactivity of the substrate was influenced by
the electronic properties of substituents on the phenyl ring of the α-diazoarylacetates. α-
Diazoarylacetates containing electron-donating groups such as methyl and methoxy (Scheme 2,
2b–d) required shorter reaction time to reach complete conversion and high yields. However, α-
diazoarylacetates containing electron-withdrawing groups, such as Br, F, Cl (Scheme 2, 2e–k),
required an increased reaction time to reach complete conversion.
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Scheme 2. Copper-catalyzed Si–H insertion reaction of methyl α-diazoarylacetatea
aReaction conditions: [(CH3CN)4Cu]PF6 (5 mol %), Et3SiH (1 mmol), α-diazoarylacetate (0.5
mmol), CH2Cl2 (1 mL), –10 °C.
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[(CH3CN)4Cu]PF6 proved to be an efficient catalyst for α-diazoester insertion reactions into the
S–H bond as well. The substrate and scope of α-diazoester were next investigated for this reac-
tion. The S–H bond insertion reactions of benzyl mercaptan and various substituted thiophenols
with different α-diazoesters were run under the optimal reaction conditions using 5 mol % of
[(CH3CN)4Cu]PF6 in dichloromethane at room temperature (Scheme 3). High yields were ob-
tained using substituted thiophenols containing electron-donating groups, such as methyl and
methoxy, and electron-withdrawing groups in the para-position such as Cl (Scheme 3, 3d-3f).
Good yields were also obtained using substituted α-diazoester substrates containing electron-
donating groups and electron-withdrawing groups in S–H bond reaction (Scheme 3, 3g-3j).
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Scheme 3. Copper-catalyzed S–H bond insertion reaction of α-diazoesters with various thi-
olsa
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aReaction conditions: [(CH3CN)4Cu]PF6 (5 mol %), thiol (1 mmol), α-diazoarylacetate (0.5
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mmol), CH2Cl2 (1 mL), 25 °C.
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The reaction of methyl α-diazophenylacetate (1a) with triethylsilane, thiophenol and styrene un-
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–
der Cu(I) catalysis afforded products of Si–H, S H insertion and cyclopropanation (Scheme 4).
This competition experiment showed that the product of Si–H insertion was formed in a better
yield vs. S–H insertion and cyclopropanation using Cu(I) as a catalyst at –10 ºC. The selectivity
of the reaction was only moderate, and running the reaction at lower temperature (at –20 °C) did
not improve it.
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Scheme 4. Competition experiments–Copper-catalyzed Si H insertion versus S–H insertion
with 1a and copper-catalyzed Si–H insertion vs. cyclopropanation with 1a
The intramolecular cyclopropanation reaction of α-phenyldiazoacetate (1n) using
[(CH3CN)4Cu]PF6 as catalyst was also examined.27 Cyclopropane 7 was formed in a 59% yield
when the reaction was performed at 25 °C without a silane. The reaction of 1n with triethylsilane
under Cu(I) catalysis at –10 ºC and 25 ºC afforded only the product of Si–H insertion (2n) in
almost quantitative yields (Scheme 5). These competition experiments led to the product of Si–H
insertion as the only product vs. intramolecular cyclopropanation. This demonstrates the com-
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plete selectivity for the intermolecular Si–H insertion reaction vs. intramolecular cyclopropana-
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tion.
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Scheme 5. Competition experiments–Copper-catalyzed Si–H insertion versus cyclopropa-
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nation with 1n
A variety of α-diazoketones (Scheme 6, eq. a, 8a-g) were studied as substrates for the Si–H inser-
tion reaction with triethylsilane. After screening, the optimal conditions found for the synthesis
of the α-silylketones involved a very low catalyst loading (0.05 mol %) of [(CH3CN)4Cu]PF6
using 5 equiv of triethylsilane in dichloromethane at room temperature. Using a higher amount
of the catalyst or less than 5 equiv of triethylsilane increased the formation of the undesired di-
merization alkene product. All substrates afforded the corresponding α-silylketones 9a-g in poor
to good yields (Scheme 6, eq. a, 26–70%). α-Diazophenylketone 8a was the most reactive, giv-
ing 70% of insertion product (C-silylated product). α-Diazophenylketone 8f gave 61% of inser-
tion product (C-silylated product) and 12% yield of the corresponding silyl enol ether (O-
silylated product). Between 1–5% of the O-silylated products were isolated using the other α-
diazoketones.
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Scheme 6. Copper-catalyzed Si–H bond insertion of α-diazoketones
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aReaction conditions: [(CH3CN)4Cu]PF6 (0.05 mol %), silane (3 mmol), α-diazoketone (0.6
mmol), CH2Cl2 (1.2 mL), 25 °C. bReaction was performed using 4Å molecular sieves (50 mg).
However, the reactivity of the substrate was influenced by the electronic properties of substitu-
ents on the phenyl ring of the α-diazoketones. α-Diazoketones containing electron-donating
groups such as methyl and dioxolane group led to the silylated product in higher yields (Scheme
6, 9b and 9e) than α-diazoketones containing electron-withdrawing groups such as F and Cl
(Scheme 6, eq. a, 9c and 9d). Only traces of α-silylketone were obtained using 2-diazo-1-
phenylbutan-1-one (8h) as substrate and gave 1-phenyl-2-buten-1-one (9h') (E/Z = 1:0.03) as
undesired product (Scheme 6, eq. b, 45% yield). The preparation of unsaturated carbonyl com-
pounds through β-hydride elimination of α-diazo carbonyl derivatives has already been disclosed
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in the literature.28 Moreover, in an attempt of running a competition experiment using an α-
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diazoketone vs. an α-diazoester (Scheme 4), the reaction of α-diazoketone (8a) with tri-
ethylsilane and styrene under Cu(I) catalysis only afforded the product of Si–H insertion without
any traces of cyclopropanation.
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The obtained α-silylesters 2 can readily be used and transformed into other useful products. α-
Silylester 2a was converted into α-hydroxylester 10, using MCPBA as an oxidant (Scheme 7, eq.
a).29 A Peterson elimination of 2a allowed the conversion in two steps into the corresponding α-
alkylated-α,β-unsaturated ester 11 via the silylation condensation-elimination sequence shown in
Scheme 7, eq. a.30 Synthesis of allylsilane 16 was also performed starting from α-hydroxy silane
2a. Davies' procedure to synthesize various allylsilanes originally took advantage of a
Rh2(OAc)4-catalyzed C–H insertion on 14, through β-lactone intermediate 15.31 We advanta-
geously replaced this Rh(II) catalyst in the last key step, using the same copper catalyst em-
ployed for the Si–H insertion. Reduction of the ester using LiAlH4 afforded 12 in 83% yield.32
Subsequent esterification of 12 with phenacetyl chloride and diazo synthesis produced 14 in
good overall yield. Allylsilane 16 was formed using 5 mol % of [(CH3CN)4Cu]PF6 as catalyst
(Scheme 7, eq. b). (E)-Stereochemistry of the allylsilane was confirmed by NOE.43
Scheme 7. Derivatization of 2a
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CONCLUSION
To sum up, we have successfully developed an efficient copper-catalyzed protocol for the carbe-
noid insertion reaction of α-diazoesters and α-diazoketones into Si–H and S–H bonds. By using
[(CH3CN)4Cu]PF6, a wide range of α-silylesters were synthesized in good to excellent yields
using this catalyst. For the first time, the insertion of α-diazoketones into Si–H bonds using the
same catalyst, though in much lower loading, has been reported. The desired products were ob-
tained in excellent yields using low catalytic loadings, i.e. 5 mol % for α-silylesters and 0.05 mol
% for α-silylketones, and short reaction times. This catalyst has been shown to be efficient for
carbenoid insertion into S–H bond in high yields as well. Further developments will be reported
in due course.
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EXPERIMENTAL SECTION
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General procedures. All reactions were performed in flame-dried flasks and tubes under an at-
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mosphere of argon. Solvents (CH2Cl2, THF, MeOH, Et2O, CHCl3, …) were distilled prior to use.
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[(CH3CN)4Cu]PF6
Thin-layer chromatography (TLC) was
was purchased from Sigma-Aldrich.
carried out on 250 µm commercial silica gel plates and compounds were visualized using UV
absorbance and/or aqueous KMnO4. Flash column chromatography was performed on silica gel
1
(230–400 mesh). H and 13C{H} NMR spectra were recorded on a 400 MHz spectrometer in
CDCl3. For 1H NMR (400 MHz), chemical shifts were reported in ppm downfield from tetrame-
thylsilane (TMS) used as internal standard (δ = 0 ppm), and coupling constant and integration (in
Hz). High-resolution mass spectra (HRMS) were recorded on ESI TOF (time of flight) mass
spectrometer. IR spectra were recorded on a FT–IR spectrometer with ZnSe ATR accessory and
are reported in reciprocal centimeter (cm–1). Melting points (mp) are uncorrected and were rec-
orded on a melting point apparatus.
Preparation of p-tosyl azide.33 To a flask of 100 mL, a solution of sodium azide (2.86 g, 44
mmol) in water (12 mL) and acetone (20 mL) was rapidly added a solution of p-
toluenesulfonylchloride (7.62 g, 40 mmol) in acetone (20 mL). The mixture warmed slightly and
two phases were formed. After stirring at room temperature for 4 h, acetone was evaporated un-
der reduced pressure (bath temperature 35 ºC), the residue was extracted with CH2Cl2 (3 x 25
mL), washed with water (2 x 25 mL), dried over MgSO4 and concentrated under reduced pres-
sure (bath temperature 35 ºC) to give the compound as a colorless oil (7.78 g, 39.45 mmol, 98%
1
yield). H NMR (400 MHz, CDCl3): δH 7.86 (d, J = 8.0 Hz, 2H), 7.42 (d, J = 8.0 Hz, 2H), 2.48
(s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 146.3, 135.2, 130.2, 127.2, 21.3 ppm.
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Preparation of N-acetylsulfanilyl azide.33 A solution of sodium azide (6.14 g, 94 mmol) in ace-
tone (300 mL) in a flask of 500 mL was cooled at 0 °C and N-acetylsulfanilyl chloride (20 g,
85.8 mmol) was added in small portions. After stirring at room temperature for 24 h, acetone was
evaporated under reduced pressure (bath temperature 35 ºC), the residue was extracted with
CH2Cl2 (3 x 75 mL), washed with water (2 x 30 mL), dried over MgSO4 and concentrated under
reduced pressure (bath temperature 35 ºC) to give compound as a white solid (19.2 g, 80.0 mmol,
93%). 1H NMR (400 MHz, CDCl3) δH 8.07 (s, 1H), 7.87 (d, J = 8.9 Hz, 2H), 7.78 (d, J = 8.9 Hz,
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2H), 2.23 (s, 3H); C{H} NMR (100 MHz, CDCl3): δC 168.7, 143.8, 132.7, 129.0, 119.5, 24.8
ppm.
Preparation of methanesulfonyl azide.33 To a flask of 500 mL, a solution of sodium azide (17
g, 0.26 mol) in water (100 mL) and acetone (160 mL) at 0 °C was added dropwise methanesul-
fonyl chloride (6.8 mL, 0.17 mol). After stirring at room temperature for 15 h, acetone was
evaporated under reduced pressure (bath temperature 35 ºC), the residue was extracted with
CH2Cl2 (3 x 75 mL), washed with water (2 x 35 mL), dried over MgSO4 and concentrated under
reduced pressure (bath temperature 35 ºC) to give compound as a colorless oil (7.78 g, 0.064
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13
mol, 98%). H NMR (400 MHz, CDCl3) δH 3.25 (s, 3H) C{H} NMR (100 MHz, CDCl3): δC
42.8 ppm.
General procedure for preparation of α-diazoesters.17 To a mixture of ester (10 mmol) and
tosyl azide (2.96 g, 15 mmol) in anhydrous CH3CN (15 mL), 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) (2.24 mL, 2.28 g, 15 mmol) was added. The reaction mixture was stirred at room temper-
ature for overnight. Upon complete consumption of the starting materials, the reaction mixture
was quenched with saturated aqueous solution of NH4Cl (5 mL), extracted with CH2Cl2 (3 x 30
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mL), washed with brine (3 x 10 mL), dried over MgSO4 and concentrated under reduced pres-
sure to give the product. The residue was purified by flash chromatography (Hexane/EtOAc) to
afford the α-diazoester.
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Methyl α-diazophenylacetate (1a).17 The product was obtained as a red oil (1.67 g, 9.48 mmol,
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95% yield). H NMR (400 MHz, CDCl3): δH 7.49 (d, J = 8.0 Hz, 2H), 7.38 (t, J = 8.0 Hz, 2H),
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7.18 (t, J = 8.0 Hz, 1H), 3.81 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 165.3, 128.8,
125.6, 125.4, 123.7, 63.3, 51.8 ppm; IR (ZnSe): 2951, 2078, 1693, 1243, 1048, 1023, 750, 688
cm–1.
Methyl α-diazo-4-methylphenylacetate (1b).17 The product was obtained as an orange solid (1.43
1
g, 7.52 mmol, 75% yield). mp: 40–42 °C; H NMR (400 MHz, CDCl3): δH 7.37 (d, J = 8.0 Hz,
2H), 7.21 (d, J = 8.0 Hz, 2H), 3.85 (s, 3H), 2.34 (s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3):
δC 165.8, 135.7, 129.6, 124.1, 122.0, 62.9, 51.9, 21.0 ppm; IR (ZnSe): 2956, 2078, 1689, 1469,
1245, 1151, 1044, 798 cm–1.
Methyl α-diazo-2-methylphenylacetate (1c).17 The product was obtained as a yellow oil (1.69 g,
8.89 mmol, 89% yield). 1H NMR (400 MHz, CDCl3): δH 7.42–7.40 (m, 1H), 7.26–7.23 (m, 3H),
3.80 (s, 3H), 2.31 (s, 3H) ppm. 13C{H} NMR (100 MHz, CDCl3): δC 166.1, 137.6, 130.8, 130.7,
128.8, 126.3, 124.2, 60.5, 51.9, 19.8 ppm; IR (ZnSe): 2951, 2082, 1693, 1433, 1251, 1222, 1030
cm–1.
Methyl α-diazo-4-methoxylphenylacetate (1d).17 The product was obtained as a red solid (2.00 g,
9.70 mmol, 97% yield). mp: 48–50 °C; 1H NMR (400 MHz, CDCl3): δH 7.39 (d, J = 8.0 Hz, 2H),
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6.95 (d, J = 8.0 Hz, 2H), 3.85 (s, 3H), 3.80 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC
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166.1, 158.0, 125.9, 116.8, 114.5, 62.3, 55.3, 51.9 ppm; IR (ZnSe): 2956, 2082, 1693, 1455,
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1244, 1026, 831, 738 cm–1.
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Methyl α-diazo-4-fluorophenylacetate (1e).17 The product was obtained as an orange oil (1.90 g,
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9.79 mmol, 98% yield). H NMR (400 MHz, CDCl3): δH 7.46–7.42 (m, 2H), 7.11 (t, J = 8.0 Hz,
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2H), 3.86 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 165.6, 161.01 (d, J = 246.3 Hz),
125.86 (d, J = 7.9 Hz), 121.19 (d, J = 3.2 Hz), 116.01 (d, J = 21.9 Hz), 62.5, 52.0 ppm; IR
(ZnSe): 3020, 2954, 2080, 1692, 1507, 1434, 1153, 1039, 828 cm–1
Methyl α-diazo-3-fluorophenylacetate (1f).17 The product was obtained as an orange oil (1.73 g,
8.91 mmol, 89% yield). 1H NMR (400 MHz, CDCl3): δH 7.35–7.31 (m, 2H), 7.17 (d, J = 7.6 Hz,
1H), 6.88 (t, J = 9.3 Hz, 1H), 3.87 (s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 165.0,
163.18 (d, J = 245.5 Hz), 130.31 (d, J = 8.8 Hz), 128.03 (d, J = 9.5 Hz), 118.78 (d, J = 2.8 Hz),
112.44 (d, J = 21.4 Hz), 111.01 (d, J = 25.5 Hz), 63.4, 52.1 ppm; IR (ZnSe): 3021, 2955, 2082,
1696, 1243, 1187, 1048, 771 cm–1.
Methyl α-diazo-4-chlorophenylacetate (1g).17 The product was obtained as an orange solid (2.00
g, 9.50 mmol, 95% yield). mp: 64–66 °C; 1H NMR (400 MHz, CDCl3): δH 7.43 (d, J = 9.0 Hz,
13
2H), 7.36 (d, J = 9.0 Hz, 2H), 3.87 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 165.2,
131.4, 129.0, 125.0, 124.0, 63.3, 52.1 ppm; IR (ZnSe): 2953, 2090, 1686, 1434, 1246, 1068, 856
cm–1.
Methyl α-diazo-3-chlorophenylacetate (1h).17 The product was obtained as an orange solid (1.90
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g, 9.02 mmol, 90% yield). mp: 50–52 °C; H NMR (400 MHz, CDCl3): δH 7.54 (t, J = 8.0 Hz,
1H), 7.32 (m, 2H), 7.15 (d, J = 8.0 Hz, 1H), 3.87 (s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3):
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δC 165.0, 135.0, 130.0, 127.6, 125.7, 123.6, 121.5, 63.2, 52.1 ppm; IR (ZnSe): 2955, 2089, 1694,
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Methyl α-diazo-2-chlorophenylacetate (1i).17 The product was obtained as a yellow oil (1.79 g,
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8.50 mmol, 85% yield). H NMR (400 MHz, CDCl3): δH 7.50 (d, J = 6.8 Hz, 1H), 7.33 (d, J =
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7.3 Hz, 1H), 7.22–7.15 (m, 2H), 3.74 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 165.5,
133.4, 132.1, 129.9, 129.5, 127.0, 123.8, 61.7, 52.0 ppm; IR (ZnSe): 2951, 2093, 1694, 1432,
1239, 1025 cm–1.
Methyl α-diazo-4-bromophenylacetate (1j).17 The product was obtained as an orange solid (2.42
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g, 9.49 mmol, 95% yield). mp: 40–42 °C; H NMR (400 MHz, CDCl3): δH 7.50 (d, J = 8.0 Hz,
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2H), 7.37 (d, J = 8.0 Hz, 2H), 3.86 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 165.1,
132.0, 125.2, 124.6, 119.3, 62.9, 52.1 ppm; IR (ZnSe): 2952, 2088, 1692, 1434, 1310, 1154,
1039 cm–1.
Methyl α-diazo-3-bromophenylacetate (1k).17 The product was obtained as an orange solid (2.35
1
g, 9.21 mmol, 92% yield). mp: 68–70 °C; H NMR (400 MHz, CDCl3): δH 7.36 (d, J = 8.0 Hz,
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1H), 7.20 (d, J = 8.0 Hz, 1H), 7.26–7.21 (m, 2H), 3.87 (s, 3H) ppm; C{H} NMR (100 MHz,
CDCl3): δC 164.9, 130.2, 128.6, 127.9, 126.4, 123.1, 122.0, 63.0, 52.1 ppm; IR (ZnSe): 2953,
2087, 1690, 1589, 1274, 1041, 718 cm–1.
Ethyl α-diazophenylacetate (1l).17 The product was obtained as a red oil (1.75 g, 9.20 mmol,
1
92% yield). H NMR (400 MHz, CDCl3): δH 7.51–7.49 (m, 2H), 7.39–7.35 (m, 2H), 7.19–7.15
(m, 1H), 4.35 (q, J = 7.1 Hz, 2H), 1.36 (t, J = 7.1 Hz, 3H) ppm; 13C{H} NMR (100 MHz,
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CDCl3): δC 165.0, 128.8, 125.7, 125.6, 123.8, 63.2, 60.9, 14.4 ppm; IR (ZnSe): 2980, 2077,
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Isobutyl α-diazophenylacetate (1m).26a The product was obtained as a red oil (1.85 g, 8.48 mmol,
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85% yield). H NMR (400 MHz, CDCl3): δH 7.52–7.49 (m, 2H), 7.39–7.37 (m, 2H), 7.21–7.17
(m, 1H), 4.09 (d, J = 7.1 Hz, 2H), 2.06–1.99 (m, 1H), 1.01 (d, J = 7.1 Hz, 6H) ppm; 13C{H}
NMR (100 MHz, CDCl3): δC 165.1, 128.9, 125.7, 125.6, 123.8, 70.8, 63.3, 27.9, 19.0 ppm; IR
(ZnSe): 2961, 2094, 1686, 1392, 1238, 1163, 1015, 782 cm–1.
Allyl α-diazophenylacetate (1n).26b The product was obtained as a red oil (1.88 g, 9.30 mmol,
95% yield). 1H NMR (400 MHz, CDCl3): δH 7.51 (d, J = 8.6 Hz, 2H), 7.41–7.37 (m, 2H), 7.22 (t,
J = 7.4 Hz, 1H), 6.03–5.96 (m, 1H), 5.40 (dd, J = 17.1, 1.5 Hz, 1H), 5.36 (dd, J = 10.4, 1.3 Hz,
1H), 4.79 (dt, J = 5.6, 1.4 Hz, 2H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 164.8, 132.1,
128.9, 125.8, 125.4, 123.9, 118.3, 65.4, 51.9 ppm; IR (ZnSe): 2952, 2078, 1697, 1497, 1239,
1144, 1013, 752 cm–1.
General procedure for Si–H insertion into α-diazoacetate. In a flame-dried glass tube, under
argon atmosphere, [(CH3CN)4Cu]PF6 (9.32 mg, 0.025 mmol, 5 mol %) was diluted in CH2Cl2
(0.5 mL) at room temperature. The silane (1 mmol) was then introduced into the mixture, which
was subsequently cool down to –10 ºC. Methyl α-diazoacetate (0.5 mmol), diluted in CH2Cl2
(0.5 mL), was added dropwise over 1 h using a syringe pump. The mixture was stirred for the
specified time and subsequently filtered through celite and evaporated under reduced pressure
(rotary evaporator). The residue was purified by flash chromatography (Hexane/EtOAc) to afford
the product.
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Methyl α-phenyl-α-triethylsilylacetate (2a).12 The product was obtained as a colorless oil (130
mg, 0.49 mmol, 98% yield). 1H NMR (400 MHz, CDCl3): δH 7.41 (d, J = 8.0 Hz, 2H), 7.39 (t, J
= 8.0 Hz, 2H), 7.19 (t, J = 8.0 Hz, 1H), 3.69 (s, 3H), 3.57 (s, 1H), 0.90 (t, J = 7.6 Hz, 9H), 0.71–
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0.56 (m, 6H) ppm; C{H} NMR (100 MHz, CDCl3): δC 173.5, 136.5, 128.4, 128.1, 51.3, 42.7,
42.6, 7.0, 2.7 ppm; IR (ZnSe): 2950, 2876, 1720, 1299, 1142, 1004, 785, 697 cm–1; HRMS
(ESI): calcd for C15H24O2Si ([M + H]+) = 265.1618, Found 265.1599.
Methyl α-(4-methylphenyl)-α-triethylsilylacetate (2b). The product was obtained as a colorless
1
oil (134 mg, 0.48 mmol, 96% yield). H NMR (400 MHz, CDCl3): δH 7.26 (d, J = 8.0 Hz, 2H),
7.11 (d, J = 8.0 Hz, 2H), 3.68 (s, 3H), 3.51 (s, 1H), 2.32 (s, 3H), 0.95 (t, J = 7.9 Hz, 9H), 0.68–
0.55 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.8, 135.0, 133.3, 128.8, 128.3, 51.2,
42.2, 20.9, 7.0, 2.7 ppm; IR (ZnSe): 2950, 2875, 1719, 1511, 1303, 1141, 1005, 818 cm–1;
HRMS (ESI): calcd for C16H26O2Si ([M + H]+) = 279.1775, Found 279.1770.
Methyl α-(2-methylphenyl)-α-triethylsilylacetate (2c). The product was obtained as a colorless oil
(125 mg, 0.45 mmol, 90% yield). 1H NMR (400 MHz, CDCl3): δH 7.63 (d, J = 7.8 Hz, 1H), 7.21
(t, J = 7.4 Hz, 1H), 7.13–7.05 (m, 2H), 3.82 (s, 1H), 3.67 (s, 3H), 2.29 (s, 3H), 0.92 (t, J = 7.9
Hz, 9H), 0.68–0.55 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.6, 134.9, 134.6,
130.1, 129.5, 125.7, 125.5, 51.3, 37.3, 20.5, 7.0, 3.1 ppm. IR (ZnSe): 2950, 2876, 1724, 1431,
1189, 1147, 1002 cm–1; HRMS (ESI): calcd for C16H26O2Si ([M + H]+) = 279.1775, Found
279.1770.
Methyl α-(4-methoylphenyl)-α-triethylsilylacetate (2d).12 The product was obtained as a colorless
1
oil (131 mg, 0.45 mmol, 89% yield). H NMR (400 MHz, CDCl3): δH 7.27 (d, J = 8.0 Hz, 2H),
6.84 (d, J = 8.0 Hz, 2H), 3.77 (s, 3H), 3.66 (s, 3H), 3.47 (s, 1H), 0.93 (t, J = 7.9 Hz, 9H), 0.62–
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0.57 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.9, 157.6, 129.4, 128.5, 113.5, 55.1,
51.2, 41.5, 7.0, 2.7 ppm; IR (ZnSe): 2050, 2876, 1718, 1508, 1243, 1141, 1004, 828 cm–1;
HRMS (ESI): calcd for C16H26O3Si ([M + H]+) = 295.1724, Found 295.1723.
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Methyl α-(4-fluorophenyl)-α-triethylsilylacetate (2e). The product was obtained as a colorless oil
(134 mg, 0.48 mmol, 95% yield). 1H NMR (400 MHz, CDCl3): δH 7.33 (t, J = 8.0 Hz, 2H), 6.99
(t, J = 8.0 Hz, 2H), 3.67 (s, 3H), 3.52 (s, 1H), 0.92 (t, J = 7.9 Hz, 9H), 0.61–0.56 (m, 6H) ppm;
13C{H} NMR (100 MHz, CDCl3): δC 173.6, 161.10 (d, J = 243.8 Hz), 132.23 (d, J = 3.4 Hz),
129.76 (d, J = 7.6 Hz), 114.87 (d, J = 21.2 Hz), 51.3, 41.7, 6.9, 2.6 ppm; IR (ZnSe): 2951, 2877,
1719, 1505, 1221, 1143, 1004, 705 cm–1; HRMS (ESI): calcd for C15H23FO2Si ([M + H]+) =
283.1524, Found 283.1516.
Methyl α-(3-fluorophenyl)-α-triethylsilylacetate (2f). The product was obtained as a colorless oil
(131 mg, 0.47 mmol, 93% yield). 1H NMR (400 MHz, CDCl3): δH 7.24–7.15 (m, 2H), 7.09 (d, J
= 8.0 Hz, 1H), 6.88 (t, J = 8.0 Hz, 1H), 3.68 (s, 3H), 3.54 (s, 1H), 0.93 (t, J = 7.9 Hz, 9H), 0.61–
0.56 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.1, 162.68 (d, J = 244.3 Hz), 139.11
(d, J = 8.1 Hz), 129.31 (d, J = 8.6 Hz), 124.06 (d, J = 2.7 Hz), 115.27 (d, J = 22.5 Hz), 112.38 (d,
J = 21.1 Hz), 51.4, 42.6, 6.9, 2.5 ppm; IR (ZnSe): 2951, 1733, 1589, 1434, 1235, 1139, 1011,
756 cm–1. HRMS (ESI): calcd for C15H23FO2Si ([M + H]+) = 283.1524, Found 283.1514.
Methyl α-(4-chlorophenyl)-α-triethylsilylacetate (2g).13 The product was obtained as a colorless
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oil (146 mg, 0.49 mmol, 98% yield). H NMR (400 MHz, CDCl3): δH 7.40 (d, J = 8.0 Hz, 2H),
7.25 (d, J = 8.0 Hz, 2H), 3.67 (s, 3H), 3.49 (s, 1H), 0.92 (t, J = 7.9 Hz, 9H), 0.61–0.56 (m, 6H)
ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.2, 135.6, 131.1, 130.0, 119.3, 51.4, 42.2, 7.0, 2.6
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ppm; IR (ZnSe): 2951, 2876, 1717, 1489, 1144, 1089, 1011, 708 cm–1; HRMS (ESI): calcd for
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C15H23ClO2Si ([M + H]+) = 299.1228, Found 299.1226.
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Methyl α-(3-chlorophenyl)-α-triethylsilylacetate (2h).13 The product was obtained as a colorless
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oil (127 mg, 0.43 mmol, 85% yield). H NMR (400 MHz, CDCl3): δH 7.39 (t, J = 8.0 Hz, 1H),
7.24–7.21 (m, 2H), 7.19–7.13 (m, 1H), 3.68 (s, 3H), 3.51 (s, 1H), 0.93 (t, J = 7.9 Hz, 9H), 0.62–
0.58 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.0, 138.6, 133.9, 129.2, 128.3,
126.5, 125.7, 51.4, 42.5, 6.9, 2.6 ppm; IR (ZnSe): 2951, 2876, 1720, 1329, 1196, 1145, 1005,
690 cm–1; HRMS (ESI): calcd for C15H23ClO2Si ([M + H]+) = 299.1228, Found 299.1224.
Methyl α-(2-chlorophenyl)-α-triethylsilylacetate (2i).13 The product was obtained as a colorless
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oil (139 mg, 0.47 mmol, 93% yield). H NMR (400 MHz, CDCl3): δH 7.79 (d, J = 8.0 Hz, 1H),
7.34 (d, J = 8.0 Hz, 1H), 7.26 (t, J = 8.0 Hz, 1H), 7.12 (t, J = 8.0 Hz, 1H), 4.32 (s, 1H), 3.69 (s,
3H), 0.93 (t, J = 7.9 Hz, 9H), 0.66–0.61 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC
173.1, 134.5, 132.7, 130.8, 129.1, 126.7, 126.4, 51.4, 37.6, 6.9, 2.9 ppm; IR (ZnSe): 2951, 2876,
1720, 1329, 1196, 1145, 1005, 690 cm–1; HRMS (ESI): calcd for C15H23ClO2Si ([M + H]+) =
299.1228, Found 299.1221.
Methyl α-(4-bromophenyl)-α-triethylsilylacetate (2j).15 The product was obtained as a colorless
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oil (163 mg, 0.48 mmol, 95% yield). H NMR (400 MHz, CDCl3): δH 7.31 (d, J = 8.0 Hz, 2H),
7.25 (d, J = 8.0 Hz, 2H), 3.67 (s, 3H), 3.51 (s, 1H), 0.92 (t, J = 7.9 Hz, 9H), 0.61–0.54 (m, 6H)
ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.3, 135.1, 131.3, 129.6, 128.1, 51.4, 42.1, 7.0, 2.6
ppm; IR (ZnSe): 2951, 2876, 1719, 1489, 1265, 1145, 1012, 702 cm–1; HRMS (ESI): calcd for
C15H23BrO2Si ([M + H]+) = 343.0723, Found 343.0720.
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Methyl α-(3-bromophenyl)-α-triethylsilylacetate (2k). The product was obtained as a colorless oil
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(149 mg, 0.43 mmol, 87% yield). H NMR (400 MHz, CDCl3): δH 7.54 (d, J = 8.0 Hz, 1H),
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7.31–7.27 (m, 2H), 7.5 (t, J = 8.0 Hz, 1H), 3.67 (s, 3H), 3.49 (s, 1H), 0.93 (t, J = 7.9 Hz, 9H),
0.62–0.57 (m, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 173.04, 138.9, 131.2, 129.5,
128.6, 127.0, 122.2, 51.4, 42.4, 7.0, 2.6 ppm; IR (ZnSe): 2951, 2876, 1720, 1475, 1263, 1132,
1009, 708 cm–1; HRMS (ESI): calcd for C15H23BrO2Si ([M + H]+) = 343.0723, Found 343.0709.
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Ethyl α-phenyl-α-triethylsilylacetate (2l).18 The product was obtained as a colorless oil (132 mg,
0.48 mmol, 95% yield). 1H NMR (400 MHz, CDCl3): δH 7.38 (t, J = 8.0 Hz, 2H), 7.30 (t, J = 7.6
Hz, 2H), 7.19 (t, J = 7.6 Hz, 1H), 4.18–4.10 (m, 2H), 3.52 (s, 1H), 1.30 (t, J = 7.6 Hz, 3H), 0.93
13
(t, J = 7.9 Hz, 9H), 0.63–0.56 (m, 6H) ppm; C{H} NMR (100 MHz, CDCl3): δC 173.1, 136.6,
128.4, 128.0, 125.4, 60.2, 42.8, 14.3, 7.0, 2.7 ppm; IR (ZnSe): 2949, 1731, 1452, 1432, 1276,
1142, 1001, 692 cm–1; HRMS (ESI): calcd for C16H26O2Si ([M + H]+) = 279.1774, Found
279.1776.
Isobutyl α-phenyl-α-triethylsilylacetate (2m). The product was obtained as a colorless oil (131
mg, 0.43 mmol, 86% yield). 1H NMR (400 MHz, CDCl3): δH 7.38 (d, J = 8.0 Hz, 2H), 7.30 (t, J
= 7.6 Hz, 2H), 7.19 (t, J = 7.6 Hz, 1H), 3.92–3.80 (m, 2H), 3.54 (s, 1H), 1.97–1.90 (m, 1H), 0.97
13
(t, J = 7.9 Hz, 6H), 0.63–0.58 (m, 6H) ppm; C{H} NMR (100 MHz, CDCl3): δC 173.3, 136.7,
128.5, 128.0, 125.4, 70.7, 42.8, 27.7, 19.3, 7.1, 2.7 ppm; IR (ZnSe): 2949, 1729, 1493, 1280,
1211, 1140, 1027, 762 cm–1; HRMS (ESI): calcd for C18H30O2Si ([M + H]+) = 307.2088, Found
307.2086.
Allyl α-phenyl-α-triethylsilylacetate (2n). The product was obtained as a colorless oil (142 mg,
0.49 mmol, 98% yield). 1H NMR (400 MHz, CDCl3): δH 7.37 (d, J = 8.0 Hz, 2H), 7.30 (t, J = 7.6
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Hz, 2H), 7.19 (t, J = 7.6 Hz, 1H), 5.98–5.89 (m, 1H), 5.35–5.22 (m, 2H), 4.59 (dt, J = 5.9, 1.3
Hz, 2H), 3.55 (s, 1H), 0.92 (t, J = 7.8 Hz, 9H), 0.63–0.58 (m, 6H) ppm; 13C{H} NMR (100 MHz,
CDCl3): δC 172.8, 136.4, 132.4, 128.4, 128.1, 125.5, 118.3, 65.1, 42.7, 7.0, 2.7 ppm; IR (ZnSe):
2949, 1731, 1452, 1432, 1276, 1142, 1001, 692 cm–1; HRMS (ESI): calcd for C17H26O2Si ([M +
H]+) = 291.1775, Found 291.1781.
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General procedure for S–H insertion into α-diazoesters. In a flame-dried glass tube, under
argon atmosphere, [(CH3CN)4Cu]PF6 (9.32 mg, 0.025 mmol, 5 mol %) was diluted in CH2Cl2
(0.5 mL) at room temperature. The thiol (1 mmol) was then introduced dropwise into the mix-
ture. Methyl α-diazoacetate (0.5 mmol), diluted in CH2Cl2 (0.5 mL), was added dropwise over 1
h using a syringe pump. The mixture was stirred for the specified time and subsequently filtered
through celite and evaporated under reduced pressure (rotary evaporator). The residue was puri-
fied by flash chromatography (Hexane/EtOAc) to afford the product.
Methyl 2-(benzylthio)-2-phenylacetate (3a).35 The product was obtained as a colorless oil (116
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mg, 0.42 mmol, 85% yield). H NMR (400 MHz, CDCl3): δH 7.43–7.40 (m, 2H), 7.35–7.28 (m,
8H), 4.44 (s, 1H), 3.79 (d, J = 13.5 Hz, 1H), 3.69 (s, 3H), 3.62 (d, J = 13.5 Hz, 1H) ppm; 13C{H}
NMR (100 MHz, CDCl3): δC 171.1, 137.1, 135.7, 129.0, 128.7, 128.6, 128.5, 128.2, 127.2, 52.7,
51.4, 36.2 ppm; IR (ZnSe): 2953, 2872, 1703, 1471, 1255, 1141, 1083, 1013, 708 cm–1.
Methyl 2-(benzylthio)-2-(4-chlorophenyl)-acetate (3b).35 The product was obtained as a colorless
1
oil (130 mg, 0.43 mmol, 85% yield). H NMR (400 MHz, CDCl3): δH 7.35–7.25 (m, 9H), 4.38
13
(s, 1H), 3.79 (d, J = 13.5 Hz, 1H), 3.69 (s, 3H), 3.62 (d, J = 13.5 Hz, 1H) ppm; C{H} NMR
(100 MHz, CDCl3): δC 170.7, 136.8, 134.3, 134.1, 129.9, 129.0, 128.8, 128.5, 127.3, 52.8, 50.6,
36.2 ppm; IR (ZnSe): 2950, 2873, 1711, 1478, 1262, 1139, 1080, 1001, 711 cm–1.
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Methyl 2-phenyl-2-(phenylthio)acetate (3c).36 The product was obtained as a white solid (103
mg, 0.40 mmol, 80% yield). mp: 46–48 ºC. 1H NMR (400 MHz, CDCl3): δH 7.48–7.27 (m, 10H),
4.95 (s, 1H), 3.68 (s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 170.9, 135.6, 133.6, 132.6,
129.0, 128.7, 128.5, 128.3, 128.0, 56.3, 52.7 ppm; IR (ZnSe): 2951, 2876, 1717, 1489, 1265,
1145, 1089, 1011, 705 cm–1.
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Methyl 2-((4-methoxyphenyl)thio)-2-phenylacetate (3d).35 The product was obtained as a color-
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less oil (125 mg, 0.44 mmol, 87% yield). H NMR (400 MHz, CDCl3): δH 7.42 (d, J = 8.0 Hz,
2H), 7.34–7.30 (m, 5H), 6.80 (d, J = 8.7 Hz, 2H), 4.87 (s, 1H), 3.77 (s, 3H), 3.66 (s, 3H) ppm;
13C{H} NMR (100 MHz, CDCl3): δC 171.0, 160.2, 136.2, 135.7, 128.6, 128.5, 128.2, 123.5,
114.4, 57.3, 55.2, 52.6 ppm; IR (ZnSe): 3005, 2961, 2938, 2837, 1573, 1510, 1495, 1285, 1259,
1030, 829, 775 cm–1.
Methyl 2-((4-chlorophenyl)thio)-2-phenylacetate (3e). The product was obtained as a white solid
(110 mg, 0.37 mmol, 75% yield). mp: 58–60 ºC; 1H NMR (400 MHz, CDCl3): δH 7.42–7.40 (m,
13
2H), 7.35–7.26 (m, 5H), 7.24–7.23 (m, 2H), 4.87 (s, 1H), 3.69 (s, 3H) ppm; C{H} NMR (100
MHz, CDCl3): δC 170.6, 135.2, 134.4, 134.2, 131.9, 129.1, 128.7, 128.5, 128.4, 56.4, 52.8 ppm;
IR (ZnSe): 2951, 1713, 1495, 1432, 1281, 1235, 1093, 1009, 823 cm–1; HRMS (ESI): calcd for
C15H13ClO2S ([M + H]+) = 293.0397, Found 293.0395.
Methyl 2-phenyl-2-(p-tolylthio)acetate (3f).37 The product was obtained as a white solid (122 mg,
0.45 mmol, 90% yield). mp: 60–62 ºC; 1H NMR (400 MHz, CDCl3): δH 7.43 (d, J = 9.3 Hz, 2H),
7.35–7.25 (m, 5H), 7.24 (d, J = 8.4 Hz, 2H), 4.85 (s, 1H), 3.68 (s, 3H), 2.32 (s, 3H) ppm; 13C{H}
NMR (100 MHz, CDCl3): δC 170.9, 138.4, 135.7, 133.3, 129.8, 129.7, 128.6, 128.5, 128.2, 56.7,
52.7, 21.1 ppm; IR (ZnSe): 2951, 1717, 1433, 1268, 1229, 1006, 811, 762, 695 cm–1.
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Methyl 2-(4-methoxyphenyl)-2-(phenylthio)acetate (3g).22 The product was obtained as a white
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solid (120 mg, 0.42 mmol, 83% yield). mp: 78–80 ºC; H NMR (400 MHz, CDCl3): δH 7.38–
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7.36 (m, 4H), 7.27–7.26 (m, 3H), 6.87 (d, J = 8.8 Hz, 2H), 4.89 (s, 1H), 3.79 (s, 3H), 3.67 (s, 3H)
ppm; 13C{H} NMR (100 MHz, CDCl3): δC 171.0, 159.5, 133.8, 132.5, 129.6, 128.9, 127.9,
127.4, 114.0, 55.6, 55.2, 52.6 ppm; IR (ZnSe): 3002, 2954, 2835, 1718, 1508, 1438, 1252, 1173,
1028, 1003, 830 cm–1.
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Methyl 2-(phenylthio)-2-(p-tolyl)acetate (3h).22 The product was obtained as white a solid (118
mg, 0.44 mmol, 87% yield). mp: 67–70 ºC; 1H NMR (400 MHz, CDCl3): δH 7.42–7.36 (m, 4H),
7.29–7.27 (m, 3H), 7.16 (d, J = 7.9 Hz, 2H), 4.94 (s, 1H), 3.68 (s, 3H), 2.35 (s, 3H) ppm; 13C{H}
NMR (100 MHz, CDCl3): δC 171.0, 138.2, 133.9, 132.5, 132.4, 129.4, 128.9, 128.3, 127.9, 56.0,
52.7, 21.1 ppm; IR (ZnSe): 3049, 2941, 1740, 1578, 1510, 1434, 1329, 1142, 1078, 792 cm–1.
Methyl 2-(4-chlorophenyl)-2-(phenylthio)acetate (3i).24 The product was obtained as a white
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solid (130 mg, 0.45 mmol, 89% yield). mp: 48–50 ºC; H NMR (400 MHz, CDCl3): δH 7.39–
7.34 (m, 4H), 7.27 (m, 5H), 4.88 (s, 1H), 3.68 (s, 3H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC
170.4, 134.2, 134.2, 133.1, 133.0, 129.9, 129.0, 128.8, 128.3, 55.6, 52.8 ppm; IR (ZnSe): 3050,
2951, 1716, 1488, 1470, 1293, 1235, 849, 767 cm–1.
Methyl 2-(4-bromophenyl)-2-(phenylthio)acetate (3j).24 The product was obtained as a white
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solid (147 mg, 0.44 mmol, 87% yield). mp: 48–50 ºC; H NMR (400 MHz, CDCl3): δH 7.45–
7.43 (m, 2H), 7.37–7.26 (m, 7H), 4.85 (s, 1H), 3.68 (s, 3H) ppm; 13C{H} NMR (100 MHz,
CDCl3): δC 170.4, 134.7, 133.0, 131.8, 131.7, 130.2, 129.0, 128.3, 122.4, 55.7, 52.8 ppm; IR
(ZnSe): 3051, 2949, 1713, 1483, 1469, 1290, 1231, 838, 767 cm–1.
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Ethyl 2-phenyl-2-(phenylthio)acetate (3k). The product was obtained as a colorless oil (113 mg,
0.42 mmol, 83% yield). 1H NMR (400 MHz, CDCl3): δH 7.47 (d, J = 9.5 Hz, 2H), 7.42–7.38 (m,
2H), 7.36–7.30 (m, 3H), 7.29–7.25 (m, 3H), 4.93 (s, 1H), 4.19–4.07 (m, 2H), 1.17 (t, J = 7.1 Hz,
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3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 170.4, 135.6, 133.8, 132.6, 128.9, 128.6, 128.5,
128.2, 127.9, 61.7, 56.3, 14.0 ppm; IR (ZnSe): 2948, 2881, 1719, 1469, 1257, 1139, 1010, 759
cm–1; HRMS (ESI): calcd for C16H16O2S ([M + H]+) = 273.0944, Found 273.0949.
Isobutyl 2-phenyl-2-(phenylthio)acetate (3l). The product was obtained as a colorless oil (128
mg, 0.43 mmol, 85% yield). 1H NMR (400 MHz, CDCl3): δH 7.51 (d, J = 9.6 Hz, 2H), 7.42–7.38
(m, 2H), 7.36–7.30 (m, 3H), 7.29–7.24 (m, 3H), 4.96 (s, 1H), 3.88 (d, J = 6.6 Hz, 2H), 1.90–1.83
(m, 1H), 0.84 (d, J = 6.7 Hz, 6H) ppm; 13C{H} NMR (100 MHz, CDCl3): δC 170.4, 135.7, 133.9,
132.4, 128.9, 128.6, 128.5, 128.2, 127.8, 71.7, 56.5, 27.6, 18.9 ppm; IR (ZnSe): 3049, 2950,
2881, 1719, 1469, 1257, 1139, 1010 cm–1; HRMS (ESI): calcd for C18H20O2S ([M + H]+) =
301.1257, Found 301.1255.
Methyl 1,2-diphenylcyclopropane-1-carboxylate (4).38 The product was obtained as a white soild
(34 mg, 0.13 mmol, 27% yield). mp: 57–59 °C; 1H NMR (400 MHz, CDCl3): δH 7.15–7.13 (m,
3H), 7.07–7.03 (m, 5H), 6.79–6.76 (m, 2H), 3.67 (s, 3H), 3.15 (dd, J = 9.2, 7.5 Hz, 1H), 2.17
13
(dd, J = 9.3, 4.9 Hz, 1H), 1.91 (dd, J = 7.2, 4.9 Hz, 1H); C{H} NMR (100 MHz, CDCl3): δC
174.3, 136.3, 134.7, 131.9, 128.0, 127.7, 127.6, 127.0, 126.2, 52.6, 37.3, 33.1, 20.4 ppm; IR
(ZnSe): 3073, 1751, 1248, 1114, 1011, 979, 849, 676 cm–1.
Allyl 2-phenylacetate (6).39 The product was obtained as a colorless oil (1.67 g, 9.48 mmol, 95%
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yield). H NMR (400 MHz, CDCl3): δH 7.34–7.25 (m, 5H), 5.93–5.85 (m, 1H), 5.29–5.19 (m,
13
2H), 4.60 (s, 2H), 3.65 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC 171.1, 133.9, 132.0,
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129.2, 128.5, 127.1, 118.1, 65.4, 41.3 ppm; IR (ZnSe): 3075, 1751, 1253, 1115, 1003, 985, 853,
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682 cm–1.
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1-Phenyl-3-oxabicyclo[3.1.0]hexan-2-one (7).40 The product was obtained as a colorless oil (26
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mg, 0.15 mmol, 59% yield). H NMR (400 MHz, CDCl3): δH 7.44–7.41 (m, 2H), 7.38–7.34 (m,
2H), 7.32–7.26 (m, 1H), 4.47 (dd, J = 9.2, 4.6 Hz, 1H), 4.31 (d, J = 9.3 Hz, 1H), 2.58–2.54 (m,
1H), 1.67 (dd, J = 7.8, 4.8 Hz, 1H), 1.38 (t, J = 4.8 Hz, 1H) ppm; 13C{H} NMR (100 MHz,
CDCl3): δC 176.0, 134.0, 128.6, 128.3, 127.6, 68.0, 31.7, 25.0, 20.1 ppm; IR (ZnSe): 3060, 2973,
2907, 1758, 1602, 975, 850, 675 cm–1.
General procedure for preparation of 2-diazopropiophenones. To a 25 mL flame-dried flask
under argon was added a 60% dispersion of sodium hydride in mineral oil (0.71 g, 17.79 mmol),
one drop of anhydrous ethyl alcohol and anhydrous diethyl ether (2 mL). The mixture was
cooled with an ice-bath, then a solution of corresponding propiophenone derivatives (5.93 mmol)
and ethyl formate (1.32 g, 17.79 mmol) in anhydrous diethyl ether (2 mL) was added dropwise.
The mixture was stirred for 3 h at 0 °C, then 12 h at room temperature. Then, a solution of me-
thanesulfonyl azide (2.15 g, 17.79 mmol) in anhydrous diethyl ether (5 mL) was added dropwise
and the mixture was stirred another 2h. The mixture was quenched with water (2 mL), then the
organic phases were washed with a solution of 10% NaOH in water. The organic phases were
extracted with diethyl ether (2 x 25 mL) and the organic phases were combined, dried over
MgSO4 and evaporated under reduced pressure (temperature 30 °C). The crude product was puri-
fied on flash chromatography (Hexane/EtOAc).
2-Diazo-1-phenylpropan-1-one (8a).26c The product was obtained as a yellow liquid (0.702 g,
1
4.39 mmol, 74% yield). H RMN (400 MHz, CDCl3) δH 7.59–7.55 (m, 2H), 7.51–7.46 (m, 1H),
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7.45–7.40 (m, 2H), 2.15 (s, 3H) ppm. C{H} NMR (CDCl3, 100 MHz) δC 190.1, 137.6, 131.3,
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128.5, 127.1, 62.8, 9.5 ppm; IR (ZnSe): 2062, 1600, 1571, 1445, 1277, 1000, 890, 781 cm–1.
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2-Diazo-1-(p-tolyl)propan-1-one (8b).26c The product was obtained as a yellow solid (0.494 g,
2.84 mmol, 48% yield). mp: 42–44 °C; 1H NMR (400 MHz, CDCl3): δH 7.48 (d, J = 8.1 Hz, 2H),
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7.22 (d, J = 8.5 Hz, 2H), 2.38 (s, 3H), 2.14 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC
189.9, 141.8, 134.9, 129.1, 127.6, 62.5, 21.5, 9.6 ppm; IR (ZnSe): 2072, 1592, 1340, 1277, 1022,
836, 736, 690 cm–1.
2-Diazo-1-(p-chlorophenyl)propan-1-one (8c).26d The product was obtained as a yellow solid
1
(0.433 g, 2.23 mmol, 38% yield). mp: 46–47 °C; H NMR (400 MHz, CDCl3): δH 7.52 (d, J =
13
8.3 Hz, 2H), 7.40 (d, J = 8.8 Hz, 2H), 2.14 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3): δC
188.6, 137.4, 135.8, 128.8, 128.6, 62.9, 9.6 ppm; IR (ZnSe): 2074, 1561, 1342, 1273, 1112, 997,
840, 681 cm–1.
2-Diazo-1-(p-fluorophenyl)propan-1-one (8d).26c The product was obtained as a yellow solid
1
(0.549 g, 3.08 mmol, 52% yield). mp: 57–59 °C; H NMR (400 MHz, CDCl3): δH 7.59 (dd, J =
13
8.8, 5.3 Hz, 2H), 7.10 (t, J = 8.6 Hz, 2H), 2.13 (s, 3H) ppm; C{H} NMR (100 MHz, CDCl3):
δC 188.6, 164.3 (d, J = 252.2 Hz), 133.7 (d, J = 3.2 Hz), 129.6 (d, J = 8.8 Hz), 115.6 (d, J = 21.9
Hz), 62.8, 9.5 ppm; IR (ZnSe): 2058, 1620, 1341, 1219, 1178, 1004, 780, 740 cm–1.
1-(Benzo[d][1,3]dioxol-5-yl)-2-diazopropan-1-one (8e).26e The product was obtained as a yellow
solid (0.605 g, 2.96 mmol, 50% yield). mp: 66–68 °C; 1H NMR (400 MHz, CDCl3): δH 7.12 (dd,
J = 8.0, 1.7 Hz, 1H), 7.05 (d, J = 1.7 Hz, 1H), 6.79 (d, J = 8.0 Hz, 1H), 6.00 (s, 2H), 2.11 (s, 3H)
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