Direct Decarboxylative-Decarbonylative Alkylation of α-Oxo Acids with Electrophilic Olefins via Visible-Light Photoredox Catalysis

Article abstract of DOI:10.1021/acs.joc.7b02628

The decarbonylation of primary, secondary, and tertiary alkyl-substituted acyl radicals has been investigated through photoredox catalysis. A series of quaternary carbons and γ-ketoesters have been directly constructed by the photoredox 1,4-conjugate addi

Full text of DOI:10.1021/acs.joc.7b02628

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Article
Direct Decarboxylative-Decarbonylative Alkylation of #-Oxo Acids
with Electrophilic Olefins via Visible-Light Photoredox Catalysis
Jian-Qiang Chen, Rui Chang, Yun-Long Wei, Jia-Nan Mo, Zhu-Yin Wang, and Peng-Fei Xu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b02628 • Publication Date (Web): 05 Dec 2017
Downloaded from http://pubs.acs.org on December 5, 2017
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Direct Decarboxylative-Decarbonylative Alkylation of α-Oxo Acids
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with Electrophilic Olefins via Visible-Light Photoredox Catalysis
JianꢀQiang Chen, Rui Chang, YunꢀLong Wei, JiaꢀNan Mo, ZhuꢀYin Wang and PengꢀFei Xu*
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State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, 730000, P.R.
China
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ABSTRACT
The decarbonylation of primary, secondary and tertiary alkylꢀsubstituted acyl radicals has been
investigated through photoredox catalysis. A series of quaternary carbons and γꢀketoesters have been
directly constructed by the photoredox 1,4ꢀconjugate addition of the corresponding alkyl ketoacids with
electrophilic alkenes. And, the tertiary alkyl ketoacids have proved as good precursors of tertiary alkyl
radicals.
KEYWORDS
photocatalysis, decarboxylative, decarbonylative, quaternary carbons, γꢀketoesters
INTRODUCTION
Organic carboxylic acids and their derivatives have been widely found in natural products and
commonly used in chemical synthesis.1 Harnessing carboxylic acids as inexpensive and readily
available starting materials to construct highꢀvalue organic molecules has been shown to be a
promising method in modern organic chemistry. Especially, much effort has been devoted to the
investigations of their radical decarboxylative functionalization through visibleꢀlight photoredox
catalysis under mild conditions in recent years.2ꢀ3 As shown in Scheme 1, only carbon dioxide is
released in most of these conversions.2 Compared with the decarboxylative coupling reactions,
photoredoxꢀcatalyzed decarbonylative functionalization has not received much attention, and the
considerable synthetic potential still remains largely unexploited.2c As such, the development of a
common method for the direct decarbonylative coupling reaction induced by visibleꢀlight photoredox
catalysis would make a significant complement to the field of the decarboxylative reaction. To this end,
the photocatalytic radical carbonylative reactions have been achieved (Scheme 1b).3 As the inverse
process of the carbonylative reaction, we wanted to know whether or not this photocatalyzed
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transformation would proceed. Inspired by Overman’s introduction of oxalate derivatives for
generating the alkyl radicals from alcohols after two consecutive decarboxylation steps (Scheme 1c),4aꢀc
we envisioned that the decarbonylative functionalization could be realized through visibleꢀlight
photoredox catalysis. The driving forces for the doubleꢀdecarboxylative reaction are mainly the
extrusion of stable carbon dioxide and the generation of stable tertiary carbon radicals which are useful
intermediates for constructing the complex structures.4 Therefore, we believed that when a tertiary
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carbon group was present at the αꢀposition of the acyl radical, the decarbonylative reaction would be
smoothly achieved,5 as shown in Scheme 1d. The stable tertiary carbon radicals, generated from the
acyl radical, would then be used for the construction of sterically encumbered tetraꢀsubstituted carbon
centers. During the past several years, the transformations of the alkyl radicals have been widely
investigated and precursors of alkyl radicals were mainly focused on the carboxylic acids and the alkyl
halides.2ꢀ4 In compared with the previous work, the transformation of the direct
decarboxylation-decarbonylation under visibleꢀlight photocatalysis to provide the alkyl radicals has
been less investigated.
Scheme 1. Photocatalyzed Decarboxylative Reactions of Acids
RESULTS AND DISCUSSION
As shown in Table 1, we began our investigation by screening conditions for the
decarboxylativeꢀdecarbonylative reaction of 2ꢀ(tertꢀbutyl)ꢀ2ꢀoxoacetic acid (1a). To our delight, the
only desired decarboxylativeꢀdecarbonylation product 3a4c, 6 (in a good yield of 71%) was observed at
25 °C by irradiation with blue LEDs when Ir[dF(CF3)ppy]2(dtbbpy)PF6 was used as the photocatalyst,
NaOAc as the base and benzyl acrylate (2a) as the alkyl radical acceptor (entry 1). When
Ir(ppy)2(dtbbpy)PF6 was used instead of Ir[dF(CF3)ppy]2(dtbbpy)PF6, the yield of the product 3a was
drastically decreased to 24% (entry 2). Meanwhile, the reaction did not occur when other more
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oxidizing photocatalysts at the excited states, yet less reducing at the reduced excited states, such as
Ru(bpz)3(PF6)27 and AcrꢀMes•ClO4 (entries 3ꢀ4), were used as the catalysts. The presence of the proton
might have an effect on the redox potential of Ru(bpz)3(PF6)2. And the reduced state catalyst
(Acr•ꢀMes) could not reduce the enolate radical.8 Other inorganic bases, which have been widely used
in the decarboxylative functionalization by photoredox catalysis,2 gave the slightly lower yields (entries
5ꢀ7). Unexpectedly, the screening of organic bases showed that 1,4ꢀdiazabicyclo[2.2.2]ꢀoctane
(DABCO) was more effective in this decarboxylativeꢀdecarbonylative alkylation protocol, which can
be readily oxidized by excitedꢀstate *IrIII complex (E1/2red [*IrIII/IrII] = + 1.21 V versus saturated calomel
electrode (SCE))2a (entry 8). Next, the solvent screening was performed, and the optimal one was found
to be acetone, gaving 91% yield (entry 15). Notably, when a protic solvent was used instead of acetone,
the decarbonylation reaction did not occur (entry 13). This phenomenon helped us explore the
singleꢀelectronꢀtransfer (SET) process which could occur in the ketoacid oxidization step of the
photocatalytic cycle. As expected, control experiments demonstrated that the base, the photocatalyst
and the visible light were all essential components for this reaction (entries 16ꢀ18). When the catalytic
amount of base was used, the yield of the product was decreased to 30% (entry 19) and the substrate
(2a) was completely consumed.
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Table 1. Screening of the Reaction Conditions for the Decarboxylative-Decarbonylative
Alkylation of α
-Oxo Acida
entry
photocatalyst
base
solvent
yield (%)b
1
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir(ppy)2(dtbbpy)PF6
NaOAc
NaOAc
NaOAc
NaOAc
Cs2CO3
K2HPO4
CsF
DMF
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2
DMF
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0
3
Ru(bpz)3(PF6)2
DMF
4
Acr-Mes•ClO4
DMF
0
5c
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
Ir[dF(CF3)ppy]2(dtbbpy)PF6
DMF
67
40
47
86
83
29
82
67
0
6
DMF
7
DMF
8
DABCO
TMG
DMF
9d
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12
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15
DMF
Et3N
DMF
DABCO
DABCO
DABCO
DABCO
DABCO
THF
CH3CN
MeOH
CH2Cl2
acetone
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Ir[dF(CF3)ppy]2(dtbbpy)PF6
DABCO
—
acetone
0
Ir[dF(CF3)ppy]2(dtbbpy)PF6
—
acetone
acetone
acetone
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DABCO
DABCO
0
6
19f
Ir[dF(CF3)ppy]2(dtbbpy)PF6
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aUnless otherwise noted, the reaction conditions are as follows: 1a (0.3 mmol), 2a (0.2 mmol),
photocatalyst (0.002 mmol), base (0.3 mmol), solvent (4 mL), 25 W blue LED strip, 25 °C, 2 h and
b
c
d
e
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under a N2 atmosphere. Isolated yield. Reaction time: 5 h. Reaction time: 3.5 h. In the absence of a
light source. f Base: 20 mol%. TMG = Tetramethylguanidine
Having optimized the conditions for this photoredoxꢀcatalyzed decarboxylativeꢀdecarbonylation
reaction, the scope of Michael acceptors was then explored. As shown in Table 2, a broad range of
electrophilic olefins could successfully participate in this COꢀextrusion, conjugate addition protocol.
Notably, methyl substitution at the
αꢀposition of acrylate olefins was tolerated very well to give the
corresponding decarboxylativeꢀdecarbonylation product (3b) in excellent yield. Moreover, both of the
acyclic and cyclic unsaturated ketones were well tolerated in this transformation (products 3c and 3d,
with the yield of 83% and 75%, respectively). This protocol could also be extended to the alkylation of
chromone, giving the corresponding 2ꢀsubstituted chromanone scaffold (3d), which is a privileged
structural motif found in a large number of natural products and pharmaceutical molecules, exhibiting
many biological activities.9 Sterically demanding olefins could also be readily converted into the target
compounds, although the reaction times were longer (3dꢀ3e). As expected, methyl 2ꢀphenylacrylate
and benzyl 2ꢀphenylacrylate behaved similarly (3fꢀ3g). Furthermore, both electronꢀdeficient and
electronꢀrich aryl substitution at the
αꢀposition of acrylate olefins were well accommodated in this
conversion under the photoredox catalysis (3hꢀ3q). It was also found that the substrates with a bulky
naphthyl group were converted into the target compounds with good to excellent yields (3rꢀ3s).
However, the transformation of some other substrates was not success.
Table 2. Scope of Michael Acceptors in the Decarboxylative-Decarbonylation Reactiona,b
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aUnless otherwise noted, reaction conditions are as follows: 1a (0.3 mmol),
2 (0.2 mmol),
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Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.002 mmol), DABCO (0.3 mmol), acetone (4 mL), 25 W blue
LED strip, 25 °C and under a N2 atmosphere. bIsolated yield.
Given the success of the decarboxylative and decarbonylative alkylation of
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2ꢀ(tertꢀbutyl)ꢀ2ꢀoxoacetic acid (1a), we turned our attention to other
αꢀketo acids to explore the
potential of this transformation (Table 3). A range of the tertiary alkyl ketoacids could serve as viable
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tertiary carbon radicals under the optimal conditions (4aꢀ4c). Notably, the substrate with a cyclopropyl
group at the
αꢀposition of the keto acid was entirely converted into 1,4ꢀdicarbonyl compound (4d’)
without any decarbonylated or rearranged product. This significant result shows that the coupling rate
of benzyl acrylate (2a) with the cyclopropyl formyl radical is faster than the ring opening.13b The
reactions of adamantyl and secondary alkyl ketoacids led to the decarboxylativeꢀdecarbonylative
coupling products (4eꢀ4h)10 in low yields with the major products of γꢀketoesters (4e’ꢀ4h’) derived
from the coupꢀling of the intermediate acyl radicals with benzyl acrylate. The aryl and primary alkyl
ketoacids were entirely converted into the 1,4ꢀdicarbonyl compounds (4i’ꢀ4m’).11 In conclusion, the
tertiary alkyl ketoacids are prone to rapid decarboxylationꢀdecarbonylation, the aryl and primary alkyl
substrates only undergo decarboxylation reaction, and the secondary acyl radicals will produce a small
amount of decarbonylative alkylation products12 with major decarboxylative alkylation products under
the reaction conditions.
Table 3. Scope Evaluation of the α
-Keto Acidsa,b
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aUnless otherwise noted, reaction conditions are as follows:
1 (0.3 mmol), 2a (0.2 mmol),
Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.002 mmol), DABCO (0.3 mmol), acetone (4 mL), 25 W blue
LED strip, 25 °C and under a N2 atmosphere. bIsolated yield.
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As another important parameter that can affect the decarboxylativeꢀdecarbonylative coupling
reaction, temperature effect was also investigated.13 With the temperature increased, the yield of the
target product 4f was improved. Especially at the boiling point of the solvent, the
decarboxylationꢀdecarbonylation yields of the adamantly and secondary ketoacids increased
dramatically with the simultaneous decrease of the 1,4ꢀdicarbonyl product yields. However, when
further increased the temperature to 70 or 100 °C, the reaction did not success (Table 4, 4h). The
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αꢀOxo acids might be unstable at this high temperature. In contrast, the 1,4ꢀdicarbonyl compounds
were given at the highest yields with only trace of decarboxylationꢀdecarbonylation products produced
at low reaction temperature (0 °C).
Table 4. Temperature-Dependent Decarboxylation-Decarbonylation of the Ketoacidsa,b
aUnless otherwise noted, reaction conditions are as follows: ketoacids (0.3 mmol), 2a (0.2 mmol),
Ir[dF(CF3)ppy]2(dtbbpy)PF6 (0.002 mmol), DABCO (0.3 mmol), acetone (4 mL), 25 W blue LED strip
and under a N2 atmosphere. bIsolated yield. cThe reaction vessel was sealed with a teflon screw cap.
Demonstration of the synthetic utility of this decarboxylativeꢀdecarboxylative alkylation processes
was also performed. As shown in Scheme 2, the decarbonylative alkylation reaction could also
successfully proceed under natural sunlight irradiation, affording the desired product 3a in a slightly
longer reaction time
Scheme 2. Sunlight-Driven Reaction
Based on our previous work as well as other reports,14 a plausible reaction mechanism was proposed,
as illustrated in Scheme 3. Irradiation of the groundꢀstate photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 (5)
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with visible light produces the excitedꢀstate photocatalyst (6). This photoexcited species is a strong
electron acceptor (E1/2 [∗IrIII/IrII] = + 1.21 V vs. SCE in MeCN) and undergo a single electron transfer
(SET) with the anion (8) formed by the proton translocation of ketoacid (1) in the presence of an
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organic base, which results in the generation of a αꢀoxo carboxyl radical (9). This radical can rapidly
undergo CO2ꢀextrusion and produce an acyl radical (10) along with the reduced photocatalyst (7).
Species 10 is then converted to the stabilized alkyl radical (11) through decarbonylation. The
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nucleophilic alkyl radical (11) readily undergoes the coupling reaction with an electrophilic olefin (2)
red
to generate the new
α
ꢀalkyl radical (12). The intermediate 12 (E1/2 = ꢀ 0.60 V vs. SCE)15 can be
readily reduced by the strong reducing IrII species (7) (E1/2 [IrIII/IrII] = ꢀ 1.37 V vs. SCE)2a to generate
the carbanion intermediate (13) and the groundꢀstate photocatalyst 5. The final product (4) is then
afforded by the protonation of the species 13. Likewise, in the case of the acylation reaction, acyl
radical 10 readily undergoes conjugate addition with electronꢀdeficient olefin 2 to give the
1,4ꢀdicarbonyl compounds 4’. To support the mechanism, a series of Stern–Volmer fluorescence
quenching studies were performed which clearly showed that the anion (8) could efficiently quench the
∗
excitedꢀstate photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 (no quenching was observed by ketoacids in
the absence of DABCO).
Scheme 3. A Plausible Reaction Mechanism
CONCLUSION
In summary, we have developed the visibleꢀlight photoredox catalysis to achieve the
decarboxylativeꢀdecarbonylative alkylation of ketoacids with electronꢀdeficient olefins. A series of
quaternary carbons and γꢀketoesters have been directly constructed by the photoredox 1,4ꢀconjugate
addition of the corresponding alkyl ketoacids with electrophilic alkenes. The decarbonylation of
primary, secondary and tertiary alkylꢀsubstituted acyl radicals was investigated. And, the tertiary alkyl
ketoacids have shown as good precursors of tertiary alkyl radicals. Mechanistic studies of the
transformation were also performed and a plausible reaction mechanism was proposed.
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EXPERIMENTAL SECTION
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General Information. All glassware was thoroughly ovenꢀdried. Chemicals and solvents were either
purchased from commercial suppliers or purified by standard techniques. Thinꢀlayer chromatography
plates were visualized by exposure to ultraviolet light and/or staining with phosphomolybdic acid
followed by heating on a hot plate. Flash chromatography was carried out using silica gel (200−300
1
mesh). H NMR and 13C NMR spectra were recorded on a 400 MHz spectrometer. The spectra were
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1
recorded in deuterochloroform (CDCl3) as solvent at room temperature, H and 13C NMR chemical
shifts are reported in ppm relative to the residual solvent peak. The residual solvent signals were used
as references and the chemical shifts were converted to the TMS scale (CDCl3: δH = 7.26 ppm, δC =
77.0 ppm). Data for 1H NMR are reported as follows: chemical shift (δ ppm), multiplicity (s = singlet,
d = doublet, t = triplet, m = multiplet, dd = doublet, br = broad), integration, coupling constant (Hz) and
assignment. Data for 13C NMR are reported as chemical shift. IR spectra were recorded on a FTꢀIR
instrument and are reported in wave numbers (cmꢀ1). HRMS were performed on a Bruker Apex II mass
instrument (ESI).
General procedure a for α
-oxo acids.16 To a solution of alkyl methyl ketone (5 mmol, 1.0 eq.) and
NaOH (10.0 mmol, 2.0 eq.) in 15 mL H2O cooled to 0 °C, KMnO4 (10.0 mmol, 2.0 eq.) were added
over a period of 30 minutes. The mixture was warmed to room temperature and stirred for additional 16
hours. The resulting suspension was filtered and washed several times with H2O. Under cooling, the
filtrate was treated with HClconc. (2 mL) and extracted with Et2O (3 x 10 mL). The combined organic
layers were washed with brine, dried over Na2SO4, filtered and the solvent was removed under reduced
pressure. The title compound was obtained as a white solid and was used in the following step without
further purification.
General procedure b for
α
-oxo acids.17 A solution of 1,3ꢀdiphenylimidazolidineꢀ2,4,5ꢀtrione (B)
(1.00 g, 3.76 mmol) in dry THF (5 mL) was added dropwise to a solution of Grignard reagent (1.1
equiv) in dry THF under a N2 atmosphere at −78 °C and stirred for 1 h. The reaction mixture was
poured into sat. aq. NH4Cl and then extracted with AcOEt. The organic layer was washed with brine,
dried over anhydrous Na2SO4 and concentrated in vacuo. The crude product was chromatographed on
silica gel with hexane−AcOEt (4:1) to further give product C as a yellow solid.
NaOH in H2O (4 M, 3 mL) was added to a solution of compound C (2.94 mmol) in MeOH (10 mL)
at room temperature and the mixture was heated at 50 °C for 1 h. The reaction mixture was then poured
into H2O and extracted with AcOEt to give an organic layer including N,N′ꢀdiphenylurea. The
thusꢀobtained aqueous layer was acidified with 1N HCl, and then extracted with AcOEt. The AcOEt
solution was washed with brine, dried over anhydrous Na2SO4 and concentrated in vacuo. The title
compound D was obtained as a white solid and was used in the following step without further
purification.
General procedures for the photocatalytic reaction.
α
ꢀOxo acid 1 (0.3 mmol), benzyl acrylate 2a
(0.2 mmol) and DABCO (0.3 mmol) were added to
a
solution of photocatalyst
Ir[dF(CF3)ppy]2(dtbbpy)PF6 (1 mol%) in dry acetone (4 mL) at room temperature. The heterogenous
mixture was degassed by three cycles of freezeꢀpumpꢀthaw and then placed in the irradiation apparatus
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o
equipped with a 25 W blue lightꢀemitting diode (LED) strip. The resulting mixture was stirred at 25 C
until the starting material was completely consumed as monitored by TLC. Upon completion of the
reaction, the reaction mixture was concentrated under reduced pressure, and the resulting crude mixture
was purified by flash column chromatography on silica gel (hexanes / EA = 20:1 ~ 10:1), which
furnished the title compounds as described.
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Luminescence quenching experiments. Fluorescence quenching experiments were carried out with
freshly prepared solutions of 1 mM Ir[dF(CF3)ppy]2(dtbbpy)PF6 in acetone at room temperature. The
solutions were excited at 385 nm and the fluorescence was measured from 430 nm to 600 nm. In a
typical experiment, appropriate amount of quencher was added to the measured solution in a quartz
cuvette and the emission spectrum of the sample was collected. A series of Stern–Volmer fluorescence
quenching studies clearly showed that anion 8 (1a + DABCO) could efficiently quench the
∗
excitedꢀstate photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 (no quenching was observed by ketoacids in
the absence of DABCO).
benzyl 4,4ꢀdimethylpentanoate (3a).4c Colorless oil; 40.2 mg, 91% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 0.88 (s, 9H), 1.55−1.59 (m, 2H), 2.31−2.35 (m, 2H), 5.10 (s, 2H), 7.29−7.36 (m, 5H); 13C
NMR (100 MHz, CDCl3) δ (ppm) = 29.0, 30.0, 30.1, 38.5, 66.1, 128.1, 128.2, 128.5, 136.0, 174.1; IR
(KBr, cmꢀ1): 3452, 2956, 1738, 1467, 1366, 1297, 1213, 1146, 1021, 980, 698. HRMS (ESI) for
C14H20NaO2 [M + Na]+ calcd 243.1356, found 243.1355.
benzyl 2,4,4ꢀtrimethylpentanoate (3b).18 Colorless oil; 45.4 mg, 97% yield; 1H NMR (400 MHz, CDCl3)
δ (ppm) = 0.86 (s, 9H), 1.16−1.20 (m, 4H), 1.88 (dd, J = 14.0, 9.2 Hz, 1H), 2.52−2.60 (m, 1H), 5.09 (s,
2
H), 7.30−7.36 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 20.3, 29.4, 30.7, 36.2, 47.7, 66.1,
128.1, 128.1, 128.5, 136.1, 177.7; IR (KBr, cmꢀ1): 3375, 2956, 1737, 1595, 1458, 1252, 1186, 1148,
697. HRMS (ESI) for C15H22NaO2 [M + Na]+ calcd 257.1512, found 257.1514.
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4,4ꢀdimethylꢀ1ꢀphenylpentanꢀ1ꢀone (3c).19 Colorless oil; 31.6 mg, 83% yield; H NMR (400 MHz,
CDCl3) δ (ppm) = 0.96 (s, 9H), 1.62−1.66 (m, 2H), 2.92−2.96 (m, 2H), 7.46 (t, J = 7.8 Hz, 2H), 7.56 (t,
J = 7.4 Hz, 1H), 7.97 (dd, J = 7.9, 1.2 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.2, 30.2, 34.3,
38.1, 128.0, 128.5, 132.8, 137.0, 201.1; IR (KBr, cmꢀ1): 3357, 2956, 1687, 1449, 1366, 1288, 1221, 743,
691. HRMS (ESI) for C13H18NaO [M + Na]+ calcd 213.1250, found 213.1253.
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2ꢀ(tertꢀbutyl)chromanꢀ4ꢀone (3d).20 White solid; 30.6 mg, 75% yield; mp 57−59 °C; H NMR (400
MHz, CDCl3) δ (ppm) = 1.06 (s, 9H), 2.62−2.74 (m, 2H), 4.06 (dd, J = 12.3, 4.0 Hz, 1H ), 6.97−7.01
(m, 2H), 7.45−7.49 (m, 1H), 7.87 (dd, J = 8.1, 1.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) =
25.5, 34.1, 38.4, 85.2, 117.9, 120.7, 121.0, 126.8, 135.9, 162.2, 193.6; IR (KBr, cmꢀ1): 3354, 2960,
1693, 1604, 1465, 1307, 1234, 1115, 764,. HRMS (ESI) for C13H16NaO2 [M + Na]+ calcd 227.1043,
found 227.1045.
dimethyl 2ꢀ(2,2ꢀdimethylꢀ1ꢀphenylpropyl)malonate (3e).21 White solid; 47.0 mg, 84% yield; mp
44−46 °C; 1H NMR (400 MHz, CDCl3) δ (ppm) = 0.88 (s, 9H), 3.25 (s, 3H), 3.47 (d, J = 11.0 Hz,1H),
3.77 (s, 3H), 4.03 (d, J = 11.0 Hz,1H), 7.13−7.27 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 28.1,
34.3, 52.1, 52.8, 54.7, 55.2, 126.5, 127.4, 139.9, 168.6, 169.9; IR (KBr, cmꢀ1): 3457, 2954, 1764, 1738,
1434, 1368, 1264, 1153, 1033, 707. HRMS (ESI) for C16H22NaO4 [M + Na]+ calcd 301.1410, found
301.1412.
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methyl 4,4ꢀdimethylꢀ2ꢀphenylpentanoate (3f). Colorless oil; 38.3 mg, 87% yield; H NMR (400 MHz,
CDCl3) δ (ppm) = 0.89 (s, 9H), 1.58 (dd, J = 14.0, 3.8 Hz, 1H), 2.31 (dd, J = 14.0, 9.3 Hz, 1H),
3.63−3.69 (m, 4H), 7.20−7.34 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.3, 30.9, 47.4, 48.0,
52.0, 127.0, 127.7, 128.6, 140.9, 175.2; IR (KBr, cmꢀ1): 3372, 2953, 1739, 1435, 1366, 1208, 1153, 697.
HRMS (ESI) for C14H20NaO2 [M + Na]+ calcd 243.1356, found 243.1355.
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benzyl 4,4ꢀdimethylꢀ2ꢀphenylpentanoate (3g).22 White solid; 50.9 mg, 86% yield; H NMR (400 MHz,
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CDCl3) δ (ppm) = 0.88 (s, 9H), 1.59 (dd, J = 14.0, 3.7 Hz, 1H), 2.33 (dd, J = 14.0, 9.3 Hz, 1H), 3.70
(dd, J = 9.3, 3.7 Hz, 1H), 5.01 (d, J = 12.4 Hz, 1H), 5.11 (d, J = 12.4 Hz, 1H), 7.20−7.34 (m, 10H); 13
C
NMR (100 MHz, CDCl3) δ (ppm) = 29.4, 31.0, 47.2, 48.2, 66.6, 127.0, 127.8, 128.0, 128.0, 128.4,
128.6, 135.8, 140.8, 174.5; IR (KBr, cmꢀ1): 3437, 2952, 1726, 1455, 1368, 1207, 1170, 1153, 749, 697.
HRMS (ESI) for C20H24KO2 [M + K]+ calcd 335.1408, found 335.1410.
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methyl 2ꢀ(4ꢀfluorophenyl)ꢀ4,4ꢀdimethylpentanoate (3h). Colorless oil; 43.0 mg, 90% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 0.89 (s, 9H), 1.55 (dd, J = 14.0, 4.0 Hz, 1H), 2.27 (dd, J = 14.0, 9.1 Hz,
1H), 3.59−3.68 (m, 4H), 6.98 (t, J = 8.7 Hz, 2H), 7.26−7.31 (m, 2H); 13C NMR (100 MHz, CDCl3) δ
(ppm) = 29.4, 31.0, 47.3, 47.5, 52.1, 115.4 (d, J = 21.3 Hz), 129.3 (d, J = 7.9 Hz), 136.6 (d, J = 3.1 Hz),
161.9 (d, J = 243.7 Hz), 175.1; IR (KBr, cmꢀ1): 3451, 2954, 1739, 1509, 1367, 1225, 1152, 837, 517.
HRMS (ESI) for C14H19FKO2 [M + K]+ calcd 277.1001, found 277.1004.
methyl 2ꢀ(4ꢀchlorophenyl)ꢀ4,4ꢀdimethylpentanoate (3i). White solid; 45.7 mg, 90% yield; mp 43−45 °C;
1H NMR (400 MHz, CDCl3) δ (ppm) = 0.89 (s, 9H), 1.55 (dd, J = 14.0, 4.0 Hz, 1H), 2.26 (dd, J = 14.0,
9.1 Hz, 1H), 3.62−3.65 (m, 4H), 7.24−7.29 (m, 4H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.3, 31.0,
47.3, 47.4, 52.1, 128.7, 129.1, 132.9, 139.3, 174.9; IR (KBr, cmꢀ1): 3449, 2957, 1736, 1491, 1367, 1208,
1153, 1093, 1016, 826, 740. HRMS (ESI) for C14H19ClKO2 [M + K]+ calcd 293.0705, found 293.0709.
methyl 2ꢀ(4ꢀbromophenyl)ꢀ4,4ꢀdimethylpentanoate (3j). White solid; 52.9 mg, 89% yield; mp 41−43 °C;
1H NMR (400 MHz, CDCl3) δ (ppm) = 0.88 (s, 9H), 1.54 (dd, J = 14.0, 4.0 Hz, 1H), 2.26 (dd, J = 14.0,
9.1 Hz, 1H), 3.60−3.63 (m, 4H), 7.20 (d, J = 8.4 Hz, 2H), 7.42 (d, J = 8.4 Hz, 2H); 13C NMR (100
MHz, CDCl3) δ (ppm) = 29.3, 31.0, 47.2, 47.5, 52.1, 121.0, 129.5, 131.7, 139.8, 174.8; IR (KBr, cmꢀ1):
3456, 2954, 1738, 1488, 1366, 1208, 1153, 1074, 1012, 824. HRMS (ESI) for C14H19BrKO2 [M + K]+
calcd 337.0200, found 337.0206.
methyl 2ꢀ(3ꢀchlorophenyl)ꢀ4,4ꢀdimethylpentanoate (3k). White solid; 43.2 mg, 85% yield; mp
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38−40 °C; H NMR (400 MHz, CDCl3) δ (ppm) = 0.89 (s, 9H), 1.55 (dd, J = 14.0, 3.8 Hz, 1H), 2.28
(dd, J = 14.0, 9.3 Hz, 1H), 3.61−3.70 (m, 4H), 7.18−7.22 (m, 3H), 7.32 (s, 1H); 13C NMR (100 MHz,
CDCl3) δ (ppm) = 29.3, 31.0, 47.3, 47.8, 52.1, 126.0, 127.2, 128.0, 129.8, 134.4, 142.8, 174.6; IR (KBr,
cmꢀ1): 3456, 2954, 1739, 1595, 1477, 1432, 1367, 1208, 1154, 692. HRMS (ESI) for C14H19ClKO2 [M
+ K]+ calcd 293.0705, found 293.0709.
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methyl 2ꢀ(2ꢀchlorophenyl)ꢀ4,4ꢀdimethylpentanoate (3l). Colorless oil; 44.3 mg, 87% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 0.91 (s, 9H), 1.54 (dd, J = 14.0, 4.2 Hz, 1H), 2.25 (dd, J = 14.0, 8.6 Hz,
1H), 3.65 (s, 3H), 4.29 (dd, J = 8.6, 4.2 Hz, 1H), 7.13−7.18 (m, 1H), 7.19−7.24 (m, 1H), 7.36 (dd, J =
7.8, 1.4 Hz, 1H), 7.44 (dd, J = 7.8, 1.7 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.4, 31.1,
43.5, 47.1, 52.1, 127.1, 128.1, 128.7, 129.6, 133.3, 138.4, 174.7; IR (KBr, cmꢀ1): 3370, 2953, 1740,
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1475, 1367, 1208, 1157, 1037, 749. HRMS (ESI) for C14H19ClKO2 [M + K]+ calcd 293.0705, found
293.0711.
methyl 4,4ꢀdimethylꢀ2ꢀ(4ꢀ(trifluoromethyl)phenyl)pentanoate (3m). Colorless oil; 50.1 mg, 87% yield;
1H NMR (400 MHz, CDCl3) δ (ppm) = 0.90 (s, 9H), 1.57 (dd, J = 14.0, 3.9 Hz, 1H), 2.32 (dd, J = 14.0,
9.1 Hz, 1H), 3.65 (s, 3H), 3.73 (dd, J = 9.1, 3.9 Hz, 1H), 7.45 (d, J = 8.2 Hz, 2H), 7.56 (d, J = 8.2 Hz,
2H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.3, 31.0, 47.4, 48.0, 52.2, 122.8, 125.6 (q, J = 3.7 Hz),
128.2, 129.4 (q, J = 32.2 Hz), 144.8, 174.5; IR (KBr, cmꢀ1): 3455, 2957, 1740, 1619, 1478, 1421, 1327,
1165, 1127, 1069, 1020. HRMS (ESI) for C15H19F3KO2 [M + K]+ calcd 327.0969, found 327.0973.
methyl 4,4ꢀdimethylꢀ2ꢀ(pꢀtolyl)pentanoate (3n). Colorless oil; 37.9 mg, 81% yield; 1H NMR (400 MHz,
CDCl3) δ (ppm) = 0.89 (s, 9H), 1.55 (dd, J = 14.1, 3.7 Hz, 1H), 2.26−2.31 (m, 4H), 3.58−3.64 (m, 4H),
7.10 (d, J = 7.8 Hz, 2H), 7.21 (d, J = 8.0 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 21.0, 29.3,
30.9, 47.4, 47.6, 51.9, 127.6, 129.3, 136.6, 137.9, 175.4; IR (KBr, cmꢀ1): 3456, 2954, 1738, 1513, 1435,
1366, 1206, 1152, 985, 820. HRMS (ESI) for C15H26NO2 [M + NH4]+ calcd 252.1958, found 252.1957.
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methyl 2ꢀ(4ꢀmethoxyphenyl)ꢀ4,4ꢀdimethylpentanoate (3o). Colorless oil; 42.6 mg, 85% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 0.89 (s, 9H), 1.56 (dd, J = 14.1, 6.2 Hz, 1H), 2.26 (dd, J = 14.0, 9.2 Hz,
1H), 3.59−3.63 (m, 4H), 3.77 (s, 3H), 6.83 (d, J = 8.7 Hz, 2H), 7.24 (d, J = 8.7 Hz, 2H); 13C NMR (100
MHz, CDCl3) δ (ppm) = 29.4, 30.9, 47.1, 47.4, 51.9, 55.2, 114.0, 128.7, 133.0, 158.6, 175.5; IR (KBr,
cmꢀ1): 3451, 2953, 1737, 1611, 1512, 1366, 1248, 1152, 1036, 832,. HRMS (ESI) for C15H22KO3 [M +
K]+ calcd 289.1201, found 289.1200.
methyl 2ꢀ(4ꢀ(tertꢀbutyl)phenyl)ꢀ4,4ꢀdimethylpentanoate (3p). Colorless oil; 51.8 mg, 94% yield; 1H
NMR (400 MHz, CDCl3) δ (ppm) = 0.90 (s, 9H), 1.29 (s, 9H), 1.55 (dd, J = 14.1, 3.3 Hz, 1H), 2.32 (dd,
J = 14.0, 9.8 Hz, 1H), 3.62−3.65 (m, 4H), 7.24 (d, J = 8.4 Hz, 2H), 7.31 (d, J = 8.4 Hz, 2H); 13C NMR
(100 MHz, CDCl3) δ (ppm) = 29.3, 31.0, 31.3, 34.4, 47.5, 47.5, 51.9, 125.5, 127.3, 137.8, 149.8, 175.4;
IR (KBr, cmꢀ1): 3347, 2958, 1737, 1477, 1366, 1281, 1153, 1022, 834, 740. HRMS (ESI) for
C18H28KO2 [M + K]+ calcd 315.1721, found 315.1720.
methyl 2ꢀ([1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ4,4ꢀdimethylpentanoate (3q). White solid; 50.6 mg, 85% yield; mp
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82−83 °C; H NMR (400 MHz, CDCl3) δ (ppm) = 0.92 (s, 9H), 1.62 (dd, J = 14.0, 3.7 Hz, 1H), 2.34
(dd, J = 14.0, 9.3 Hz, 1H), 3.65 (s, 3H), 3.71 (dd, J = 9.3, 3.6 Hz, 1H), 7.31 (t, J = 7.4 Hz, 1H),
7.38−7.43 (m, 4H), 7.51−7.57 (m, 4H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.4, 31.0, 47.4, 47.7,
52.0, 127.0, 127.2, 127.3, 128.2, 128.7, 139.9, 140.0, 140.7, 175.2; IR (KBr, cmꢀ1): 3454, 2954, 1737,
1487, 1366, 1210, 1153, 839, 752, 698. HRMS (ESI) for C20H24KO2 [M + K]+ calcd 335.1408, found
335.1410.
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methyl 4,4ꢀdimethylꢀ2ꢀ(naphthalenꢀ1ꢀyl)pentanoate (3r). Colorless oil; 51.4 mg, 95% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 1.00 (s, 9H), 1.69 (dd, J = 14.1, 3.2 Hz, 1H), 2.54 (dd, J = 14.0, 9.3 Hz,
1H), 3.65 (s, 3H), 4.53 (dd, J = 9.3, 3.1 Hz, 1H), 7.44−7.54 (m, 2H), 7.56−7.61 (m, 2H), 7.78 (d, J =
8.2 Hz, 1H), 7.89 (d, J = 7.9 Hz, 1H), 8.24 (d, J = 8.6 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ (ppm) =
29.4, 31.2, 42.7, 47.3, 52.1, 123.1, 125.1, 125.5, 125.6, 126.3, 127.5, 129.0, 131.0, 134.0, 137.0, 172.3;
IR (KBr, cmꢀ1): 3454, 2954, 1738, 1477, 1366, 1280, 1198, 1151, 779, 738. HRMS (ESI) for
C18H22NaO2 [M + Na]+ calcd 293.1512, found 293.1511.
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methyl 4,4ꢀdimethylꢀ2ꢀ(naphthalenꢀ2ꢀyl)pentanoate (3s). White solid; 42.5 mg, 79% yield; mp
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63−64 °C; H NMR (400 MHz, CDCl3) δ (ppm) = 0.96 (s, 9H), 1.71 (dd, J = 14.0, 3.9 Hz, 1H), 2.43
(dd, J = 14.0, 9.1 Hz, 1H), 3.67 (s, 3H), 3.87 (dd, J = 9.1, 3.9 Hz, 1H), 7.43−7.52 (m, 3H), 7.79−7.83
(m, 4H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 29.4, 31.0, 47.3, 48.2, 52.0, 125.7, 126.0, 126.1,
126.4, 127.6, 127.7, 128.3, 132.5, 133.4, 138.3, 175.2; IR (KBr, cmꢀ1): 3449, 2953, 1734, 1431, 1197,
1147, 816, 739, 481. HRMS (ESI) for C18H22KO2 [M + K]+ calcd 309.1251, found 309.1256.
benzyl 4,4ꢀdimethylhexanoate (4a). Colorless oil; 40.2 mg, 86% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 0.81 (t, J = 7.6 Hz, 9H), 1.21 (q, J = 7.5 Hz, 2H), 1.53−1.58 (m, 2H), 2.28−2.32 (m, 2H), 5.11
(s, 2H), 7.29−7.39 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 8.3, 26.2, 29.6, 32.4, 33.8, 35.9,
66.1, 128.1, 128.2, 128.5, 136.1, 174.3; IR (KBr, cmꢀ1): 3450, 2961, 1737, 1456, 1380, 1302, 1160, 996,
749, 698. HRMS (ESI) for C15H22O2Na [M + Na]+ calcd 257.1512, found 257.1514.
benzyl 4,4ꢀdimethylheptanoate (4b). Colorless oil; 44.6 mg, 90% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 0.84 (s, 6H), 0.87 (t, J = 6.9 Hz, 3H), 1.11−1.17 (m, 2H), 1.19−1.28 (m, 2H), 1.54−1.58 (m,
2H), 2.28−2.32 (m, 2H), 5.10 (s, 2H), 7.30−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 14.9,
17.1, 26.8, 29.6, 32.4, 36.4, 44.2, 66.1, 128.1, 128.2, 128.5, 136.1, 174.3; IR (KBr, cmꢀ1): 3450, 2926,
1738, 1455, 1380, 1301, 1161, 698. HRMS (ESI) for C16H24O2Na [M + Na]+ calcd 271.1669, found
271.1670.
benzyl 3ꢀ(1ꢀmethylcyclohexyl)propanoate (4c).4c Colorless oil; 44.1 mg, 85% yield; 1H NMR (400 MHz,
CDCl3) δ (ppm) = 0.84 (s, 3H), 1.19−1.32 (m, 5H), 1.37−1.47 (m, 5H), 1.58−1.62 (m, 2H), 2.29−2.33
(m, 2H), 5.11 (s, 2H), 7.30−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 21.9, 24.4, 26.4,
28.9, 32.3, 36.6, 37.4, 66.1, 128.1, 128.2, 128.5, 136.1, 174.4; IR (KBr, cmꢀ1): 3449, 2926, 1738, 1455,
1300, 1161, 697. HRMS (ESI) for C17H24O2Na [M + Na]+ calcd 283.1669, found 283.1668.
benzyl 4ꢀ(1ꢀmethylcyclopropyl)ꢀ4ꢀoxobutanoate (4d’). Colorless oil; 46.6 mg, 95% yield; 1H NMR (400
MHz, CDCl3) δ (ppm) = 0.72 (q, J = 3.9 Hz, 2H), 1.25 (q, J = 4.0 Hz, 2H), 1.36 (s, 3H), 2.62 (t, J = 6.5
Hz, 2H), 2.73 (t, J = 6.6 Hz, 2H), 5.11 (s, 2H), 7.29−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ
(ppm) = 18.3, 19.6, 26.4, 28.2, 32.7, 66.3, 128.1, 128.5, 135.8, 172.8, 209.6; IR (KBr, cmꢀ1): 3363,
2964, 1736, 1688, 1266, 1164, 1092, 737. HRMS (ESI) for C15H18O3Na [M + Na]+ calcd 269.1148,
found 269.1147.
benzyl 3ꢀ((3r,5r,7r)ꢀadamantanꢀ1ꢀyl)propanoate (4e). Colorless oil; 13.1 mg, 22% yield; 1H NMR (400
MHz, CDCl3) δ (ppm) = 1.42−1.46 (m, 8H), 1.58−1.71 (m, 6H), 1.94 (br, 3H), 2.29−2.34 (m, 2H), 5.11
(s, 2H), 7.30−7.39 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 28.2, 28.5, 31.9, 37.0, 38.9, 42.0,
66.1, 128.1, 128.2, 128.5, 136.1, 174.5; IR (KBr, cmꢀ1): 3450, 2957, 1738, 1456, 1299, 1257, 1160, 999,
748, 698. HRMS (ESI) for C20H26O2Na [M + Na]+ calcd 321.1825, found 321.1828.
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benzyl 4ꢀ((3r,5r,7r)ꢀadamantanꢀ1ꢀyl)ꢀ4ꢀoxobutanoate (4e’). Yellow oil; 49.0 mg, 75% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 1.71 (q, J = 14.1 Hz, 6H), 1.82 (d, J = 2.5 Hz ,6H), 2.03 (br, 3H), 2.61 (t,
J = 6.6 Hz, 2H), 2.78 (t, J = 6.6 Hz, 2H), 5.10 (s, 2H), 7.29−7.37 (m, 5H); 13C NMR (100 MHz, CDCl3)
δ (ppm) = 27.8, 27.9, 30.9, 36.4, 38.2, 46.0, 66.3, 128.1,128.1, 128.4, 135.8, 172.8, 213.6; IR (KBr,
cmꢀ1): 3450, 2906, 1738, 1701, 1453, 1347, 1205, 1154, 699. HRMS (ESI) for C21H26O3Na [M + Na]+
calcd 349.1774, found 349.1774.
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benzyl 4ꢀmethylpentanoate (4f).23 Colorless oil; 14.4 mg, 35% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 0.89 (d, J = 6.3 Hz, 6H), 1.52−1.60 (m, 3H), 2.36 (t, J = 7.7 Hz, 2H), 5.11 (s, 2H), 7.31−7.39
(m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 22.2, 27.7, 32.4, 33.7, 66.1, 128.2, 128.5, 136.1,
173.8; IR (KBr, cmꢀ1): 3449, 2957, 1738, 1456, 1164, 993, 749, 697. HRMS (ESI) for C13H18O2Na [M
+ Na]+ calcd 229.1199, found 229.1200.
benzyl 5ꢀmethylꢀ4ꢀoxohexanoate (4f’).24 Colorless oil; 24.2 mg, 52% yield; 1H NMR (400 MHz, CDCl3)
δ (ppm) = 1.11 (d, J = 7.0 Hz, 6H), 2.60−2.67 (m, 3H), 2.79 (t, J = 6.4 Hz, 2H), 5.11 (s, 2H), 7.29−7.38
(m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 18.2, 28.0, 34.7, 40.8, 66.4, 128.2, 128.5, 135.8,
172.7, 212.6; IR (KBr, cmꢀ1): 3407, 2970, 1737, 1713, 1384, 1164, 1093, 751, 699. HRMS (ESI) for
C14H18O3Na [M + Na]+ calcd 257.1148, found 257.1147.
benzyl 3ꢀcyclopentylpropanoate (4g). Colorless oil; 6.7 mg, 14% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 1.06−1.11 (m, 2H), 1.45−1.77 (m, 9H), 2.37 (t, J = 7.6 Hz, 2H), 5.11 (s, 2H), 7.30−7.39 (m,
5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 25.1, 31.1, 32.4, 33.7, 39.6, 66.1, 128.1, 128.2, 128.5,
136.1, 173.8; IR (KBr, cmꢀ1): 3392, 2950, 2863, 1738, 1454, 1261, 1169, 1135, 737, 697. HRMS (ESI)
for C15H20O2Na [M + Na]+ calcd 255.1356, found 255.1355.
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benzyl 4ꢀcyclopentylꢀ4ꢀoxobutanoate (4g’). Yellow oil; 36.3 mg, 70% yield; H NMR (400 MHz,
CDCl3) δ (ppm) = 1.52−1.68 (m, 4H), 1.71−1.86 (m, 4H), 2.64 (t, J = 6.7 Hz, 2H), 2.78 (t, J = 6.5 Hz,
2H), 2.85−2.93 (m, 1H), 5.11 (s, 2H), 7.29−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 25.9,
28.0, 28.8, 36.0, 51.2, 66.3, 128.1, 128.5, 135.8, 172.7, 211.0; IR (KBr, cmꢀ1): 3452, 2955, 1737, 1711,
1454, 1353, 1166, 737, 699. HRMS (ESI) for C16H20O3Na [M + Na]+ calcd 283.1305, found 283.1304.
benzyl 3ꢀcyclohexylpropanoate (4h).25 Colorless oil; 6.0 mg, 12% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 0.84−0.92 (m, 2H), 1.11−1.25 (m, 4H), 1.52−1.57 (m, 2H), 1.62−1.70 (m, 5H), 2.37 (t, J = 7.7
Hz, 2H), 5.11 (s, 2H), 7.31−7.39 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 26.2, 26.5, 31.9,
32.3, 32.9, 37.2, 66.1, 128.1, 128.2, 128.5, 136.1, 174.0; IR (KBr, cmꢀ1): 3451, 2923, 1737, 1451, 1292,
1161, 996, 736, 697. HRMS (ESI) for C16H22O2Na [M + Na]+ calcd 269.1512, found 269.1513.
benzyl 4ꢀcyclohexylꢀ4ꢀoxobutanoate (4h’). Yellow oil; 45.5 mg, 83% yield; 1H NMR (400 MHz, CDCl3)
δ (ppm) = 1.13−1.38 (m, 5H), 1.64−1.86 (m, 5H), 2.32−2.40 (m, 1H), 2.62 (t, J = 6.6 Hz, 2H), 2.76 (t,
J = 6.4 Hz, 2H), 5.10 (s, 2H), 7.29−7.37 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 25.5, 25.7,
27.8, 28.3, 34.8, 50.6, 66.3, 128.1, 128.4, 135.8, 172.6, 211.8; IR (KBr, cmꢀ1): 3449, 2930, 1737, 1710,
1451, 1349, 1163, 999, 751, 699. HRMS (ESI) for C17H22O3Na [M + Na]+ calcd 297.1461, found
297.1463.
benzyl 4ꢀoxoꢀ4ꢀphenylbutanoate (4i’).26 Yellow oil; 42.9 mg, 80% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 2.82 (t, J = 6.6 Hz, 2H), 3.33 (t, J = 6.6 Hz, 2H), 5.15 (s, 2H), 7.28−7.36 (m, 5H), 7.46 (t, J =
7.8 Hz, 2H), 7.54−7.58 (m, 1H), 7.96−7.99 (m, 2H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 28.2, 33.3,
66.4, 128.0, 128.1, 128.5, 128.6, 133.2, 135.8, 136.5, 172.7, 197.9; IR (KBr, cmꢀ1): 3454, 2918, 1736,
1687, 1450, 1216, 1160, 749, 693. HRMS (ESI) for C17H16O3Na [M + Na]+ calcd 291.0992, found
291.0992.
benzyl 4ꢀoxoꢀ6ꢀphenylhexanoate (4j’). Yellow oil; 52.4 mg, 89% yield; 1H NMR (400 MHz, CDCl3) δ
(ppm) = 2.62−2.65 (m, 2H), 2.69−2.73 (m, 2H), 2.74−2.79 (m, 2H), 2.90 (t, J = 7.2 Hz, 2H), 5.11 (s,
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2H), 7.15−7.20 (m, 3H), 7.24−7.38 (m, 7H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 27.9, 29.6, 37.1,
44.2, 66.4, 126.1, 128.1, 128.2, 128.2, 128.4, 128.5, 135.8, 140.9, 172.5, 207.8; IR (KBr, cmꢀ1): 3413,
2927, 1736, 1717, 1454, 1173, 1096, 699. HRMS (ESI) for C19H20O3Na [M + Na]+ calcd 319.1305,
found 319.1305.
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benzyl 4ꢀoxodecanoate (4k’). Yellow oil; 50.0 mg, 90% yield; H NMR (400 MHz, CDCl3) δ (ppm) =
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0.88 (t, J = 6.5 Hz, 3H), 1.26−1.32 (m, 6H), 1.53−1.59 (m, 2H), 2.43 (t, J = 7.4 Hz, 2H), 2.63 (t, J = 6.6
Hz, 2H), 2.73 (t, J = 6.5 Hz, 2H), 5.11 (s, 2H), 7.30−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ
(ppm) = 14.0, 22.4, 23.7, 27.9, 28.8, 31.5, 36.9, 42.7, 66.4, 128.1, 128.1, 128.5, 135.8, 172.6, 209.0; IR
(KBr, cmꢀ1): 3414, 2931, 1738, 1717, 1456, 1163, 1003, 738, 698. HRMS (ESI) for C17H24O3Na [M +
Na]+ calcd 299.1618, found 299.1618.
benzyl 4ꢀoxododecanoate (4l’). Yellow oil; 43.2 mg, 71% yield; 1H NMR (400 MHz, CDCl3) δ (ppm) =
0.88 (t, J = 6.6 Hz, 3H), 1.26 (br, 10H), 1.57 (t, J = 7.1 Hz, 2H), 2.43 (t, J = 7.4 Hz, 2H), 2.64 (t, J =
6.4 Hz, 2H), 2.73 (t, J = 6.5 Hz, 2H), 5.11 (s, 2H), 7.29−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ
(ppm) = 14.1, 22.6, 23.7, 27.9, 29.1, 29.2, 29.3, 31.8, 36.9, 42.8, 66.4, 128.1, 128.2, 128.5, 135.8, 172.6,
209.1; IR (KBr, cmꢀ1): 3403, 2921, 1731, 1709, 1163, 749, 737, 698. HRMS (ESI) for C19H28O3Na [M
+ Na]+ calcd 327.1931, found 327.1931.
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benzyl 6ꢀmethylꢀ4ꢀoxoheptanoate (4m’).24 Colorless oil; 39.2 mg, 79% yield; H NMR (400 MHz,
CDCl3) δ (ppm) = 0.91 (d, J = 6.6 Hz, 6H), 2.08−2.21 (m, 1H), 2.31 (d, J = 7.0 Hz, 2H), 2.61−2.64 (m,
2H), 2.69−2.73 (m, 2H), 5.11 (s, 2H), 7.29−7.38 (m, 5H); 13C NMR (100 MHz, CDCl3) δ (ppm) = 22.5,
24.6, 27.8, 37.5, 51.6, 66.4, 128.1, 128.1, 128.5, 135.8, 172.6, 208.5; IR (KBr, cmꢀ1): 3366, 2957, 1737,
1716, 1456, 1164, 993, 740, 699. HRMS (ESI) for C15H20O3Na [M + Na]+ calcd 271.1305, found
271.1307.
AUTHOR INFORMATION
Corresponding Author
* E-mail: xupf@lzu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
We are grateful to the NSFC (21632003, 21372105 and 21572087), and the “111” program from the
MOE of P. R. China for financial support.
Supporting Information
1
Devices for the photocatalytic reactions, H and 13C NMR spectra of the products. This material is
available free of charge via the Internet at http://pubs.acs.org.
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