Pd-catalyzed Suzuki-Miyaura cross-coupling of pentafluorophenyl esters

Article abstract of DOI:10.3390/molecules23123134

Although the palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl esters has received significant attention, there is a lack of methods that utilize cheap and readily accessible Pd-phosphane catalysts, and can be routinely carried out with high cross-coupling selectivity. Herein, we report the first general method for the cross-coupling of pentafluorophenyl esters (pentafluorophenyl = pfp) by selective C–O acyl cleavage. The reaction proceeds efficiently using Pd(0)/phosphane catalyst systems. The unique characteristics of pentafluorophenyl esters are reflected in the fully selective cross-coupling vs. phenolic esters. Of broad synthetic interest, this report establishes pentafluorophenyl esters as new, highly reactive, bench-stable, economical, ester-based, electrophilic acylative reagents via acyl-metal intermediates. Mechanistic studies strongly support a unified reactivity scale of acyl electrophiles by C(O)–X (X = N, O) activation. The reactivity of pfp esters can be correlated with barriers to isomerization around the C(acyl)–O bond.

Full text of DOI:10.3390/molecules23123134

molecules
Communication
Pd-Catalyzed Suzuki-Miyaura Cross-Coupling of
Pentafluorophenyl Esters
Jonathan Buchspies, Daniel J. Pyle, Huixin He * and Michal Szostak *
Department of Chemistry, Rutgers University, 73 Warren Street, Newark, NJ 07102, USA;
jonathan.buchspies@gmail.com (J.B.); danielj.pyle@gmail.com (D.J.P.)
*
Correspondence: huixinhe@rutgers.edu (H.H.); michal.szostak@rutgers.edu (M.S.);
Tel.: +1-973-353-5329 (M.S.)
ꢀ
ꢁꢂꢀꢃꢄꢅꢆꢇ
Received: 12 October 2018; Accepted: 23 November 2018; Published: 29 November 2018
ꢀ
ꢁꢂꢃꢄꢅꢆ
Abstract: Although the palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl esters has
received significant attention, there is a lack of methods that utilize cheap and readily accessible
Pd-phosphane catalysts, and can be routinely carried out with high cross-coupling selectivity.
Herein, we report the first general method for the cross-coupling of pentafluorophenyl esters
(pentafluorophenyl = pfp) by selective C–O acyl cleavage. The reaction proceeds efficiently using
Pd(0)/phosphane catalyst systems. The unique characteristics of pentafluorophenyl esters are
reflected in the fully selective cross-coupling vs. phenolic esters. Of broad synthetic interest,
this report establishes pentafluorophenyl esters as new, highly reactive, bench-stable, economical,
ester-based, electrophilic acylative reagents via acyl-metal intermediates. Mechanistic studies strongly
support a unified reactivity scale of acyl electrophiles by C(O)–X (X = N, O) activation. The reactivity
of pfp esters can be correlated with barriers to isomerization around the C(acyl)–O bond.
Keywords: Suzuki-Miyaura; cross-coupling; aryl esters; C–O activation; Pd-catalysis
1
. Introduction
The recent emergence of Suzuki-Miyaura cross-coupling of amide and ester electrophiles by
selective C(acyl)–X cleavage represents one of the most promising approaches to functionalization
of the traditionally inert amide and ester bonds in organic synthesis [ ]. Although a broad range
of amide precursors have been explored [ ], N.B. benefiting from amide twist [ 13], Pd-catalyzed
cross-coupling of esters has received significantly less attention. The seminal study by Newman in
017 reported the [Pd(NHC)(cin)Cl]-catalyzed cross-coupling of aryl esters at high temperature [14].
1–3
4–8
9–
2
Subsequently, we have reported a general method for the cross-coupling of both esters and amides
at room temperature [15]. Further studies established that various Pd(II)-NHC precatalysts are
significantly more reactive after optimizing conditions [16,17]. Moreover, Hazari demonstrated the
cross-coupling of aryl esters at room temperature conditions using strong bases [18].
This strategy to develop cross-coupling reactions of aryl esters hinges upon ground-state
destabilization of the barrier to rotation around the C(acyl)–O bond [19]. In contrast to amides,
esters feature significant stabilization in the transition state. Given the established capacity of
pentafluorophenyl esters as acyl transfer reagents in nucleophilic addition reactions [20–22], we recently
questioned whether the ground-state-destabilization principle might enable facile cross-coupling of
pentafluorophenyl esters under chemoselective conditions that are inaccessible to the current-state-
of-the-art phenolic esters [1–3]. In this Special Issue on Amide Bond Activation, we report the
successful realization of this approach, and report the first general method for the cross-coupling of
pentafluorophenyl esters by selective C–O acyl cleavage. Notable features of our findings include: (1)
The first Pd-phosphane-catalyzed Suzuki cross-coupling of esters by C–O activation; (2) unprecedented
Molecules 2018, 23, 3134; doi:10.3390/molecules23123134
www.mdpi.com/journal/molecules

Molecules 2018, 23, 3134
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selectivity of the cross-coupling; (3) establishment of the reactivity scale in the cross-coupling of
bench-stable acyl electrophiles catalyzed by Pd-phosphanes.
Notably, this study establishes pentafluorophenyl esters as new, highly reactive, bench-stable,
economical, ester-based, electrophilic acylative reagents via acyl-metals [1–3]. Considering the versatile
role of pfp esters in organic synthesis [20 22], we expect that this approach will find wide application
–
in the development of cross-coupling reactions of bench-stable ester electrophiles by acyl [
1] and
decarbonylative pathways [2,7,23,24] (Scheme 1).
Scheme 1. Cross-coupling of amides and esters by C–N and C–O activation.
2
. Results
Cross-coupling of pentafluorophenyl benzoate with 4-tolyl boronic acid was selected as our
model system. From the outset we sought to develop a catalytic system based on phosphane ligands,
due to the low price, ready availability and orthogonal selectivity compared to the more -donating
NHCs. Selected optimization results are presented in Table 1. As expected, the choice of base (entries
–6), phosphane ligand (entries 7–12), palladium catalyst (entries 13–15), palladium to ligand ratio
entries 16–18), stoichiometry (entries 19–20) and concentration (entries 21–22) had a major impact
on the cross-coupling efficiency. Finally, we established that the optimum conditions involved using
Pd (dba) (3.0 mol%) as a catalyst, PCy HBF (12 mol%) as a ligand, and Na CO (4.5 equiv) as a
σ
1
(
2
3
3
4
2
3
◦
base in dioxane at 120 C (entry 20). Importantly, under the optimized conditions cleavage of the
alternative O–C(Ar) bond or nucleophilic addition to the activated pfp group were not observed.
To our knowledge, the reaction represents the first example of a Pd-phosphane-catalyzed Suzuki
cross-coupling of an ester group by selective C–O cleavage [1–3,23,24]. It should be noted that all
reaction components are easy-to-handle bench-stable solids, which represents a significant practical
advantage over related cross-coupling protocols.
With optimized conditions in hand, the scope of the cross-coupling with respect to the
boronic acid component was examined (Figure 1). We were pleased to find the reaction readily
accommodates a range of electronically-diverse boronic acids, including neutral (3a) electron-rich (3b,

Molecules 2018, 23, 3134
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3c), electron-deficient bearing electrophilic carbonyl (3d), sterically-hindered (3e), as well as fluorinated
boronic acids relevant from the medicinal chemistry standpoint (3f–3i).
Table 1. Optimization of the Suzuki-Miyaura cross-coupling of Pfp esters. 1
Entry
Catalyst
Ligand
PCy HBF
Base
Na CO
3
KHCO3
[Pd]:L
Yield (%)
1
2
3
4
5
6
7
8
9
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(dba)2
PdCl2
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:4
1:2
1:2
1:1
2:1
1:4
1:2
1:2
1:2
52
53
30
12
47
56
60
5
3
4
4
4
4
4
4
2
PCy HBF
3
PCy HBF
NaHCO3
3
PCy HBF
K CO
3
2
3
4
PCy HBF
K PO
3
3
PCy HBF
KF
3
PPhCy2
Na CO
Na CO
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
PPh Cy
2
PPh3
DPPB
Na CO
5
2
1
1
1
1
1
1
0
1
2
3
4
5
Na CO
13
<5
<5
23
25
74
85
44
30
83
92
75
89
2
Xantphos
Pt-Bu HBF
Na CO
2
Na CO
3
4
2
PCy HBF
Na CO
3
4
2
PCy HBF
Na CO
2
3
4
4
4
4
4
4
4
4
4
Pd (dba)3
PCy HBF
Na CO
2
3
2
2
1
6
7
8
9
0
1
2
Pd (dba)3
PCy HBF
Na CO
2
2
3
3
4
5
5
6
7
1
1
1
2
2
2
Pd (dba)3
PCy HBF
Na CO
2
3
2
Pd (dba)3
PCy HBF
Na CO
2
2
3
Pd(OAc)2
PCy HBF
Na CO
3
2
Pd (dba)3
PCy HBF
Na CO
2
2
3
Pd (dba)3
PCy HBF
Na CO
2
3
2
Pd (dba)3
PCy HBF
Na CO
2
2
3
1
Conditions: Ester (1.0 equiv), 4-Tol-B(OH)
2
(2.0 equiv), base (2.5 equiv), [Pd] (3 mol%), ligand (12 mol%), solvent
◦
2
3
(
(
(
0.25 M), 120 C, 15 h. [Pd] (1.5 mol%), ligand (12 mol%), 4-Tol-B(OH)
3 mol%), ligand (6 mol%), 4-Tol-B(OH)
3.0 equiv), base (4.5 equiv). 4-Tol-B(OH)2 (3.0 equiv), base (4.5 equiv). Dioxane (0.10 M). Dioxane (0.50 M).
2
(3.0 equiv), base (4.5 equiv). [Pd]
4
2
(3.0 equiv), base (4.5 equiv). [Pd] (3 mol%), ligand (3 mol%), 4-Tol-B(OH)
2
5
6
7
We next explored the generality of this cross-coupling with respected to the ester electrophile
Figure 2). Pleasingly, the reaction tolerates electron-deficient substituents (3f’ 3d’ 3j), including
electrophilic carbonyls (3d’ 3j), electron-rich deactivating substituents (3c’), sterically-hindered (3e’),
(
,
,
,
as well as aliphatic pfp ester precursors (3k). It is worthwhile to note that the reaction proceeded with
full selectivity for the cross-coupling of a pfp ester in the presence of an aliphatic ester (3j), as expected
from the C–O isomerization and our design (vide infra) [15,19].
Next, to emphasize the synthetic utility of this transformation, we conducted a series of
competition experiments between pfp esters and ester and amide electrophiles previously established
in cross-coupling protocols (Scheme 2) [3–8]. Most importantly, as expected on the basis of C–O isomerization,
the reaction is fully selective for the cross-coupling in the presence of an activated phenolic ester (Scheme 2A).
A separate experiment using phenyl benzoate under the optimized conditions for the cross-coupling
of pfp esters resulted in a quantitative recovery of PhCO Ph.
2

Molecules 2018, 23, 3134
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Figure 1. Boronic acid scope in the Pd-catalyzed cross-coupling of Pfp esters. Conditions: Ester
1.0 equiv), ArB(OH) (3.0 equiv), Na CO (4.5 equiv), Pd (dba) (3 mol%), PCy HBF (12 mol%),
(
2
◦
2
3
2
3
3
4
dioxane (0.25 M), 120 C, 15 h. See SI for details.
Figure 2. Ester scope in the Pd-catalyzed cross-coupling of Pfp esters. Conditions: Ester (1.0 equiv),
ArB(OH) (3.0 equiv), Na CO (4.5 equiv), Pd (dba) (3 mol%), PCy3HBF4 (12 mol%), dioxane (0.25 M),
2
2
3
2
3
◦
1
20 C, 15 h. See SI for details.

Molecules 2018, 23, 3134
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Scheme 2. Competition experiments.
Furthermore, the reaction is slightly less selective for the cross-coupling of pfp esters cf. N-Ts
sulfonamides (Scheme 2B; Ts/Ph:pfp = 1.3:1), whereas full selectivity is observed in the cross-coupling
of N-acylglutarimides vs. pfp esters (Scheme 2C; >20:1), as expected on the basis of amide bond
destabilization [6,11]. Overall, the competition experiments demonstrate high chemoselectivity of
the cross-coupling of pfp esters, and permit to establish a unified reactivity scale in cross-coupling of
esters and amides catalyzed by Pd-phosphanes (Scheme 3). It is well-established that cross-coupling of
anilides is performed in the presence of N,N-dialkylamides [12].
To gain insight into the reaction mechanism additional experiments were conducted (not shown).
(1) Competition experiments with differently substituted pfp esters revealed that electron-deficient
arenes are more reactive (4-CF :4-MeO > 20:1); while (2) differently substituted boronic acids revealed
3

Molecules 2018, 23, 3134
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a small preference for electron-rich boronic acids (4-MeO:4-CF = 1.1:1). Overall, these findings suggest
3
that Pd insertion may be the rate limiting step in this reaction.
Scheme 3. Reactivity scale in C(acyl)–N and C(acyl)–O Suzuki-Miyaura cross-coupling. Note that
thus far only N-Acyl-glutarimides, N-Ts-sulfonamides and O-pfp esters have been shown to react with
Pd-PR catalytic systems [1–3]. The reactivity of OPh esters, N-Ar amides and N-Me amides is based
3
on Pd-NHC catalysts [1,15].
Finally, we demonstrated that catalytic systems in the Suzuki-Miyaura cross-coupling of pfp
esters are not limited to the in situ formed Pd(0)-phosphane catalysts. For example, preformed
Pd-phosphane catalysts [25], as well as Pd(II)-NHCs [1], such as Pd(PCy ) Cl and Pd-PEPPSI-IPr
3 2 2
afford the coupling product in excellent yields (Scheme 4), highlighting the generality and rich synthetic
potential of pentafluorophenyl esters as electrophiles in transition-metal catalysis. Future work will
focus on the expansion of the catalyst portfolio in the cross-coupling of activated esters. With the
availability of various catalyst systems, the pfp reagents should expand the implementation of ester
C–O cross-coupling in organic synthesis [14–18].
Scheme 4. Cross-coupling using preformed Pd-phosphine and Pd(II)-NHC precatalysts.
3
. Discussion
In summary, we have reported the Suzuki-Miyaura cross-coupling of pentafluorophenyl esters.
The reaction is notable for the first use of Pd-phosphane catalysis in chemoselective Suzuki-Miyaura
ester coupling by C–O cleavage. Furthermore, this method introduces pfp esters as new, ester-based,
electrophilic reagents for transition-metal catalyzed cross-coupling reactions. Given the broad

Molecules 2018, 23, 3134
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utility of pfp esters in nucleophilic addition reactions, we believe that these reagents will find
wide application in the cross-coupling chemistry. In particular, this study highlights the utility
of ground-state destabilization of acyl electrophiles to achieve chemoselective bond activation. Since
pentafluorophenyl esters are easily prepared, bench-stable solids, and highly reactive, these reagents
should be considered along phenolic esters in the future development of cross-coupling reactions by
acyl [1–3] and decarbonylative pathways [2,7,23,24].
4
. Materials and Methods
4
.1. General Information
General methods have been published [13].
4
.2. General Procedure for Cross-Coupling of Pentafluorophenyl Esters
An oven-dried vial equipped with a stir bar was charged with an ester substrate (neat, 1.0 equiv),
boronic acid (typically, 3.0 equiv), sodium carbonate (typically, 4.5 equiv), Pd (dba) (typically, 3 mol%),
2
3
and PCy HBF (typically, 12 mol%), placed under a positive pressure of argon, and subjected to three
3
4
evacuation/backfilling cycles under high vacuum. Dioxane (typically, 0.25 M) was added with vigorous
◦
stirring at room temperature, the reaction mixture was placed in a preheated oil bath at 120 C, and
◦
stirred for the indicated time at 120 C. After the indicated time, the reaction mixture was cooled
down to room temperature, diluted with CH Cl (10 mL), filtered, and concentrated. The sample was
2
2
1
analyzed by H-NMR (CDCl , 500 MHz) and GC-MS to obtain conversion, selectivity and yield using
3
internal standard and comparison with authentic samples. Purification by chromatography afforded
the pure product.
4
.3. Representative Procedure for Cross-Coupling of Pentafluorophenyl Esters
An oven-dried vial equipped with a stir bar was charged with perfluorophenyl benzoate (neat,
2
88.2 mg, 1.0 mmol), p-tolylboronic acid (408.0 mg, 3.0 mmol, 3.0 equiv), Na CO (477.0 mg, 4.5 mmol,
2
3
4
.5 equiv), Pd (dba) (27.5 mg, 0.03 mmol, 3 mol%), and PCy HBF (44.2 mg, 0.12 mmol, 12 mol%)
2
3
3
4
placed under a positive pressure of argon, and subjected to three evacuation/backfilling cycles under
high vacuum. Dioxane (0.25 M) was added with vigorous stirring at room temperature, the reaction
◦
◦
mixture was placed in a preheated oil bath at 120 C, and stirred for 15 h at 120 C. After the indicated
time, the reaction mixture was cooled down to room temperature, diluted with CH Cl (10 mL),
2
2
1
filtered, and concentrated. A sample was analyzed by H-NMR (CDCl , 500 MHz) and GC-MS to
3
obtain conversion, yield and selectivity using internal standard and comparison with authentic samples.
Purification by chromatography on silica gel (hexanes/ethyl acetate) afforded the title product. Yield
8
6% (168.5 mg). White solid. Characterization data are included in the section below.
4
.4. Characterization Data for Products 3a–3k (Figures 1 and 2)
1
Benzophenone (3a). White solid. H-NMR (500 MHz, CDCl )
δ
7.83 (d, J = 8.9 Hz, 4 H), 7.62 (t, J = 7.4 Hz,
3
2
H), 7.51 (t, J = 7.6 Hz, 4 H). 13C-NMR (125 MHz, CDCl ) δ 196.75, 137.61, 132.42, 130.07, 128.28.
3
1
Phenyl(p-tolyl)methanone (3b). White solid. H-NMR (500 MHz, CDCl )
δ
7.81 (d, J = 7.7 Hz, 2 H), 7.75
3
(
d, J = 7.5 Hz, 2 H), 7.60 (t, J = 7.4 Hz, 1 H), 7.50 (t, J = 7.2 Hz, 2 H), 7.31 (d, J = 7.7 Hz, 2 H), 2.47 (s, 3 H).
1
3
C-NMR (125 MHz, CDCl3)
δ
196.49, 143.22, 137.98, 134.90, 132.14, 130.31, 129.93, 128.97, 128.20, 21.66.
1
(
4-Methoxyphenyl)(phenyl)methanone (3c). White solid. H-NMR (500 MHz, CDCl )
δ
7.86 (d, J = 8.0 Hz,
3
2
3
H), 7.78 (d, J = 7.6 Hz, 2 H), 7.59 (t, J = 7.3 Hz, 1 H), 7.50 (t, J = 7.4 Hz, 2 H), 6.99 (d, J = 8.0 Hz, 2 H),
.92 (s, 3 H). 13C-NMR (125 MHz, CDCl3)
δ
195.56, 163.23, 138.30, 132.57, 131.89, 130.17, 129.74, 128.19,
1
13.56, 55.51.
1
1
-(4-Benzoylphenyl)ethan-1-one (3d). White solid. H-NMR (500 MHz, CDCl )
δ
8.09 (d, J = 8.2 Hz, 2 H),
3
7
.89 (d, J = 8.2 Hz, 2 H), 7.83 (d, J = 7.5 Hz, 2 H), 7.65 (t, J = 7.4 Hz, 1 H), 7.53 (t, J = 7.7 Hz, 2 H), 2.70

Molecules 2018, 23, 3134
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(
1
s, 3 H). 13C-NMR (125 MHz, CDCl3)
28.17, 26.92.
δ
197.52, 195.96, 139.57, 136.92, 133.00, 130.11, 130.05, 128.49,
1
Phenyl(o-tolyl)methanone (3e). White solid. H-NMR (500 MHz, CDCl ) δ 7.83 (d, J = 7.7 Hz, 2 H), 7.60
3
(
1
1
d, J = 6.9 Hz, 1 H), 7.49 (t, J = 7.6 Hz, 2 H), 7.42 (t, J = 7.5 Hz, 1 H), 7.37 –7.30 (m, 2 H), 7.30–7.27 (m,
H), 2.36 (s, 3 H). 13C-NMR (125 MHz, CDCl3)
30.14, 128.52, 128.46, 125.20, 20.00.
δ
198.64, 138.63, 137.75, 136.75, 133.14, 131.00, 130.24,
1
Phenyl(4-(trifluoromethyl)phenyl)methanone (3f). White solid. H-NMR (500 MHz, CDCl )
δ 7.93 (d, J =
3
8
2
.0 Hz, 2 H), 7.84 (d, J = 7.7 Hz, 2 H), 7.79 (d, J = 8.0 Hz, 2 H), 7.66 (t, J = 7.4 Hz, 1 H), 7.54 (t, J = 7.6 Hz,
13
F
H). C-NMR (125 MHz, CDCl )
δ 195.53, 140.74, 136.74, 133.73 (J = 32.5 Hz), 133.09, 130.14, 130.11,
3
F
F
19
1
28.54, 125.36 (J = 7.5 Hz), 123.70 (J = 273.0 Hz). F-NMR (471 MHz, CDCl ) δ 63.41.
3
1
Phenyl(3-(trifluoromethyl)phenyl)methanone (3g). White solid. H-NMR (500 MHz, CDCl )
δ 8.07 (s, 1 H),
3
7
.98 (d, J = 7.8 Hz, 1 H), 7.85 (d, J = 8.0 Hz, 1 H), 7.80 (d, J = 7.7 Hz, 2 H), 7.63 (t, J = 7.6 Hz, 2 H), 7.52 (t,
13
F
J = 7.6 Hz, 2 H). C-NMR (125 MHz, CDCl )
Hz), 130.16, 129.09, 128.97 (J = 7.5 Hz), 128.71, 126.84 (J = 8.8 Hz), 123.84 (J = 272.9 Hz). F-NMR
δ
195.32, 138.45, 136.92, 133.25, 133.14, 131.17 (J = 32.7
3
F
F
F
19
(
471 MHz, CDCl ) δ 62.77.
3
1
(
4-Fluorophenyl)(phenyl)methanone (3h). White solid. H-NMR (500 MHz, CDCl )
δ
7.90–7.84 (m, 2 H),
3
7
.79 (d, J = 7.7 Hz, 2 H), 7.62 (t, J = 6.9 Hz, 1 H), 7.51 (t, J = 7.4 Hz, 2 H), 7.18 (t, J = 8.2 Hz, 2 H).
13
F
F
F
C-NMR (125 MHz, CDCl3) δ 195.26, 165.39 (J = 254.1 Hz), 137.51, 133.81 (J = 2.5 Hz), 132.67 (J =
F
19
8
.8 Hz), 132.47, 129.88, 128.36, 115.45 (J = 21.4 Hz). F-NMR (471 MHz, CDCl ) δ 105.98.
3
1
(
1
3,5-Difluorophenyl)(phenyl)methanone (3i). White solid. H-NMR (500 MHz, CDCl )
δ
7.35 (dt, J = 40.7,
3
13
8.4 Hz, 4 H), 7.03–6.87 (m, 1 H), 6.40 (d, J = 41.0 Hz, 2 H), 6.13 (d, J = 40.9 Hz, 2 H). C-NMR (125
δ 193.95, 162.74 (J = 250.3 Hz), 162.65 (J = 251.6 Hz), 136.40, 133.16, 129.98, 128.59,
12.96 (J = 20.1 Hz), 107.73 (J = 25.8 Hz). F-NMR (471 MHz, CDCl ) δ 108.15.
F
F
MHz, CDCl )
1
3
F
F
19
3
1
Methyl 4-benzoylbenzoate (3j). White solid. H-NMR (500 MHz, CDCl )
δ
8.17 (d, J = 8.2 Hz, 2 H), 7.87
3
(
3
d, J = 8.2 Hz, 2 H), 7.83 (d, J = 7.5 Hz, 2 H), 7.64 (t, J = 7.4 Hz, 1 H), 7.53 (t, J = 7.6 Hz, 2 H), 3.99 (s,
13
H). C-NMR (125 MHz, CDCl3)
δ
196.03, 166.32, 141.33, 136.96, 133.22, 132.95, 130.11, 129.78, 129.50,
1
28.47, 52.48.
1
Cyclohexyl(phenyl)methanone (3k). White solid. H-NMR (500 MHz, CDCl )
δ
7.98–7.96 (d, J = 8.2 Hz,
3
2
(
=
2
H), 7.58–7.56 (t, J = 7.5 Hz, 1 H), 7.50–7.47 (t, J = 7.7 Hz, 2 H), 3.31–3.27 (t, J = 11.5 Hz, 1 H), 1.93–1.86
m, 4 H), 1.78–1.75 (d, J = 11.7 Hz, 1 H), 1.54–1.49 (t, J = 13.4 Hz, 2 H), 1.46–1.39 (m, 2 H), 1.34–1.31 (d, J
12.5 Hz, 1 H). 13C-NMR (125 MHz, CDCl3)
203.92, 136.38, 132.73, 128.59, 128.27, 45.65, 29.44, 25.98,
5.88.
δ
Supplementary Materials: Experimental procedures and characterization data are available online.
Author Contributions: J.B. conducted experimental work and analyzed the data with contributions from D.J.P.;
H.H. and M.S. supervised the project, designed experiments to develop this reaction, and wrote the paper.
Funding: This research was funded by Rutgers University and the NSF (CAREER CHE-1650766, CBET 1438493)
are acknowledged for support. The 500 MHz spectrometer was supported by the NSF-MRI grant (CHE-1229030).
Conflicts of Interest: The authors declare no conflict of interest.
References
1
.
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