Binuclear Tridentate Hemilabile Copper(I) Catalysts for Utilization of CO2into Oxazolidinones from Propargylic Amines

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Binuclear Tridentate Hemilabile Copper(I) Catalysts for Utilization of

CO₂into Oxazolidinones from Propargylic Amines

Fei Chen, Sheng Tao, Qian-Qian Deng, Donghui Wei,* Ning Liu,* and Bin Dai*

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ABSTRACT: Four binuclear tridentate copper(I) complexes were synthesized based

on the trans eﬀect of the hybrid ligands. The catalytic performance and behavior of the

prepared copper(I) complexes were evaluated in the carboxylative cyclization of

propargylic amines with CO₂. The combined use of copper(I) complexes and 1,5,7-

triazabicyclo[4.4.0]dec-5-ene (TBD) provided a catalytic system for the synthesis of a

wide range of oxazolidinones from various propargylic amines and CO₂under mild

reaction conditions (room temperature40 °C and 1 bar CO₂). The key factor for the

success of the protocol is the use of copper complexes possessing the quality of

hemilabile properties between N-heterocyclic carbenes and nitrogen donors. NMR

measurements, density functional theory (DFT) calculations, and previous reports for

the coordination behavior of the nickel complexes support the existence of the trans

eﬀect between N-heterocyclic carbenes and nitrogen donors.

method,¹⁸have been presented for the carboxylative

cyclization of propargylic amines with CO₂. He and co-

workers reported a series of promising non-noble metal

catalytic systems, such as CoBr₂/1,5,7-triazabicyclo[4.4.0]dec-

5-ene (TBD) (Table 1, entry 4),¹⁰ZnCl₂(TBD)₂(Table 1,

entry 5),¹¹and Cu-substituted polyoxometalate-based ionic

liquids (Table 1, entry 6).^12aWang and co-workers^12breported

an extraordinary work that converted various propargylic

amines and CO₂to oxazolidinones using an eﬃcient CuI/DBU

catalytic system with a broad range of substrates (Table 1,

entry 7). Most of the methods above show poor functional

group tolerance when R¹is an aryl group. Zhou and co-

workers^6breported the coupling-carboxylative cyclization

reaction in which various N-aryl 2-oxazolidinones were

successfully synthesized using silver as the catalyst (Table 1,

entry 8).

Despite the great progress and achievements in this area,

most of the catalytic systems reported suﬀered from limited

substrate scopes to various degrees; current non-noble metal

catalytic systems needed high catalyst loadings; a solvent is

required. Therefore, it is highly desirable to develop a more

powerful method for the synthesis of oxazolidinones employ-

ing cheap and abundant metal as catalysts under mild reaction

conditions. Pincer-type transition metal complexes with

INTRODUCTION

■

The establishment of eﬃcient strategies for the consumption

and utilization of CO₂has attracted considerable attention

worldwide due to the continuously increasing CO₂concen-

tration in the atmosphere.¹One strategy for addressing this

issue involves chemical ﬁxation of CO₂into high value-added

oxazolidinones using commercially available propargylic

amines as starting materials.²As a consequence of the

importance of oxazolidinones, a wide range of noble metal-

based catalysts, such as Ru,³Pd,⁴Au,⁵and Ag,⁶have been

developed for preparing such chemicals through the carbox-

ylative cyclization of propargylic amines with CO₂. A noble

contribution to the transition metal catalysis for preparing

oxazolidinones was reported by Yamada and co-workers.⁷

Their studies showed that 2 mol % of AgOAc or 0.5 mol % of

AgNO₃and 2 equiv of 1,8-diazabicyclo[5.4.0]-7-undecene

(DBU) under atmospheric pressure of CO₂and at room

temperature enable eﬃcient synthetic access to the synthesis of

oxazolidinones (Table 1, entry 1). Ikariya and co-workers⁸

described an appealing base-free strategy for the synthesis of

oxazolidinones using AuCl(IPr) as the catalyst in methanol

under mild conditions (Table 1, entry 2). Another

contribution to this ﬁeld was reported by Bourissou and co-

workers in 2017.⁹They employed a Pd sulfur−carbon−sulfur

(SCS) pincer complex as the catalyst to eﬀectively catalyze the

conversion of propargylic amines and CO₂to form

oxazolidinones in the absence of bases at 40−80 °C (Table

1, entry 3). Recently, non-noble metal catalysts based on Co,¹⁰

Zn,¹¹Cu,¹²and W,¹³and organocatalysts, such as ionic

liquids,¹⁴organobases,¹⁵organoacids,¹⁶and N-heterocyclic

carbene,¹⁷as well as a catalyst-free supercritical CO₂-promoted

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A

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Table 1. Transition Metal Catalytic Strategies for the Synthesis of Oxazolidinones

diﬀerent ligands, so-called hybrid ligands, have attracted wide

attention in transition metal catalysis.¹⁹Inspired by our

previous research for the design and synthesis of hemilabile

transition metal catalysts, such as Fe,²⁰Pd,²¹Ru,²²and Ni.²³

Herein, we report a simple, practical, and convenient synthetic

procedure for hemilabile binuclear Cu(I) complexes. As

expected, the Cu(I) complexes show high activity for the

carboxylative cyclization of propargylic amines with CO₂with

a low catalyst loading (0.3 mol %) under mild reaction

conditions, that is, at 25−40 °C (Table 1, entry 9).

Scheme 1. Synthesis and X-ray for Copper Complexes 1a−d

RESULTS AND DISCUSSION

■

The pyridine-bridged pincer-type imidazolium salts L1−4 were

synthesized according to our reported method.²⁴Four Cu(I)

complexes 1a−d were prepared through the reaction of

imidazolium salts L1−4 with Cu₂O in air and MeCN (without

purity), as shown in Scheme 1. To demonstrate the structure

of the Cu(I) complexes, the structure and atom connectivity of

the Cu(I) complex 1a was conﬁrmed by X-ray crystallography,

as depicted in Scheme 1. All of the Cu(I) complexes were

found to be air and moisture stable, even after two weeks

under an air atmosphere.

In initial studies, the reaction of N-benzylpropynylamine

(2a) with CO₂was used as a benchmark reaction to probe the

reaction conditions (Table 2). To our delight, we found that

the reaction proceeded eﬃciently at room temperature and

atmospheric pressure for CO₂, utilizing an extremely low

catalyst loading (0.3 mol % of Cu complex) to give the

oxazolidinone 3a product. Eight diﬀerent bases, such as N,N′-

dimethylethylenediamine (DMEDA), 4-dimethylaminopyri-

dine (DMAP), N,N,N′,N′-tetramethylethylenediamine

(TMEDA), diisopropylethylamine (DIPEA), 1,4-

diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]-

7-undecene (DBU), triethylamine (TEA), and 1,5,7-

triazabicyclo[4.4.0]dec-5-ene (TBD), were employed to

investigate the inﬂuence of bases on the catalytic performance

(Table 2, entries 1−8). For the investigation of the bases,

DIPEA, DABCO, DBU, TEA, and TBD showed high

performances, aﬀording excellent yields for 3a (Table 2,

entries 4−8), and TBD was found to be the most eﬀective base

for the transformation (Table 2, entry 8).

To further understand the inﬂuences of N-substituted alkyl

in benzimidazolium salts on the catalytic performance, two

diﬀerent chain lengths N-propyl (Table 2, entries 8 and 10)

and N-butyl substituents (Table 2, entries 9 and 11), were

explored. The result indicated that the inﬂuence of the N-

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a

6−10), and cyclohexyl (Table 3, entry 11), were found to

smoothly react with CO₂, resulting in excellent yields. It is

noteworthy that N-tert-butyl 2j is a challenging substrate in the

transformation due to steric hindrance. We were delighted to

ﬁnd that the substrate 2j was readily tolerated for this copper-

catalyzed system, with a yield of 87% after 12 h, even at room

temperature and atmospheric pressure for CO₂(Table 3, entry

10). To the best of our knowledge, only two examples of

palladium-catalyzed methods have been developed for such a

transformation with substrate 2j featuring a tertiary alkyl

group. The ﬁrst example for such a transformation was

reported by Nevado and co-workers^4bwith PdCl₂(dppf),

which aﬀorded 38% yield at 40 °C for 3 days. Another example

was reported recently by Bourissou and co-workers⁹using Pd

SCS pincer catalysts, with 88% isolated yield at 70 °C for 90 h.

This work provides the ﬁrst example of a non-noble metal

approach to produce 3j from highly sterically hindered 2j at

room temperature and atmospheric pressure for CO₂. In

addition, the primary propargylic amines 2l and 2m, containing

a dimethyl group or cyclohexyl group at the methylene carbon,

also reacted with CO₂to aﬀord the corresponding products 3l

and 3m in excellent yields (Table 3, entries 12 and 13).

To further enhance the utility of the developed copper-

catalyzed carboxylative cyclization method, we next examined

the scope for the internal alkyne-based propargylic amines in

Table 4. Taking N-alkyl phenyl-substituted internal alkyne as a

benchmark structure, substituents at the propargylic position

were explored. Isopropyl (Table 4, entry 1), n-propyl (Table 4,

entry 2), cyclopropyl (Table 4, entry 3), cyclohexyl (Table 4,

entry 4), phenylethyl (Table 4, entry 5), and phenyl internal

alkynes (Table 4, entry 10) were eﬃciently coupled with CO₂

to produce the corresponding oxazolidinones 5a−e and 5j in

excellent yields. Taking substrates with the n-butyl group at the

propargylic position as a benchmark structure, N-substituents

with propargylic amines were also evaluated in this copper-

catalyzed system. Additionality, various N-butyl (Table 4, entry

2), N-pentyl (Table 4, entry 6), N-cyclohexyl (Table 4, entry

7), and N-phenylethyl internal alkynes (Table 4, entry 8) were

tolerated, delivering the corresponding products 5b and 5f−h

in excellent yields. Taking propargylic amines with a phenyl

group at the propargylic position as a benchmark structure, N-

cyclohexyl (Table 4, entry 9), N-butyl (Table 4, entry 10), and

N-cyclopropylmethyl (Table 4, entry 11) propargylic amines

were smoothly accommodated in copper-catalyzed carbox-

ylative cyclization. The phenyl ring bearing an electron-

withdrawing group, such as the ﬂuoro group (Table 4, entries

13 and 14), shows an obviously lower reactivity in comparison

with those bearing an electron−neutron and an electron-

donating group (Table 4, entries 10 and 12). Therefore, the

electronic eﬀect of N-aryl substituents bearing a terminal

alkyne is signiﬁcantly evident for such transformations. A

complete conversion of 4m was observed when the temper-

ature was elevated to 40 °C (Table 4, entry 13, yield in

brackets). The eﬀect of substituents at the propargyl carbon

position on the reactivity was also observed, and the substrate

4n with an alkyl group (Table 4, entry 14) showed higher

reactivity than 4m with an aryl group (Table 4, entry 13).

Encouraged by these promising results obtained using the

aforementioned terminal alkynes and internal alkynes, we next

proceeded to evaluate the scope for the challenging propargylic

amines, as shown in Table 5. The electron-withdrawing eﬀect

of the N-aryl group bearing propargylamines weakened the

nucleophilicity of the amino group, which hinders the nitrogen

Table 2. Optimization of Reaction Conditions

b

entry

catalyst (mol %)

base (mol %)

time (h)

yield (%)

1

2

3

4

5

6

7

8

1a (0.3)

1b (0.3)

1c (0.3)

1d (0.3)

1a (0.3)

1a (0.15)

1a (0.3)

1a (0)

DMEDA (5)

DMAP (5)

TMEDA (5)

DIPEA (5)

DABCO (5)

DBU (5)

TEA (5)

TBD (5)

TBD (2.5)

TBD (5)

TBD (0)

12

15

10

8

21

52

16

87

88

91

82

94

90

81

80

96

88

82

87

83

5

9

10

11

12

13

14

15

16

17

18

12

15

1a (0.3)

40

a

Reaction conditions unless speciﬁed otherwise: N-benzylpropynyl-

amine 2a (1.0 mmol), Cu catalyst (as indicated in this table), organic

bases (as indicated in this table), CO₂balloon, room temperature

(25−27 °C), neat, in a 25 mL of Schlenk tube. Isolated yield.

b

substituent chain length on catalytic eﬃciency was negligible

(Table 2, entries 8 vs 9 and 10 vs 11). The inﬂuence of

diﬀerent coordination groups bearing pyridine rings on the

catalytic performance was also explored. Cu complexes 1a and

1b, which coordinated with a pyrazole-bearing pyridine ring

(Table 2, entries 8 and 9) showed a higher catalytic activity

than that of 1c and 1d coordinated with indazole (Table 2,

entries 10 and 11), and Cu complex 1a probed to be optimal

among a variety of Cu complexes (Table 2, entry 8). The

inﬂuence of the reaction time and loading amount of catalyst

and base was explored (Table 2, entries 8 and 12−16), and it

was demonstrated that the optimized conditions were a

reaction time of 15 h, together with a catalyst 1a loading

amount of 0.3 mol % and an organic TBD amount of 5 mol %

(Table 1, entry 12). The combined use of Cu catalyst 1a and

TBD gave the best performance (Table 2, entry 12); in

contrast, the use of TBD alone made it diﬃcult to trigger the

reaction (Table 2, entry 17) and the use of 1a in the absence of

TBD only led to a 40% yield for 3a under similar conditions

(Table 2, entry 18). This clearly shows the beneﬁcial character

of using a binary system, which is comprised of a copper

complex 1a with an organic base (TBD), exhibiting a stronger

cooperation eﬀect than that for TBD or a copper complex

alone.

To explore the scope of the established protocol based on

the combination of the Cu complex of 1a with TBD as a binary

catalytic system, a wide range of propargylamines were

investigated in the carboxylative cyclization of CO₂under

the optimized reaction conditions (Table 3). A broad range of

secondary propargylic amines with a terminal alkyne was

converted into the desired products in excellent yields (Table

3, entries 1−11). Various N-substituted propargylic amines,

including benzyl (Table 3, entries 1−5), alkyl (Table 3, entries

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a

Table 3. Scope of Terminal Alkyne-Based Propargylic Amines

a

Reaction conditions unless speciﬁed otherwise: propargylic amines (1.0 mmol), copper catalyst 1a (0.3 mol %), TBD (5 mol %), CO₂balloon,

b

room temperature (25−27 °C), 12 h, neat. Isolated yield.

atom’s nucleophilic attack at CO₂. To the best of our

knowledge, limited examples of such a transformation with

N-aryl-substituted propargylamine have been previously

reported.^6b,11For example, the ZnCl₂(TBD)₂catalytic system

was reported by He and co-workers¹¹to give a 52% yield for

7b under atmospheric pressure for CO₂at 60 °C. In addition,

Zhou and co-workers^6bhave developed a Ag/1,3-diphenylgua-

nidine (DPG) catalyzed system, which was successfully applied

in the synthesis of a series of N-aryl 2-oxazolidinones in high

product yields via multicomponent tandem coupling-carbox-

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a

Table 4. Scope for the Internal Alkyne-Based Propargylic Amines

a

Reaction conditions unless speciﬁed otherwise: propargylic amines (1.0 mmol), copper catalyst 1a (0.3 mol %), TBD (5 mol %), CO₂balloon,

b

c

room temperature (25−27 °C), 12 h, neat. Isolated yield. 40 °C, 24 h.

ylative cyclization. It is crucial to note that the copper catalytic

system is eﬃcient for the conversion of N-aryl-substituted

substrates 6a and 6b, aﬀording 93 and 87% yields at room

temperature (Table 5, entries 1 and 2).

E

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a

Table 5. Scope for Challenging Propargylic Amines

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Table 5. continued

a

Reaction conditions unless speciﬁed otherwise: propargylic amines (1.0 mmol), copper catalyst 1a (0.3 mol %), TBD (5 mol %), CO₂balloon, 40

b

c

°C, 36 h, neat. Isolated yield. Isolated yield for 8e.

Figure 1. FT-IR spectra for (a) copper complex 1a, neat; (b) a mixture of copper complex 1a (10 mg, 9.8 × 10⁻³mmol) and N-

benzylpropynylamine 2a (20 mg, 0.14 mmol, 14 equiv) detected immediately after being stirred at room temperature, neat; (c) a mixture of copper

complex 1a (10 mg, 9.8 × 10⁻³mmol) and substrate 2a (20 mg, 0.14 mmol, 14 equiv) after being stirred at room temperature for 10 min, neat; (d)

a mixture of copper complex 1a (10 mg, 9.8 × 10⁻³mmol) and N-benzylpropynylamine 2a (20 mg, 0.14 mmol, 14 equiv) after being stirred at

room temperature for 20 min, neat; (e) N-benzylpropynylamine 2a, neat.

Bourissou⁹reported that the regioselectivity of the

cyclization is dependent on the electron nature of substituents

bearing alkyne. In their Pd catalytic system, the phenyl-

substituted substrate preferentially underwent 5-exo cycliza-

tion. However, the 8.25/1 mixture of 5-exo/6-endo oxazolidi-

nones was observed when a methyl-substituted substrate was

employed in this reaction. This is similar to our developed

copper catalytic system, and the phenyl-substituted substrate

(6c and 6d) gave the desired products 7c and 7d with high

selective 5-exo cyclization (Table 5, entries 3 and 4). However,

the methyl-substituted substrate (6e) was converted to a

23.33/1 mixture of 5-exo/6-endo oxazolidinones (7e/8e).

Next, the inﬂuence of the steric hindrance of substituents

bearing a nitrogen atom was investigated. When an isopropyl

group was introduced to a nitrogen atom, a moderate yield of

7f was obtained (Table 5, entry 6). This indicates that the

steric eﬀect of the N-substituent has a signiﬁcant impact on

reactivity.

Primary propargylic amines are generally challenging

substrates because of the side reaction arising from the NH₂

group.⁹To our delight, four primary propargylic amines 6h−k

were suitable for the copper catalytic system, aﬀording 80−

93% product yields (Table 5, entries 8−11).

He and co-workers^12areported that the introduction of the

cyclohexyl group in the α-carbon position to nitrogen showed

low reactivity due to steric hindrance. Next, a series of

disubstituted substrates 6l−q in the α-carbon position to

nitrogen were synthesized and were evaluated in the copper

catalytic system. The tested substrates, including the cyclohexyl

group and the alkyl group, showed high reactivity, giving

corresponding products 7l−q in 76−93% yields (Table 5,

entries 12−17).

A control experiment using the Fourier transform infrared

(FT-IR) method to study the interaction between copper

complex 1a and substrate 2a was performed (Figure 1). The

absorption peak at 3293 cm⁻¹can be assigned to the stretching

vibration peak of alkynyl terminal hydrogen, which was

explored by the FT-IR spectra. When N-benzylpropynylamine

2a was added to the copper complex 1a, the C−H bond

stretching vibrations for the terminal alkyne at a wavenumber

of 3293 cm⁻¹became evidently weaker in wavelength with a

The homopropargyl amine 6g showed a low reactivity and

poor selectivity in the Pd catalytic system,⁹while 6g proved

viable and proceeded with good reactivity with a moderate

yield of six-membered product 7g in our developed copper

catalytic system (Table 5, entry 7).

G

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Figure 2. ¹³C NMR spectra of (a) copper complex 1a (0.015 mmol, 15 mg) in dimethyl sulfoxide (DMSO)-d₆(0.6 mL) at 298 K; (b) a mixture of

copper complex 1a (0.015 mmol, 15 mg) and N-benzylpropynylamine 2a (0.1 mmol, 15 mg) in DMSO-d₆(0.6 mL) immediately detected after

being stirred at 298 K; (c) N-benzylpropynylamine 2a (0.1 mmol, 15 mg) in DMSO-d₆(0.6 mL) at 298 K.

prolonged reaction time. This result indicated that a

coordination phenomenon may occur between copper

complex 1a and substrate 2a, which changed the chemical

environment of alkynyl terminal hydrogen. There were also

two obvious changes at 699 and 743 cm⁻¹, respectively, and

these may be the bending vibration peak of alkynyl terminal

hydrogen and amino hydrogen. Through comparative IR

spectra, we found that the absorption peaks at 699 and 743

cm⁻¹gradually get weaker; this indicated that the copper

catalyst 1a not only activated alkynyl hydrogen but also

activated amino hydrogen. A recent Co catalytic system¹⁰and

Ag catalytic system²⁵independently revealed that the metal

center of transition metal catalysts can coordinate with the

amino groups of propargylamines. Therefore, these results

suggested that copper complex 1a plays a signiﬁcant role in

activating both the alkynyl group and amino hydrogen.

To investigate the interaction between the copper complex

1a and substrate 2a, ¹³C NMR studies were carried out (Figure

2). Upon addition of substrate 2a to the copper complex 1a, a

shift in the resonances of the CC triple bond from δ 82.80

and 73.74 ppm to 82.07 and 74.03 ppm was observed, which

was consistent with what was observed in FT-IR analysis,

suggesting that a coordination interaction between copper

complex 1a and substrate 2a has occurred.

148.01 ppm when substrate 2a was added to the copper

complex 1a. These results indicated that the coordination

environments for the nitrogen atom bearing pyridine and

pyrazole rings were changed because of the removal of the

pyridine and pyrazole rings from the copper center.

It is well known that metal catalysts can activate substrates

through the interaction between the metal center with the

alkynyl group bearing propargylamine.^2aTherefore, the copper

complex 1a released one or multiple ligands or coordination

sites before interacting with substrate 2a. The pyridine-bridged

ligand bearing copper complex 1a contains three diﬀerent

coordination sites, including a NHC ligand, pyridine nitrogen,

and pyrazole nitrogen. Normally, coordination sites preferred

to dissociate from the copper center and oﬀered one or

multiple coordination sites for the activation of the substrate

molecule at the copper atom to form an intermediate.

To explore which coordination sites of the catalyst 1a prefer

to dissociate and interact with the alkynyl group bearing

substrate 2a, we performed density functional theory (DFT)

calculations to compare the Gibbs free energy changes ΔG

associated with the three possible structures 1aa, 1ab, and 1ac.

All of the computations were performed using the Gaussian 09

program.²⁶The geometries were fully optimized using the

B3LYP method.²⁷The basis set 6-31+G(d,p) was employed

for all of the atoms. As shown in Scheme 2, ΔG for the

formation of 1aa, 1ab, and 1ac was determined to be 13.5,

11.7, and 21.1 kcal/mol, respectively, indicating that 1ab is the

most stable structure and the possible intermediate for the

catalytic cycle. DFT calculations demonstrated that copper

complexes exhibited the trans eﬀect between the NHC ligand

To explore the trans eﬀect between diﬀerent coordinated

sites of the copper complex 1a, ¹³C NMR experiments were

used to investigate the change in the coordination environment

of the copper complex 1a (Figure 2). As indicated in Figure 2,

the resonance of the carbon in the C2 position of the pyridine

ring was observed to be shifted downﬁeld from δ 147.73 to

H

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Scheme 2. Relative Energies of the Reactants and Intermediates

Scheme 3. Trans Eﬀect between NHC Ligands and Nitrogen Donors

and nitrogen donors bearing the copper complex 1a, in which

the pyridine ring and the pyrazole ring were preferred to

dissociate from the copper center in comparison with the

NHC ligand. In addition, the results of IR experiments (Figure

1) are in agreement with the DFT calculation. IR experiments

indicated that the copper complex 1a needs to provide two

active sites for activating the alkynyl group and amino

hydrogen, respectively, which is consistent with the results of

DFT calculation.

ligands. The NMR and IR spectroscopic measurements and

experimental results suggested that copper complex 1a

underwent removal of the pyridine and pyrazole rings due to

hemilability between the NHC ligands and nitrogen donors,

which provided two coordination sites for the activation of the

substrate 2a and amino nitrogen atom, respectively, with the

copper center (Scheme 3).

Normally, TBD has two functions in the carboxylative

cyclization of propargylic amines with CO₂. On the one hand,

TBD reacts with CO₂to form TBD−CO₂complexes.²⁸On the

other hand, TBD deprotonates the amino group of the

substrates.^25,29Nguyen and co-workers^15binvestigated the

function of TBD in the carboxylative cyclization of propargylic

amines with CO₂. They found that the basicity of the bases

(TBD, DBU, DABCO, and TEA), rather than their ability to

Our previous studies for the synthesis of nickel complexes²³

have revealed that the N-heterocyclic carbene (NHC) ligands

preferentially bind to the nickel atom compared to those

molecules containing nitrogen donors, such as pyridine and

pyrazole rings; in other words, the nitrogen donors prefer to

dissociate from a copper atom in comparison with NHC

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form complexes with CO₂, is the origin of the catalytic activity

of bases. Based on the aforementioned FT-IR and NMR

experiments and our previous results,²³a possible formation

process for the active intermediate is proposed in Scheme 4

hindered propargylamines and propargylamines. The ¹³C

NMR measurements, DFT calculations, and previous exper-

imental results of the coordination behavior of the nickel

complexes suggest that the pyridine and the pyrazole rings

bearing the copper complex 1a preferred to dissociate from the

copper center based on the hemilability between NHC ligands

and nitrogen donors, which will oﬀer one coordination copper

site for the activation of the CC triple bond and, thus, lead

to high reactivity. Following the completion of the reaction, the

pyridine and pyrazole rings once again coordinated with the

copper center to stabilize the copper active center. Therefore,

the trans eﬀect between the NHC ligands and nitrogen donors

plays an important role in regulating the activity and stability of

copper catalysts. This study provides insight into the rational

design and synthesis of transition metal catalysts.

Scheme 4. Proposed Reaction Mechanism Catalyzed by Cu

Complexes

EXPERIMENTAL SECTION

■

General Procedure for the Synthesis of Cu Complexes 1a−

d. The pyridine-bridged pincer-type imidazolium salts were initially

prepared according to the literature (characterization data see the

Supporting Information for details).²⁴The imidazolium salts (0.6

mmol) and Cu₂O (0.3 mmol) were successively added into a 25 mL

Schlenk tube and dissolved in 2.0 mL CH₃CN under an air

atmosphere. The mixtures were subsequently heated to 80 °C in a

heating mantle for 36 h. The reaction mixture was washed three times

with ethyl acetate (3 × 50 mL) and tetrahydrofuran (3 × 50 mL),

respectively, and the Cu complexes 1a−d were obtained after drying.

Data for 1a are as follows: a yellowish solid (215.0 mg, 70%), M.P.

= 269.7−270.4 °C; high-resolution mass spectrometry (HRMS)

(electrospray ionization (ESI)) m/z: [M − 2PF₆]²⁺calcd for

C₃₆H₃₄N₁₀Cu₂366.0780; found 366.0780. IR (KBr): 3188, 1608,

1587, 1522, 1465, 1391, 1334, 1199, 1059, 838, 555 cm⁻¹. For single-

crystal data, see Figure S62 in the Supporting Information for details.

Data for 1b are as follows: a yellowish solid (205.1 mg, 65%), M.P.

= 252.4−253.2 °C; HRMS (ESI) m/z: [M − 2PF₆]²⁺calcd for

C₃₈H₃₈N₁₀Cu₂380.0936; found 380.0928. IR (KBr): 3133, 1620,

1579, 1522, 1465, 1403, 1338, 1063, 846, 563 cm⁻¹. For single-crystal

data, see Figure S63 in the Supporting Information for detail.

Data for 1c are as follows: a yellowish solid (134.9 mg, 40%), M.P.

= 293.2−296.3 °C; HRMS (ESI) m/z: [M − 2PF₆]²⁺calcd for

C₄₄H₃₈N₁₀Cu₂416.0936; found 416.0935. IR (KBr): 2964, 1567,

1460, 1408, 1341, 1211, 842, 744, 547 cm⁻¹. For single-crystal data,

see Figure S64 in the Supporting Information for detail.

(top). First, pyridine and pyrazole rings bearing the copper

complex 1a dissociated from the copper atom in the presence

of substrates, which then produced an intermediate copper

complex [Cu] based on the trans eﬀect between the NHC

ligand and nitrogen donors, as experimentally conﬁrmed by

our previously reported results. Therefore, a possible reaction

pathway is shown in Scheme 4 (bottom). First, the alkynyl

group with 2a was activated through the coordination

interaction with the copper center of the intermediate [Cu]

and, simultaneously, a hydrogen bonding interaction between

the amino hydrogen bearing [Cu] and TBD occurred to form

an intermediate I. Then, the intermediate I reacted with CO₂

to produce the carbamic acid II. Finally, the negatively charged

oxygen atom attacked the CC triple bond through an

intramolecular nucleophilic substitution to produce III, which

underwent protodemetalation to release the desired product

and active species [Cu].

Data for 1d are as follows: a yellowish solid (127.9 mg, 37%), M.P.

= 248.2−249.7 °C; HRMS (ESI) m/z: [M − 2PF₆]²⁺calcd for

C₄₆H₄₂N₁₀Cu₂430.1093; found 430.1088. IR (KBr): 2970, 1571,

1456, 1411, 1350, 1207, 1149, 834, 748, 555 cm⁻¹. For single-crystal

data, see Figure S65 in the Supporting Information for detail.

General Procedure for the Synthesis of Oxazolidinones.

Propargylic amines (1.0 mmol), Cu complex 1a (0.003 mmol), and

TBD (0.05 mmol) were successively added into a 25 mL Schlenk

ﬂask. The reaction mixture was stirred at room temperature (25−27

°C) for 24 h under a CO₂atmosphere (1 atm, using a balloon). The

reaction that required heating was heated to the required temperature

in the heating mantle. After the reaction, excess CO₂was carefully

vented oﬀ. The reaction mixtures were added to brine (15 mL) and

extracted three times with dichloromethane (3 × 15 mL). The solvent

was removed under reduced pressure, and the products were isolated

by ﬂash chromatography.

CONCLUSIONS

■

In conclusion, we have developed new copper catalysts based

on the concept of the trans eﬀect of hybrid ligands. The

combined use of copper complexes and TBD has provided an

eﬀective catalytic system for the carboxylative cyclization of

propargylic amines with CO₂, leading to the formation of a

wide range of the oxazolidinones in good to excellent yields at

room temperature. It is worthwhile to note that this strategy

shows an unprecedented scope for a wide range of propargylic

amines and functional group tolerance, including sterically

Data for 3-Benzyl-5-methyleneoxazolidin-2-one (3a).^12aPuriﬁ-

cation by ﬂash chromatography (petroleum/EtOAc = 5:1): a colorless

1

oil (177.9 mg, 94%); H NMR (400 MHz, CDCl₃) δ 7.39−7.33 (m,

3H), 7.29−7.26 (m, 2H), 4.75 (q, J = 2.8 Hz, 1H), 4.47 (s, 2H),

4.25−4.23 (m, 1H), 4.02 (t, J = 2.4 Hz, 2H); ¹³C{¹H} NMR (100

MHz, CDCl₃) δ 155.8, 149.1, 135.1, 129.1, 128.4, 128.3, 86.9, 48.0,

47.3.

Data for 3-(4-Chlorobenzyl)-5-methyleneoxazolidin-2-one

(3b).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

J

https://dx.doi.org/10.1021/acs.joc.0c02065

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

5:1): a white solid (212.4 mg, 95%), M.P. = 89.7−90.7 °C; ¹H NMR

(400 MHz, CDCl₃) δ 7.35 (d, J = 8.4 Hz, 2H), 7.23 (d, J = 8.4 Hz,

2H), 4.77−4.75 (m, 1H), 4.44 (s, 2H), 4.27−4.25 (m, 1H), 4.02 (t, J

= 2.4 Hz, 2H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.8, 148.8,

134.4, 133.7, 129.7, 129.3, 87.2, 47.3, 47.3.

Data for 3-(4-Bromobenzyl)-5-methyleneoxazolidin-2-one

(3c).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

5:1): a white solid (249.2 mg, 93%), M.P. = 85.4−86.0 °C; ¹H NMR

(400 MHz, CDCl₃) δ 7.50 (d, J = 8.4 Hz, 2H), 7.16 (d, J = 8.4 Hz,

2H), 4.76−4.74 (m, 1H), 4.41 (s, 2H), 4.26 (m, 1H), 4.02 (t, J = 2.2

Hz, 2H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.7, 148.8, 134.2,

132.3, 129.9, 122.4, 87.2, 47.4, 47.3.

Data for 3-(4-Methoxybenzyl)-5-methyleneoxazolidin-2-one

(3d).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

10:1): a yellow oil (208.3 mg, 95%); ¹H NMR (400 MHz, CDCl₃) δ

7.21 (d, J = 8.8 Hz, 2H), 6.89 (d, J = 8.4 Hz, 2H), 4.73−4.71 (m,

1H), 4.40 (s, 2H), 4.23−4.21 (m, 1H), 3.99 (t, J = 2.4 Hz, 2H), 3.80

(s, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 159.7, 155.7, 149.2,

129.7, 127.1, 114.4, 86.8, 55.4, 47.4, 47.2.

1.45 (s, 6H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 162.3, 155.8, 84.4,

58.5, 29.5.

Data for 4-Methylene-3-oxa-1-azaspiro[4.5]decan-2-one (3m).⁹

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 2:1): a

white solid (155.5 mg, 93%), M.P. = 206.5−208.3 °C; ¹H NMR (400

MHz, CDCl₃) δ 7.14 (brs, 1H), 4.67 (dd, J = 3.2, 0.8 Hz, 1H), 4.23

(d, J = 3.6 Hz, 1H), 1.87−1.74 (m, 5H), 1.60−1.53 (m, 2H), 1.48−

1.23 (m, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 162.2, 156.1,

84.9, 61.6, 38.4, 24.9, 22.4.

Data for (Z)-5-Benzylidene-3-butyl-4-isopropyloxazolidin-2-one

(5a).^12bPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

15:1): a yellow oil (248.3 mg, 91%); ¹H NMR (400 MHz, CDCl₃) δ

7.60 (d, J = 7.2 Hz, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.23 (t, J = 7.4 Hz,

1H), 5.49 (d, J =1.6 Hz, 1H), 4.31−4.30 (m, 1H), 3.69−3.62 (m,

1H), 3.09−3.02 (m, 1H), 2.18−2.10 (m, 1H), 1.64−1.53 (m, 2H),

1.39−1.33 (m, 2H), 1.11 (t, J = 7.2 Hz, 3H), 0.97−0.91 (m, 6H);

¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.4, 145.1, 133.7, 128.5,

126.9, 104.3, 63.8, 41.4, 30.3, 29.2, 20.0, 17.6, 15.5, 13.8.

Data for (Z)-5-Benzylidene-3-butyl-4-propyloxazolidin-2-one

(5b).^12bPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

15:1): a yellow oil (251.2 mg, 92%); ¹H NMR (400 MHz, CDCl₃) δ

7.59 (d, J = 7.6 Hz, 2H), 7.33 (t, J = 7.8 Hz, 2H), 7.20 (t, J = 8.0 Hz,

1H), 5.46 (d, J = 2.0 Hz, 1H), 4.89 (s, 1H), 3.60−3.53 (m, 1H),

3.03−2.96 (m, 1H), 1.86−1.78 (m, 1H), 1.68−1.51 (m, 3H), 1.39−

1.30 (m, 4H), 0.96−0.92 (m, 6H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 155.1, 147.0, 133.6, 128.4, 128.2, 126.6, 102.2, 58.4, 41.1,

34.3, 29.2, 19.8, 15.7, 13.8, 13.6.

Data for 3-(4-Methylbenzyl)-5-methyleneoxazolidin-2-one

(3e).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

1

10:1): a yellow solid (193.0 mg, 95%), M.P. = 50.0−51.0 °C; H

NMR (400 MHz, CDCl₃) δ 7.16 (s, 4H), 4.73−4.71 (m, 1H), 4.42 (s,

2H), 4.23−4.21 (m, 1H), 4.00 (t, J = 8.4 Hz, 2H), 2.34 (s, 3H);

¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.6, 149.1, 138.0, 131.9,

129.6, 128.2, 86.6, 47.5, 47.1, 21.1.

Data for 5-Methylene-3-phenethyloxazolidin-2-one (3f).^12a

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a

Data for (Z)-5-Benzylidene-3-butyl-4-cyclopropyloxazolidin-2-

1

yellow oil (186.9 mg, 92%); H NMR (400 MHz, CDCl₃) δ 7.34−

one (5c). Puriﬁcation by ﬂash chromatography (petroleum/EtOAc

1

7.30 (m, 2H), 7.25−7.20 (m, 3H), 4.71−4.69 (m, 1H), 4.22−4.21

(m, 1H), 3.99 (t, J = 2.4 Hz, 2H), 3.56 (t, J = 3.2 Hz, 2H), 2.88 (t, J =

7.2 Hz, 2H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.6, 149.1,

138.1, 128.9, 128.7, 127.0, 86.6, 48.6, 45.3, 34.1.

= 5:1): a yellow solid (241.2 mg, 89%), M.P. = 103.0−104.0 °C; H

NMR (400 MHz, CDCl₃) δ 7.61 (d, J = 7.2 Hz, 2H), 7.33 (t, J = 7.6

Hz, 2H), 7.26 (t, J = 7.4 Hz, 1H), 5.71 (s, 1H), 3.65−3.62 (m, 1H),

3.58−3.49 (m, 1H), 3.43−3.36 (m, 1H), 1.63−1.53 (m, 2H), 1.42−

1.33 (m, 2H), 1.07−0.99 (m, 1H), 0.98 (t, J = 7.2 Hz, 3H), 0.79 (d, J

= 7.6 Hz, 2H), 0.49−0.47 (m, 2H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 154.8, 147.1, 133.8, 128.6, 128.6, 126.9, 102.9, 64.2, 41.8,

29.6, 20.1, 14.9, 13.9, 3.5, 1.4. HRMS (ESI) m/z: [M + Na]⁺calcd for

C₁₇H₂₁NO₂Na 294.1465; found 294.1466.

Data for 3-Butyl-5-methyleneoxazolidin-2-one (3g).^12aPuriﬁca-

tion by ﬂash chromatography (petroleum/EtOAc = 5:1): a yellow oil

1

(139.7 mg, 90%); H NMR (400 MHz, CDCl₃) δ 4.70−4.68 (m,

1H), 4.26−4.24 (m, 1H), 4.13 (t, J = 2.4 Hz, 2H), 3.27 (t, J = 7.2 Hz,

2H), 1.55−1.47 (m, 2H), 1.36−1.27 (m, 2H), 0.91 (t, J = 7.6 Hz,

3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.6, 149.3, 86.4, 47.8,

43.5, 29.3, 19.8, 13.7.

Data for (Z)-5-Benzylidene-3-butyl-4-cyclohexyloxazolidin-2-

one (5d).¹⁶Puriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 10:1): a colorless oil (284.8 mg, 91%); ¹H NMR (400

MHz, CDCl₃) δ 7.61 (d, J = 7.6 Hz, 2H), 7.33 (t, J = 7.6 Hz, 2H),

7.21 (J = 7.4 Hz, 1H), 5.48 (d, J = 4.0 Hz, 1H), 4.25 (s, 1H), 3.68−

3.61 (m, 1H), 3.09−3.02 (m, 1H), 1.87−1.52 (m, 8H), 1.41−1.08

(m, 7H), 0.98 (t, J = 7.4 Hz, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃)

δ 155.5, 145.7, 133.7, 128.6, 128.6, 126.9, 104.2, 63.5, 41.5, 40.8, 29.3,

28.1, 26.5, 26.3, 26.2, 26.1, 20.0, 13.8.

Data for 3-Isopropyl-5-methyleneoxazolidin-2-one (3h).⁹Puriﬁ-

cation by ﬂash chromatography (petroleum/EtOAc = 5:1): a yellow

1

oil (132.5 mg, 94%); H NMR (400 MHz, CDCl₃) δ 4.74−4.72 (m,

1H), 4.29−4.27 (m, 1H), 4.19−4.14 (m, 1H), 4.11 (t, J = 2.4 Hz,

2H), 1.20 (d, J = 6.8 Hz, 6H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ

154.9, 149.5, 86.5, 44.8, 43.3, 19.9.

Data for 5-Methylene-3-(1-phenylethyl)oxazolidin-2-one (3i).³⁰

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a

colorless oil (182.7 mg, 90%); ¹H NMR (400 MHz, CDCl₃) δ 7.39−

7.29 (m, 5H), 5.28−5.23 (m, 1H), 4.71−4.69 (m, 1H), 4.22−4.20

(m, 1H), 4.12−4.08 (m, 1H), 3.79−3.74 (m, 1H), 1.60 (d, J = 7.2 Hz,

3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.2, 149.3, 138.9, 128.9,

128.2, 127.1, 86.6, 51.4, 43.8, 16.5.

Data for (Z)-5-Benzylidene-3-isopropyl-4-phenethyloxazolidin-

2-one (5e).^7bPuriﬁcation by ﬂash chromatography (petroleum/

1

EtOAc = 10:1): a yellow oil (305.0 mg, 95%); H NMR (400 MHz,

CDCl₃) δ 7.62 (d, J = 7.2 Hz, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.29 (t, J

= 7.4 Hz, 2H), 7.25−7.20 (m, 2H), 7.17 (t, J = 5.8 Hz, 2H), 5.52 (d, J

= 2.0 Hz, 1H), 4.66−4.64 (m, 1H), 4.01−3.95 (m, 1H), 2.71 (t, J =

8.4 Hz, 2H), 2.23−2.17 (m, 1H), 2.10−2.0 (m, 1H), 1.41 (dd, J = 6.8,

2.0 Hz, 6H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 154.7, 146.9,

140.8, 133.7, 128.8, 128.6, 128.5, 128.4, 127.0, 126.4, 102.4, 58.5,

46.5, 36.2, 28.7, 21.3, 19.8. HRMS (ESI) m/z: [M + Na]⁺calcd for

C₂₁H₂₃NO₂Na 344.1621; found 344.1624.

Data for (Z)-5-Benzylidene-3-pentyl-4-propyloxazolidin-2-one

(5f). Puriﬁcation by ﬂash chromatography (petroleum/EtOAc =

15:1): a yellow oil (261.2 mg, 91%); ¹H NMR (400 MHz, CDCl₃) δ

7.59 (d, J = 7.6 Hz, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.22 (t, J = 7.0 Hz,

1H), 5.47 (d, J = 2.0 Hz, 1H), 4.53 (m, 1H), 3.63−3.56 (m, 1H),

3.05−2.99 (m, 1H), 1.89−1.81 (m, 1H), 1.73−1.51 (m, 3H), 1.42−

1.29 (m, 6H), 0.97−0.90 (m, 6H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 155.3, 147.1, 133.8, 128.6, 128.4, 126.9, 102.4, 58.5, 41.5,

34.6, 28.9, 27.0, 22.4, 16.0, 14.1, 14.0. HRMS (ESI) m/z: [M + Na]⁺

calcd for C₁₈H₂₅NO₂Na 310.1783; found 310.1772.

Data for 3-(tert-Butyl)-5-methyleneoxazolidin-2-one (3j).⁹Puri-

ﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a white

1

solid (134.9 mg, 87%), M.P. = 54.0−54.7 °C; H NMR (400 MHz,

CDCl₃) δ 4.65−4.63 (m, 1H), 4.22 (t, J = 2.4 Hz, 2H), 4.21−4.19

(m, 1H), 1.39 (s, 9H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 154.3,

149.2, 85.5, 53.9, 46.8, 27.5.

Data for 3-Cyclohexyl-5-methyleneoxazolidin-2-one (3k).^12a

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a

yellow oil (168.5 mg, 93%); ¹H NMR (400 MHz, CDCl₃) δ 4.69 (dd,

J = 2.8, 5.6 Hz, 1H), 4.25 (dd, J = 5.2, 2.4 Hz, 1H), 4.10 (t, J = 2.4 Hz,

2H), 3.69−3.66 (m, 1H), 1.80−1.77 (m, 4H), 1.66−1.62 (m, 1H),

1.34−1.29 (m, 4H), 1.12−1.01 (m, 1H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 154.9, 149.6, 86.2, 52.3, 44.1, 30.2, 25.3, 25.2.

Data for 4,4-Dimethyl-5-methyleneoxazolidin-2-one (3l).⁹Puri-

ﬁcation by ﬂash chromatography (petroleum/EtOAc = 2:1): a

1

colorless oil (115.9 mg, 91%); H NMR (400 MHz, CDCl₃) δ 6.71

Data for (Z)-5-Benzylidene-3-cyclohexyl-4-propyloxazolidin-2-

(brs, 1H), 4.53 (dd, J = 3.6, 1.2 Hz, 1H), 4.22 (d, J = 3.6 Hz, 1H),

one (5g).^12bPuriﬁcation by ﬂash chromatography (petroleum/

K

https://dx.doi.org/10.1021/acs.joc.0c02065

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

pubs.acs.org/joc

Article

EtOAc = 15:1): a white solid (260.5 mg, 87%), M.P. = 130.5−131.4

°C; ¹H NMR (400 MHz, CDCl₃) δ 7.58 (d, J = 7.6 Hz, 2H), 7.34 (t, J

= 7.8 Hz, 2H), 7.21 (t, J = 7.4 Hz, 1H), 5.42 (d, J = 1.6 Hz, 1H),

4.56−4.53 (m, 1H), 3.55−3.47 (m, 1H), 1.98−1.94 (m, 1H), 1.92−

1.76 (m, 5H), 1.76−1.63 (m, 2H), 1.60−1.56 (m, 1H), 1.46−1.27

(m, 4H), 1.23−1.15 (m, 1H), 0.96 (t, J = 7.2 Hz, 3H); ¹³C{¹H} NMR

(100 MHz, CDCl₃) δ 154.8, 147.6, 133.9, 128.6, 128.4, 126.8, 101.9,

58.9, 54.4, 36.9, 31.5, 30.1, 26.0, 26.0, 25.4, 15.7, 14.0.

Data for (Z)-3-Butyl-5-(4-ﬂuorobenzylidene)-4-propyloxazolidin-

2-one (5n).^12bPuriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 15:1): a yellow oil (247.3 mg, 85%); H NMR (400 MHz,

CDCl₃) δ 7.57 (m, 2H), 7.03 (m, 2H), 5.43 (d, J = 2.0 Hz, 1H), 4.51

(s, 1H), 3.64−3.56 (m, 1H), 3.06−2.99 (m, 1H), 1.89−1.81 (m, 1H),

1.71−1.65 (m, 1H), 1.60−1.54 (m, 2H), 1.44−1.28 (m, 4H), 0.97 (t,

J = 7.2 Hz, 6H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 162.8, 160.4,

155.2, 146.7, 130.1, 130.0, 129.9, 129.9, 115.6, 115.4, 101.4, 58.5,

41.3, 34.5, 29.4, 20.1, 16.0, 14.0, 13.8.

1

Data for (Z)-5-Benzylidene-4-ethyl-3-phenethyloxazolidin-2-one

Data for 3-(4-Methoxyphenyl)-5-methyleneoxazolidin-2-one

(7a).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

10:1): a yellow oil (190.7 mg, 93%); ¹H NMR (400 MHz, CDCl₃) δ

7.45 (d, J = 9.2 Hz, 2H), 6.92 (d, J = 8.8 Hz, 2H), 4.85−4.83 (m,

1H), 4.82 (s, 2H), 4.41−4.40 (m, 1H), 3.81 (s, 3H); ¹³C{¹H} NMR

(100 MHz, CDCl₃) δ 156.9, 152.8, 148.0, 130.5, 120.4, 114.6, 87.1,

55.7, 49.1. HRMS (ESI) m/z: [M + Na]⁺calcd for C₁₁H₁₁NO₃Na

228.0631; found 228.0643.

(5h). Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1):

1

a yellow solid (270.2 mg, 88%), M.P. = 125.9−126.4 °C; H NMR

(400 MHz, CDCl₃) δ 7.58 (d, J = 7.6 Hz, 2H), 7.35−7.30 (m, 4H),

7.26−7.21 (m, 4H), 5.41 (d, J = 1.6 Hz, 1H), 4.34−4.32 (m, 1H),

3.93−3.86 (m, 1H), 3.26−3.19 (m, 1H), 3.01−2.86 (m, 2H), 1.94−

1.84 (m, 1H), 1.74−1.64 (m, 1H), 0.88 (t, J = 7.2 Hz, 3H); ¹³C{¹H}

NMR (100 MHz, CDCl₃) δ 155.3, 146.6, 138.2, 133.7, 128.9, 128.8,

128.6, 128.4, 127.0, 126.9, 102.6, 59.6, 42.9, 33.9, 25.0, 6.7; HRMS

(ESI) m/z: [M + Na]⁺calcd for C₂₀H₂₁NO₂Na 330.1470; found

330.1461.

Data for 5-Methylene-3-phenyloxazolidin-2-one (7b).¹¹Puriﬁca-

tion by ﬂash chromatography (petroleum/EtOAc = 10:1): a white

solid (152.4 mg, 87%), M.P. = 134.1−135.0 °C; ¹H NMR (400 MHz,

CDCl₃) δ 7.55 (d, J = 8.0 Hz, 2H), 7.42 (t, J = 7.2 Hz, 2H), 7.19 (t, J

= 7.4 Hz, 1H), 4.87−4.84 (m, 1H), 4.65 (t, J = 2.4 Hz, 2H), 4.44−

4.23 (m, 1H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 152.5, 147.8,

137.3, 129.4, 124.7, 118.3, 87.3, 48.6.

Data for (Z)-5-Benzylidene-3-cyclohexyl-4-phenyloxazolidin-2-

one (5i).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc

1

= 15:1): a white solid (307.7 mg, 93%), M.P. = 127.4−129.6 °C; H

NMR (400 MHz, CDCl₃) δ 7.50−7.7.15 (m, 10H), 5.40 (d, J = 1.6

Hz, 1H), 5.15 (d, J = 2.0 Hz, 1H), 3.57−3.51 (m, 1H), 1.78−1.53 (m,

6H), 1.28−0.93 (m, 4H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 154.9,

148.5, 139.7, 133.7, 129.2, 128.5, 128.4, 127.9, 126.9, 104.3, 63.3,

54.8, 31.3, 30.1, 25.8, 25.2.

Data for (Z)-5-Benzylidene-3-isopropyloxazolidin-2-one (7c).⁹

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 10:1): a

yellow oil (197.5 mg, 91%); ¹H NMR (400 MHz, CDCl₃) δ 7.47 (d, J

= 7.6 Hz, 2H), 7.06 (t, J = 7.8 Hz, 2H), 7.12 (t, J = 7.6 Hz, 1H), 5.40

(t, J = 2.0 Hz, 1H), 4.13−4.07 (m, 3H), 1.13 (d, J = 6.8 Hz, 6H);

¹³C{¹H} NMR (100 MHz, CDCl₃) δ 154.7, 142.4, 133.7, 128.4,

Data for (Z)-5-Benzylidene-3-butyl-4-phenyloxazolidin-2-one

(5j).^12aPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

1

5:1): a yellow oil (276.3 mg, 90%); H NMR (400 MHz, CDCl₃) δ

128.2, 126.7, 102.8, 44.9, 44.2, 19.8.

7.52 (d, J = 7.2 Hz, 2H), 7.45−7.40 (m, 3H), 7.34−7.25 (m, 4H),

7.20−7.16 (m, 1H), 5.38 (d, J = 2.0 Hz, 1H), 5.25 (d, J = 2.0 Hz,

1H), 3.55−3.41 (m, 1H), 2.86−2.79 (m, 1H), 1.50−1.41 (m, 2H),

1.35−1.21 (m, 2H), 0.88 (t, J = 7.4 Hz, 3H); ¹³C{¹H} NMR (100

MHz, CDCl₃) δ 155.2, 147.8, 137.4, 133.6, 129.5, 129.4, 128.5, 128.4,

127.9, 127.0, 104.6, 64.0, 41.7, 29.1, 19.9, 13.7. HRMS (ESI) m/z: [M

+ H]⁺calcd for C₂₀H₂₁NO₂H 308.1652; found 308.1645.

Data for (Z)-3-Benzyl-5-benzylideneoxazolidin-2-one (7d).⁹

Puriﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a

1

yellow solid (238.5 mg, 90%), M.P. = 164.9−165.3 °C; H NMR

(400 MHz, CDCl₃) δ 7.56 (d, J = 8.8 Hz, 2H), 7.41−7.30 (m, 7H),

7.22 (t, J = 7.2 Hz, 1H), 5.46 (t, J = 2.0 Hz, 1H), 4.53 (s, 2H), 4.18

(d, J = 2.4 Hz, 2H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.8,

141.8, 135.0, 133.5, 129.2, 128.6, 128.5, 128.4, 128.3, 127.0, 103.3,

48.3, 48.1.

Data for (Z)-5-Benzylidene-3-(cyclopropylmethyl)-4-phenyloxa-

zolidin-2-one (5k).³¹Puriﬁcation by ﬂash chromatography (petro-

leum/EtOAc = 10:1): a white solid (271.5 mg, 89%), M.P. = 130.7−

Data for (Z)-3-Benzyl-5-ethylideneoxazolidin-2-one (7e).⁹Puri-

ﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a yellow

1

131.6 °C; H NMR (400 MHz, CDCl₃) δ 7.53 (d, J = 7.6 Hz, 2H),

1

solid (142.1 mg, 70%), M.P. = 39.4−39.9 °C; H NMR (400 MHz,

7.46−7.38 (m, 3H), 7.35−7.33 (m, 2H), 7.29 (t, J = 7.6 Hz, 2H),

7.18 (t, J = 7.4 Hz, 1H), 5.56 (s, 1H), 5.25 (s, 1H), 3.59 (dd, J = 6.4,

14.4 Hz, 1H), 2.61 (dd, J = 8.0, 14.8 Hz, 1H), 1.56 (s, 1H), 0.57−

0.48 (m, 1H), 0.46−0.37 (m, 1H), 0.14−0.08 (m, 2H); ¹³C{¹H}

NMR (100 MHz, CDCl₃) δ 155.3, 148.0, 137.5, 133.6, 129.4, 129.4,

128.6, 128.5, 127.9, 127.0, 104.6, 63.9, 46.8, 9.0, 4.8, 2.6.

CDCl₃) δ 7.38−7.26 (m, 5H), 4.58−4.52 (m, 1H), 4.46 (s, 2H),

3.97−3.95 (m, 2H), 1.68−1.65 (m, 3H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 156.1, 141.8, 135.3, 129.0, 128.2, 97.7, 47.9, 47.2, 10.0.

HRMS (EI) m/z: [M]⁺calcd for C₁₂H₁₃NO₂203.0946; found

203.0939.

Data for 3-Benzyl-6-methyl-3,4-dihydro-2H-1,3-oxazin-2-one

(8e).⁹Puriﬁcation by ﬂash chromatography (petroleum/EtOAc =

Data for (Z)-3-Butyl-5-(4-methylbenzylidene)-4-phenyloxazoli-

din-2-one (5l).^12aPuriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 15:1): a yellow solid (295.3 mg, 92%), M.P. = 129.1−129.7

1

5:1): a yellow oil (142.1 mg, 70%); H NMR (400 MHz, CDCl₃) δ

7.37−7.30 (m, 5H), 4.76−4.75 (m, 1H), 4.57 (s, 2H), 3.68−3.70 (m,

2H), 1.85 (d, J = 1.2 Hz, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ

151.1,148.2, 135.8, 128.9, 128.4, 128.0, 94.6, 52.2, 44.8, 18.5.

Data for (Z)-5-Benzylidene-3-isopropyl-4-propyloxazolidin-2-

one (7f).⁹Puriﬁcation by ﬂash chromatography (petroleum/EtOAc

= 10:1): a yellow oil (139.9 mg, 54%); ¹H NMR (400 MHz, CDCl₃)

δ 7.58 (d, J = 7.6 Hz, 2H), 7.32 (d, J = 7.6 Hz, 2H), 7.20 (d, J = 7.2

Hz, 1H), 5.43 (d, J = 1.6 Hz, 1H), 4.55−4.53 (m, 1H), 3.94−3.88 (m,

1H), 1.88−1.81 (m, 1H), 1.74−1.66 (m, 1H), 1.47−1.41 (m, 2H),

1.39−1.33 (m, 6H), 0.95 (t, J = 7.2 Hz, 3H); ¹³C{¹H} NMR (100

MHz, CDCl₃) δ 154.6, 147.4, 133.8, 128.6, 128.4, 126.8, 102.0, 58.9,

46.3, 36.7, 21.1, 19.7, 15.7, 14.0. HRMS (ESI) m/z: [M + H]⁺calcd

for C₁₆H₂₁NO₂H 260.1647; found 260.1645.

1

°C; H NMR (400 MHz, CDCl₃) δ 7.45−7.39 (m, 5H), 7.34−7.32

(m, 2H), 7.11 (d, J = 8.4 Hz, 2H), 5.38 (d, J = 1.6 Hz, 1H), 5.22 (d, J

= 2.0 Hz, 1H), 3.55−3.47 (m, 1H), 2.85−2.78 (m, 1H), 2.31 (s, 3H),

1.49−1.42 (m, 2H), 1.34−1.25 (m, 2H), 0.89 (t, J = 7.4 Hz, 3H);

¹³C{¹H} NMR (100 MHz, CDCl₃) δ 155.3, 147.1, 137.6, 136.9,

130.7, 129.4, 129.4, 129.3, 128.4, 128.0, 104.6, 64.0, 41.7, 29.1, 21.3,

19.9, 13.8. HRMS (ESI) m/z: [M + H]⁺calcd for C₂₁H₂₃NO₂H

322.1804; found 322.1802.

Data for (Z)-3-Butyl-5-(4-ﬂuorobenzylidene)-4-phenyloxazoli-

din-2-one (5m).³²Puriﬁcation by ﬂash chromatography (petrole-

1

um/EtOAc = 15:1): a yellow oil (243.8 mg, 75%); H NMR (400

MHz, CDCl₃) δ 7.51−7.47 (m, 2H), 7.44−7.41 (m, 3H), 7.34−7.32

(m, 2H), 6.97 (t, J = 8.8 Hz, 2H), 5.38 (d, J = 1.6 Hz, 1H), 5.22 (d, J

= 2.0 Hz, 1H), 3.55−3.47 (m, 1H), 2.86−2.80 (m, 1H), 1.50−1.42

(m, 2H), 1.34−1.23 (m, 2H), 0.88 (t, J = 7.2 Hz, 3H); ¹³C{¹H} NMR

(100 MHz, CDCl₃) δ 162.9, 160.4, 155.0, 147.5, 147.4, 137.3, 130.1,

130.0, 129.8, 129.7, 129.5, 129.5, 127.9, 115.5, 115.3, 103.5, 63.9,

41.7, 29.0, 19.9, 13.7. HRMS (ESI) m/z: [M + Na]⁺calcd for

C₂₀H₂₀FNO₂Na 348.1376; found 348.1388.

Data for 3-Benzyl-6-methylene-1,3-oxazinan-2-one (7g).⁹Puri-

ﬁcation by ﬂash chromatography (petroleum/EtOAc = 5:1): a

colorless oil (123.8 mg, 61%); ¹H NMR (400 MHz, CDCl₃) δ

7.37−7.28 (m, 5H), 4.63 (d, J = 1.2 Hz, 1H), 4.58 (s, 2H), 4.23 (d, J

= 0.8 Hz, 1H), 3.21 (t, J = 6.2 Hz, 2H), 2.54 (t, J = 6.4 Hz, 2H);

¹³C{¹H} NMR (101 MHz, CDCl₃) δ 152.8, 151.3, 136.2, 128.9,

128.2, 128.0, 93.0, 52.8, 43.2, 26.3.

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Article

Data for 5-Methyleneoxazolidin-2-one (7h). Puriﬁcation by ﬂash

128.7, 128.6, 128.5, 128.3, 127.0, 126.3, 101.1, 65.6, 41.8, 40.6, 31.5,

30.1, 27.5, 20.5, 13.9. HRMS (ESI) m/z: [M + Na]⁺calcd for

C₂₃H₂₇NO₂Na 372.1934; found 372.1926.

chromatography (petroleum/EtOAc = 2:1): a white solid (158.4 mg,

1

80%), M.P. = 56.2−57.5 °C; H NMR (400 MHz, CDCl₃) δ 5.95

Data for (Z)-3-Benzyl-5-benzylidene-4,4-dimethyloxazolidin-2-

(brs, 1H), 4.79−4.76 (m, 1H), 4.31−4.30 (m, 1H), 4.26−4.24 (m,

2H); ¹³C{¹H} NMR (101 MHz, CDCl₃) δ 157.5, 151.4, 87.1, 44.4.

Data for (Z)-4-Benzylidene-3-oxa-1-azaspiro[4.5]decan-2-one

(7i).^7bPuriﬁcation by ﬂash chromatography (petroleum/EtOAc =

one (7p).¹⁶Puriﬁcation by ﬂash chromatography (petroleum/EtOAc

1

= 15:1): a white solid (263.7 mg, 90%), M.P.= 83.0−84.2 °C; H

NMR (400 MHz, CDCl₃) δ 7.61−7.59 (m, 2H), 7.38 (m, 7H), 7.24−

7.19 (m, 1H), 5.45 (s, 1H), 4.52 (s, 2H), 1.39 (s, 6H); ¹³C{¹H} NMR

(100 MHz, CDCl₃) δ 154.9, 153.5, 137.6, 133.7, 128.9, 128.6, 128.5,

127.9, 127.9, 127.0, 100.8, 62.6, 44.3, 27.9.

1

10:1): a white solid (226.0 mg, 93%), M.P. = 198.4−199.0 °C; H

NMR (400 MHz, CDCl₃) δ 7.95 (s, 1H), 7.60 (d, J = 7.2 Hz, 2H),

7.33 (t, J = 7.8 Hz, 2H), 7.21 (t, J = 7.4 Hz, 1H), 5.47 (s, 1H), 1.97

(d, J = 12.0 Hz, 2H), 1.84 (d, J = 11.2 Hz, 3H), 1.69−1.62 (m, 2H),

1.56−1.45 (m, 2H), 1.30−1.24 (m, 1H); ¹³C{¹H} NMR (100 MHz,

CDCl₃) δ 156.3, 154.9, 133.7, 128.6, 128.5, 126.9, 101.3, 62.6, 38.6,

24.9, 22.6.

Data for (Z)-5-Benzylidene-3-butyl-4,4-dimethyloxazolidin-2-

one (7q).¹⁶Puriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 20:1): a colorless oil (238.3 mg, 92%); ¹H NMR (400

MHz, CDCl₃) δ 7.60−7.58 (m, 2H), 7.34−7.31 (m, 2H), 7.22−7.18

(m, 1H), 5.45 (s, 1H), 3.21 (t, J = 8.0 Hz, 2H), 1.70−1.62 (m, 2H),

1.50 (s, 6H), 1.43−1.33 (m, 2H), 0.98 (t, J = 7.2 Hz, 3H); ¹³C{¹H}

NMR (100 MHz, CDCl₃) δ 154.3, 153.6, 133.8, 128.6, 128.4, 126.9,

100.5, 62.3, 40.6, 31.7, 27.8, 20.4, 13.9.

Data for (Z)-4-(Pyridin-2-ylmethylene)-3-oxa-1-azaspiro[4.5]-

decan-2-one (7j).^7bPuriﬁcation by ﬂash chromatography (petro-

leum/EtOAc = 5:1): a brown solid (219.6 mg, 90%), M.P. = 182.6−

1

183.9 °C; H NMR (400 MHz, CDCl₃) δ 8.53−8.51 (m, 1H), 7.97

Preparation of Single Crystals. The crystalline material was

prepared via a layer-to-layer diﬀusion method. The copper complexes

1a−d were added into the mixture solution of dichloromethane

(DCM)/MeOH = 10:1 (1 mL) and layered with hexane. After 1 day,

a crystal suitable for single-crystal X-ray diﬀraction was obtained.

Crystallographic data of the structures were deposited in the

Cambridge Crystallographic Database Center, supplementary pub-

lication nos. CCDC 2006734, 2007143, 2007142, and 2006733 for

copper complexes 1a−d, respectively.

Analytical Methods. The NMR spectra were recorded on a

Bruker Avance III HD 400 spectrometer using tetramethylsilane

(TMS) as an internal standard (400 MHz for ¹H NMR and 101 MHz

for ¹³C NMR). High-resolution mass spectroscopy (HRMS) data

were collected on a Bruker solanX 70 FT-MS and Agilent 6224 TOF

mass spectrometer. Single-crystal structure determination was

conducted on a Bruker D8 Venture X-ray diﬀractometer equipped

with a PHOTON II CPAD detector. FT-IR spectra were recorded on

a Shimadzu IRTracer-100.

Computational Methods. The DFT calculations were performed

using the Gaussian 09 program,²⁶which has been widely used in

transition metal catalytic reactions.³³The geometries were fully

optimized using the B3LYP method.²⁷The basis set 6-31+G(d,p) was

employed for all of the atoms. Then, frequency calculations at the

same level of theory were carried out to identify all of the stationary

points as minima (zero imaginary frequency) and to provide

corrections for potential energy (E + ZPVE).

(d, J = 8.8 Hz, 1H), 7.91(s, 1H), 7.67−7.63 (m, 1H), 7.11−7.07 (m,

1H), 5.79 (s, 1H), 1.97−1.91 (m, 2H), 1.84−1.81 (m, 3H), 1.73−

1.66 (m, 2H), 1.53−1.44 (m, 2H), 1.37−1.22 (m, 1H); ¹³C{¹H}

NMR (100 MHz, CDCl₃) δ 157.8, 155.9, 153.3, 149.3, 136.5, 123.7,

121.5, 102.9, 62.9, 38.4, 24.9, 22.5; HRMS (ESI) m/z: [M + H]⁺

calcd for C₁₄H₁₆N₂O₂H 245.1285; found 245.1292.

Data for (Z)-4-(Thiophen-2-ylmethylene)-3-oxa-1-azaspiro[4.5]-

decan-2-one (7k).^7bPuriﬁcation by ﬂash chromatography (petro-

leum/EtOAc = 2:1): a brown solid (229.0 mg, 92%), M.P. = 250.7−

1

251.3 °C; H NMR (400 MHz, CDCl₃) δ 7.58 (s, 1H), 7.25 (d, J =

5.6 Hz, 1H), 7.14 (d, J = 3.6 Hz, 1H), 7.10−6.99 (m, 1H), 5.77 (s,

1H), 1.95 (d, J = 12.8 Hz, 2H), 1.82 (d, J = 10.4 Hz, 3H), 1.66−1.59

(m, 2H), 1.54−1.44 (m, 2H), 1.35−1.23 (m, 1H); ¹³C{¹H} NMR

(100 MHz, CDCl₃) δ 155.8, 153.4, 136.4, 127.1, 126.1, 125.3, 95.6,

62.1, 38.4, 24.9, 22.5.

Data for (Z)-4-Benzylidene-1-butyl-3-oxa-1-azaspiro[4.5]decan-

2-one (7l).^12bPuriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 10:1): a colorless oil (239.2 mg, 80%); ¹H NMR (400 MHz,

CDCl₃) δ 7.63 (d, J = 7.2 Hz, 2H), 7.33 (t, J = 7.6 Hz, 2H), 7.20 (t, J

= 7.8 Hz, 1H), 5.80 (s, 1H), 3.18 (t, J = 8.0 Hz, 2H), 1.86−1.78 (m,

7H), 1.15−1.69 (m, 2H), 1.69−1.61 (m, 2H), 1.41−1.32 (m, 2H),

1.29−1.26 (m, 1H), 0.95 (t, J = 7.2 Hz, 3H); ¹³C{¹H} NMR (100

MHz, CDCl₃) δ 154.4, 152.5, 134.1, 128.8, 128.5, 126.9, 103.8, 64.1,

40.3, 34.3, 31.8, 24.3, 21.7, 20.4, 13.9.

Data for (Z)-1-Butyl-4-(4-methylbenzylidene)-3-oxa-1-azaspiro-

[4.5]decan-2-one (7m).^12bPuriﬁcation by ﬂash chromatography

(petroleum/EtOAc = 10:1): a colorless oil (237.9 mg, 76%); ¹H

NMR (400 MHz, CDCl₃) δ 7.52 (d, J = 8.0 Hz, 2H), 7.14 (d, J = 7.2

Hz, 2H), 5.77 (s, 1H), 3.17 (t, J = 8.0 Hz, 2H), 2.33 (s, 3H), 1.85−

1.78 (m, 7H), 1.74−1.61 (m, 4H), 1.41−1.32 (m, 2H), 1.28−1.24

(m, 1H), 0.95 (t, J = 7.2 Hz, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃)

δ 154.5, 151.8, 136.6, 131.2, 129.2, 128.7, 103.7, 64.0, 40.3, 34.3, 31.8,

24.3, 21.7, 21.3, 20.4, 13.9.

Data for (Z)-5-Benzylidene-3-butyl-4-methyl-4-propyloxazoli-

din-2-one (7n). Puriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 15:1): a colorless oil (266.9 mg, 93%); ¹H NMR (400 MHz,

CDCl₃) δ 7.60 (d, J = 7.2 Hz, 2H), 7.33 (t, J = 8.0 Hz, 2H), 7.21 (t, J

= 7.4 Hz, 1H), 5.41 (s, 1H), 3.33−3.26 (m, 1H), 3.04−2.97 (m, 1H),

1.82−1.55 (m, 4H), 1.48 (s, 3H), 1.43−1.15 (m, 4H), 0.96 (t, J = 7.4

Hz, 3H), 0.90 (t, J = 7.4 Hz, 3H); ¹³C{¹H} NMR (100 MHz, CDCl₃)

δ 154.8, 152.3, 133.9, 128.6, 128.4, 126.8, 100.7, 65.6, 42.3, 40.5, 31.5,

27.4, 20.5, 17.0, 13.9, 13.9. HRMS (ESI) m/z: [M + Na]⁺calcd for

C₁₈H₂₅NO₂Na 310.1778; found 310.1773.

ASSOCIATED CONTENT

* Supporting Information

■

sı

The Supporting Information is available free of charge at

https://pubs.acs.org/doi/10.1021/acs.joc.0c02065.

Single-crystal data of the copper complexes 1a−d and

NMR spectra of the prepared oxazolidinones (PDF)

Accession Codes

CCDC 2006733−2006734 and 2007142−2007143 contain

the supplementary crystallographic data for this paper. These

data can be obtained free of charge via www.ccdc.cam.ac.uk/

data_request/cif, or by emailing data_request@ccdc.cam.ac.

uk, or by contacting The Cambridge Crystallographic Data

Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44

1223 336033.

Data for (Z)-5-Benzylidene-3-butyl-4-methyl-4-phenethyloxazo-

lidin-2-one (7o). Puriﬁcation by ﬂash chromatography (petroleum/

EtOAc = 20:1): a colorless oil (317.6 mg, 91%); ¹H NMR (400 MHz,

CDCl₃) δ 7.64 (d, J = 7.2 Hz, 2H), 7.35 (t, J = 7.8 Hz, 2H), 7.28−

7.22 (m, 3H), 7.21−7.16 (m, 1H), 7.12 (d, J = 6.8 Hz, 2H), 5.50 (s,

1H), 3.33−3.26 (m, 1H), 3.08−3.01 (m, 1H), 2.67−2.59 (m, 1H),

2.51−2.43 (m, 1H), 2.16−2.10 (m, 1H), 1.95−1.91 (m, 1H), 1.78−

1.63 (m, 2H), 1.53 (s, 3H), 1.44−1.35 (m, 2H), 0.97 (t, J = 7.4 Hz,

3H); ¹³C{¹H} NMR (100 MHz, CDCl₃) δ 154.8, 151.8, 140.7, 133.7,

AUTHOR INFORMATION

Corresponding Authors

■

Donghui Wei − College of Chemistry, Center of

Computational Chemistry, Zhengzhou University, Zhengzhou

450001, China; orcid.org/0000-0003-2820-282X;

Email: donghuiwei@zzu.edu.cn

M

https://dx.doi.org/10.1021/acs.joc.0c02065

J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry

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Article

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W.; Zhou, Z.-H.; He, L.-N. Efficient, selective and sustainable catalysis

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Ning Liu − School of Chemistry and Chemical Engineering,

Key Laboratory for Green Processing of Chemical Engineering

of Xinjiang Bingtuan, Shihezi University, Shihezi, Xinjiang

832003, China; orcid.org/0000-0001-7299-0400;

Phone: (+0086)-0993-205-7277; Email: ningliu@

shzu.edu.cn, ninglau@163.com; Fax: (+0086)-0993-205-

7270

Bin Dai − School of Chemical Engineering and Technology,

Tianjin University, Tianjin 300072, China; School of

Chemistry and Chemical Engineering, Key Laboratory for

Green Processing of Chemical Engineering of Xinjiang

Bingtuan, Shihezi University, Shihezi, Xinjiang 832003,

China; Email: dbinly@126.com

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Authors

Fei Chen − School of Chemical Engineering and Technology,

Tianjin University, Tianjin 300072, China

Sheng Tao − School of Chemistry and Chemical Engineering,

Key Laboratory for Green Processing of Chemical Engineering

of Xinjiang Bingtuan, Shihezi University, Shihezi, Xinjiang

832003, China

Qian-Qian Deng − College of Chemistry, Center of

Computational Chemistry, Zhengzhou University, Zhengzhou

450001, China

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catalyzed selective synthesis of enol carbamates by fixation of carbon

dioxide. Tetrahedron Lett. 1987, 28, 4417−4418.

Complete contact information is available at:

https://pubs.acs.org/10.1021/acs.joc.0c02065

̈

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(f) Fujita, K.-i.; Inoue, K.; Sato, J.; Tsuchimoto, T.; Yasuda, H.

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Author Contributions

N.L., B.D., and F.C. conceived the idea and designed the

experiments. F.C. performed the synthetic experiments and

instrumental analysis. S.T. carried out the synthetic experi-

ments of Cu complexes. Q.-Q.D. and D.W. contributed to the

DFT theoretical calculations. N.L., F.C., and B.D. wrote the

paper, and proposed valuable advice for improving the paper.

All authors discussed the results and commented on the

manuscript.

Notes

The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

This work was supported by the National Natural Science

Foundation of China (21868033), the Xinjiang Bingtuan

Young and Middle-Aged Leading Scientists Program

(2020CB027), the Shihezi Young and Middle-Aged Leading

Scientists Program (2019RC01), the International Partnership

Program of Shihezi University (GJHZ201908), and the

Double First-Class Program of Shihezi University (SHYL-

ZD201801). We thank Ji-Xing Zhao for his assistance with the

single-crystal X-ray diﬀraction, located at the Analysis and

Testing Center, Shihezi University.

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Binuclear Tridentate Hemilabile Copper(I) Catalysts for Utilization of CO2into Oxazolidinones from Propargylic Amines

DOI: 10.1021/acs.joc.0c02065

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