Hollow organic polymeric nano-bowls-supported BINOL-derived chiral phosphoric acid: enhanced catalytic performances in the enantioselective allylation of aromatic aldehydes

Article abstract of DOI:10.1016/j.mcat.2018.12.014

To improve the catalytic efficiency of expensive and versatile 1, 1′-binaphthol-derived chiral phosphoric acid with 2, 4, 6-tris(isopropyl)phenyl substituents and mass transfer of reactants in heterogeneous catalysis, a hollow organic polymeric nano-bowl

Full text of DOI:10.1016/j.mcat.2018.12.014

MolecularCatalysis464(2019)39–47
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
Hollow organic polymeric nano-bowls-supported BINOL-derived chiral
phosphoric acid: enhanced catalytic performances in the enantioselective
allylation of aromatic aldehydes
Zhengwei Yan, Guangxin Xie, Jianing Zhang, Xuebing Ma⁎
Key Laboratory of Applied Chemistry of Chongqing Municipality, College of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
To improve the catalytic efficiency of expensive and versatile 1, 1′-binaphthol-derived chiral phosphoric acid
with 2, 4, 6-tris(isopropyl)phenyl substituents and mass transfer of reactants in heterogeneous catalysis, a hollow
organic polymeric nano-bowl was used as an effective catalyst support to anchor chiral phosphoric acid through
the copolymerization of vinylated 1, 1′-binaphthol with 2, 4, 6-tris(isopropyl)phenyl substituents with styrene on
the surface of polystyrene nanosphere core, etching polystyrene nanosphere by DMF and then phosphorylation
by POCl3. From the comparative kinetic investigation on the reaction rate of reactant in the asymmetric allyl-
boration of 4-chlorobenzaldehyde with allylboronic pinacol ester, the as-fabricated hollow organic polymeric
nano-bowl-supported chiral phosphoric acid displayed higher catalytic rates than ever-reported similar catalyst
and possessed a constant catalytic rate (0.031 mol L−1 h−1) during the whole process. The expanded scope of
aromatic aldehydes further proved that the hollow organic polymeric nano-bowl-supported chiral phosphoric
acid was more highly active and enantioselective owing to its thin shell thickness (18 nm) and hollow structure.
Due to the constant phosphorus content and well-shaped morphology of the 6th-reused catalyst, the yield of (R)-
1-phenylbut-3-en-1-ol (95%) with a slightly lowered enantioselectivity (94% ee) remained constant in the sixth
run. Moreover, the lowered enantioselectivity of the 6th-reused catalyst could be restored by hydrochloric acid
to achieve its original enantioselectivity (96% ee), and the prothetic hollow organic polymeric nano-bowl-
supported chiral phosphoric acid could effectively promote the asymmetric allylboration reaction in high yields
(92–95%) with excellent enantioselectivities (94–96% ee) for another six cycles.
Heterogeneous organocatalysis
Chiral phosphoric acid
Enhanced catalytic performance
Hollow nano-bowl
Allylation
1. Introduction
enantioselective Brønsted acid catalyst [8–12], and was widely used in
the various asymmetric catalytic transformations such as transfer hy-
The driving force for the development of heterogeneous en-
antioselective metal catalyst and organocatalyst stemmed from the
practical advantages they might offer over their homogeneous coun-
terparts in terms of process scalability, catalyst reusability, cost and
purification [1–3]. Recently, due to the spectacular synthesis of well-
shaped metal catalysts, heterogeneous metal catalysis paid special at-
tention to the morphology-dependant catalytic performance of metal
catalysts [4,5]. Although the well-controlled construction of organic
polymer-supported organocatalyst was still in its infancy, the clues in
enhanced catalytic activity had also gradually drawn more attentions
[6].
drogenation [13–17], cycloaddition [18–20], cascade multi-component
reaction [21–23], rearrangement [24,25], Mannich reaction [26], hy-
droxyalkylation [27], desymmetrization [28], Friedel-Crafts reactions
[29–31] and miscellaneous cyclizations [32,33]. However, versatile
TRIP presented a main disadvantage of long and tedious reaction se-
quences required for its preparation from chiral BINOL, resulting in the
extremely high cost of TRIP in large-scale application. From the per-
spective of large-scale application, achieving the sustainability and ef-
ficiency of TRIP could significantly reduce its high cost, although ad-
ditional modifications were needed. One strategy was the
immobilization of TRIP onto solid support to effectively reduce its high
cost owing to the recovery and reuse of TRIP [34–38]. Among them,
polystyrene-supported TRIP (PS-TRIP) was used as a famous abun-
dantly recyclable catalyst for the highly enantioselective allylboration
1, 1′-binaphthol (BINOL)-derived chiral phosphoric acid with the 2,
4, 6-tris(isopropyl)phenyl substituents in the 3, 3′ positions, commonly
known as TRIP [7], had proved to be the most successful and versatile
⁎ Corresponding author.
E-mail address: zcj123@swu.edu.cn (X. Ma).
https://doi.org/10.1016/j.mcat.2018.12.014
Received 21 October 2018; Received in revised form 17 December 2018; Accepted 18 December 2018
Availableonline28December2018
2468-8231/©2018ElsevierB.V.Allrightsreserved.

Z. Yan et al.
MolecularCatalysis464(2019)39–47
of aldehydes in batch and flow [36]. Another strategy was the further
enhancement of catalytic efficiency of supported TRIP by improving the
accessibility of reactants to the catalytic sites of TRIP. However, to the
best of our knowledge, no attention was paid on the further improve-
ment in mass transfer of reactants and effectiveness factor (η) of an-
chored TRIP.
ppm relative to the hydrogen and carbon resonances of TMS. The
loading capacity of phosphoric acid was determined by ICP-OES/ICP-
MS Agilent 725 after the sample was digested. The morphology was
observed by JEM-2100 F scanning electron microscopy and S-4800
transmission electron microscope, respectively operated at 10 kV and
200 kV. FT-IR spectroscopy was performed on a Perkin-Elmer model GX
spectrometer using the KBr pellet. The enantiomeric excesses (% ee) of
products were determined by Agilent LC-1200 HPLC with a UV–vis
detector on Daicel Chiralpak chiral column using heptane/isopropanol
as the eluents.
The enhancement of mass transfer of reactants to active catalytic
sites had always been one of the most consistently pursued research
topics in the field of heterogeneous catalysis. Owing to hollow interior
and well-shaped morphology, hollow nanospheres displayed the ex-
quisite advantages such as large specific surface area and pore volume,
high loading capacity of catalyst and internal/external concentration
difference in heterogeneous catalysis [39,40]. Recently, the hollow
structures [41–44] and well-shaped nanosphere [45] in the improved
mass transfer of reactants and products into and out catalyst backbone
in heterogeneous organocatalysis were highlighted. In this paper, to
take advantage of the merits of hollow structure and thin shell thick-
ness, hollow organic polymeric nano-bowls-supported BINOL-derived
chiral phosphoric acid (HOPBs-TRIP) was fabricated for the first time
via the first copolymerization of (R)-6 with styrene on the surface of
poly(styrene/acrylic acid) nanosphere (PS), subsequent etching PS by
DMF and final functionalization by POCl3 (Scheme 1). Due to the ef-
fective improvement in the mass transfer of reactants resulted from
hollow structure and thin shell thickness (18 nm), the as-fabricated
HOPBs-TRIP displayed higher catalytic performances including activ-
ities and enantioselectivities than ever-reported PS-TRIP in the het-
erogeneous enantioselective allylation of aldehydes [36] and showed
better economical efficiency than homogeneous TRIP.
2.2. General preparation of hollow organic polymeric nano-bowls-supported
HOPBs-BINOL
After PS core (800 mg) was well-dispersed under magnetic stirring
for 12 h at room temperature in the mixed solvents of DMSO (21 mL)
and DI water (7 mL) containing polyvinyl alcohol (PVA, 0.5 wt%), a
DMSO solution (4 mL) of styrene (208 mg, 2.0 mmol), (R)-6 (270 mg,
0.3 mmol) and ethylene glycol dimethyl acrylate (EGDMA, 320 mg,
1.6 mmol) was injected by syringe and irradiated by ultrasound for
30 min. The translucent emulsion was added 3 mL of aqueous po-
tassium persulfate (KPS, 60 mg, 0.45 mmol), heated to 100 °C and
stirred for 48 h. Then 9 mL of the resulting emulsion was sampled,
added 1 mL of ethanol and isolated by centrifugal separation. The
combined solids (CS-BINOL) were dispersed in DMF (10 mL), irradiated
by ultrasound for 30 min and stirred for 3 h to remove PS core. The
isolated solid was repeatedly dealt with DMF twice, washed with
ethanol (10 m-l × 3) and dried naturally at room temperature to afford
hollow organic polymeric nano-bowls-supported HOPBs-BINOL
(423 mg) as a slightly yellow solid.
2. Experimental
2.1. Materials and sample characterization
2.3. Preparation of hollow organic polymeric nano-bowls-supported chiral
phosphoric acid (HOPBs-TRIP)
Styrene (St) was purified by distillation under reduced pressure
before use. Styryl-derived monomer (R)-6 and poly(styrene/acrylic
In a dried Schlenk tube (25 mL), HOPBs-BINOL (300 mg) was sus-
pended in a solution (5 mL) of dioxane containing triethylamine (3.0 u-
l, 4.0 × 10−3 mmol) under Ar for 0.5 h. Then, POCl3 (18 μ-l,
2.0 × 10−3 mmol) was added, and the reaction mixture was heated to
75 °C and stirred for 14 h. The resulting reaction mixture was added
THF (1 mL) and HCl solution (1 mol L-1, 1.5 mL) at room temperature,
heated to 50 °C, stirred for 15 h and diluted by ethanol (7 mL). The solid
acid) nanospheres (PS) (327
15 nm, n = 50) were synthesized ac-
cording to the procedures shown in ESI†. The other chemicals were of
analytical grade and used as received from commercial suppliers
without any further purification.
1H and 13C NMR spectra were conducted on a Bruker av-600 NMR
instrument, in which all chemical shifts were reported down-field in
Scheme 1. Preparation route to hollow organic polymeric nano-bowls-supported BINOL-derived chiral phosphoric acid (HOPBs-TRIP).
40

Z. Yan et al.
MolecularCatalysis464(2019)39–47
Fig. 1. SEM images of core-shelled CS-BINOL (a1–f1) and hollow nano-bowls-supported HOPBs–BINOL (a–f) under preparation conditions: (a1) 500 mg PS, 24 h,
40 mg KPS; (b1) 800 mg PS, 24 h, 40 mg KPS; (c1) 800 mg PS, 48 h, 40 mg KPS; (d1) 800 mg PS, 72 h, 40 mg KPS; (e1) 800 mg PS, 48 h, 60 mg KPS; (f1) 800 mg PS,
72 h, 80 mg KPS.
was isolated by centrifugal separation, washed with ethanol (10 m-
l × 3) and dried naturally at room temperature to give brown HOPBs-
TRIP (303 mg).
40 mg KPS in 35 mL of DMSO/H2O (v/v = 2.5) mixed solvents for 24 h.
As expected, two types of solid spheres, CS-BINOL (300–400 nm) and
nanospheres (20–40 nm) with different sizes, were observed from the
SEM image (Fig. 1a1), which were resulted from the copolymerization
under the control of PS and out of control of PS through different
emulsion models, respectively. Subsequently, by means of weight gain
of PS from 500 mg to 800 mg, the number of solid nanospheres
(20–40 nm) dropped to a large extent (Fig. 1b1) and the yield of PS-
templated HOPBs-BINOL increased from 370 mg to 418 mg (Fig. 1b),
which elucidated that the increased PS core strengthened the adsorp-
tion area and could effectively prevent the out of control generation of
self-polymeric nanospheres. Furthermore, the enhanced coating of
monomers on the surface of PS core was achieved by prolonging re-
action time (24 h→48 h →72 h) and increasing the dosage of initiator
KPS (40 mg → 80 mg), which was verified by the increased yields
(418 mg → 435 mg→452 mg) of PS-templated HOPBs-BINOL (Fig. 1c–f)
and the thicker outer shell thicknesses of CS-BINOL (22 nm → 28 nm→
32 nm, Fig. S2).
2.4. General procedure for heterogeneous enantioselective allylation of
aromatic aldehydes
A screw-cap reaction tube containing HOPBs-TRIP (66.7 mg, 5 mol
%) was evacuated, flushed with Ar and charged with freshly distilled
benzaldehyde (21.2 mg, 0.2 mmol) in toluene (1.0 mL). The reaction
mixture was cooled to −30 °C, followed by the addition of allylboronic
acid pinacol ester (36.9 mg, 0.22 mmol) dropwise and stirred for 6 h.
HOPBs-TRIP was recovered by centrifugal separation and directly re-
used in the following catalytic cycles. The centrifugate was loaded on a
silica gel column and purified by flash chromatography using PE/EA (v/
v = 10:1) to afford (R)-1-phenylbut-3-en-1-ol (28.1 mg, 95%) with 96%
ee as a colorless oil.
According to the following relationship of effectiveness factor (η)
and sphere radius (R) of catalyst in heterogenous catalysis [46,47], the
more effective diffusion coefficient (De) and shorter sphere radius (R)
are favorable for achieving a better effectiveness factor (η).
3. Results and discussion
3.1. Morphological control of HOPBs-TRIP
The EGDMA-cross-linked copolymerization of styryl-attached (R)-6
and styrene on the surface of PS core to successfully prepare well-
shaped spherical CS-BINOL was the most important and committed
step. According to the ever-reported investigation [42], the emulsifi-
cation of organic monomers together with PS in aqueous DMSO solu-
tion had two emulsion models—desired monomers around PS core and
adverse monomers without PS core. First, we set about preparing CS-
BINOL under the preliminary conditions: acrylamide (AA, 0.6 mmol),
EGDMA (1.6 mmol), St (2.0 mmol), (R)-6 (0.17 mmol), 500 mg PS and
3
1
1
⎛
⎜
⎞
⎟
η =
−
ϕ
tanhϕ
ϕ
(.1)
s
s
s
⎝
⎠
K1
De
ϕ = R
s
(.2)
where ϕs is Thiele modulus for sphere, k1 is first-order kinetic constant
(s−1), R is sphere radius (cm) and De is effective diffusion coefficient
(cm2 s-1). To achieve the shorter transmission distance (R) of reactants
41

Z. Yan et al.
MolecularCatalysis464(2019)39–47
42

Z. Yan et al.
MolecularCatalysis464(2019)39–47
regions at the bottom of HOPBs-BINOL, emblazoned with an arrow,
represented voids between two semi-shells and the dark regions were
the particle shells, which stated clearly that a part of the shells caved in
to enclose a void inside HOPBs-BINOL with a kippah structure.
3.2. Characterization of HOPBs-TRIP
In view of thin shell thickness in favor of mass transfer of reactants
and high content of (R)-6 beneficial to form more TRIP, the hollow
bowl-like HOPBs-BINOL with an average shell thickness of 18 nm was
selected as a precursor to prepare supported chiral phosphoric acid
HOPBs-TRIP by the reaction of phenolic hydroxyl groups in HOPBs-
BINOL with POCl3 and then hydrolysis of phosphoryl chloride (Scheme
1). From the SEM (Fig. 4b) and TEM (Fig. 4c) images, the as-prepared
HOPBs-TRIP remained the similar hollow bowl-like shape as its own
precursor HOPBs- BINOL. From FT-IR spectra, the successful phos-
phorylation of phenolic hydroxyl groups to form phosphoric acid –O)2P
(=O)OH was qualitatively confirmed by the emerging stretching vi-
bration absorption of P]O bond at 1531 cm−1 and the disappeared
stretching vibration, in-plane flexural vibration and out-plane flexural
,
vibration of phenolic OeH bond at 3512 cm−1 1374 cm-1 and
650 cm−1 (Fig. 4a). Furthermore, the quantitative functionalization
level of phenolic hydroxyl groups in HOPBs-BINOL to form phosphoric
acid by phosphorylation and hydrolysis was determined to be
0.15 mmol g−1 by elemental analysis of P content. In particular, the
disappeared IR absorption peak of water in HOPBs-BINOL at
1677 cm−1 was attributed to the dehydration of adsorbed water in the
presence of POCl3.
3.3. Screening of reaction conditions
Fig. 3. TEM images of hollow organic polymeric nano-bowls HOPBs-BINOL
with a kippah structure.
Given the versatility of chiral homoallylic alcohols as building
blocks in synthesis and the simplicity of reaction protocol [47–52], the
asymmetric allylboration of aromatic aldehydes was selected as a model
reaction to investigate the catalytic performance of hollow bowl-like
HOPBs-TRIP. From Table 1, it was found that HOPBs-TRIP (5 mol%)
promoted the asymmetric allylboration of benzaldehyde with allyl-
boronic pinacol ester in tolue ne at 25 °C toafford allylic alcohol 3a in
96% yield with 90% ee (Entry 1). When the reaction temperature de-
creased from 25 °C to−30 °C, the enantioselectivities were significantly
improved to 96% ee in constant yields (entry 2, 3). Although the re-
action gave the excellent yield (96%) and enantioselectivity (95%ee) at
0 °C in the first run, the enantioselectivity in recycled runs at 0 °C
descended quicker than that at -30 °C. To maintain the high excellent
enantioselectivity, the low temperature (-30 C) was selected as a sui-
table parameter to carry out the following reactions. Further lowering
the used amount of HOPBs-TRIP to 1 mol % allowed the reaction to
reach the similar yield (95%) but low enantioselectivity (90% ee, entry
5), whereas no further significantly improved yield and % ee were
achieved upon increasing the dosage of HOPBs-TRIP to 10 mol% (entry
4). Solvent played an important role in the catalytic performances. In
other solvents such as EtOAc and CH2Cl2, HOPBs-TRIP promoted the
reaction in lower yields with poorer enantioselectivities (entries 7, 9).
Even worse: no product was obtained in THF (entry 9), which eluci-
dated that the catalytic performances of the heterogeneous nano-bowls
were closely related with solvent properties. It was ever-reported that
the reaction proceeded via a transition state involving both a hydrogen-
bonding interaction from the catalyst hydroxyl group to the pseu-
doaxial oxygen of cyclic boronate and a stabilizing interaction from the
phosphoryl oxygen of TRIP to the formyl hydrogen of the aldehyde
[53]. Then, it was conjectured that the formation of hydrogen bond
between oxygen atoms in EtOAc and THF and hydroxyl group of TRIP
interfered with the hydrogen-bonding interaction of the hydroxyl group
in TRIP with the oxygen of cyclic boronate, and ultimately resulted in
the decreased yields of products or even inactive allylboration.
through heterogeneous catalyst, the shell thickness of HOPBs-BINOL
was further optimized by tuning the dosages of AA and EGDMA under
the following parameters (St: 2.0 mmol, (R)-6: 0.17 mmol, PS: 800 mg,
AA: 0.6 mmol, EGDMA:1.6 mmol and KPS: 60 mg at 100 °C for 48 h).
When no directing agent AA was added, the average particle size of
core-shelled CS-BINOL decreased from 388 nm to 353 nm and the
average outer shell thickness decreased from 31 nm to 13 nm (Fig. 2a2).
Further halving the dosages of crosslinking agent EGDMA to 160 mg
(0.8 mmol), the average outer shell thickness of core-shelled CS-BINOL
(345
25 nm, n = 50) was shortened to 9 nm (Fig. 2b2). Meanwhile,
it was found that the loading capacity of (R)-6 (0.09 mmol g-1) was too
low to meet the requirement of highly loaded TRIP. Therefore, the
dosages of (R)-6 increased from 150 mg (0.17 mmol) to 270 mg
(0.3 mmol) to achieve the higher loading capacity of (R)-6 (0.15 mmol
g-1), and then the average outer shell thickness of core-shelled CS-
BINOL (362
30 nm, n = 50) was thickened to 18 nm (Fig. 2c2).
After the as-fabricated core-shelled CS-BINOL was etched with DMF
to remove PS core, the shells would withstand the actions of osmotic
pressure (P) of escaped DMF and centrifugal force (Fc). It is well-known
that the pressure difference between the center and the edge of the
container of radius (r) in centrifugal process is ΔP = ρω2 r2/2, where ρ
(kg m−3) is the density of the fluid and ω (rad/s) is the angular velocity.
Then, the pressure which acted on the shell of HOPBs-BINOL was cal-
culated to be 2.18 × 10-8 N um-2 in DMF (945 Kg m-2) at a rotation
speed ω = 8100/60 × 2π. From the SEM images (Fig. 1c–f and
Fig. 2a3–c3), all the shells with different average shell thicknesses
(9–32 nm) could not withstand the imbalance induced by the resultant
forces, i.e., osmotic pressure (P) and centrifugal force(Fc), and then one
part of the shell caved in toward the opposite side to form hollow bowl-
shaped HOPBs-BINOL with circular opening, symmetrical wall and
hemi-spherical profile. As shown in TEM images (Fig. 3), the bright
43

Z. Yan et al.
MolecularCatalysis464(2019)39–47
Fig. 4. IR spectra (a) of HOPBs-BINOL and HOPBs-TRIP, SEM (b) and TEM(c) images of hollow bowl-like HOPBs-TRIP.
found that the concentrations of 4-chlorobenzaldehyde and yields of
(R)-1-(4-chlorophenyl)but-3-en-1-ol displayed the different reaction
kinetics for HOPBs-TRIP and PS-TRIP. Hollow bowl-like HOPBs-TRIP
exhibited the higher catalytic activities than PS-TRIP in the whole
process, which was attributed to the shorter seepage distance and in-
ternal and external concentration difference of reactants for HOPBs-
TRIP. The reaction kinetics of 4-chlorobenzaldehyde, promoted by
HOPBs-TRIP, followed a linear Eq. (3)in the whole reaction with a high
degree of fitting (R2 = 0.981). However, in PS-TRIP-promoted allyl-
boration, the concentrations of 4-chlorobenzaldehyde versus reaction
time could be expressed by a exponential function (Eq. (4)) during the
first 3 h and then a linear Eq. (5), respectively with the high degrees of
fitting (R2 = 0.990 and 0.960).
Table 1
Screening of catalytic reaction conditions of HOPBs-TRIP in the asymmetric
allylboration of benzaldehyde with allylboronic pinacol ester.a.
Solvent
Cat. (mg/mol%)
T (°C)
t (h)
Yield (%)b
Ee (%)c
1
2
3
4
5
6
7
8
9f
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
EtOAc
66.7/5
66.7/5
66.7/5
133.4/10
13.3/1
66.7/5
66.7/5
66.7/5
66.7/5
25
0
6
6
6
6
6
16
6
6
6
96
96
95
96
95
96
65
traces
90
90
95
96
96
90
97
48
n.d.
80
−30
−30
−30
−30
−30
−30
−30
THF
CH2Cl2
a
Reactions carried out in 1.0 mL of solvent, benzaldehyde (21.2 mg,
HOPBs-TRIP: c1 = -0.031 t + 0.188, R2 = 0.981
PS-TRIP: c2 = 0.06 exp (-t/0.598) + 0.140, R2 = 0.990 (0–3 h)
c3 = -0.034 t + 0.221, R2 = 0.960 (3–6 h)
(3)
(4)
(5)
0.2 mmol) and allyl boronic acid pinacol ester (36.9 mg, 0.22 mmol).
b
Isolated yields.
c
Determined by chiral HPLC on Daicel Chiralpak OD-H column.
3.4. Enhanced catalytic activity of hollow bowl-like HOPBs-TRIP
Then, differentiating the concentration (c) with respect to time (t),
the reaction rates of 4- chlorobenzaldehyde at time (t) were expressed
by the following equation.
To elucidate the morphology-dependent catalytic activity of HOPBs-
TRIP, the contrast PS-TRIP with a diameter of 3–5 um and no hollow
structure (Fig. S3) was prepared according to the ever-reported proce-
dure [36]. In the asymmetric allylboration of 4-chlorobenzaldehyde
with allylboronic pinacol ester under the fine-tuned conditions (5 mol
% TRIP, 0.2 mol L−1 in toluene, −30 °C, 6 h), the concentrations of 4-
chlorobenzaldehyde and the yields of corresponding product (R)-1-(4-
chlorophenyl)but-3-en-1-ol, plotted versus reaction time during the
whole reaction, were obtained by HPLC and shown in Fig. 5. It was
HOPBs-TRIP: d[c1]/dt = -0.031
PS-TRIP: d[c2]/dt = -0.1003exp(-t/0.6028) + 7.534e – 5 (0–3 h) (7)
d[c3]/dt = -0.034 (3–6 h) (8)
The initial reaction rates at 1 h are calculated to be 0.031 mol
(6)
L
−1 h−1 and 0.019 mol L-1 −1, respectively for HOPBs-TRIP and PS-
TRIP. At the beginning of the reaction, the reaction rate mainly
h
44

Z. Yan et al.
MolecularCatalysis464(2019)39–47
Fig. 5. Concentrations of 4-chlorobenzaldehyde (a: HOPBs-TRIP, b: PS-TRIP) and yields of (R)-1-(4-chlorophenyl)but-3-en-1-ol (c: HOPBs-TRIP, d: PS- TRIP) versus
reaction time in the allylboration of 4-chlorobenzaldehyde with allylboronic pinacol ester.
Fig. 6. Yields and enantioselectivities of homoallylic alcohol products in the heterogeneous asymmetric allylboration of aromatic aldehydes with allylboronic pinacol
ester promoted by hollow bowl-like HOPBs-TRIP.
depended on surface reaction. Owing to the larger surface area
(17.6 m2 g-1) of HOPBs-TRIP than that of PS-TRIP (2.1 m2 g-1), the
higher catalytic rate of HOPBs-TRIP was observed. As the reaction
progressed, HOPBs-TRIP possessed the constant catalytic rate and PS-
TRIP. Based on the above-mentioned catalytic reaction kinetics and
enhanced catalytic activity of HOPBs-TRIP, it was concluded that the
short seepage distance and hollow strucutre, obtained by the con-
trollable fabrication of hollow nano-bowl with a thin shell thickness,
were favorable for the fast mass transfer of reactants to access the
catalytic sites and improved the effectiveness factor (η) of supported
heterogeneous TRIP [43,54].
TRIP showed
a
sharply decreased catalytic rate (6.8 × 10-4 mol
L
−1 h−1) at 3 h. At this point, the gap in catalytic rate between HOPBs-
TRIP and PS-TRIP reached the maximum, which was likely involved in
the slower molecule diffusion in the inner of PS-TRIP resulted from the
longer seepage distance and the lack of internal/external concentration
difference of reactants. After 4 h, the reaction rate of PS-TRIP was en-
hanced to a constant value (0.034 mol L−1 h−1) owing to the estab-
lishment of internal molecular diffusion equilibrium in the inner of PS-
3.5. Scope of aromatic aldehydes promoted by hollow bowl-like HOPBs-
TRIP
Encouraged by the enhanced catalytic activity of hollow bowl-like
45

Z. Yan et al.
MolecularCatalysis464(2019)39–47
HOPBs-TRIP in the asymmetric allylboration of 4-chlorobenzaldehyde
with allylboronic pinacol ester, the scope was extended to various
aromatic aldehydes under the optimal conditions: 5 mol % TRIP,
0.2 mol L−1 of aromatic aldehydes in toluene (1 mL), −30 °C, 6 h).
From Fig. 6, HOPBs-TRIP proved to be an effective heterogeneous chiral
phosphoric acid in the synthesis of highly enantioenriched homoallylic
alcohols. It was found that the electron-poor and electron-rich aromatic
aldehydes were generally well-tolerated to afford the products 3a − k
in moderate to high yields (70–98%) with good to excellent enantios-
electivities (88–98% ee). More importantly, most of the products gave
the higher enantioselectivities, compared with the ever-reported results
[36]. Especially, different from the ever-reported moderate enantios-
electivity of ortho-chlorinated derivative (72% ee), HOPBs-TRIP pro-
mote the allylboration of ortho- substituted aromatic aldehydes to af-
ford the corresponding derivatives (3c, 3f and 3i) in high yields
(93–98%) with excellent enantioselectivities (92–98% ee). Un-
fortunately, (R)-4-(1-Hydroxybut-3-en-1-yl)benzonitrile (3 j) and (R)-2-
(1-Hydroxybut-3-en-1-yl)benzonitrile (3k) seemed to be the exception,
giving the lower yield (70%) with a poorer enantioselectivity (88% ee).
The reason for this decreased activity of HOPBs-TRIP was possibly at-
tributed to the interaction of basic cyano (-CN) group with the phos-
phoric acid in HOPBs-TRIP.
organic polymeric nano-bowls-supported BINOL-derived chiral phos-
phoric acid (HOPBs-TRIP) was fabricated for the first time via the co-
polymerization of functional monomers on the surface of poly(styrene/
acrylic acid) nanospheres (PS), etching of PS by DMF and functionali-
zation by POCl3. Owing to the thin shell thickness and hollow structure,
the as-fabricated hollow bowl-like HOPBs-TRIP displayed the higher
catalytic activity and enantioselectivities than ever-reported PS-TRIP in
the allylboration of aromatic aldehydes, and showed outstanding sta-
bility in bowl-like morphology and good reusability in catalytic per-
formance (92% and 94%ee in the twelfth cycle) with an accumulated
TONs as high as 226. It is believed that HOPBs-TRIP has great attraction
for the large-scale synthesis and the heterogenization of other suc-
cessful homogeneous catalysis, especially for mass transfer-limited
multi-component reactions.
Acknowledgement
This work was supported by Basic Science and Advanced
Technology Research Project of Chongqing Science & Technology
commission (cstc 2017jcyjBX0027).
Appendix A. Supplementary data
3.6. Reusability and comprehensive evaluation of hollow bowl-like HOPBs-
TRIP
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2018.12.014.
After the completion of the allylboration reaction, HOPBs-TRIP
could be simply recovered by centrifugal separation and directly reused
in the following catalytic cycles. It was found that the remained yield
(95%) of (R)- 1-Phenylbut-3-en-1-ol (3a) with a slightly lowered en-
antioselectivity (94% ee) was achieved in the sixth run. To remain an
excellent enantioselectivity (> 95%ee), the 6th-reused HOPBs-TRIP
was dispersed in 5 mL of DI water and adjusted to pH = 1–2 by HCl
(1 mol L−1). The recovered HOPBs-TRIP regained the same excellent
catalytic performances (95%, 96%ee) as its fresh HOPBs-TRIP, and
could further catalyze another six cycles in high yields (92–95%) with
excellent enantioselectivities (94–96% ee) in an accumulated TONs of
226 (Table S2). The outstanding stability of HOPBs-TRIP was further
confirmed by no significant loss of phosphorus in elemental analysis
(0.14 mmol g−1) and no obvious change in morphology from its SEM
image (Fig. S5).
Although the total yield (12%) of chiral monomer (R)-6 starting
from (R)-BINOL via six steps was much lower than that (22%) of
homogeneous TRIP via four steps, HOPBs-TRIP afforded the higher
accumulated TONs of 226 in > 92% yield with > 95% ee than homo-
geneous TRIP with the TONs of 20 in 99% yield with 98% ee [48],
which was attributed to the disposable use of homogeneous TRIP and
calculated after a total of 12 cycles of catalyst reuse (Table S2). From a
TOF's point of view, there was still a big gap in TOF between hetero-
geneous HOPBs-TRIP (3.2 h−1) and homogeneous TRIP (19.8 h−1) in
the asymmetric allylboration of benzaldehyde. Moreover, HOPBs-TRIP
with a thin shell thickness (18 nm) and hollow structure possessed the
faster initial catalytic reaction rate (0.031 mol L-1 h-1) than ever-re-
ported heterogeneous PS-TRIP (0.019 mol L-1 h-1). Therefore, based on
the resource utilization of TRIP, the as-fabricated hollow bowl-like
HOPBs-TRIP could be considered to be more effective than hetero-
geneous PS-TRIP and homogeneous TRIP in the asymmetric allylbora-
tion of benzaldehydes with allylboronic pinacol ester.
References
[1] B. Pugin, H.U. Blaser, Top. Catal. 53 (2010) 953–962.
[2] S. Itsuno, M.M. Hassan, RSC Adv. 4 (2014) 52023–52043.
[3] D.B. Zhao, K.L. Ding, ACS Catal. 3 (2013) 928–944.
[4] S.W. Cao, F.L. Tao, Y. Tang, Y.T. Li, J.G. Yu, Chem. Soc. Rev. 45 (2016) 4747–4765.
[5] Y. Li, W.J. Shen, Chem. Soc. Rev. 43 (2014) 1543–1574.
[6] F. Teng, G.X. Xie, L. Zhang, X.B. Ma, ChemCatChem 10 (2018) 4586–4593.
[7] S. Hoffmann, A.M. Seayad, B. List, Angew. Chem., Int. Ed. 44 (2005) 7424–7427.
[8] F. Auria-Luna, E. Marques-Lopez, R.P. Herrera, Adv. Synth. Catal. 359 (2017)
2161–2175.
[9] S.K. Nimmagadda, S.C. Mallojjala, L. Woztas, S.E. Wheeler, J.C. Antilla, Angew.
Chem. Int. Ed. 56 (2017) 2454–2458.
[10] Z.M. Liu, H. Zhao, M.Q. Li, Y.B. Lan, Q.B. Yao, J.C. Tao, X.W. Wang, Adv. Synth.
Catal. 354 (2012) 1012–1022.
[11] F.E. Held, D. Grau, S.B. Tsogoeva, Molecules 20 (2015) 16103–16126.
[12] A. Zamfir, S. Schenker, M. Freund, S.B. Tsogoeva, Org. Biomol. Chem. 8 (2010)
5262–5276.
[13] S. Hoffmann, A.M. Seayad, B. List, Angew. Chem., Int. Ed. 44 (2005) 7424–7427.
[14] M. Rueping, A.P. Antonchick, T. Theissmann, Angew. Chem., Int. Ed. 45 (2006)
3683–3686.
[15] M. Rueping, A.P. Antonchick, Angew. Chem., Int. Ed. 46 (2007) 4562–4565.
[16] J.P. Reid, J.M. Goodman, Org. Biomol. Chem. 15 (2017) 6943–6947.
[17] J.G. de Vries, N. Mrsic, Catal. Sci. Technol. 1 (2011) 727–735.
[18] Z.H. Zhang, W.S. Sun, G.M. Zhu, J.X. Yang, M. Zhang, L. Hong, R. Wang, Chem.
Commun. (Camb.) 52 (2016) 1377–1380.
[19] K. Bera, C. Schneider, Org. Lett. 18 (2016) 5660–5663.
[20] K. Bera, C. Schneider, Chem. Eur. J. 22 (2016) 7074–7078.
[21] Y. Zhang, Y.F. Ao, Z.T. Huang, D.X. Wang, M.X. Wang, J.P. Zhu, Angew. Chem., Int.
Ed. 55 (2016) 5282–5285.
[22] J. Calleja, A.B. Gonzalez-Perez, A.R. de Lera, R. Alvarez, F.J. Fananas, F. Rodriguez,
Chem. Sci. 5 (2014) 996–1007.
[23] Y.M. Deng, S. Kumar, K. Wheeler, H. Wang, Chem. Eur. J. 21 (2015) 7874–7880.
[24] H. Wu, Q. Wang, J.P. Zhu, Angew. Chem., Int. Ed. 55 (2016) 15411–15414.
[25] H. Wu, Q. Wang, J.P. Zhu, Angew. Chem., Int. Ed. 56 (2017) 5858–5861.
[26] F.T. Zhou, H. Yamamoto, Angew. Chem., Int. Ed. 55 (2016) 8970–8974.
[27] M. Biedrzycki, A. Kasztelan, P. Kwiatkowski, ChemCatChem 9 (2017) 2453–2456.
[28] S.K. Nimmagadda, S.C. Mallojjala, L. Woztas, S.E. Wheeler, J.C. Antilla, Angew.
Chem., Int. Ed. 56 (2017) 2454–2458.
[29] J.P. Reid, J.M. Goodman, Chem. Eur. J. 23 (2017) 14248–14260.
[30] Z. Yan, X. Gao, Y.G. Zhou, Chin. J. Catal. 38 (2017) 784–792.
[31] L.M. Overvoorde, M.N. Grayson, Y. Luo, J.M. Goodman, J. Org. Chem. 80 (2015)
2634–2640.
[32] C. Lalli, P. van de Weghe, Chem. Commun. (Camb.) 50 (2014) 7495–7498.
[33] L.M. Overvoorde, M.N. Grayson, Y. Luo, J.M. Goodman, J. Org. Chem. 80 (2015)
2634–2640.
[34] D.S. Kundu, J. Schmidt, C. Bleschke, A. Thomas, S. Blechert, Angew. Chem., Int. Ed.
51 (2012) 5456–5459.
4. Conclusions
The enhancement of mass transfer of reactants to active catalytic
sites has always been one of the most consistently pursued research
topics in the field of heterogeneous catalysis. In this paper, to take
advantage of the merits of the short seepage distance and hollow
structure in favor of mass transfer in heterogeneous catalysis, hollow
[35] B.H. Zhang, L.X. Shi, R.X. Guo, Catal. Lett. 145 (2015) 1718–1723.
[36] L. Clot-Almenara, C. Rodríuez-Escrich, L. Osorio-Planes, M.A. Pericàs, ACS Catal. 6
(2016) 7647–7651.
46

Z. Yan et al.
MolecularCatalysis464(2019)39–47
[37] L. Clot-Almenara, C. Rodríuez-Escrich, M.A. Pericàs, RSC Adv. 8 (2018) 6910–6914.
[38] X. Zhang, A. Kormos, J. Zhang, Org. Lett. 19 (2017) 6072–6075.
[39] X.J. Wang, J. Feng, Y.C. Bai, Q. Zhang, Y.L. Yin, Chem. Rev. 116 (2016)
10983–11060.
[40] A.M. El-Toni, M.A. Habila, J.P. Labis, Z.A. ALOthman, M. Alhoshan, A.A. Elzatahry,
F. Zhang, Nanoscale 8 (2016) 2510–2531.
[47] Z.P. Lu, M.M. Dias, J.C.B. Lopes, G. Carta, A.E. Rodrigues, Ind. Eng. Chem. Res. 32
(1993) 1839–1853.
[48] P. Jain, J.C. Antilla, J. Am. Chem. Soc. 132 (2010) 11884–11886.
[49] P. Jain, H. Wang, K.N. Houk, J.C. Antilla, Angew. Chem., Int. Ed. 51 (2012)
1391–1394.
[50] M. Chen, W.R. Roush, J. Am. Chem. Soc. 134 (2012) 10947–10952.
[51] C.A. Incerti-Pradillos, M.A. Kabeshov, A.V. Malkov, Angew. Chem., Int. Ed. 52
(2013) 5338–5341.
[41] J.H. Ko, N. Kang, N. Park, H.W. Shin, S. Kang, S.M. Lee, H.J. Kim, T.K. Ahn,
S.U. Son, ACS Macro Lett. 4 (2015) 669–672.
[42] Z.W. Zhao, D.D. Feng, G.X. Xie, X.B. Ma, J. Catal. 359 (2018) 36–45.
[43] F.Q. Dai, Z.W. Zhao, G.X. Xie, D.D. Feng, X.B. Ma, ChemCatChem 9 (2017) 89–93.
[44] A. Modak, A. Bhaumik, Chemistryselect 1 (2016) 1192–1200.
[45] J.H. Xu, J. Pang, D.D. Feng, X.B. Ma, Mol. Catal. 443 (2017) 139–147.
[46] D. Cheng, S. Wang, J.A.M. Kuipers, Chem. Eng. Sci. 160 (2017) 80–84.
[52] E. Rodríguez, M.N. Grayson, A. Asensio, P. Barrio, K.N. Houk, S. Fustero, ACS Catal.
6 (2016) 2506–2514.
[53] M.N. Grayson, S.C. Pellegrinet, J.M. Goodman, J. Am. Chem.Soc. 134 (2012)
2716–2722.
[54] G.X. Xie, J.K. Tian, S. Wei, X.Z. Liu, X.B. Ma, Appl. Catal. A Gen. 565 (2018) 87–97.
47