Tri(pentaflurophenyl)borane-catalyzed reduction of cyclic imides with hydrosilanes: Synthesis of pyrrolidines

Article abstract of DOI:10.1016/j.tet.2018.01.051

B(C₆F₅)₃-catalyzed hydrosilylation of cyclic imides afforded an efficient synthetic method of pyrrolidines. In the presence of 5 mol% B(C₆F₅)₃, various aromatic, aliphatic and polycyclic imides were smoothly reduced by PhSiH₃ to generate the corresponding pyrrolidines in high yields. The reaction profiles monitored by ¹H NMR spectroscopy disclosed the reduction process of cyclic imides and the effect of difference structure of the hydrosilanes on the hydrosilylation.

Full text of DOI:10.1016/j.tet.2018.01.051

Accepted Manuscript
Tri(pentaflurophenyl)borane-catalyzed reduction of cyclic imides with hydrosilanes:
Synthesis of pyrrolidines
Guangni Ding, Xiaoyu Wu, Bin Lu, Wenkui Lu, Zhaoguo Zhang, Xiaomin Xie
PII:
S0040-4020(18)30111-X
10.1016/j.tet.2018.01.051
TET 29266
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 27 December 2017
Revised Date: 27 January 2018
Accepted Date: 30 January 2018
Please cite this article as: Ding G, Wu X, Lu B, Lu W, Zhang Z, Xie X, Tri(pentaflurophenyl)borane-
catalyzed reduction of cyclic imides with hydrosilanes: Synthesis of pyrrolidines, Tetrahedron (2018), doi:
10.1016/j.tet.2018.01.051.
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ACCEPTED MANUSCRIPT
Graphical Abstract
Leave this area blank for abstract info.
Tri(pentaflurophenyl)borane-catalyzed
reduction of cyclic imides with hydrosilanes:
synthesis of pyrrolidines
Guangni Ding a, Xiaoyu Wu a, Bin Lu a, Wenkui Lu a, Zhaoguo Zhang a,b, , and Xiaomin Xie a,
School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road,
Shanghai 200240, China

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Tri(pentaflurophenyl)borane-catalyzed reduction of cyclic imides with hydrosilanes:
synthesis of pyrrolidines
Guangni Ding a, Xiaoyu Wu a, Bin Lu a, Wenkui Lu a, Zhaoguo Zhang a,b, , and Xiaomin Xie a,
a School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
b Shanghai Institute of Organic Chemistry, Chines Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
B(C6F5)3-catalyzed hydrosilylation of cyclic imides afforded an efficient synthetic method of
pyrrolidines. In the presence of 5 mol% B(C6F5)3, various aromatic, aliphatic and polycyclic
imides were smoothly reduced by PhSiH3 to generate the corresponding pyrrolidines in high
yields. The reaction profiles monitored by 1H NMR spectroscopy disclosed the reduction
process of cyclic imides and the effect of difference structure of the hydrosilanes on the
hydrosilylation .
Available online
Keywords:
Hydrosilylation
Reduction
2009 Elsevier Ltd. All rights reserved
.
Cyclic imides
Tri(pentaflurophenyl)borane
Pyrrolidines
Corresponding author. Tel.: +86-021-5474-8925; fax: +86-021-5474-8925; e-mail: xiaominxie@sjtu.edu.cn
Corresponding author. Tel.: +86-021-5474-8925; fax: +86-021-5474-8925; e-mail: zhaoguo@sjtu.edu.cn

2
1. Introduction
The reduction of carbonyl compounds is one of the most
2. Results and Discussion
ACCEPTED MANUSCRIPT
N-benzyl phthalimide (1a) was chosen as the model substrate
to optimize boron catalyzed reduction of cyclic imides with
hydrosilanes. BF3·Et2O was initially examined in the reduction
which was efficient for the reduction of aldehydes and ketones
with hydrosilanes.21 Nevertheless, no reduction occurred (Table
1, entry 1). The catalyst was changed to B(C6F5)3 that was
commercially available Lewis acid of comparable strength to BF3
but without the problems associated with reactive B-F bonds.22
Gratifyingly, the pyrrolidine (2a) was obtained as the sole
product in 95% yield (Table 1, entry 2). Replacing B(C6F5)3 with
the moderately Lewis acidic triphenylborane (BPh3) which was
found to catalyze the selective hydrosilylation of CO2 and tertiary
amides,23 no desired product (2a) was generated (Table 1, entry
fundamental and widely employed transformations in synthetic
organic chemistry.1 Hydrosilanes are air- and moisture-stable
hydride sources and can be readily activated under mild
conditions. It is attractive to develop a catalytic reduction system
of the carbonyl compounds with hydrosilanes which enable the
fine-tuning of activity to improve chemo- and regioselectivity.2
Various catalysts had been explored for the chemo-, regio-,
and/or stereoselective hydrosilylation of aldehydes, ketones,
esters, amides, carboxylic acid derivatives and nitriles.2 Among
these catalysts, boron based catalytic systems are important for
the
hydrosilylations.3
For
example,
Tris(pentafluorophenyl)borane (B(C6F5)3) shows high effective
for the hydrosilylation of alcohols,4 olefins,5 imines,6 ethers,7
amides,8 carboxylic acids and their derivatives.9 Moreover, the
mechanisms of B(C6F5)3 catalyzed hydrosilylations were
different from typical Lewis acid catalyzed hydrosilylations in
which B(C6F5)3 activated hydrosilanes by an unusual ŋ1
coordination rather than carbonyl groups.10 However, there is no
report about boron catalyzed the reduction of cyclic imides with
hydrosilanes.
3).
In
the
cases
of
organo-borane
reagents,
benzo[b]thiophen-2-ylboronic acid and PhB(OH)2, also any
reduced products did not observed (Table 1, entries 4 and 5).
Other metal or Lewis acid catalyzed the reduction could not
afford selectively the pyrrolidine (2a) (Table 1, entries 6 - 8).
Consequently, B(C6F5)3 was an efficient catalyst for the
hydrosilylation of the imides to the pyrrolidine (2a). When
B(C6F5)3 was used as the catalyst, less active silanes like Ph2SiH2
or PHMS led to the desired pyrrolidine (2a) albeit in lower yield
of 71% and 76%, respectively (Table 1, entries 9 and 11). The
high yield of 2a was also obtained as TMDS
(tetramethyldisiloxane) was used (Table 1, entry 10), however 5%
of isoindole (5a) as the byproduct was observed in the reduction
products. Reduced dosage of PhSiH3 resulted in a decreased yield
of 2a, wherein the mono-reduction product (4a) was detected in
10% yield (Table 1, entry 12).
The reduction of available cyclic imides gives several
nitrogen containing compounds such as ω-hydroxylactams,11
lactams,12 substituted pyrroles13 or pyrrolidines14 which are
versatile building blocks for organic synthesis (Scheme 1).13d,15
The classical reduction process employing metal hydrides always
resulted in the formation of byproducts and suffered from
practical issues due to the moisture sensitive nature of metal
hydrides.1,16 Therefore, the reduction of the cyclic imides with
hydrosilanes is an appealing method. Zn(OAc)2 catalyzed
reduction of cyclic imides with polymethylhydrosiloxane
(PMHS) provided effectively ω-hydroxylactams.17 Lewis base
catalyzed hydrosilylations of cyclic imides can afford selectively
lactams or ω-hydroxylactams.18 Pyrrolidines as the important
reduction products of cyclic imides are present in numerous
natural products, biomacromolecules and pharmaceuticals with
diverse biological activities such as moxifloxacin and mitiglinide
calcium.19 There are only two literature examples about the
hydrosilylation of cyclic imides to pyrrolidines. Ito and
coworkers gave one example of Rh-catalyzed hydrosiylation of
N-benzyl succinimide with Ph2SiH2 to N-benzylpyrrolidine in
70% yield.20 Beller and coworkers reported a sequential
reduction of N-benzylphthalimide to 2-benzylisoindoline by
n-Bu4NF/PMHS and Fe3(CO)12/PMHS in moderate yield.18b
Therefore, it is attractive to develop a convenient and effective
method for the reduction of cyclic imides to pyrrolidines. Due to
boron catalytic systems allowing for deoxygenation of the amide
functionality8, we envision that boron based catalytic systems
will display high chemoselectivity for the reduction of the cyclic
imides to pyrrolidines. Herein, we report an efficient reduction of
cyclic imides to the corresponding pyrrolidines by a convenient
tri(penta-flurophenyl)borane catalyzed hydrosilylation.
Table 1. The effect of catalysts and hydrosilanes on the
reduction of cyclic imides a
Yield (%)
Conv.
Entry
Cat.
Silane
(%)
2a 3a 4a
1
2
3
4
BF3·Et2O
B(C6F5)3
PhSiH3
PhSiH3
PhSiH3
PhSiH3
0
100
0
--
95
0
--
0
0
0
--
0
0
0
BPh3
PhB(OH)2
benzo[b]thiophen-2-yl
boronic acid
Zn(OAc)2·2H2O
Ti(OiPr)4
0
0
5
PhSiH3
0
0
0
0
6
7
PhSiH3
PhSiH3
PhSiH3
Ph2SiH2
TMDS
PMHS
PhSiH3
100
25
0
0
88 13
18
15
0
0
0
8
In(OAc)2
20
0
9
B(C6F5)3
100
100
94
71
92
76
75
0
10b
11
12c
B(C6F5)3
0
0
B(C6F5)3
0
0
B(C6F5)3
85
0
10
a Reaction conditions: N-benzyl phthalimide (1a, 1.0 mmol), Silane (9.0
o
equiv. H), catalyst (10.0 mol%), dioxane (2.0 mL), 110 C, 16 h; conversion
and yields were determined by 1H NMR analysis (internal standard:
4,4’-di-tert-butyl-1,1’-biphenyl).
b 5% of isoindole (5a) as the byproduct was observed.
c The amount of PhSiH3 is 2.0 eq. (2.0 mmol), 10% of 4a as the byproduct
was observed.
Next, the influence of solvents (Table 2, entris 1-5), the
catalyst loading (Table 2, entries 6 and 7) and temperature (Table
2, entries 8 and 9) on the B(C6F5)3 catalyzed hydrosilylation of
Scheme 1. The reduction of cyclic imides

3
the imides with PhSiH3 were explored. Highest activity was
found in dioxane and toluene (Table 2, entries 1 and 2).
Incomplete-reduced product was observed when CHCl3 was used
as the solvent (Table 2, entry 4). Quantitative yields of 2a were
generated with a lower catalyst loading of 5 mol % (Table 2,
entry 6). Lowering the reaction temperature caused a decrease in
yield (Table 2, entries 8 and 9), so the reduction was performed
well at 110 °C.
imide and cyano group was observed, and the amino substituent
ACCEPTED MANUSCRIPT
isoindolines (2u) was obtained in moderate yield. Similarly, the
reduction of the cyclic imide with amide group (1v) generated the
diamine (2v) in good yields. Regrettably, when ethyl
4-phthalimido-butyric ester (1w) was reduced under the catalytic
system, only little of the object product was observed and most of
the imide (1w) was recovered.
In addition, the scalability of
this procedure was exemplified by the reduction of 5 gram of
N-benzyl phthalimide (1a) with PhSiH3 which afforded a 90%
isolated yield of 2a.
Table 2. The effect of solvent, catalyst loading and
temperature on the hydrosilylation of cyclic imides a
Table 3. B(C6F5)3-catalyzed reduction of cyclic imides (1) to
pyrrolidines (2) with hydrosilanes a
B(C6F5)3
(y
mol%)
Yield
(%)
2a
Temp. Conv.
Entry
Solvent
(oC)
(%)
1
2
Dioxane
Toluene
CH3OCH2CH2OCH3
CHCl3
10
10
10
10
10
5.0
2.5
5.0
110
110
85
65
85
110
110
80
100
100
54
90
58
100
100
90
95
95
52
76
58
95
92
89
3
4b
5
ClCH2CH2Cl
Dioxane
Dioxane
6
7
8
Dioxane
9
Dioxane
5.0
25
20
20
a Reaction condition: N-phenmethyl phthalimide (1a, 1 mmol), PhSiH3
(3.0 eq., 3.0 mmol), B(C6F5)3 (y mol%), solvent (2 mL), 110 oC, 16 h; Yields
were determined by 1H NMR analysis (internal standard:
4,4’-di-tert-butyl-1,1’-biphenyl).
b 8% of the lactam (4a) was observed in this condition.
Under the above optimized conditions, the scope of the
B(C6F5)3-catalyzed reduction of cyclic imides (1) to pyrrolidines
(2) with PhSiH3 was probed. As shown in Table 3,
B(C6F5)3-catalyzed hydrosilylation afforded effectively a range of
the cyclic amines (2). The reduction system displayed the high
efficiency for the reduction of various aryl imides (1) to the
corresponding isoindolines (2a-2i). The effect of the electronic
nature of the substituents at aromatic rings was not obvious on
the reductions. The methoxyl substituted phthalimide (1e) and
the naphthalinic imide (1f) were reacted in excellent yields.
Notably, full reduction of pyromellitic diimide (1g) to the
corresponding product (2g) was achieved in excellent yield
without increasing the catalyst loading. The reduction of N-alkyl
phthalimides (1h and 1i) also afforded the isoindolines (2h and
2i) in good yield. Moreover, the reduction of aliphatic imides
(1j-1n) was executed smoothly with this reduction system. The
polycyclic substrate (1j) was reduced well in 94% yield, and the
less sterically hindered N-benzyl succinimide (1l) was reduced in
82% isolated yield. The catalyst system was also applicable for
the reduction of six-membered cyclic imide (1m), in which
1-benzylpiperidine (2m) was obtained in 90% yield. The
nitrogenous heterocyclic substrate (1n) was reacted efficiently to
afford N-benzyl-2,8-diazabicyclo[4.3.0]-nonane (2n) in 85%
yield which is an important building block for the synthesis of
moxifloxacin.19e The reduction system also tolerated aryl halides,
alkenes and nitro groups. N-benzyl 5,6-dibromo phthalimide (1p)
and N-benzyl 5,6-dichlorophthalimide (1o) gave the isoindolines
(2p and 2o) in 78% and 85% yield, respectively. For N-allylic
and cinnamyl imides (1q, 1r and 1s), the carbonyl groups were
reduced selectively to afford the corresponding isoindolines with
the alkene unaffected.5 However, the steric hindrance of allyl
group at C4 position of cyclic imides resulted the yield of 2s to
drop slightly. The reduction of N-(4-nitrobenzyl) phthalimide (1t)
afforded the corresponding isoindoline (2t) in 71% yield. For the
cyclic imides (1u) with cyano group, the reduction of both the
a
Reaction condition: cyclic imide (1, 1.0 mmol), PhSiH3 (3.0 mmol),
B(C6F5)3 (5.0 mol%), dioxane (2.0 ml), 110 oC, 16 h, isolated yield.
b PhSiH3 (6.0 eq., 6.0 mmol).
c PhSiH3 (4.0 eq., 4.0 mmol), B(C6F5)3 (15.0 mol%), 130 oC, 48 h.
O
O
B(C6F5)3
Si-H
B(C6F5)3
N
Bn
N
Bn
R1
Si-H
R2
R3
H
OSi
O
Step 2
Step 1
1a
3a'
H
O
N
H
B(C6F5)3
N
Bn
Bn
Si-H
H
H
H
H
Step 3
2a
4a
Scheme 2. The possible reduction process of cyclic imides
catalyzed by B(C6F5)3
The reduction of cyclic imides to pyrrolidines may go through
several intermediates as shown in Scheme 2. To investigate the
reaction pathway of B(C6F5)3-catalyzed hydrosilylation of cyclic
imides, the reaction profile for the reduction of 1a with the
1
hydrosilane was monitored by H NMR spectroscopy (Figure 1)
(1H NMR spectra copies shown in the Supporting Information,
Figure S1). In PhSiH3/B(C6F5)3 reduction system (A), only the
lactam (4a) was observed in a low concentration at the initial
stage of the reaction, and it disappeared after 60 minutes, while
the nearly complete conversion of 1a to the pyrrolidine (2a) is
achieved after 5.0 h. These results suggested that in the reduction
system the conversion of the intermediate (4a) was faster than
that of the imide (1a). Furthermore, the hypothesis can be
demonstrated by the intramolecular competitive reduction of the

4
amide group and the imide group (Scheme 3). When the cyclic
effect of difference structure of the hydrosilanes on the
hydrosilylation.
ACCEPTED MANUSCRIPT
imide with amide group (1t) was reacted in PhSiH3/B(C6F5)3
reduction system, the preferential reduction of the amide group
was observed, and the compound (6t) was generated in 85%
yield after 2 hrs. Then the yield of full reduced product (2t)
increased gradually after the catalyst and the hydrosilane were
added supplementally. However, in TMDS/B(C6F5)3 reduction
system (B, Figure 1), ω-hydroxy lactam derivative (3a’) was the
only observed intermediate during the reduction, and the build-up
and decay of 3a’ is evident. This phenomenon indicated that the
conversion of 3a’ might be slower than that of imide (1a) and the
intermediates (4a).
4. Experimental section
4.1. General information
Unless otherwise noted, all reactions were carried out under an
atmosphere of nitrogen using standard Schlenk techniques.
Materials were purchased from commercial suppliers and used
without further purification. Anhydrous dioxane was freshly
distilled from Sodium. H NMR and 13C NMR spectra were
1
recorded on a 400 MHz spectrometer. The chemical shifts for 1H
NMR were recorded in ppm downfield from tetramethylsilane
(TMS) with the solvent resonance as the internal standard. The
chemical shifts for 13C NMR were recorded in ppm downfield
using the central peak of deuterochloroform (77.16 ppm) as the
internal standard. Coupling constants (J) are reported in Hz and
refer to apparent peak multiplications. HRMS were obtained on
an ESI-TOF mass spectrometer. Flash column chromatography
was performed on silica gel (300-400 mesh).
Figure 1. Reaction profile of B(C6F5)3 catalyzed reduction of 1a
with PhSiH3 and TMDS (A: PhSiH3 reduction system; B: TMDS
reduction system).
4.2. General
experimental
procedures
of
tri(pentaflurophenyl)-borane-catalyzed reduction of cyclicimides
(1)
To the mixture of B(C6F5)3 (5.0 mol%) and cyclic imides (1.0
mmol) in dioxane, was added PhSiH3 (3.0 mmol) slowly under
an atmosphere of nitrogen. The reaction mixture was stirred and
o
refluxed at 110 C under an atmosphere of nitrogen. After the
imide was consumed completely (detected by TLC) the mixture
was added with aqueous ammonia (15 mL) and extracted with
CH2Cl2 (10 mL×3). The combined organic phase was dried over
Na2SO4, after removing the solvent under vacuum, the residue
was purified by column chromatography to give the product.
4.2.1. 2-Benzylisoindoline (2a)18b
Reddish brown solid, 196.7 mg, yield: 94%, Mp: 33.0 – 35.3
Scheme 3. B(C6F5)3-catalyzed reduction of the cyclic imide
(1t) with an amide group with PhSiH3
1
oC. H NMR (400 MHz, CDCl3): δ 7.44 – 7.42 (m, 2H), 7.38 –
7.34 (m, 2H), 7.31 – 7.26 (m, 1H), 7.18 (s, 4H), 3.94 (s, 4H),
3.92 (s, 2H). 13C NMR (100 MHz, CDCl3): δ 140.3, 139.2, 128.9,
128.5, 127.2, 126.7, 122.4, 60.4, 59.0.
a
Reaction conditions: 1t (1.0 mmol), PhSiH3 (4.0 mmol), B(C6F5)3 (10.0
mol%), dioxane (2.0 mL), 130 oC; yields were determined by 1H NMR
analysis (internal standard: 4,4’-di-tert-butyl-1,1’-biphenyl).
4.2.2. 2-(4-Methylbenzyl)isoindoline (2b)25
bAfter 5 hr, B(C6F5)3 (5.0 mol%) and PhSiH3 (2.0 mmol) were added again.
Reddish brown solid, 198.8 mg, yield: 89%, Mp: 33.0 – 35.3
1
oC. H NMR (400 MHz, CDCl3): δ 7.32 – 7.30 (m, 2H), 7.20 –
These results demonstrated the reduction of cyclic imides to
pyrrolidines processed via three steps. Firstly, the hydrosilane
was activated by B(C6F5)3 and then added to the carbonyl group
of 1a to generate ω-hydroxy lactam derivative (3a’). Further, 3a’
was reduced to lactam (4a). Finally, B(C6F5)3 catalyzed the
reduction of 4a with the hydrosilane to pyrrolidine (2a).
Moreover, the difference structure of the hydrosilanes may affect
the reaction rate of the three steps and result that the different
intermediates was observed in the two reduction systems. The
synergetic effect24 of PhSiH3, poly-hydrogen atoms attached to
the same silicon atom, may result in prompt transformation of the
possible intermediate (3a’) to the lactam (4a), so 3a’ can not be
observed in the PhSiH3/B(C6F5)3 reduction reaction.
7.16 (m, 6H), 3.92 (s, 4H), 3.88 (s, 2H), 2.36 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 140.3, 136.7, 136.1, 129.1, 128.8, 126.7,
122.3, 60.0, 58.9, 21.2.
4.2.3. 2-(4-(Trifluoromethyl)benzyl)isoindoline (2c)
o
1
Brown solid, 246.8 mg, yield: 89%, Mp: 50.2 – 52.8 C. H
NMR (400 MHz, CDCl3): δ 7.62 – 7.60 (m, 2H), 7.55 – 7.53 (m,
2H), 7.20 (s, 4H), 3.97 (s, 2H), 3.94 (s, 4H). 13C NMR (100 MHz,
CDCl3): δ 143.5, 140.1, 129.5 (q, J = 32.1 Hz), 129.0, 126.9,
125.5 (q, J = 3.7 Hz), 124.4 (q, J = 270.1 Hz), 122.5, 59.9, 59.1.
HRMS-ESI (m/z): Calculated for C16H15F3N (M + H)+:278.1157,
Found: 278.1156.
4.2.4. 2-Benzyl-5-methylisoindoline (2d)
o
Brown solid, 196.7 mg, yield: 89%, Mp: 51.8 – 53.7 C. 1H
3. Conclusions
NMR (400 MHz, CDCl3): δ 7.43 – 7.42 (m, 2H), 7.38 – 7.34 (m,
2H), 7.31 – 7.26 (m, 1H), 7.08 – 7.06 (m, 1H), 7.00 – 6.99 (m,
2H), 3.91 (s, 2H), 3.90 (s, 4H), 2.33 (s, 3H). 13C NMR (100 MHz,
CDCl3): δ 140.4, 139.2, 137.3, 136.3, 128.8, 128.4, 127.4, 127.1,
123.0, 122.1, 60.4, 58.9, 58.8, 21.4. HRMS-ESI (m/z):
Calculated for C16H18N (M + H)+:224.1439, Found: 224.1439.
In summary, we have developed a convenient and efficient
reduction method of cyclic imides to pyrrolidines via
B(C6F5)3-catalyzed hydrosilylations. Various cyclic imides,
including aromatic, aliphatic, polycyclic substrates, were
effectively reduced to the corresponding cyclic amines in high
yield with PhSiH3/B(C6F5)3 reduction system. This catalytic
protocol showed good tolerance for alkenes, halogens, nitro
groups and heterocyclic compounds. The reaction profiles
4.2.5. 2-Benzyl-5-methoxyisoindoline (2e)
Reddish brown solid, 210.6 mg, yield: 88%, Mp: 64.8 – 66.8
1
oC. H NMR (400 MHz, CDCl3): δ 7.45 – 7.43 (m, 2H), 7.39 –
monitored
by
1H
NMR
spectroscopy
displayed
7.35 (m, 2H), 7.32 – 7.26 (m, 1H), 7.10 – 7.08 (m, 1H), 6.76 –
6.75 (m, 2H), 3.93 (s, 4H), 3.90 (s, 2H), 3.79 (s, 3H). 13C NMR
(100 MHz, CDCl3): δ 159.1, 141.7, 139.1, 132.3, 128.9, 128.5,
B(C6F5)3-catalyzed reduction process of cyclic imides and the

5
127.2, 123.0, 112.6, 108.2, 60.4, 59.2, 58.4, 55.5. HRMS-ESI
(m/z): Calculated for C16H18NO (M + H)+: 240.1388, Found:
240.1389.
4.2.15. 2-Benzyl-5,6-dichloroisoindoline (2o)
ACCEPTED MANUSCRIPT
o
1
Yellow solid, 236.4 mg, yield: 85%, Mp: 59.8 – 61.9 C. H
NMR (400 MHz, CDCl3): δ 7.39 – 7.26 (m, 5H), 7.25 (s, 2H),
3.89 (s, 2H), 3.87 (s, 4H). 13C NMR (100 MHz, CDCl3): δ 140.6,
138.6, 130.5, 128.7, 128.5, 127.3, 124.3, 60.0, 58.2. HRMS-ESI
(m/z): Calculated for C15H1435Cl2N (M + H)+: 278.0503, Found:
278.0502.
4.2.6. 2-Benzyl-2,3-dihydro-1H-benzo[f]isoindole (2f)
o
Yellow solid, 228.3 mg, yield: 88%, Mp: 138.2 – 140.3 C. 1H
NMR (400 MHz, CDCl3): δ 7.81 – 7.79 (m, 2H), 7.63 (s, 2H),
7.49 – 7.39 (m, 6H), 7.35 – 7.32 (m, 1H), 4.06 (s, 4H), 3.97 (s,
2H). 13C NMR (100 MHz, CDCl3): δ 139.4, 139.1, 133.1, 129.0,
128.5, 127.8, 127.3, 125.4, 120.6, 60.6, 58.7. HRMS-ESI (m/z):
Calculated for C19H18N (M + H)+: 260.1439, Found:260.1439.
4.2.16. 2-Benzyl-5,6-dibromoisoindoline (2p)
Yellow solid, 285.1 mg, yield: 78%, Mp: 75.9 – 78.1 C. 1H
o
NMR (400 MHz, CDCl3): δ 7.42 – 7.29 (m, 7H), 3.88 (s, 2H),
3.85 (s, 4H). 13C NMR (100 MHz, CDCl3): δ 141.7, 138.6, 128.8,
128.6, 127.5, 127.4, 122.5, 60.0, 58.1. HRMS-ESI (m/z):
Calculated for C15H1479Br2N (M + H)+: 365.9493, Found:
365.9491.
4.2.7. 2,6-Bibenzyl-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole
(2g)
o
1
Brown solid, 295.6 mg, yield: 86%, Mp: 137.8 – 140.1 C. H
NMR (400 MHz, CDCl3): δ 7.41 – 7.39 (m, 4H), 7.36 – 7.32 (m,
4H), 7.29 – 7.27 (m, 2H), 6.97 (s, 2H), 3.89 (s, 4H), 3.87 (s, 8H).
13C NMR (100 MHz, CDCl3): δ 139.2, 139.0, 128.9, 128.5,
127.2, 116.5, 60.5, 58.9. HRMS-ESI (m/z): Calculated for
C24H25N2 (M + H)+: 341.2018, Found: 341.2016.
4.2.17. 2-Allylisoindoline (2q)
Brown oil, 128.0 mg, yield: 80%. 1H NMR (400 MHz,
CDCl3): δ 7.20 (s, 4H), 6.05 – 5.94 (m, 1H), 5.29 (dd, J = 17.2,
1.6 Hz, 1H), 5.18 (dd, J = 10.4, 1.6 Hz, 1H), 3.97 (s, 4H), 3.40
(d, J = 6.4 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 140.2, 136.0,
126.8, 122.4, 117.3, 59.0, 58.9. HRMS-ESI (m/z): Calculated for
C11H14N (M + H)+: 160.1126, Found: 160.1127.
4.2.8. 2-Ethylisoindoline (2h)26
Reddish brown oil, 117.8 mg, yield: 80%. 1H NMR (400 MHz,
CDCl3): δ 7.22 – 7.18 (m, 4H), 3.93 (s, 4H), 2.78 (q, J = 7.2 Hz,
2H), 1.21 (t, J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3): δ
140.1, 126.8, 122.3, 58.9, 50.1, 14.1.
4.2.18. 2-Cinnamylisoindoline (2r)
Reddish brown oil, 190.5 mg, yield: 81% (with reaction
system B). 1H NMR (400 MHz, CDCl3): δ 7.42 – 7.40 (m, 2H),
7.34 – 7.30 (m, 2H), 7.24 – 7.22 (m, 1H), 7.20 (s, 4H), 6.63 (d, J
= 16.0 Hz, 1H), 6.46 – 6.35 (m, 1H), 4.00 (s, 4H), 3.55 (dd, J =
6.4, 1.2 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 140.0, 137.1,
132.4, 128.7, 127.6, 127.3, 126.8, 126.5, 122.4, 58.9, 58.2.
HRMS-ESI (m/z): Calculated for C17H18N (M + H)+:236.1439,
Found: 236.1437.
4.2.9. 2-Isopropylisoindoline (2i)14b
Brown oil, 129.3 mg, yield: 80%. 1H NMR (400 MHz,
CDCl3): δ 7.22 – 7.17 (m, 4H), 3.97 (s, 4H), 2.77 – 2.71 (m, 1H),
1.20 (d, J = 6.0 Hz, 6H). 13C NMR (100 MHz, CDCl3): δ 140.1,
126.7, 122.3, 57.2, 54.5, 21.9.
4.2.10. 2-Benzyloctahydro-1H-4,7-methanoisoindole (2j)
Yellow oil, 211.5 mg, yield: 93%. 1H NMR (400 MHz,
CDCl3): δ 7.36 – 7.28 (m, 4H), 7.24 – 7.21 (m, 1H), 3.52 (s, 2H),
2.76 (d, J = 10.0 Hz, 2H), 2.35 – 2.34 (m, 2H), 2.11 (s, 2H), 2.02
– 1.98 (m, 2H), 1.77 – 1.75 (m, 2H), 1.41 – 1.33 (m, 2H), 1.26 –
1.24 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 140.5, 128.5,
128.2, 126.7, 60.7, 55.4, 44.1, 42.3, 41.4, 24.1. HRMS-ESI
(m/z): Calculated for C16H22N (M + H)+: 228.1752, Found:
228.1751.
4.2.19. 4-allyl-2-methylisoindoline (2s)
Reddish brown oil, 120.8 mg, yield: 70%. 1H NMR (500 MHz,
CDCl3) δ 7.21 – 7.18 (m, 1H), 7.09 – 7.04 (m, 2H), 5.92 – 5.84
(m, 1H), 5.08 – 5.00 (m, 2H), 4.13 (s, 2H), 4.09 (s, 2H), 3.31 (d,
J = 6.5 Hz, 2H), 2.72 (s, 3H). 13C NMR (125 MHz, CDCl3) δ
138.4, 137.7, 135.7, 134.4, 128.0, 127.9, 120.5, 116.4, 61.0, 59.6,
42.6, 37.9. HRMS-ESI (m/z): Calculated for C12H16N (M +
H)+:174.1283, Found: 174.1288.
4.2.11. 2-Benzyloctahydro-1H-isoindole (2k)
4.2.20. 2-(4-nitrobenzyl)isoindoline (2t)
Yellow oil, 193.8 mg, yield: 90%. 1H NMR (400 MHz,
CDCl3): δ 7.38 – 7.32 (m, 4H), 7.29 – 7.24 (m, 1H), 3.76 (s, 2H),
2.83 – 2.79 (m, 2H), 2.57 – 2.53 (m, 2H), 2.21 – 2.16 (m, 2H),
1.60 – 1.46 (m, 6H), 1.38 – 1.32 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ 139.9, 128.8, 128.3, 126.9, 61.4, 58.4, 37.3, 27.0, 23.0.
HRMS-ESI (m/z): Calculated for C15H22N (M + H)+:216.1752,
Found: 216.1751.
o
Pale yellow solid, Mp: 63.5 – 65.8 C. 180.1 mg, yield: 71%.
1H NMR (400 MHz, CDCl3) δ 8.21 (d, J = 8.4 Hz, 2H), 7.60 (d, J
= 8.4 Hz, 2H), 7.21 (s, 4H), 4.02 (s, 2H), 3.97 (s, 4H). 13C NMR
(101 MHz, CDCl3) δ 147.3, 147.2, 139.9, 129.3, 127.0, 123.8,
122.4, 59.6, 59.2. HRMS-ESI (m/z): Calculated for C15H15N2O2
(M + H)+:255.1134, Found: 255.1135.
4.2.21. 5-(Isoindolin-2-yl)pentan-1-amine (2u)
Red oil, 133.2 mg, yield: 55%. 1H NMR (400 MHz, CDCl3): δ
7.18 (s, 4H), 3.91 (s, 4H), 3.69 (br, 2H), 2.74 – 2.69 (m, 4H),
1.63 – 1.50 (m, 4H), 1.44 – 1.37 (m, 2H). 13C NMR (100 MHz,
CDCl3): δ 139.8, 126.8, 122.3, 59.0, 55.9, 40.4, 29.9, 28.4, 24.5.
HRMS-ESI (m/z): Calculated for C13H21N2 (M + H)+: 205.1705,
Found: 205.1708.
4.2.12. 1-Benzylpyrrolidine(2l)
1
Yellow oil, 193.8 mg, yield: 82%. H NMR (400 MHz,
CDCl3): δ 7.35 – 7.23 (m, 5H), 3.65 (s, 2H), 2.55 – 2.53 (m, 4H),
1.82 – 1.78 (m, 4H). 13C NMR (100 MHz, CDCl3): δ 139.2,
129.0, 128.3, 127.0, 60.8, 54.2, 23.5. HRMS-ESI (m/z):
Calculated for C11H16N (M + H)+:162.1283, Found: 162.1283.
4.2.13. 1-Benzylpiperidine(2m)27
4.2.22. 3-(Isoindolin-2-yl)-N,N-dimethylpropan-1-amine (2v)
Yellow oil, 159.2 mg, yield: 78%. 1H NMR (400 MHz,
CDCl3): δ 7.17 (s, 4H), 3.90 (s, 4H), 2.74 (t, J = 7.2 Hz, 2H),
2.36 (t, J = 7.6 Hz, 2H), 2.23 (s, 6H), 1.79 – 1.72 (m, 2H). 13C
NMR (100 MHz, CDCl3): δ 140.1, 126.7, 122.3, 59.2, 57.8, 54.3,
45.6, 27.2 HRMS-ESI (m/z): Calculated for C13H21N2 (M + H)+:
205.1705, Found: 205.1701.
Yellow oil, 157.6 mg, yield: 90%. 1H NMR (400 MHz, CDCl3)
δ 7.32 – 7.23 (m, 5H), 3.49 (s, 2H), 2.46 – 2.32 (m, 4H), 1.61 –
1.55 (m, 4H), 1.47 – 1.38 (m, 2H). 13C NMR (100 MHz, CDCl3)
δ 138.6, 129.4, 128.2, 127.0, 64.0, 54.6, 26.1, 24.5.
4.2.14. 6-Benzyloctahydro-1H-pyrrolo[3,4-b]pyridine (2n)
Yellow oil, 183.7 mg, yield: 85%. 1H NMR (400 MHz,
CDCl3): δ 7.34 – 7.29 (m, 4H), 7.27 – 7.22 (m, 1H), 3.82 – 3.69
(m, 2H), 3.28 – 3.26 (m, 1H), 3.04 – 3.00 (m, 1H), 2.87 – 2.84
(m, 1H), 2.80 – 2.75 (m, 1H), 2.71 – 2.55 (m, 3H), 2.29 – 2.21
(m, 1H), 1.69 – 1.64 (m, 2H), 1.52 – 1.43 (m, 2H). 13C NMR (100
MHz, CDCl3): δ 139.0, 128.7, 128.2, 126.9, 60.5, 59.8, 56.1,
55.0, 43.8, 36.2, 23.9, 21.4. HRMS-ESI (m/z): Calculated for
C14H21N2 (M + H)+: 217.1705, Found: 217.1705.
4.2.23. 2-Benzyl-3-hydroxyisoindolin-1-one (3a)17
o
1
White solid, Mp: 141.7 – 143.8 C. H NMR (400 MHz,
CDCl3) δ 7.79 – 7.77 (m, 1H), 7.58 – 7.56 (m, 2H), 7.52 – 7.48
(m, 1H), 7.33 – 7.25 (m, 5H), 5.63 (d, J=11.6 Hz, 1H), 5.03 (d,
J=14.8 Hz, 1H), 4.35 (d, J=14.8 Hz, 1H), 2.63 (d, J=11.6 Hz,
1H). 13C NMR (100 MHz, CDCl3) δ 167.4, 144.0, 136.6, 132.3,
131.0, 130.0, 128.7, 128.4, 127.6, 123.4, 123.2, 80.9, 42.4.

6
4.2.24. 2-Benzylisoindolin-1-one (4a)18a
9. For examples of (B(C6F5)3) catalyzed hydrosilylation of
ACCEPTED MANUSCRIPT
o
Pale yellow solid, Mp: 83.3 –84.5 C. 1H NMR (400 MHz,
CDCl3) δ 7.91 – 7.89 (m, 1H), 7.54 – 7.45 (m, 2H), 7.39 – 7.36
(m, 1H), 7.34 – 7.26 (m, 5H), 4.81 (s, 2H), 4.27 (s, 2H). 13C
NMR (100 MHz, CDCl3) δ 168.5, 141.3, 137.1, 132.7, 131.4,
128.8, 128.2, 128.1, 127.7, 123.9, 122.8, 49.5, 46.4.
carboxylic acids and their derivatives, see: (a) Gevorgyan V, Rubin
M, Liu J-X, Yamamoto Y, J Org Chem. 2001; 66: 1672-1675; (b)
Bezier D, Park S, Brookhart M, Org Lett. 2013; 15: 496-499; (c)
Feghali E, Jacquet O, Thuery P, Cantat T, Catal Sci Technol. 2014;
4: 2230-2234; (d) Tan M, Zhang Y, Tetrahedron Lett. 2009; 50:
4912-4915.
4.2.25. 2-Benzyl-2H-isoindole (5a)28
10. Parks D J, Blackwell J M, Piers W E, J Org Chem. 2000; 65:
3090-3098.
1
White solid yield. H NMR (400 MHz, CDCl3): δ 7.52 –
7.45 (m, 2H), 7.27 – 7.22 (m, 3H), 7.15 – 7.03 (m, 4H), 6.92 –
6.88 (m, 2H), 5.20 (s, 2H). 13C NMR (100 MHz, CDCl3): δ
137.4, 128.8, 128.0, 127.3, 124.6, 120.9, 119.7, 111.3, 54.8.
11. For examples of the reduction of the cyclic imides to
ω-hydroxylactams with metal hydrides, see: (a)Hubert J C,
Wijnberg J B P A, Speckamp W N, Tetrahedron 1975; 31:
1437-41; (b) Zielinski T, Epsztajn J, Jatczak M, Rocz Chem.
1975; 49: 1671-9; (c) Wijnberg J B P A, Schoemaker H E,
Speckamp W N, Tetrahedron 1978; 34: 179-87; (d) Flann C,
Malone T C, Overman L E, J Am Chem Soc. 1987; 109: 6097-107;
(e) Shimizu M, Nishigaki Y, Wakabayashi A, Tetrahedron Lett.
1999; 40: 8873-8876.
4.2.26. 2-(3-(Dimethylamino)propyl)isoindoline-1,3-dione (6v)29
Yellow oil, 204.3 mg, yield: 88%. 1H NMR (400 MHz,
CDCl3): δ 7.85 – 7.83 (m, 2H), 7.72 – 7.70 (m, 2H), 3.74 (t, J =
6.8 Hz, 2H), 2.45 (t, J = 7.2 Hz, 2H), 2.28 (s, 6H), 1.93 – 1.86
(m, 2H). 13C NMR (100 MHz, CDCl3): δ 168.3, 134.0, 132.1,
123.2, 56.3, 44.4, 36.1, 25.8.
12. For examples of the reduction of the cyclic imides to lactams
with metal hydrides or metal, see: (a) Brewster J H, Fusco A M,
Carosino L E, Corman B G, J Org Chem. 1963; 28: 498-501; (b)
Cerny M, Malek J, Capka M, Chvalovsky V, Collect Czech Chem
Commun. 1969; 34: 1033-41; (c) McAlees A J, McCrindle R,
Sneddon D W, J Chem Soc Perkin Trans. 1 1977: 2038-40; (d)
Bedat J, Levacher V, Dupas G, Queguiner G, Bourguignon J,
Chem. Lett. 1995: 327-8; (e) Jozwiak A, Zagorski P M, Plotka M
W, Cal D, Tetrahedron Lett. 2014; 55: 2420-2422.
Acknowledgments
We thank the National Natural Science Foundation of China
(No. 21672143) for the financial support.
Supplementary Material
Supplementary data related to this article can be found at
References and notes
13. For examples of the reduction of the cyclic imides to pyrroles
with metal hydrides, see: (a) Carpino L A, Padykula R E, Barr D
E, Hall F H, Krause J G, Dufresne R F, Thoman C J, J Org Chem.
1988; 53: 2565-72; (b) Wu J, Vetter W, Gribble G W, Schneekloth
J S, Jr., Blank D H, Gorls H, Angew Chem Int Ed. 2002; 41:
1740-1743; (c)Verniest G, De Kimpe N, Synlett 2003: 2013-2016;
(d) Ward J W, Dodd K, Rigby C L, De Savi C, Dixon D J, Chem
Commun. 2010; 46: 1691-1693.
14. For examples of the reduction of the cyclic imides to
pyrrolidines with metal hydrides, see: (a) Ohmura T, Kijima A,
Suginome M, Org Lett. 2011; 13: 1238-1241; (b) Ohmura T,
Kijima A, Suginome M, J Am Chem Soc. 2009; 131: 6070-6071;
(c) Hou D-R, Hsieh Y-D, Hsieh Y-W, Tetrahedron Lett. 2005; 46:
5927-5929; (d) Watson T J, Ayers T A, Shah N, Wenstrup D,
Webster M, Freund D, Horgan S, Carey J P, Org. Process Res.
Dev. 2003; 7: 521-532.
1.Málek J. In Organic Reactions; John Wiley & Sons, Inc.; 2004.
2.(a) Tarverdiev S E, Azerb. Khim. Zh. 1998: 33-37; (b)Addis D, Das
S, Junge K, Beller M, Angew Chem Int Ed. 2011; 50: 6004-6011;
(c) Li B, Sortais J-B, Darcel C, RSC Adv. 2016; 6: 57603-57625;
(d) Larson G L, Fry J L, Org. React. (Hoboken, NJ, U. S.) 2008;
71: 1-737; (e) Diez-Gonzalez S, Nolan S P, Org Prep Proced Int.
2007; 39: 523-559; (f) Tokitoh, N.; Okazaki, R. In: The Chemistry
of Organic Silicon Compounds, John Wiley & Sons, Ltd, 2003; pp
1063–1103.
3.Oestreich M, Hermeke J, Mohr J, Chem Soc Rev. 2015; 44:
2202-2220.
4. For examples of (B(C6F5)3) catalyzed hydrosilylation of alcohols,
see: (a) Gevorgyan V, Liu J-X, Rubin M, Benson S, Yamamoto Y,
Tetrahedron Lett. 1999; 40: 8919-8922; (b) Nimmagadda R D,
McRae C, Tetrahedron Lett. 2006; 47: 5755-5758; (c) Gevorgyan
V, Rubin M, Benson S, Liu J-X, Yamamoto Y, J Org Chem. 2000;
65: 6179-6186; (d) Adduci L L, McLaughlin M P, Bender T A,
Becker J J, Gagne M R, Angew Chem Int Ed. 2014; 53: 1646-1649.
5. For examples of (B(C6F5)3) catalyzed hydrosilylation of olefins,
see: (a) Gandhamsetty N, Park J, Jeong J, Park S-W, Park S, Chang
S, Angew Chem Int Ed. 2015; 54: 6832-6836; (b) Rubin M,
Schwier T, Gevorgyan V, J Org Chem. 2002; 67: 1936-1940; (c)
Kim Y, Chang S, Angew Chem Int Ed. 2016; 55: 218-222.
6. For examples of (B(C6F5)3) catalyzed hydrosilylation of imines,
see: (a) Hermeke J, Klare H F T, Oestreich M, Chem - Eur J. 2014;
20: 9250-9254; (b) Hog D T, Oestreich M, Eur J Org Chem. 2009:
5047-5056,.
7. For examples of (B(C6F5)3) catalyzed hydrosilylation of ethers,
see: (a) Heo J, Kang T, Jang S G, Hwang D S, Spruell J M, Killops
K L, Waite J H, Hawker C J, J Am Chem Soc. 2012; 134:
20139-20145; (b)Taber D F, Malcolm S C, J Org Chem. 2001; 66:
944-953; (c) McGrath N A, Bartlett E S, Sittihan S, Njardarson J T,
Angew Chem Int Ed. 2009; 48: 8543-8546.
8. For examples of (B(C6F5)3) catalyzed hydrosilylation of amides,
see: (a) Blondiaux E, Cantat T, Chem Commun. 2014; 50:
9349-9352; (b) Chadwick R C, Kardelis V, Lim P, Adronov A, J
Org Chem. 2014; 79: 7728-7733; (c) Huang P-Q, Lang Q-W,
Wang Y-R, J Org Chem. 2016; 81: 4235-4243.
15. (a) Krysko A A, Samoylenko G V, Polishchuk P G, Fonari M S,
Kravtsov V C, Andronati S A, Kabanova T A, Lipkowski J,
Khristova T M, Kuz'min V E, Kabanov V M, Krysko O L, Varnek
A A, Bioorg. Med. Chem. 2013; 21: 4646-4661; (b) Luzzio F A,
Mayorov A V, Ng S S W, Kruger E A, Figg W D, J Med Chem.
2003; 46: 3793-3799.
16. (a) Parchinsky V Z, Koleda V V, Ushakova O, Talismanova T D,
Kravchenko D V, Krasavin M, Lett. Org. Chem. 2006; 3: 379-383;
(b) Ciganek E, J Org Chem. 1980; 45: 1512-13; (c) Miller S A,
Chamberlin A R, J Org Chem. 1989; 54: 2502-2504.
17. Ding G, Lu B, Li Y, Wan J, Zhang Z, Xie X, Adv Synth Catal.
2015; 357: 1013-1021.
18. (a) Ding G, Li C, Shen Y, Lu B, Zhang Z, Xie X, Adv Synth
Catal. 2016; 358: 1241-1250; (b) Das S, Addis D, Knoepke L R,
Bentrup U, Junge K, Brueckner A, Beller M, Angew Chem Int
Ed. 2011; 50: 9180-9184.
19. (a)Kreituss I, Chen K-Y, Eitel S H, Adam J-M, Wuitschik G,
Fettes A, Bode J W, Angew Chem Int Ed. 2016; 55: 1553-1556; (b)
Berger D, Citarella R, Dutia M, Greenberger L, Hallett W, Paul R,
Powell D, J Med Chem. 1999; 42: 2145-2161; (c) Jiang W-T, Chen
Y-S, Hsu T, Wu S-H, Chien C-H, Chang C-N, Chang S-P, Lee S-J,
Chen X, Bioorg Med Chem Lett. 2005; 15: 687-691; (d) Austin N
E, Avenell K Y, Boyfield I, Branch C L, Hadley M S, Jeffrey P,
Johnson C N, Macdonald G J, Nash D J, Riley G J, Smith A B,
Stemp G, Thewlis K M, Vong A K K, Wood M D, Bioorg Med
Chem Lett. 2001; 11: 685-688; (e) Torres E, Leiva R, Gazzarrini S,

7
Rey-Carrizo M, Frigole-Vivas M, Moroni A, Naesens L, Vazquez
S, ACS Med Chem Lett. 2014; 5: 831-836.
ACCEPTED MANUSCRIPT
20. Kuwano R, Takahashi M, Ito Y, Tetrahedron Lett. 1998; 39:
1017-1020.
21. (a) Doyle M P, West C T, Donnelly S J, McOsker C C, J
Organomet Chem. 1976; 117: 129-40; (b) Kobayashi Y, Ito Y,
Terashima S, Bull Chem Soc Jpn. 1989; 62: 3041-2; (c) Kursanov
D N, Zinaida N P, Russ Chem Rev. 1969; 38: 812.
22. Parks D J, Piers W E, J Am Chem Soc. 1996; 118: 9440-9441.
23. (a) Mukherjee D, Shirase S, Mashima K, Okuda J, Angew Chem
Int Ed. 2016; 55: 13326-13329; (b) Mukherjee D, Sauer D F,
Zanardi A, Okuda J, Chem - Eur J. 2016; 22: 7730-7733.
24. Hanada S, Tsutsumi E, Motoyama Y, Nagashima H, J Am Chem
Soc. 2009; 131: 15032-15040.
25. Subbarayappa A, Patoliya P U, Indian J Chem, Sect B: Org
Chem Incl Med Chem. 2009; 48B: 545-552.
26. Rabjohn N, Drumm M F, Elliott R L, J Am Chem Soc. 1956; 78:
1631-1634.
27. Fujita K-i, Enoki Y, Yamaguchi R, Org Synth. 2006; 83:
217-221.
28. Ding G, Wu X, Jiang L, Zhang Z, Xie X, Org Lett. 2017; 19:
6048-6051.
29. Abdel-Hafez A A-M, Arch Pharmacal Res. 2004; 27: 495-501.