Electrophilic [N—F]+ catalysed asymmetric allylation of (E)-N,1-diphenylmethanimine

Article abstract of DOI:10.1002/chir.23039

New efficient catalysts based on electrophilic N-fluoro quaternary ammonium salts are reported for catalytic allylation of (E)-N,1-diphenylmethanimine. The chiral version of the catalyst based on cinchonidine (F-CD-BF₄) shows high catalytic activity with approximately 94% ee and TOF (>800?h^?1). The F-CD-BF₄ is prepared from cinchonidine and Selectfluor by one-step transfer fluorination.

Full text of DOI:10.1002/chir.23039

Received: 7 September 2018
DOI: 10.1002/chir.23039
Revised: 1 November 2018
Accepted: 7 November 2018
S H O R T C O M M U N I C A T I O N
+
Electrophilic [N—F] catalysed asymmetric allylation of
E)‐N,1‐diphenylmethanimine
(
Poonam Sharma
| Rakesh K. Sharma
Department of Chemistry, Indian Institute
of Technology Jodhpur, Jodhpur, India
Abstract
New efficient catalysts based on electrophilic N‐fluoro quaternary ammonium
salts are reported for catalytic allylation of (E)‐N,1‐diphenylmethanimine. The
Correspondence
Rakesh K. Sharma, Department of
Chemistry, Indian Institute of Technology
Jodhpur, Jodhpur, India.
chiral version of the catalyst based on cinchonidine (F‐CD‐BF ) shows high
4
−
1
catalytic activity with approximately 94% ee and TOF (>800 h ). The F‐CD‐
BF4 is prepared from cinchonidine and Selectfluor by one‐step transfer
fluorination.
Email: rks@iitj.ac.in
Funding information
DST‐RFBR, Grant/Award Number: INT/
RFBR/P‐134; IIT Jodhpur; CASE facilities
KEYWORDS
asymmetric allylation, cinchonidine, circular dichroism, time‐dependent NMR, transfer fluorination
1
| INTRODUCTION
version of reaction is also explored with new chiral
N‐fluoro quaternary ammonium salt of cinchonidine (1e;
Stereoselective allylation of imines and aldehydes is the
common building block for chiral organic compounds in
agrochemicals and pharmaceutical. For instance, chiral
F‐CD‐BF , Figure 2). As per limited reports, F‐CD‐BF
4
4
and Selectfluor have been reagent of choice for electro-
1
23-26
philic fluorination.
The only example pertains to
homoallylic amines are the synthetic intermediate of nat-
Selectfluor‐mediated allystannation of aldehydes and
27
urally occurring compounds and chiral drugs such as (−)‐
imines was studied by Wong in 2002. Although cinchona
alkaloids have been used as a chiral source in indium‐
catalysed asymmetric allylation of aldehydes with moder-
2
3
quinolizidine 207I, (−)‐histrionicotoxin 259A, NNZ
2
4
5
591, and ORG 34167 (Figure 1). Recently, development
28
of mild synthetic methods has been the focus area to pre-
ate enantioselectivity, there is no report available on
6-12
pare optically active homoallylic amines (Table S1).
Usually, allylation of imines is promoted and activated
F‐CD‐BF ‐catalysed asymmetric allylation of imine. In
4
the
present
study,
allylation
of
(E)‐N,1‐
1
3
14
by Lewis or Bronsted acid, metal triflates, and chiral
diphenylmethanimine is investigated as a representative
example using catalytic amount of 1a‐1e and
allyltributylstannane. Allyltributyltin is used as an allylic
reagent due to several advantages such as easy availability,
air and moisture stability, and compatibility with a variety
15-22
metal complexes.
However, chiral transfer agent
14
requires inert and dry conditions. Although first asym-
metric allylation has been reported in 1993 by Mikami
using air‐ and moisture‐sensitive BINOL/Ti (IV) com-
20
29
plex, surprisingly, limited attention has been paid
of functional groups.
towards asymmetric allylation of C ═ O and C ═ N groups
18,19
under ambient conditions.
Herein, we present a series of nonhydroscopic [N—F]
reagents such as Selectfluor (1a, (1‐chloromethyl‐4‐fluoro‐
+
2 | MATERIALS AND METHODS
1
1
1
,4‐diazoniabicyclo[2.2.2]octane bis(tetrafluoro‐borate)),
‐fluoro‐2,4,6‐trimethylpyridium tetrafluoroborate (1b),
‐fluoropyridium tetrafluoroborate (1c), and 1‐
Reactions were carried out in inert atmosphere and
monitored by thin‐layer chromatography (TLC). Products
were purified by column chromatography and packed
with silica gel of 230‐400 mesh. Scanning electron micros-
copy (SEM, EVO18 Ziess) was used for morphological
fluoropyridium trifluoromethanesulfonate (1d) for
allylation of imine under mild conditions. The asymmetric
Chirality. 2018;1–6.
wileyonlinelibrary.com/journal/chir
© 2018 Wiley Periodicals, Inc.
1

2
SHARMA AND SHARMA
FIGURE 1 Natural products and chiral
drugs
+
FIGURE 2 [N—F] catalysts
analysis of F‐CD‐BF and Selectfluor. UV‐visible spectra
catalysts were tested for allylation of imine SI
4
were recorded by UV‐visible spectrophotometer (Varian
Cary 4000). Fourier‐transform infrared spectra (FTIR)
were performed on a Vertex 70v spectrometer (Bruker).
(Figure 3B).
1
19
13
H NMR (500 MHz), F NMR (470 MHz), and
C
2.1 | F‐CD‐BF (1e)
4
NMR (125 MHz) spectra were recorded on Bruker. Enan-
tiomers were separated by HPLC (waters 2489, Daicel
Chiral Cell CHIRALPAK ID 0.46 cm/25 cm) using n‐hex-
ane/isopropanol solvent system. The specific rotation was
measured from polarimeter (Rudolph, APII/2W). The CD
spectra were obtained from circular dichroism (JASCO, J‐
1
H NMR (500 MHz, CD CN): δ 8.98 (d, 4.53 Hz, 1H), 8.17
3
(d, J = 8.54 Hz, 1H), 8.00 (d, J = 8.54 Hz, 1H), 7.78‐7.73
(m, 2H), 6.43 (d, J = 3.31 Hz, 1H), 5.73 (m, 1H), 5.12
(dd, 1H), 5.00 (s, 1H), 4.10‐3.86 (m, 5H), 3.20‐3.41 (m,
13
1H), 1.23‐1.97 (m, 5H). C NMR (125 MHz, CD CN): δ
3
8
15 CD‐Spectrometer) in N atmosphere in the wave-
149.4, 149.3, 148.0, 137.5, 129.6, 129.4.0, 127.1, 125.2,
2
length range of 200 to 400 nm with a quartz cuvette cell.
120.7, 118.3, 117.6, 80.9, 66.3, 62.3, 59.2, 34.3, 27.9, 21.6,
19
Imine (SI), (E)‐N,1‐diphenylmethanimine was synthe-
19.2. F NMR (470 MHz, CD CN): δ = 40.7 ppm
3
30,31
+
¯
sized by previously reported method (see Scheme S1).
(—N—F ), −151.09 ppm (BF ).
4
Catalysts 1a‐1d were purchased commercially while F‐
CD‐BF4 1e was synthesized according to Bank's
fluorine‐transfer procedure, in which cinchonidine and
Selectfluor 1a were mixed in equimolar amount in dry
acetonitrile under optimized reaction conditions
2.2 | (E)‐N,1‐diphenylmethanimine (SI)
1
H NMR (500 MHz, CDCl ): δ 8.42 (s, 1H), 7.58‐7.76 (m,
3
13
19
1
32
(Figure 3A) and characterized by F and H NMR.
5H), 7.07‐7.47 (m, 5H). C NMR (125 MHz, CDCl ): δ
3
Chiral‐fluorinated cinchonidine 1e and other fluorinated
160.0, 152.0, 136.4, 131.0, 130.0, 129.2, 128.2, 127.2, 122.3.
FIGURE 3 A, Synthesis of fluorinated cinchonidine, F‐CD‐BF
4
, and, B, asymmetric allylation of (E)‐N,1‐diphenylmethanimine (SI)

SHARMA AND SHARMA
3
3
4
2
.2.1 | N‐(1‐phenylbut‐3‐en‐1‐yl)aniline
for fluorine transfer, as no transfluorination were
+
(P1)
observed with other monocataionic [N—F] reagents
1b‐1c). The fluorine transfer is also established by EDX
mapping (Figures S3 and S4). In FTIR, stretching and
vibration frequencies related to [N—F] are observed at
924, 769.7, 715, and 1477 cm . Other bands are slightly
similar to cinchonidine (Figure S5). In situ UV‐vis spectra
were recorded in acetonitrile (Figure S6), where
cinchonidine bands were observed at 205, 225, and
(
1
H NMR (500 MHz, CDCl ): δ 7.36‐7.27 (m, 5H), 7.08 (t,
3
+
J = 7.2 Hz, 1H), 6.83 (d, J = 8.0 Hz, 2H), 6.67 (t,
J = 7.2 Hz, 1H), 5.82 (m, 1H), 5.13 (m, 1H), 4.88 (m,
−
1 35
1
H), 3.94 (dd, J = 8.0, 5.2 Hz, 1H), 2.63‐2.36 (m, 2H).
1
3
C NMR (125 MHz, CDCl ): δ 147.6, 140.6, 134.3,
3
1
29.5, 128.5, 126.9, 126.7, 120.8, 116.4, 113.5, 63.4, 44.4
20°C
36
(Figures S8 and S9). [α]D
= +15 (C = 1.0 in CHCl3)
278 nm. The bands at 205 and 278 nm related to
π → π* and n → π* transitions, respectively. Upon addi-
tion of Selectfluor, band intensity of n → π* transition
lowered, indicating the involvement of the fluorine atom
in bonding with the N atom of the cinchonidine.
3
| RESULTS AND DISCUSSION
The fluorine transfer was monitored by time‐dependent
F NMR study in 10‐second interval at room tempera-
Allylation reaction was optimized with Selectflour 1a
using allyltributylstannane in dry CH CN. Maximum
3
19
ture (293 K). It has been observed that the fluorine trans-
fer started quickly and slowed down to complete in
conversion was found with 0.1 mol% of Selectfluor within
1 hour (Table 1). The typical optimized process involved
0.10 mol% (0.25 mg) Selectfluor dissolved in 5 mL of ace-
tonitrile followed by sonication for 10 minutes. After
5 minutes, 0.13 g (0.7 mmol) of imine SI and 0.25 mL
(0.8 mmol) of allyltributyltin were added and stirred for
1 hour. The product was extracted with dichloromethane
(5 mL × 2) after quenching with water. The product was
isolated with 10% ethyl acetate in n‐hexane using silica
column to get 98% semisolid racemic homoallylic amine
(Figure S11 inset). No allylation product was observed
in absence of Selectfluor under similar reaction condition
1
9
1
4
2 hours. The chemical shift of F NMR moved to
0.7 ppm from 48.0 ppm. The peak at 40.7 ppm indicates
the formation of [N—F] bond in cinchonidine (Figure
S1). The counterion [BF ] also shows a slight shift due
+
−
4
to change the electronic environment (see Figure S2).
Furthermore, it is noteworthy that quinuclidine ring of
cinchonidine is analogous to Selectfluor, which could
assist in one‐step transfer‐fluorination to form F‐CD‐BF
4
23,33
(
1e).
The conversion of dicationic Selectfluor to two
monocations of ammonium salts is also a driving force
a
TABLE 1 Optimization of allylation of imine (SI) with Selectfluor 1a
b
Entry
1a, mol%
Time, h
Yield, %
1
2
3
4
5
6
7
8
0.0
1
0.0
40
55
77
83
98
98
98
0.01
0.05
0.09
0.10
0.10
0.10
0.15
0.5
0.5
0.5
0.5
1.0
1.5
1.5
Standard reaction condition:
a
3
To a solution of imine SI (0.7 mmol, Table S1) in dry CH CN (5 mL), and allyltributylstannane (0.8 mmol) were added and stirred for 10 minutes at RT.
Catalyst 1a was added and stirred for the given time.
b
The product was separate by HPLC and by NMR (see Figures S8, S9, and S11).

4
SHARMA AND SHARMA
+
(Table 1, entry 1). This result encouraged us to screen
TABLE 3 Measured pH value of aqueous [N―F] catalysts
other catalysts 1b‐1d (Table 2), under optimized condi-
tions that showed good catalytic activity.
+
19
Entry [N―F] Catalysts pH
F Chemical Shift, ppm
1
2
3
4
5
1a
1b
1c
1d
1e
2.9
4.1
3.1
3.0
3.9
48.0
15.9
46.1
46.2
40.7
The catalyst 1d with triflate counterion exhibited
37
good activity due to its acidic nature. Catalysts 1b and
c with monocationic trifluoroborate counterion showed
1
lesser activity with moderate conversion. To study asym-
metric version of this reaction, F‐CD‐BF 1e was tested
4
under similar reaction condition, which gave low conver-
−
1
sion (80%, TOF
=
800 h ) and excellent
enantioselectivity (94%). The low conversion and high
ee could be consequence of steric discrimination of
cinchonidine moiety. No fluorinated side products were
observed in current allylation process, although fluorina-
tion of amines has been reported with Selectfluor under
To understand the mechanistic aspect, proton NMR
studies were carried out between (E)‐N,1‐
diphenylmethanimine and catalysts 1e that shows down-
field shift of imine proton, suggesting C—H activation
towards nucleophilic addition (Figure S10), although no
conclusive interactions were observed between
27,38
different reaction conditions.
+
Although the mechanism for this transformation is
allyltributyltin and [N—F] . However, It can be assumed
+
still under investigation, it can be stated that [N—F]
that tributyltin cation could be an effective Lewis acid,
reagents may act as a Lewis acid to activate the imine
generated in conjunction with allylfluoride during the
reaction of allyltributyltin and [N—F] reagents.
27
+
39
for nucleophilic addition. The low activity is aligning
+
with decreasing the Lewis acidity of [N—F] reagents.
Optical purity of P1 was determined by HPLC and
polarimeter. Chiral product was separated by a normal‐
phase Daicel CHIRALPAK ID (0.46 cm/25 cm) chiral col-
umn under isocratic and isothermal (at 30°C) conditions
using respective mixture of n‐hexane/isopropanol
(90/10) as the mobile phase with 1.0‐mL/min flow rate.
Specific rotation measurement revealed that R enantio-
mer is first eluted (Table 2). To evaluate the optical activ-
ity of samples, circular dichroism (CD) spectra were
The Lewis acidity was assumed by pH of the aqueous
+
solution of [N—F] reagents and found maximum in case
of 1a while minimum in case of 1b (Table 3). This may be
+
because of the presence of extra —N CH Cl that makes it
2
more electron deficient (Lewis acidity 2.9), and other
+
[
N—F] reagents are relatively electron rich with aro-
matic ring (1b‐1e). The chemical shift of all reagents
+
revealed the electron‐deficient order of [N—F] bond in
19
+
−1
F NMR, and it was observed that the [N—F] bond of
recorded at 20°C with 50 nm min sweep rates between
1
a catalyst is more electron deficient while 1b is compara-
400 and 200 nm (Figure S7). The smoothed CD spectra of
cinchona alkaloids show the cotton effect in the range of
208 to 330 nm including two positive cotton and two
tively rich (Table 3) due to electron‐donating methyl
groups.
+
a
TABLE 2 Allylation of (E)‐N,1‐diphenylmethanimine (SI) with [N—F] catalysts (1a‐e)
b
c
20°C d
Catalysts
Yield, %
ee, %
[α]
D
1
1
1
1
1
a
b
c
d
e
98
88
89
92
80
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
93.9
+15
a
Reaction condition is similar to Table 1. Catalysts/reaction time/imine/allyltributylstannane:0.1 mol%/1 hour/0.7 mmol/0.8 mmol
b
c
The products were separated by column chromatography.
Determined by chiral column under isocratic and isothermal conditions using respective mixture of n‐hexane/isopropanol as the mobile phase.
d
The optical activity was measured by polarimeter (C 1.00; Chloroform).

SHARMA AND SHARMA
5
negative cotton shifts at the range 330 to 278, 259 to 228,
6. Huo H‐X, Duvall JR, Huang M‐Y, Hong R. Catalytic asymmetric
allylation of carbonyl compounds and imines with allylic
boronates. Org Chem Front. 2014;1:303‐320.
40
2
78 to 259, and 228 to 208 nm, respectively. For cincho-
nine, opposite cotton shifts were observed (Figure S7A).
The cotton shifts of F‐CD‐BF4 were opposite of
cinchonidine and similar to cinchonine, indicating con-
figurational changes during fluorination (Figure S7B).
7. Robak MT, Herbage MA, Ellman JA. Synthesis and applications
of tert‐butanesulfinamide. Chem Rev. 2010;110:3600‐3740.
8
. Kobayashi S, Mori Y, Fossey JS, Salter MM. Catalytic
enantioselective formation of C−C bonds by addition to imines
and hydrazones: a ten‐year update. Chem Rev. 2011;111:2626‐2704.
The optical activity of F‐CD‐BF was transferred into
4
the product of allylation as indicated by CD spectra
9
. Yus M, González‐Gómez JC, Foubelo F. Diastereoselective
allylation of carbonyl compounds and imines: application to the
synthesis of natural products. Chem Rev. 2013;113:5595‐5698.
(Figure S7C) with wavelength shifts due to counterion
change.
1
0. van der Mei FW, Miyamoto H, Silverio DL, Hoveyda AH. Lewis
acid catalyzed borotropic shifts in the design of diastereo‐ and
enantioselective γ‐additions of allylboron moieties to aldimines.
Angew Chem. 2016;128:4779‐4784.
4
| CONCLUSION
+
In summary, a series of highly active electrophilic [N—F]
catalytic reagents have been investigated for allylation of
E)‐N,1‐diphenylmethanimine using allyltributyltin under
ambient and non‐inert conditions. High chemical yield
approximately 98%) of homoallylic amines has been
attained. For chiral catalyst (F‐CD‐BF4), high
enantioselectivity of approximately 94% was achieved.
Investigation towards detailed mechanism and scope of
substrate will be involved in future work.
11. Lou S, Moquist PN, Schaus SE. Asymmetric allylboration of acyl
imines catalyzed by chiral diols. Am Chem Soc.
007;129:15398‐15404.
(
J
2
(
12. Killinger TA, Boughton NA, Runge TA, Wolinsky J. Alcohols as
solvent for the generation and reaction of allylic zinc halides with
aldehydes and ketones. J Organomet Chem. 1977;124:131‐134.
1
1
1
3. Puentes CO, Kouznetsov V. Recent advancements in the
homoallylamine chemistry. J Heterocyclic Chem. 2002;39:595‐614.
4. Bloch R. Additions of organometallic reagents to CN bonds:
reactivity and selectivity. Chem Rev. 1998;98:1407‐1438.
ACKNOWLEDGMENTS
5. Fang X, Johannsen M, Yao S, Gathergood N, Hazell RG,
Jørgensen KA. Catalytic approach for the formation of optically
active allyl α‐amino acids by addition of allylic metal com-
pounds to α‐imino esters. J Org Chem. 1999;64:4844‐4849.
The authors are grateful to acknowledge CASE facilities,
IIT Jodhpur, and DST‐RFBR (INT/RFBR/P‐134) for
financial support.
16. Yamamoto Y, Asao N. Selective reactions using allylic metals.
Chem Rev. 1993;93:2207‐2293.
ORCID
1
7. Yamamoto H, Wadamoto M. Silver‐catalyzed asymmetric
allylation: allyltrimethoxysilane as a remarkable reagent. Chem
Asian J. 2007;2:692‐698.
Poonam Sharma https://orcid.org/0000-0001-9112-003X
Rakesh K. Sharma https://orcid.org/0000-0002-0984-8281
1
8. Loh T‐P, Xu J, Hu Q‐Y, Vittal JJ. A highly chemoselective and
diastereoselective trifluoromethane sulfonic acid catalyzed addi-
tion of allyltributylstannanes to a steroidal aldehyde in aqueous
media. Tetrahedron: Asymmetry. 2000;11:1565‐1569.
REFERENCES
1
. Nugent TC. Chiral Amine Synthesis: Methods, Developments and
Applications. John Wiley & Sons; 2010.
1
9. Sharma RK, Samuelson AG. Asymmetric allylation of aldehydes
with chiral platinum phosphinite complexes. Tetrahedron:
Asymmetry. 2007;18:2387‐2393.
2
. Toyooka N, Nemoto H. First enantioselective synthesis of (+)‐
quinolizidine 207I: determination of the absolute stereochemis-
try. Tetrahedron Lett. 2003;44:569‐570.
20. Aoki S, Mikami K, Terada M, Nakai T. Enantio‐ and
diastereoselective catalysis of addition reaction of allylic silanes
and stannanes to glyoxylates by binaphthol‐derived titanium
complex. Tetrahedron. 1993;49:1783‐1792.
3
. Smith CJ, Holmes AB, Press NJ. The total synthesis of alkaloids
(
2
−)‐histrionicotoxin 259A, 285C and 285E. Chem Commun.
002;1214‐1215.
2
1. Bedeschi P, Casolan S, Costa AL, Tagliavini E, Umani‐Ronchi A.
Catalytic asymmetric synthesis promoted by a chiral zirconate:
highly enantioselective allylation of aldehydes. Tetrahedron Lett.
1995;36:7897‐7900.
4
. Guan J, Zhang R, Dale‐Gandar L, Hodgkinson S, Vickers MH.
NNZ‐2591, a novel diketopiperazine, prevented scopolamine‐
induced acute memory impairment in the adult rat. Behav Brain
Res. 2010;210:221‐228.
2
2. Yanagisawa A, Ishiba A, Nakashima H, Yamamoto H.
Enantioselective addition of methallyl‐ and crotyltins to aldehydes
catalyzed by BINAP× Ag (I) complex. Synlett. 1997;1:88‐90.
5
. Kelder J, Grootenhuis PD, Bayada DM, Delbressine LP,
Ploemen J‐P. Polar molecular surface as a dominating determi-
nant for oral absorption and brain penetration of drugs. Pharm
Res. 1999;16:1514‐1519.
23. Cahard D, Audouard C, Plaquevent J‐C, Toupet L, Roques N. N‐
Fluorocinchonidinium tetrafluoroborate F‐CD‐BF 4: purifica-
tion and structure elucidation of this novel enantioselective

6
SHARMA AND SHARMA
electrophilic
fluorinating
agent.
Tetrahedron
Lett.
and chiral ligands/metal complexes.
J
Fluorine Chem.
2
001;42:1867‐1869.
2007;128:469‐483.
2
4. Cahard D, Audouard C, Plaquevent J‐C, Roques N. Design, syn-
thesis, and evaluation of a novel class of enantioselective
electrophilic fluorinating agents: N‐fluoro ammonium salts of
cinchona alkaloids (F‐CA‐BF4). Org Lett. 2000;2:3699‐3701.
35. Lascola R, Withnall R, Andrews L. Infrared spectra of
fluoroimide, nitrogen trifluoride, phosphorus trifluoride, and
phosphorus trichloride and complexes with hydrogen fluoride
in solid argon. J Phys Chem. 1988;92:2145‐2149.
2
5. Motoyama Y, Okano M, Narusawa H, Makihara N, Aoki K,
Nishiyama H. Bis(oxazolinyl)phenylrhodium (III) aqua com-
plexes: synthesis, structure, enantioselective allylation of
aldehydes, and mechanistic studies. Organometallics.
36. Deka J, Satyanarayana L, Karunakar G, Bhattacharyya PK,
Bania KK. Chiral modification of copper exchanged zeolite‐Y
with cinchonidine and its application in the asymmetric Henry
reaction. Dalton Trans. 2015;44:20949‐20963.
2
001;20:1580‐1591.
3
7. Vincent SP, Burkart MD, Tsai C‐Y, Zhang Z, Wong C‐H. Elec-
trophilic fluorination−nucleophilic addition reaction mediated
by Selectfluor: mechanistic studies and new applications. J Org
Chem. 1999;64:5264‐5279.
2
6. Cozzi PG, Orioli P, Tagliavini E, Umani‐Ronchi A.
Enantioselective allylation of aldehydes promoted by chiral zinc
bis(oxazoline) complexes. Tetrahedron Lett. 1997;38:145‐148.
TM
2
7. Liu J, Wong C‐H. Selectfluor™‐mediated allylstannation of alde-
hydes and imines. Tetrahedron Lett. 2002;43:3915‐3917.
38. Singh RP, Jean'ne MS. The first application of Selectfluor in
electrophilic fluorination of amines: a new route to –NF2, –NHF,
and >NF compounds. Chem Commun. 2001;1196‐1197.
2
8. Loh T‐P, Zhou J‐R, Yin Z. A highly enantioselective indium‐
mediated allylation reaction of aldehydes. Org Lett.
39. Nyffeler PT, Durón SG, Burkart MD, Vincent SP, Wong CH.
Selectfluor: mechanistic insight and applications. Angew Chem
Int Ed. 2005;44:192‐212.
1
999;1:1855‐1857.
2
9. Grindley TB, Williams DR, Nag PP, et al. Tin in organic synthe-
sis. Tin chemistry: fundamentals, frontiers, and applications.
40. Margitfalvi JL, El T, Tfirst E, Kumar C, Gergely A. The role of
cinchona alkaloids in enantioselective hydrogenation reactions:
are they modifiers or hosts involved in supramolecular heteroge-
neous catalysis. Appl Catal, A. 2000;191:177‐191.
2
008;497‐665.
3
0. Silverberg LJ, Coyle DJ, Cannon KC, Mathers RT, Richards JA,
Tierney J. Azeotropic preparation of a C‐phenyl N‐aryl imine:
an introductory undergraduate organic chemistry laboratory
experiment. J Chem Educ. 2016;93:941‐944.
SUPPORTING INFORMATION
3
1. Touchette KM. Reductive amination: a remarkable experiment
for the organic laboratory. J Chem Educ. 2006;83:929.
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
3
2. Abdul‐Ghani M, Banks ER, Besheesh MK, Sharif I, Syvret RG.
N‐Halogeno compounds. Part 14.“Transfer fluorination” of
TM
quinuclidine using F‐TEDA‐BFc (Selectfluor reagent): labora-
tory synthesis of N‐fluoroquinuclidinium salts not requiring the
use of elemental fluorine. J Fluorine Chem. 1995;73:255‐257.
How to cite this article: Sharma P, Sharma RK.
Electrophilic [N—F] catalysed asymmetric
allylation of (E)‐N,1‐diphenylmethanimine.
Chirality. 2018;1–6. https://doi.org/10.1002/
chir.23039
+
3
3
3. Cahard D. Enantioselective electrophilic fluorination: two
approaches using cinchona alkaloids, In 4th Int'l Electronic
Conf. On Syn. Organic Chem (ECSOC‐4), 2000.
4. Shibata N, Ishimaru T, Nakamura S, Toru T. New approaches to
enantioselective fluorination: cinchona alkaloids combinations