Synthesis of Triarylamines via Sequential C-N Bond Formation

Article abstract of DOI:10.1021/acs.joc.7b01778

A one-pot domino N-arylation protocol is described using diaryliodonium reagents under copper catalysis. The reaction uses both aryl groups of the diaryliodonium reagent to generate triarylamines starting from simple anilines, representing an atom-economical preparation of an important class of organic material building blocks.

Full text of DOI:10.1021/acs.joc.7b01778

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Note
Synthesis of Triarylamines via Sequential C-N Bond Formation
Sachinkumar G. Modha, Mihai V Popescu, and Michael F Greaney
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b01778 • Publication Date (Web): 28 Aug 2017
Downloaded from http://pubs.acs.org on August 29, 2017
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Synthesis of Triarylamines via Sequential C-N Bond Formation
Sachin G. Modha, Mihai V. Popescu and Michael F. Greaney*
School of Chemistry, University of Manchester, Oxford Rd, Manchester M13 9PL, UK
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ABSTRACT: A oneꢀpot domino Nꢀarylation protocol is described using diaryliodonium reagents under copper
catalysis. The reaction uses both aryl groups of the diaryliodonium reagent to generate triarylamines starting
from simple anilines, representing an atomꢀeconomical preparation of an important class of organic material
building blocks.
1
Diaryliodonium reagents, discovered in 1894, have seen extensive development as
2
electrophilic arylating agents for carbon and heteroatom nucleophiles. They exhibit an appealing
combination of stability, being crystalline solids that are easy to handle and store, and reactivity:
3
Recent applications encompass aryl radical generation and utilization under photoredox catalysis,
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5
6
metalꢀfree arylation, stereoꢀcontrolled arylation of double bonds, aryne generation, and extensive
metalꢀcatalyzed arylation processes. Despite this extremely versatile portfolio of reactivity, almost all
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of these applications share the common drawback of generating at least one equivalent of an
iodobenzene as a waste product – ca. 50% of the atomic mass of the iodonium reagent, depending on
the counterion. Whilst the iodobenzene can in principle be separated from the product mixture and
recycled, this poor atom economy is clearly an obstacle to wider application of these reagents on scale.
Scheme 1. Atom economical use of diaryliodonium reagents
We have addressed this atom economy issue by designing domino processes that can capture
8
the aryl iodide side product in a second arylation step in situ (Scheme1A). Copperꢀcatalyzed CꢀH
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arylation of indole with a diaryliodonium salt, for example, can be followed by Nꢀarylation with the
liberated aryl iodide to yield diꢀarylated products. This concept of domino arylation was subsequently
demonstrated by Muñiz and coꢀworkers who reported borylation / SuzukiꢀMiyaura coupling of
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diaryliodoniums and diboron reagents, and further developed by Jiang and coꢀworkers, who
described double arylation of a sulfur salt under copper catalysis to produce diarylsulfides from
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0
diaryliodoniums (Scheme 1B and C). Similar doubleꢀfunctionalization ideas have been explored with
ArI(OAc) by Dauban and coꢀworkers, and alkynyl iodine(III) derivatives by the Yoshikai and Waser
2
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groups. Collectively, these reports demonstrate that aryliodine(III) reagents can be used as powerful
arene synthons in a variety of contexts, without having to sacrifice atomꢀeconomy. Indeed, by offering
the possibility of two transformations from a single reagent, they create new opportunities for
streamlined reaction design.
We were interested in further exploring the scope of domino applications of iodonium reagents, and
chose to investigate the synthesis of triarylamines (Scheme 1D). Triarylamines are important building
blocks in organic electronics, where their electron donor properties and characteristic propeller shapes
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have seen extensive application in the field of photovoltaics. They are commonly accessed through
variants of the Ullman coupling, using excess aryl halide and high temperatures to drive reaction to
completion. Synthesis using a single equivalent of iodonium reagent would present an alternative, and
very direct route, to their preparation. The groups of Nachtsheim and Wen have described the domino
assembly of Nꢀaryl carbazoles through reaction of anilines with cyclic iodonium salts, but the
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synthesis of triarylamines remains unexplored.
Our initial trial reactions examined the coupling of pꢀtoluidine, 1a, with one equivalent of
diphenyliodonium triflate, 2a, to give either the mono or diꢀphenylated products 3a and 5a (Table 1),
using toluene as the solvent of choice. It was apparent that monophenylation was straightforward
1
4
under both copperꢀcatalysis at room temperature and metalꢀfree conditions at 130 ºC, but there was
no trace of the diphenylated product in either case (Entries 1 and 2). Despite the good yields of 3a, a
small amount of starting pꢀtoluidine remained in each case, which would potentially complicate the
second Nꢀarylation. Switching to the organic base 2,6ꢀdiꢀtertꢀbutylpyridine (DTBPY) gave complete
conversion and improved the yield up to 86% (entry 3), and catalyst loading could be decreased to 2
mol% without loss of yield or conversion (entry 4).
With conditions established for high conversions of one equivalent of iodonium reagent in the first Nꢀ
arylation, we turned to the twoꢀstep oneꢀpot sequence. Copperꢀcatalyzed Nꢀarylation of weakly
nucleophilic diarylamines usually requires a strong base and ligand system – we initially trialed an
1
5
addition of CuI (10 mol%), bis(2,6ꢀdiisopropylphenyl)diazaꢀbutadiene (DAB) (12 mol%) and
o
KOtBu (2.2 equiv) to the reaction following initial Nꢀphenylation, and stirring at 120 C for 24 h. The
desired N,Nꢀdiphenylꢀ4ꢀmethylaniline (5a) could be isolated in 35% yield, but significant amounts of
unreacted 3a (42%) were present (entry 5). Increased ligand loading did not improve the yield (entry
6), and a switch to Pdꢀcatalysis for the second step was completely ineffective (entry 7). Using
phenanthroline as ligand was initially unsuccessful when paired with K PO (entry 8), but changing
3 4
back to KOtBu in the presence of 10% CuI, gave good conversions to the product 5a (59% yield over
two steps) along with a small amount of 3a (Table 1, entry 10).
Having optimized conditions in hand for the oneꢀpot double Nꢀarylation sequence, we examined the
diphenylation of various aniline substrates. A variety of substituents (o, m, pꢀmethyl, o, pꢀfluoro, pꢀ
chloro, pꢀmethoxy and mꢀphenyl) were wellꢀtolerated to give substituted triarylamines in good yields
over two steps (Table 2). As for pꢀtoluidine, small amounts of the monoꢀarylated product were isolated
as side products in some cases (Table 2, entries 1, 5ꢀ7, 9). Variously substituted diaryliodonium
triflates were employed next, to study the scope of the reagent with aniline. Iodonium reagents
containing tertꢀbutyl, fluoro, chloro, methoxy, and methyl reacted smoothly to give the desired
triarylamines in good yields (Table 3), with a single equivalent of iodonium reagent being employed in
2
each case. In terms of limitations, anilines containing strong electron withdrawing groups (e.g. pꢀNO )
were ineffective, being too deactivated to undergo the second arylation step. Attempts at selective aryl
transfer using unsymmetrical diaryliodoniums were also unsuccessful under the current protocol,
giving low yields of mixtures of Nꢀarylated material in the first step.
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a
Table 1. Reaction optimization
o
yield (%)
entry
catalyst (mol%)/ligand (mol%)
CuI (10)
base (equiv)
CO (1.5)
temp ( C)
time (h)
24
(3a:5a)
b
1
2
3
4
5
K
ꢀ
2
3
rt
72:0
68:0
86:0
87:0
b
ꢀ
130
24
CuI (10)
CuI (2)
DTBPY (1.1)
DTBPY (1.03)
rt
24
rt
12
CuI (2); then
DTBPY (1.03); then
KOtBu (2.2)
rt; then 120
12; then 24
42:35
CuI (10) and DAB (12)
6
7
8
9
CuI (2); then
CuI (10) and DAB (30)
DTBPY (1.03); then
KOtBu (4)
rt; then 120
rt; then 120
rt; then 120
rt; then 120
rt; then 120
12; then 24
12; then 24
12; then 24
12; then 24
12; then 24
35:32
CuI (2); then
DTBPY (1.03); then
KOtBu (2.2)
62:traces
56:traces
52:15
Pd(OAc) (4) and BINAP (8)
2
CuI (2); then
DTBPY (1.03); then
K PO (2.5)
3 4
CuI (5) and 1,10ꢀphenanthroline (6)
CuI (2); then
DTBPY (1.03); then
KOtBu (2.5)
CuI (5) and 1,10ꢀphenanthroline (6)
10
CuI (2); then
DTBPY (1.03); then
KOtBu (4.5)
15:59
CuI (10) and 1,10ꢀphenanthroline (30)
a
Unless otherwise noted, all reaction were run with 1a (0.3 mmol) and 2a (1.02 equiv) in a crimped cap glass vial under an inert
atmosphere. Incomplete conversion.
b
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a
Table 2. Scope of aniline substrate
a
Table 3. Scope of diaryliodonium reagents
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% yield 5
% yield 3)
entry
R
product
(
1
entry
R
product
% yield 5
1
4-Me
59 (15)
1
4-tBu
69
5a
5j
2
3
4
4-F
53
66
59
2
3
4-F
65
75
5
b
5k
H
5c
4-OMe
5l
4-Cl
Cl
5d
Cl
4
5
6
4-Cl
4-Me
3-Me
N
48
50
54
5m
5
6
7
4-OMe
2-Me
44 (5)
47 (17)
68 (18)
5
e
5
n
5
f
N
5o
3-Me
a
All reactions were run with 1c (1 mmol), 2 (1.02 mmol)
under optimized condition in a Schlenk flask under inert
atmosphere.
5g
8
2-F
40
5h
9
3-Ph
47 (8)
5i
a
All reactions were run with 1 (0.98 mmol), 2a (1 mmol)
under optimized condition in a Schlenk flask under inert
atmosphere.
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A mechanistic pathway for the two step process is set out in Scheme 2, and likely involves a switch in
mechanism between the first and second arylation steps. Whilst initial aniline arylation with the
reactive diaryliodonium salt 2 proceeds through familiar Cu(I) / Cu(III) oxidative addition / reductive
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elimination processes, Shyu and coꢀworkers have implicated an electron transfer pathway for the
1
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second arylation of Nꢀarylaniline 3 under KOtBu and CuI / phenanthroline conditions. Electron
transfer from the potassium complex of phenanthroline and diarylamine D’ to aryl iodide 4a generates
an aryl radical which can be trapped with the Cu(I)ꢀphenanthroline diarylamine species B’. One
electron oxidation by radical cation E’ then enables reductive elimination to furnish the triarylamine
5a and regenerate a Cu(I)ꢀphenanthroline species to continue the catalytic cycle.
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Scheme 2. Mechanistic pathway for one-pot double N-arylation.
In summary, we have developed a copperꢀcatalyzed, oneꢀpot, domino Nꢀarylation sequence to generate
triarylamines starting from simple anilines. The protocol uses both aryl groups of diaryliodonium
reagents, from a single equivalent of reagent, and a common CuI catalyst. Further atomꢀeconomical
transformations of aryliodine (III) reagents are under investigation in our laboratory.
EXPERIMENTAL
General Information. Nuclear Magnetic Resonance (NMR) spectra were recorded on 500 or 400
MHz Bruker NMR spectrometers in CDCl
values are reported in parts per million (ppm) relative to the solvent signal (1H NMR: δ = 7.26 ppm.
3C NMR: δ = 77.16 ppm) with coupling constant (J) values reported in Hz. The notation of signals is:
3
at 298 K (unless stated otherwise). All chemical shift
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Proton: δ chemical shift in ppm (number of protons, multiplicity, J value(s), proton assignment).
Carbon: δ chemical shift in ppm. Fluorine: δ chemical shift in ppm (Fluorine assignment). Splitting
patterns are assigned s = singlet, b = broad, d = doublet, td = triplet of doublet, dt = doublet of triplet, t
=
2
triplet, q = quartet, bs = broad singlet. Reactions were carried out under N using preꢀdried glassware.
All reaction were carried out in Schlenk flask and heated in oil baths with a thermocouple temperature
control. Toluene, THF and dichloromethane were freshly distilled over sodium or calcium hydride and
2
stored under N . Other solvents, unless otherwise stated, were purchased in reagent grade or anhydrous
quality and used as received. Reagents were either purchased directly from commercial suppliers or
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prepared according to literature procedures. TLC: MachereyꢀNagel, TLC plates Alugram® Sil
G/UV254. Detection under UV light at 254 nm. Chromatography: Separations were carried out on
®
Biotage Isolera Four flash chromatography instrument, with dryloading on Biotage SNAP Ultra
columns using ethyl acetate / hexane (5 / 95 ꢀ 20 / 80 for triaryl amines, rising to 70 / 30 for elution of
diarylamines when they were present). High Resolution Mass Spectrometry (HRMS) were recorded
on Thermo Finnigan MAT95XP (ion trap). Melting points were determined using a Buchi M565
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melting point apparatus. Iodonium salts 2a-g were prepared according to literature procedures.
Representative procedure for domino C-N bond formation: 4-Methyl-N,N-diphenylaniline (5a).
To an oven dried 25 mL Schlenk flask containing a stir bar was added the 4ꢀmethylaniline (1a) (105
mg, 0.98 mmol, 1.00 equiv), CuI (3.8 mg, 0.02 mmol, 2 mol %) and diphenyliodonium triflate (2a)
(
430 mg, 1 mmol, 1.02 equiv). The Schlenk flask was sealed with a glass stopper. A vacuum / N
cycle was applied three times to the flask in order to ensure the removal of air. To this flask was added
,6ꢀdiꢀtertꢀbutylpyridine (227 µL, 1.0094 mmol, 1.03 equiv) via glass syringe (250 µL capacity) and
2
2
dry Toluene (10 mL) via disposable syringe. The reaction mixture was allowed to stir at room
temperature for 12 h. After confirming completion of the reaction by TLC (Hexane/diethyl ether –
8/2); CuI (18.7 mg, 0.098 mmol, 10 mol %), 1, 10ꢀphenanthroline (53 mg, 0.294 mmol, 30 mol %)
t
and KO Bu (495 mg, 4.41 mmol, 4.5 equiv) were added to the flask followed by N
2
flush to ensure the
inert atmosphere and sealed again with the glass stopper. The flaskꢀstopper joint was sealed by taflon
o
tape and secured with a clip. The reaction mixture was then allowed to stir at 120 C for 24 h. After
confirming the product formation by TLC (Hexane/diethyl ether – 9/1) the reaction mixture was
diluted with EtOAc (100 mL) and washed with water (50 mL) (In case of emulsion, it was passed
through a celite plug). The organic layer was further washed with brine (50 mL) dried over MgSO4,
filtered and evaporated under reduced pressure. The crude was purified by Biotage flash
chromatography instrument to yield 4ꢀmethylꢀN,Nꢀdiphenylaniline 5a (156 mg, 59% yield) as a white
1
solid; MP 72ꢀ73 °C; HꢀNMR (500 MHz, CDCl
3
): δ 7.24 – 7.20 (m, 4H), 7.08 – 7.05 (m, 6H), 7.02 –
13
6
.99 (m, 2H), 6.97 (tt, J = 7.3, 1.1 Hz, 2H), 2.32 (s, 3H); CꢀNMR (126 MHz, CDCl ): δ 148.0, 145.2,
3
+
1
32.7, 129.9, 129.1, 124.9, 123.6, 122.2, 20.8; HRꢀMS (EI) m/z calcd for C19H18N [M+H] 260.1439,
o
1
found 260.1433; and 4ꢀmethylꢀNꢀphenylaniline 3a (27 mg, 15%) as a white solid; MP 88ꢀ90 C; Hꢀ
NMR (500 MHz, CDCl ): δ 7.28 – 7.24 (m, 2H), 7.12 – 7.10 (m, 2H), 7.04 – 7.02 (m, 4H), 6.90 (bt, J
7.3, 1.0 Hz, 1H), 5.62 (bs, 1H), 2.33 (s, 3H); CꢀNMR (126 MHz, CDCl
29.8, 129.3, 120.3, 118.9, 116.8, 20.7; HRꢀMS (EI) m/z calcd for C13
184.1128.
3
1
3
=
3
): δ 143.9, 140.3, 130.9,
+
1
H
14N [M+H] 184.1126, found
o
1
4-Fluoro-N,N-diphenylaniline (5b). White solid (137 mg, 53%). MP 98ꢀ100 C; HꢀNMR (400 MHz,
1
3
CDCl
CDCl
3
3
): δ 7.27 – 7.23 (m, 4H), 7.11 – 7.04 (m, 6H), 7.03 – 6.96 (m, 4H); CꢀNMR (101 MHz,
): δ 158.90 (d, J = 243 Hz), 147.8, 143.8 (d, J = 2.8 Hz), 129.2, 126.5 (d, J = 8.0 Hz), 123.5,
1
9
1
3
22.5, 116.0 (d, J = 22.5 Hz); F NMR (376 MHz, CDCl ): ꢀ119.7 (s, 1F); HRꢀMS (EI) m/z calcd for
+
C
18
H
15FN [M+H] 264.1189, found 264.1180.
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o
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Triphenylamine (5c). White solid (158 mg, 66%). MP 127ꢀ129 C; HꢀNMR (400 MHz, CDCl
3
): δ
13
7
.28 – 7.24 (m, 6H), 7.13 – 7.09 (m, 6H), 7.05 – 7.0 (m, 3H); CꢀNMR (101 MHz, CDCl
3
): δ 147.8,
+
129.2, 124.1, 122.6; HRꢀMS (EI) m/z calcd for C18
H
16N [M+H] 246.1283, found 246.1277.
o
1
4-Chloro-N,N-diphenylaniline (5d). White solid (162 mg, 59%). MP 108ꢀ109 C; HꢀNMR (500
MHz, CDCl ): δ 7.27 – 7.24 (m, 4H), 7.20 – 7.17 (m, 2H), 7.08 – 7.06 (m, 4H), 7.03 – 6.99 (m, 4H);
3
10
11
12
13
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48
49
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1
3
CꢀNMR (126 MHz, CDCl
3
): δ 147.4, 146.5, 129.3, 129.2, 127.3, 124.9, 124.3, 123.1; HRꢀMS (EI)
+
m/z calcd for C18
H15ClN [M+H] 280.0893, found 280.0885.
o
1
4
-Methoxy-N,N-diphenylaniline (5e). White solid (120 mg, 44%). MP 102ꢀ103 C; HꢀNMR (500
3
MHz, CDCl ): δ 7.23 – 7.19 (m, 4H), 7.08 – 7.06 (m, 2H), 7.05 – 7.03 (m, 4H), 6.94 (tt, J = 7.3, 1.1
1
3
Hz, 2H) 6.86 – 6.83 (m, 2H), 3.80 (s, 3H); CꢀNMR (101 MHz, CDCl
3
): δ 156.1, 148.1, 140.7, 129.0,
+
1
27.3, 122.8, 121.8, 114.7, 55.5; HRꢀMS (EI) m/z calcd for C19
H
18NO [M+H] 276.1388, found
276.1380; and 4-Methoxy-N-phenylaniline (3e). White solid (9 mg, 5%) Data of this compound were
14b
in accordance with those reported in literature.
o
1
2
-Methyl-N,N-diphenylaniline (5f). White solid (120 mg, 47%). MP 57ꢀ59 C; HꢀNMR (400 MHz,
13
3
CDCl ): δ 7.29 – 7.15 (m, 8H), 7.02 – 6.98 (m, 4H), 6.97 – 6.93 (m, 2H), 2.07 (s, 3H); CꢀNMR (101
MHz, CDCl ): δ 147.4, 145.3, 136.5, 131.7, 129.6, 129.0, 127.3, 126.0, 121.5, 121.3, 18.6; HRꢀMS
3
+
(
EI) m/z calcd for C19
H18N [M+H] 260.1439, found 260.1432; and 2-methyl-N-phenylaniline (3f).
White solid (30 mg, 17%). Data of this compound were in accordance with those reported in
19
literature.
o
1
3
-Methyl-N,N-diphenylaniline (5g). White solid (173 mg, 68%). MP 67ꢀ68 C; HꢀNMR (400 MHz,
CDCl ): δ 7.28 – 7.24 (m, 4H), 7.16 (t, J = 7.7 Hz, 1H), 7.12 – 7.09 (m, 4H), 7.04 – 7.0 (m, 2H), 6.95 ꢀ
.90 (m, 2H), 6.88 – 6.85 (m, 1H), 2.29 (s, 3H); CꢀNMR (101 MHz, CDCl ): δ 147.9, 147.7, 139.0,
3
1
3
6
3
+
129.1, 129.0, 124.9, 124.0, 123.7, 122.4, 121.5, 21.4; HRꢀMS (EI) m/z calcd for C19
H18N [M+H]
2
60.1439, found 260.1434; and 3-methyl-N-phenylaniline (3g). Oil (32 mg, 18%). Data of this
2
0
compound were in acordance with those reported in literature.
o
1
2
-Fluoro-N,N-diphenylaniline (5h). White solid (105 mg, 40%). MP 70ꢀ72 C; HꢀNMR (500 MHz,
1
3
3
CDCl ): δ 7.28 – 7.24 (m, 4H), 7.22 – 7.19 (m, 1H), 7.17 – 7.09 (m, 3H), 7.06 – 7.0 (m, 6H); Cꢀ
NMR (126 MHz, CDCl ): δ 158.4 (d, J = 250 Hz), 147.2, 134.6 (d, J = 10.3 Hz), 129.2 (d, J = 2Hz),
3
19
129.1, 126.0 (d, J = 7.9 Hz), 124.9 (d, J = 3.7 Hz), 122.4, 122.3, 117.1 (d, J = 19.9 Hz); F NMR (376
+
MHz, CDCl
3
): ꢀ119.2 (m, 1F); HRꢀMS (EI) m/z calcd for C18
H
15FN [M+H] 264.1189, found
264.1184.
o
1
N,N-diphenyl-[1,1'-biphenyl]-3-amine (5i). White solid (148 mg, 47%). MP 153ꢀ155 C; HꢀNMR
500 MHz, CDCl ): δ 7.51 – 7.49 (m, 2H), 7.40 – 7.37 (m, 2H), 7.30 (bt, J = 1.9 Hz, 1H), 7.3 (t, J =
.6 Hz, 2H), 7.28 – 7.23 (m, 5H), 7.15 – 7.13 (m, 4H) 7.07 – 7.01 (m, 3H); CꢀNMR (101 MHz,
(
3
13
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CDCl
3
): δ 148.3, 147.7, 142.3, 140.9, 129.5, 129.2, 128.6, 127.3, 127.1, 124.2, 122.9, 122.8, 122.7,
+
121.5; HRꢀMS (EI) m/z calcd for C24
H
20N [M+H] 322.15996, found 322.1584.
o
1
N-phenyl-[1,1'-biphenyl]-3-amine (3i). White solid (19 mg, 8%). MP 86ꢀ88 C; HꢀNMR (400 MHz,
3
CDCl ): δ 7.59 – 7.57 (m, 2H), 7.45 – 7.42 (m, 2H), 7.37 – 7.28 (m, 5H), 7.18 – 7.12 (m, 3H), 7.08 –
1
3
3
7.06 (m, 1H), 6.96 (tt, J = 7.3, 1.1 Hz, 1H), 5.78 (bs, 1H); CꢀNMR (101 MHz, CDCl ): δ 143.5,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
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5
6
7
8
9
0
142.9, 142.5, 141.1, 129.7, 129.4, 128.7, 127.4, 127.1, 121.2, 120.0, 118.0, 116.6, 116.4; HRꢀMS (EI)
+
m/z calcd for C18
H
16N [M+H] 246.1283, found 246.1277.
4-(tert-butyl)-N-(4-(tert-butyl)phenyl)-N-phenylaniline (5j). White solid (238 mg, 69%). MP 106ꢀ
o
1
1
3
08 C; HꢀNMR (500 MHz, CDCl ): δ 7.26 – 7.20 (m, 6H), 7.08 – 7.06 (m, 2H), 7.03 – 7.0 (m, 4H),
1
3
6.95 (tt, J = 7.3, 1.1 Hz, 1H), 1.31 (s, 18H); CꢀNMR (126 MHz, CDCl
25.9, 123.7, 123.3, 121.8, 34.2, 31.4; HRꢀMS (EI) m/z calcd for C26
358.2529.
3
): δ 148.1, 145.4, 145.1, 129.0,
+
1
H
32N [M+H] 358.2535, found
o
1
4-fluoro-N-(4-fluorophenyl)-N-phenylaniline (5k). White solid (183 mg, 65%). MP 92ꢀ93 C; Hꢀ
13
NMR (500 MHz, CDCl ): δ 7.27 – 7.24 (m, 2H), 7.07 – 6.96 (m, 11H); CꢀNMR (126 MHz, CDCl ):
3
3
δ 158.8 (d, J = 243 Hz), 148.0, 143.9 (d, J = 2.8 Hz), 129.2, 125.9 (d, J = 7.8 Hz), 122.8, 122.3, 116.1
19
(
[
d, J = 22.5 Hz); F NMR (376 MHz, CDCl ): ꢀ119.8 (m, 2F); HRꢀMS (EI) m/z calcd for C H F N
3
18 14
2
+
M+H] 282.1094, found 282.1084.
o
4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline (5l). White solid (229 mg, 75%). MP 104ꢀ106 C;
1
HꢀNMR (500 MHz, CDCl
3
): δ 7.19 – 7.16 (m, 2H), 7.06 – 7.03 (m, 4H), 6.95 – 6.93 (m, 2H), 6.88 –
13
6.85 (m, 1H), 6.84 – 6.81 (m, 4H), 3.80 (s, 6H); CꢀNMR (126 MHz, CDCl ): δ 155.6, 148.7, 141.1,
3
+
128.9, 126.4, 120.9, 120.5, 114.6, 55.5; HRꢀMS (EI) m/z calcd for C20
H
2
20NO [M+H] 306.1494,
found 306.1486.
o
1
4-chloro-N-(4-chlorophenyl)-N-phenylaniline (5m). White solid (150 mg, 48%). MP 76ꢀ78 C; Hꢀ
NMR (500 MHz, CDCl ): δ 7.28 – 7.25 (m, 2H), 7.21 – 7.18 (m, 4H), 7.06 – 7.03 (m, 3H), 7.0 – 6.97
3
13
(
m, 4H); CꢀNMR (126 MHz, CDCl
3
): δ 147.0, 146.1, 129.5, 129.3, 127.8, 125.0, 124.4, 123.5; HRꢀ
+
MS (EI) m/z calcd for C H Cl N [M+H] 314.0503, found 314.0498.
18
14
2
o
1
4
-methyl-N-phenyl-N-(p-tolyl)aniline (5n). White solid (137 mg, 50%). MP 113ꢀ114 C; HꢀNMR
(500 MHz, CDCl ): δ 7.22 – 7.18 (m, 2H), 7.06 – 7.02 (m, 6H), 7.0 – 6.98 (m, 4H), 6.94 (bt, J = 7.25
Hz, 1H), 2.31 (s, 6H); CꢀNMR (101 MHz, CDCl
121.6, 20.8; HRꢀMS (EI) m/z calcd for C20
3
13
3
): δ 148.2, 145.4, 132.3, 129.8, 129.0, 124.4, 122.9,
+
H
20N [M+H] 274.1596, found 274.1591.
o
1
3-methyl-N-phenyl-N-(m-tolyl)aniline (5o). White solid (147 mg, 54%). MP 68ꢀ70 C; HꢀNMR
(
500 MHz, CDCl
3
): δ 7.27 – 7.24 (m, 2H), 7.16 (t, J = 7.8 Hz, 2H) 7.10 – 7.08 (m, 2H), 7.01 (bt, J =
13
7.3 Hz, 1H), 6.94 (bs, 2H), 6.92 – 6.89 (m, 2H), 6.87 – 6.84 (m, 2H), 2.29 (s, 6H); CꢀNMR (126
MHz, CDCl
3
): δ 148.0, 147.8, 139.0, 129.1, 128.9, 124.9, 123.9, 123.5, 122.3, 121.4, 21.4; HRꢀMS
+
(
EI) m/z calcd for C20
H
20N [M+H] 274.1596, found 274.1588.
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ASSOCIATED CONTENT
AUTHOR INFORMATION
Corresponding Author
*Eꢀmail: Michael.Greaney@manchester.ac.uk
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ACKNOWLEDGMENT
We thank the EPSRC for funding (postdoctoral support for S.G.M. and Leadership fellowship to
M.F.G). We also thank the RSC for Undergraduate Research Bursary to M.V.P.
Supporting information
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Copies of H and C NMR spectra are available free of charge on the ACS Publications website.
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