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Cosolvent-promoted electrophilic amination of organozinc reagents.

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Full Paper
Received: 27 January 2009
Revised: 12 March 2009
Accepted: 12 March 2009
Published online in Wiley Interscience: 16 April 2009
(www.interscience.com) DOI 10.1002/aoc.1498
Cosolvent-promoted electrophilic amination of
organozinc reagents
Tahir Daşkapan∗, Ferhat Yeşilbağ and Selçuk Koca
In this study, we aimed to develop a simple and efficient method for the electrophilic amination of organozinc reagents. For this
reason, 12 cosolvents were screened in the electrophilic amination of ordinary organozinc reagents. By the use of a cosolvent,
an easily applicable and high-yielding method for the preparation of arylamines by electrophilic amination of arylzinc reagents
c 2009 John Wiley & Sons, Ltd.
was developed. Copyright Keywords: electrophilic amination; organozinc reagents; amines; cosolvent; aminating agent
Introduction
Appl. Organometal. Chem. 2009 , 23, 213–218
Results and Discussion
Our work started with the determination of optimal reaction
conditions for each class of organozinc reagents using the
amination reactions of phenylzinc chloride, diphenylzinc and
bromomagnesium triphenylzicate with 1 as model reactions. We
tried various values of PhM–1 and cosolvent–PhM (M: ZnCl, 1/2 Zn,
1/3 ZnMgBr). We aimed to obtain maximum yield of amine using
minimum amounts of PhM and cosolvent. Then the amination
of naphthylzinc and some functionalized arylzinc reagents with
1 was performed under optimal reaction conditions to broaden
the scope of this procedure from the point of aryl group. The
best results are given in Table 1. It is observed that Et3 N and
TMEDA did not promote the amination reaction of organozinc
reagents and the yield of aniline was low. When TMEDA was used
as cosolvent in the amination of phenylzinc reagents, a white solid
which melted at 173–175 ◦ C was isolated as the side product. We
∗
Correspondence to: Tahir Daşkapan, Ankara University Science Faculty,
Chemistry, Ankara, Turkey. E-mail: daskapan@science.ankara.edu.tr
Ankara University, Science Faculty, Department of Chemistry, 06100 Beşevler,
Ankara, Turkey
c 2009 John Wiley & Sons, Ltd.
Copyright 213
Aromatic amines are key intermediate products in the synthesis
of various practically important organic compounds such as
pharmaceuticals, agricultural chemicals, rubber chemicals and
dyes.[1] Therefore, the development of methods allowing the
synthesis of arylamines in high yields is of great importance.[2 – 5]
Electrophilic amination is now one of the most important synthetic
process for the formation of C–N bonds.[6 – 10] On the other hand,
due to their functional group tolerance, organozinc reagents allow
preparation of functionalized arylamines without the necessity to
use protecting groups or functional group interconversions.[11]
For this reason, we decided to focus on the electrophilic amination
of organozinc reagents.
Only a few electrophilic amination processes have been
reported so far in the literature employing organozinc
reagents.[12 – 19] In 1998 Rieke and co-workers reported a procedure
to prepare primary amines using organozinc halides and di-tertbutyl azodicarboxylate (DBAD) in three steps.[20] Electrophilic amination of organozinc reagents with benzenediazonium tetrafluoroborate has been investigated by Erdik and Koçoğlu.[21] Primary
arylamines were obtained as a mixture with aniline. Recently, Ghoraf and Vidal have reacted diorganozinc reagents with oxaziridines
to synthesize primary amines.[22] Knochel and co-workers have
described a procedure for the preparation of secondary amines
by electrophilic amination of alkylzinc reagents with functionalized arylazo tosylates.[23] The synthesis of tertiary amines via
electrophilic amination of organozinc chlorides and diorganozinc
reagents has been described by Johnson’s group.[24 – 26]
Previously, we reported a CuCN catalyzed electrophilic amination method for organozinc reagents, which produced primary
amines in low to moderate yields.[27] We thought the addition of
a cosolvent would improve this amination.
In this study, the effect of cosolvent on the reaction
conditions and on the yield of amine in the electrophilic
amination of organozinc chlorides, diorganozincs and
bromomagnesium triorganozincates with acetone O-(2,4,6trimethylphenylsulfonyl)oxime (1), acetone oxime O-tosylate (2)
and O-methylhydroxylamine (3) (Scheme 1) was investigated.
Compounds 1 and 2 are sp2 -N containing reagents and they
react with organometallic reagents by displacement of mesitylsulfonyloxy group and p-toluensulfonyloxy group, respectively,
to give an imine. Compound 3 is an sp3 -N containing reagent
and it reacts by displacement of methoxyl group to form an
amine (Scheme 2). We screened 1,3-dimethyl-3,4,5,6-tetrahydro2(1H)-pyrimidinone (DMPU), hexamethylphosphoramide (HMPA),
N,N,N ,N -tetramethylethylenediamine (TMEDA), triethylamine
(Et3 N), dimethyl sulfoxide (DMSO), N-methyl-pyrrolidin-2-one
(NMP), propylene carbonate (PC), 1,3-dimethyl-2-imidazolidinone
(DMEU), N,N-dimethylacetamide (DMAC), tetrahydrothiophene
1,1-dioxide (sulfolane), N,N,N ,N -tetramethylurea (TMU) and N,Ndimethylformamide (DMF) as cosolvents. All cosolvents were
removed from the reaction mixture by simply washing with water.
Yields of amines isolated as the N-benzoyl derivatives and the
known compounds were identified from their melting points[28]
and FT-IR analysis. Organozinc reagents used in this work were prepared by transmetallation of corresponding organomagnesium
bromides with ZnCl2 in THF.
T. Daşkapan F. Yeşilbağ and S. Koca
H3 C
CH3
(CH3)2C=NOSO2
H3 C
(CH3)2C=NOSO2
1
CH3
CH3ONH2
2
3
Scheme 1. Electrophilic amination reagents.
thought that it was ZnCl2 –TMEDA complex. For this reason, we
prepared this complex according to the published procedure[29]
(m.p. 173–176 ◦ C, literature 176–177 ◦ C). Comparison of the 1 H
NMR spectrums of the both solids [(CD3 )2 SO, 500 MHz, δ 2.699 (4 H),
2.434 (6 H)] showed that TMEDA reacted with organozinc reagents
to form ZnCl2 –TMEDA complex. Upon these observations we
turned our attention on the use of DMPU, HMPA, DMSO, NMP,
PC, DMEU, DMAC, sulfolane, TMU and DMF as cosolvents. These
solvents are dipolar aprotic in nature and they coordinate to metal
ions, therefore increasing the nucleophilicity of their counterions and influencing the reaction kinetics. In addition, since
they allowed solubilisation of organozinc reagents and CuCN,
we thought that they facilitated the formation of catalytic zinc
cyanocuprates which are the real catalysts.
In the previous method, arylamines mentioned here were
synthesized in 40–54% yields by reacting 2 mmol of arylzinc
chlorides with 1 mmol of 1 in the presence of 20 mol% CuCN.[27]
In our recent work, DMPU was found to be useful for electrophilic
amination of arylzinc chlorides with 1. Moreover, it was observed
that, by using 2 equiv. of DMPU, the yields could be improved up
to 72–78% with 10 mol% catalyst.[30] HMPA and TMU enhanced
the reaction as much as DMPU (Table 1 entries 5–7 and 23). These
three solvents were the most effective cosolvents in the amination
of arylzinc chlorides with 1. In addition, HMPA can be hydrolyzed
in acidic media.[31] Therefore, in our method its toxic effects can
be lessened by the action of concentrated HCl. Other solvents
improved the reaction conditions and allowed arylamines to be
prepared in good yields.
Although, in the absence of any cosolvent,[27] it was necessary to
use 2 equiv. of Ar2 Zn and 20 mol% CuCN to prepare arylamines in
moderate yields, in our new method the desired arylamines were
synthesized in high yields by using 1 equiv. of Ar2 Zn (Table 1).
For example, in the previous method p-anisidine was prepared in
51% yield; on the other hand, by employing DMAC this amine was
obtained in excellent yield (Table 1, entry 19). The best results were
supplied by DMPU, HMPA, PC, DMEU, DMAC and TMU. Reaction
of 0.66 equiv. of Ph2 Zn with 1 equiv. of 1 gave aniline in 65% yield
in the presence of HMPA (without HMPA, it was necessary to use
2 equiv. of Ph2 Zn to prepare aniline in 51% yield).
The best improvement was observed in the amination of
bromomagnesium triarylzincates. All the dipolar aprotic solvents
affected the reaction to give arylamines in high yields. Previously,
RM + 1 or 2
p-CH3C6H4M + 3
THF, CS,CuCN, r.t., 1-3h
1.THF, CS,CuCN,
r.t., 1.5-3h
2. Concd HCl
aniline, p-toluidine and p-anisidine were synthesized in 76, 55
and 61% yields, respectively, by the electrophilic amination of
Ar3 ZnMgBr with 1 (Ar3 ZnMgBr–1 = 2 : 1) in the presence of CuCN
alone.[27] As seen in Table 1, bromomagnesium triarylzincates were
aminated almost in quantitative yields (Ar3 ZnMgBr–1 = 1 : 1) in
the presence of an aprotic dipolar solvent (entries, 1, 3, 4,6, 10,
11, 16, 23, 24). Aniline was obtained in high yields even when
the reaction time was decreased to 1.5 h or when 0.66 equiv. of
Ph3 ZnMgBr was employed (78 and 79%, respectively).
Turnover number (TON) is a measure of catalyst efficiency. The
TON of a catalyst preferred to be as high as possible. To show
the effect of cosolvent on the catalytic activity of CuCN, the TON
of CuCN in the electrophilic amination of organozinc reagents
with 1 in the presence of HMPA, PC and DMEU are tabulated
and the turnover numbers of CuCN in the amination reaction of
organozinc reagents without the use of cosolvent are also included
for comparison (Table 2). The results show that using a cosolvent
improved the TON of CuCN from 1.13–1.38 to 8–18.2.
The amination of 2 and 3 were carried out in the presence
of various cosolvents to know about the scope of our method
from the point of aminating agent. Cosolvent-free amination of
organozinc reagents with 2 resulted in low to moderate yields. As
seen in Table 3, cosolvent enhanced the amination procedure
and allowed preparation of aniline in high yield after 1.5 h.
On the other hand this procedure applied to the amination
of alkyl, cycloalkyl and benzylzinc species with 2 using DMPU.
Unfortunately, aminations of these organozinc reagents resulted
in 11–59% yields (Table 3).
The effect of cosolvent on the reactivity of organozinc reagents
in the amination reaction was investigated using reactions
of phenylzinc chloride, diphenylzinc and bromomagnesium
triphenylzincate with 2 under catalyst-free conditions at room
temperature and at 40 ◦ C (Table 4). Diphenylzinc and phenylzinc
chloride did not react with 2 at room temperature. Addition of
DMPU (entry, 10) or increasing the reaction temperature (entries 7
and 11) did not change this result. Amination of these organozinc
reagents took place by the addition of DMPU at 40 ◦ C and aniline
was obtained in good yields (entries 8 and 12). Bromomagnesium
triphenylzincate reacted with 2 at room temperature to give aniline
in 55 and 21% yields after 3 and 1.5 h, respectively (entries 1 and
2). While a dramatic decrease in the yield of aniline was observed
by the addition of DMPU at room temperature (entry 3), a dramatic
increase was observed at 40 ◦ C (entry 4). These results show that
solvent-separated ion pairs of organozinc reagents are unreactive
in the amination reaction at room temperature but reactive at
temperatures higher than room temperature.
We applied the cosolvent-promoted amination method to
the reaction of organozinc reagents with 3 using p-tolylzinc
reagents (Table 5). We used DMPU as cosolvent in the amination of
CH3)2C=N-R
p-CH3C6H4NH2.HCl
1. Concd HCl
2. PhCOCl
PhCOCl
PhCONHR
p-CH3C6H4NHCOPh
M : ZnCl, 1/2 Zn, 1/3 ZnMgBr
R
: Phenyl, 4-tolyl, 4-anisyl, 1-naphthyl, n-butyl, c-hexyl, benzyl
CS : DMPU, HMPA, Et3N, TMEDA, DMSO, NMP, PC, DMEU, DMAC,
Sulfolane, TMU, DMF
214
Scheme 2. Electrophilic amination of organozinc reagents in the presence of cosolvent.
www.interscience.wiley.com/journal/aoc
c 2009 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2009, 23, 213–218
Cosolvent-promoted electrophilic amination of organozinc reagents
Table 1. Electrophilic amination of arylzinc reagents with 1 in the presence of cosolvent
ArMa + 1
1. THF, CuCN, CS, r.t., 3 h.
2. Concd HCl
ArNH2
ArNH2 (%)
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Ar
CS
CS/ArM
CuCN (%)
M: ZnCl
1/2Zn
1/3 ZnMgBr
C6 H5
p-CH3 C6 H4
p-CH3 OC6 H4
1-C10 H7
C6 H5
p-CH3 OC6 H4
1-C10 H7
C6 H5
C6 H5
p-CH3 OC6 H4
p-CH3 C6 H4
C6 H5
p-CH3 C6 H4
p-CH3 OC6 H4
C6 H5
p-CH3 C6 H4
p-CH3 OC6 H4
C6 H5
p-CH3 OC6 H4
C6 H5
p-CH3 C6 H4
p-CH3 OC6 H4
p-CH3 C6 H4
p-CH3 OC6 H4
p-CH3 OC6 H4
DMPU
DMPU
DMPU
DMPU
HMPA
HMPA
HMPA
DMSO
NMP
NMP
NMP
PC
PC
PC
DMEU
DMEU
DMEU
DMAC
DMAC
Sulfolane
Sulfolane
Sulfolane
TMU
TMU
DMF
1.5
1.5
1.5
1.5
1.5
1.5
1.5
2
2
2
2
2
2
2
2
2
2
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
–
–
–
–
75b
79b
78b
64
62
57
–
65
59
57
60
63
66
63
61
61
–
–
82
–
55
74
74
75
81
90
73
90
69d
63b
65b
–
82
90
–
71d
78d
86d
71
93
70
70
–
83
76
60
94
84
94
90
82
93
89
82c
78
93
91
81d
–
84d
83c
91c
80c
87b
85b
–
88b
88b
92
93
80
ArZnCl : 1 = 2 : 1, Ar2 Zn : 1 = 1, Ar3 ZnMgBr : 1 = 1
CuCN : 5%
c
CS/ArM = 1.5, CuCN : 5%
d CS/ArM = 1.5.
a
b
Table 2. The effect of cosolvent on the catalytic activity of CuCN in
the electrophilic amination of organozinc reagents with 1
p-CH3C6H4M + 1
Entry
1a
2
3a
4
5a
6
1. THF, CuCN, CS, r.t., 3 h.
2. Concd HCl
p-CH3C6H4NH2
M
CS
CuCN
(mmol)
p-CH3 C6 H4NH2
(mmol)
TONb
ZnCl
ZnCl
1/2 Zn
1/2 Zn
1/3 ZnMgBr
1/3 ZnMgBr
–
HMPA
–
PC
–
DMEU
0.4
0.1
0.4
0.1
0.4
0.05
0.49
0.8
0.45
0.9
0.55
0.91
1.23
8
1.13
9
1.38
18.2
a
Reference 27.
b TON = mmoles of p-CH C H NH /mmoles of CuCN.[32]
3 6 4
2
Appl. Organometal. Chem. 2009, 23, 213–218
Conclusions
The effects of 12 cosolvents on the synthesis of various arylamines
were investigated in the electrophilic amination of ordinary
organozinc reagents with 1–3 and a simple and high-yielding
preparation for primary arylamines has been described. It is
observed that, by using a cosolvent the required amount of
CuCN for a high yielding reaction was reduced from 20 to 5 mol%
for all organozinc reagents and the amounts of diarylzincs and
bromomagnesium triarylzincates could be lessened by as much
as 50%. In the case of amination with 2 the amount of arylzinc
chloride lessened too.
c 2009 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
215
arylzinc chlorides. We observed that while amination of phenylzinc
chloride resulted in very low yields (entries 1 and 2) amination
of p-tolylzinc chloride gave p-toluidine in moderate yields after
3 h (entries 3 and 4). In the case of amination of diarylzinc,
cosolvent did not increase the yield. It only lessened the amount
of catalyst (from 20 to 5 mol%) and reaction time (from 3 to
1.5 h).[27] DMPU was the most useful cosolvent in the amination
of bromomagnesium triarylzincate reagents with 3. It raised the
yield and decreased the amount of catalyst and reaction time
(entry 11). Sulfolane increased the yield as much as DMPU but the
amount of catalyst was higher. NMP, DMEU and DMAC improved
the reaction conditions. Surprisingly, PC inhibited the amination
reaction (entries 13 and 14).
T. Daşkapan F. Yeşilbağ and S. Koca
Table 3. Electrophilic amination of organozinc reagents with 2 in the
presence of cosolvent
RMa + 2
2. Concd. HCl
PhMa + 2
RNH2
RM
CSc
RNH2 , %
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(C6 H5 )3 ZnMgBr
(n-C4 H9 )3 ZnMgBr
(c-C6 H11 )3 ZnMgBr
(C6 H5 CH2 )3 ZnMgBr
(C6 H5 )2 Zn
(C6 H5 )2 Zn
(C6 H5 )2 Zn
(C6 H5 )2 Zn
(n-C4 H9 )2 Zn
(c-C6 H11 )2 Zn
(C6 H5 CH2 )2 Zn
C6 H5 ZnCl
n-C4 H9 ZnCl
c-C6 H11 ZnCl
C6 H5 CH2 ZnCl
HMPA
DMSO
NMP
PC
DMEU
DMAC
Sulfolane
DMPU
DMPU
DMPU
HMPA
NMP
PC
DMEU
DMPU
DMPU
DMPU
HMPA
DMPU
DMPU
DMPU
84
93
86
93
87
82
80
20
20
59
94
94
76
94
11
13
51
92
20
20
59
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
1. THF, CS, CuCNb, r.t., 1.5 h.
Table 4. The effect of the temperature on the electrophilic aminatio
of organozinc reagents with 2 in the presence of cosolvent
R3 ZnMgBr : 2 = 1 : 1, R2 Zn : 2 = 1 : 1, RZnCl : 2 = 1.5 : 1
CuCN, %: in the case of R3 ZnMgBr and R2 Zn, 10%, in the case of RZnCl,
5%.
c CS/R ZnMgBr = 1.5, CS/R Zn = 2, CS/RZnCl = 1.5
3
2
a
1. THF, DMPU, r.t., 40 °C, 1-3 h.
2. Concd. HCl
PhNH2
Entry
M
DMPU/RM
Temperature
(◦ C),
Time, h.
PhNH2
1
2
3
4
5
6
7
8
9
10
11
12
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/2 Zn
1/2 Zn
1/2 Zn
ZnCl
ZnCl
ZnCl
ZnCl
–
–
1.5
1
0.5
–
–
2
–
1.5
–
1.5
r.t.
r.t.
r.t.
40
40
r.t.
40
40
r.t.
r.t.
40
40
3
1.5
3
1.5
1
3
1.5
1.5
3
3
1.5
1.5
55
21
20
64
60
0
0
58
0
0
0
61
a
Ph3 ZnMgBr : 2 = 1 : 1, Ph2 Zn : 2 = 1 : 1, PhZnCl: 2 = 1.5 : 1
conventional standard methods and their concentrations were
determined by the method of Watson and Eastham.[35]
Acetone O-(2,4,6-trimethylphenylsulfonyl)oxime[36] 1, acetone
oxime O-tosylate[37] 2 and O-methylhydroxylamine[38] 3 were
prepared and purified according to the methods described in the
literature.
b
This method not only raised the yield but also reduced
significantly the amount of waste. Therefore, compared with
previously reported methods, in the absence of any cosolvent,
the method reported here is more economic, more efficient and
safer.
Experimental
General Procedures
216
All reactions involving organozinc reagents were performed
in flame-dried glassware with standard syringe/cannula
techniques[33] under an atmosphere of dry, oxygen-free argon.
Melting points were determined on a Gallencamp capillary melting point. IR spectra were recorded on a Perkin-Elmer Spectrum
100 FT-IR spectrometer.
THF was freshly distilled from a solution of sodium–
benzophenone under dry argon. All of the cosolvents were distilled under reduced pressure prior to use and kept over molecular
sieves (4 Å, 4–8 mesh) and under argon atmosphere. CuCN was
purified according to the published procedure.[34]
Organozinc chlorides, diorganozincs and bromomagnesium
triorganozincates were prepared from 1, 2, or 3 equiv. of
corresponding organomagnesium bromides, respectively, via
transmetallation with 1 equiv. of ZnCl2 , in THF at −3 ◦ C.
Benzylmagnesium bromide was prepared in diethylether and
other organomagnesium bromides were prepared in THF by
www.interscience.wiley.com/journal/aoc
Amination of Organozinc Reagents
Amination of RZnCl
A solution of ZnCl2 (0.546 g, 4 mmol) in anhydrous THF (4 ml) was
cooled to −3 ◦ C under argon atmosphere and 4 mmol of organomagnesium bromide in THF was added dropwise by syringe (in
the case of 2 the amount of RZnCl was 3 mmol). The reaction
mixture was stirred for an additional 5 min, the cooling bath
was removed and the resulting white suspension was allowed to
warm to room temperature. To this mixture, CuCN (5–10 mmol%),
cosolvent (in the amination; with 2, 4.5 mmol, with 3, 8 mmol,
with 1, DMSO and PC were 8 mmol; the others were 6 mmol) and
a solution of 1–3 (2 mmol) in dry THF (3 ml) were added. The
reaction mixture was stirred at room temperature for 1–3 h and
then worked up by addition of concentrated HCl with stirring
at room temperature for 4 h. The aqueous phase was washed
with diethyl ether (2 × 50 ml), made basic with concd NaOH and
the free amine was extracted with diethyl ether (3 × 50 ml). The
organic layer was dried over Na2 SO4 , the solvent was evaporated
and the crude product was converted to its N-benzoyl derivative
by reaction with benzoyl chloride in the presence of NaOH. The
product was recrystallized from ethanol : water (4 : 1).
In the case of amination of PhZnCl with 2 at 40 ◦ C, reaction flask
was transferred to an oil bath that had been warmed to 40 ◦ C after
addition of 2 and the mixture was stirred under positive pressure
of argon for 1.5–3 h.
Amination of R2 Zn
A solution of ZnCl2 (0.273 g, 2 mmol) in dry THF (4 ml) was cooled
to −3 ◦ C under argon atmosphere and 4 mmol of organomagnesium bromide in THF was added dropwise by syringe. The reaction
c 2009 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2009, 23, 213–218
Cosolvent-promoted electrophilic amination of organozinc reagents
Table 5. Electrophilic amination of organozinc reagents with 3 in the presence of cosolvent
p-CH3C6H4Ma + 3
Entry
M
1b
2b
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
ZnCl
ZnCl
ZnCl
ZnCl
ZnCl
1/2 Zn
1/2 Zn
1/2 Zn
1/2 Zn
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
1/3 ZnMgBr
a
b
1. THF, CS, CuCN, r.t., 1.5-3 h.
2. Concd. HCl
CS, CS/p-CH3 C6 H4 M
p-CH3C6H4NH2
CuCN, %
Time, h
p-CH3 C6 H4 NH2 , %
10
10
10
10
5
10
5
5
5
10
5
5
5
10
5
10
10
1.5
3
3
3
3
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
14
17
66
60
32
70
70
60
61
83
81
70
0
0
73
73
80
DMPU, 2
DMPU, 2
DMPU, 2
DMPU, 1.5
DMPU, 2
DMPU, 2
DMPU, 2
DMEU, 2
DMAC, 2
DMPU, 1.5
DMPU, 1.5
NMP, 1.5
PC, 1.5
PC, 1.5
DMEU, 1.5
DMAC, 2
Sulfolane, 2
p-CH3 C6 H4 ZnCl/3 = 2 : 1, (p-CH3 C6 H4 )2 Zn/3 = 1 : 1, (p-CH3 C6 H4 )3 ZnMgBr/3 = 1 : 1
R: C6 H5 and C6 H5 ZnCl/3 = 2 : 1
mixture was stirred for an additional 5 min, the cooling bath
was removed and the resulting white suspension was allowed to
warm to room temperature. To this mixture, CuCN (5–10 mmol%),
cosolvent (in the amination; with 2 and 3, 4 mmol, with 1, NMP and
PC were 4 mmol, the others were 3 mmol) and a solution of 1–3
(2 mmol) in dry THF (3 ml) were added. The reaction was carried
out and worked up in the same way as in the previous section.
In the case of amination of Ph2 Zn with 2 at 40 ◦ C, reaction flask
was transferred to an oil bath that had been warmed to 40 ◦ C after
addition of 2 and the mixture was stirred under positive pressure
of argon for 1.5–3 h.
Amination of R3 ZnMgBr
A solution of ZnCl2 (0.273 g, 2 mmol) in anhydrous THF (4 ml)
was cooled to −3 ◦ C under argon atmosphere and 6 mmol of
organomagnesium bromide in THF was added dropwise via
syringe. The reaction mixture was stirred for an additional 5 min,
the cooling bath was removed and the resulting white suspension
was allowed to warm to room temperature. To this mixture, CuCN
(5–10 mmol%), cosolvent (in the amination; with 1, NMP was
4 mmol, the others were 3 mmol; with 2, 3 mmol and with 3, DMAC
and sulfolane were 4 mmol, the others were 3 mmol) and a solution
of 1–3 (2 mmol) in dry THF (3 ml) were added. The reaction was
carried out and worked up by the same way as described above.
In the case of amination of Ph3 ZnMgBr with 2 at 40 ◦ C, reaction
flask was transferred to an oil bath that had been warmed to 40 ◦ C
after addition of 2 and the mixture was stirred under positive
pressure of argon for 1–3 h.
Acknowledgments
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