Enantioselective synthesis of N-heterocycles via intramolecular Pd(0)-catalysed allylic amination

Article abstract of DOI:10.1016/j.tet.2013.09.043

An efficient and stereoselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles is described by the intramolecular Pd(0)-catalysed cyclisation of amino allylic carbonates. The use of chiral ligands gave the corresponding heterocyclic derivatives having er values that were from moderate to good.

Full text of DOI:10.1016/j.tet.2013.09.043

Tetrahedron 69 (2013) 9551e9556
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Enantioselective synthesis of N-heterocycles via intramolecular
Pd(0)-catalysed allylic amination
*
Beata Olszewska, Bogus1aw Kryczka, Anna Zawisza
ꢀ ꢀ
ꢀ ꢀ
Department of Organic and Applied Chemistry, University of Łodz, Tamka 12, 91-403 Łodz, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 June 2013
Received in revised form 4 September 2013
Accepted 16 September 2013
Available online 20 September 2013
An efficient and stereoselective synthesis of pyrrolidine-, piperidine-, and azepane-type N-heterocycles is
described by the intramolecular Pd(0)-catalysed cyclisation of amino allylic carbonates. The use of chiral
ligands gave the corresponding heterocyclic derivatives having er values that were from moderate to
good.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Allylic carbonate
Cyclisation
Homogeneous catalysis
Nitrogen heterocycles
Palladium
1. Introduction
a route to functionalised nitrogen heterocycles, and methods
employing catalysts based on Au,15 Bi,16 Pd,17 Ru,18 Hg, Sn, Ga, Bi,
Nitrogen heterocycles are ubiquitous in natural products,
pharmaceuticals, organic materials, and numerous functional
molecules.1 For these reasons the efficient stereoselective con-
struction of these molecules, particularly in a catalytic enantiose-
lective manner, has been of long-standing interest. Several
powerful new transformations have been developed that involve
the use of transition metal-catalysed CeN bond-forming reactions
for the construction of heterocyclic rings. These transformations
frequently occur under mild conditions, tolerate a broad array of
functional groups and proceed with high stereoselectivity.
Recently, a variety of late transition metal complexes based on
Pt2 and Rh, in which the enantioselective hydroamination of
unactivated alkenes with amines has been presented.3 Futhermore,
Ir,4 Pd,5 Au,6 and Cu7 based catalysts have been reported as catalysts
for intramolecular hydroamination.
and Fe16,19 have been reported.
The groups of Helmchen have reported enantioselective intra-
molecular amination of allylic acetates and carbonates catalysed by
Ir complexes.20 This method gave 2-vinylpyrrolidine and 2-
vinylpiperidine derivatives in good yields and ee values of >90%.
By extending our previous work on the use of allyl carbonates in
the synthesis of O- and N-heterocycles,21 in this paper we report
results on enantioselective intramolecular Pd(0)-catalysed allylic
amination.
2. Results and discussion
2.1. Synthesis of the starting materials
The starting allylic carbonates 5aei were prepared according to
Scheme 1.
Intramolecular cyclisation of allenes with tethered amines in the
presence of a transition metal catalyst represents a second route for
generating nitrogen-containing heterocycles. These trans-
formations have been developed with metal salts or complexes of
Zr, Ti,8 Cu,9 lanthanides,10 Pd,11 Au,12 Ag,13 and Hg.14
The reduction of bromoesters 1aec to the corresponding alde-
hydes,22 followed by elongation of the chain via the Wittig re-
action23 afforded unsaturated esters 2aec in 75, 72, and 70% yields,
respectively. Compounds 3aec were obtained in 85, 98, and 76%
yields, respectively, by the reduction of esters 2aec with DIBALeH
in diethyl ether.24
The intramolecular enantioselective amination of allylic alco-
hols with amines or carbamates has also attracted attention as
Condensation of these alcohols with methyl or isobutyl chlor-
oformate at 0 ꢀC afforded allylic carbonates 4aee in 82e96% yield.
Finally, substitution of the bromine atom with
methylbenzenesulfonamide group (tosyl group), benzyl group,
a
4-
* Corresponding author. Tel.: þ48 42 6355764; fax: þ48 42 6655162; e-mail
address: azawisza@chemia.uni.lodz.pl (A. Zawisza).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.09.043

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B. Olszewska et al. / Tetrahedron 69 (2013) 9551e9556
Scheme 1. Pd0-catalysed synthesis of heterocycles 6aeg. Reagents and conditions: (a) 1. DIBALeH, CH2Cl2, ꢁ78 ꢀC, 2. Ph3P]CHCO2C2H5, CH2Cl2, rt; (b) DIBALeH, Et2O, 0 ꢀC; (c)
R1OCOCl, C5H5N, CH2Cl2, 0 ꢀC/rt; (d) TsNHNa, TsNH2, DMSO, 60 ꢀC or R2NH2, i-Pr2EtN, DMF, rt for R2¼Bn, C6H11, t-Bu; (e) Pd2(dba)3, ligand.
cyclohexyl or tert-butyl group gave corresponding amino-
carbonates 5aei (45e85% yield).
2.3. Pd(0)-catalysed asymmetric cyclisation
Asymmetric cyclisation was performed only with N-tosyl and N-
benzyl isobutyl carbonates 5b, 5c, 5e and 5f. The results presented
in Table 1 and our previous studies21b,c have shown that using
isobutyl carbonates as a starting material gave higher reactivities
and selectivities in comparison with methyl carbonates. Several
types of ligands were selected for testing.
Phosphines were the first class of ligands (Fig. 1) applied to the
Pd(0)-catalysed allylic substitutions (Table 2, entries 1e10). Ring-
closure of 5b occurred slowly (48 h) at room temperature in the
presence of (S)-Binap and provided 1-tosyl-2-vinylpyrrolidine 6a as
a 41:59 mixture of enantiomers in 97% overall yield (Table 2, entry
1). Longer chain isobutyl carbonate 5e was less reactive under the
same conditions and gave piperidine 6c in 45% yield and in a 65:35
ratio (Table 2, entry 2). Carbonate 5b in the presence of the Josiphos
ligand, similar to the results observed for (S)-Binap, gave pyrroli-
dine 6a in good yield (87%) and with an enantioselectivity ratio of
41:59 (Table 2, entry 3).
2.2. Pd(0)-catalysed cyclisation of allylic carbonates 5aei
The cyclisation was first studied with methyl carbonate 5a as the
substrate. The ring-closure of 5a occurred readily in THF at room
temperature in the presence of a catalytic amount of Pd2(dba)3 and
PPh3, which provided exclusively 1-tosyl-2-vinylpyrrolidine 6a21b
in 98% yield (Table 1, entry 1). Under the same conditions iso-
butyl carbonate 5b quantitatively gave pyrrolidine 6a (Table 1, en-
try 2). The cyclisation of N-benzyl carbonate 5c occurred slowly at
room temperature and provided 1-benzyl-2-vinylpyrrolidine
6b15b,20d,25 in 95% yield (Table 1, entry 3). Longer chain, methyl
and isobutyl carbonates 5d and 5e were also submitted to this
cyclisation procedure, 1-tosyl-2-vinylpiperidine 6c21b was obtained
in a very good yield after 30 min in both cases (97 and 98%, re-
spectively, Table 1, entries 4 and 5). The reaction with N-benzyl
carbonate 5f required a longer reaction time (48 h) but gave an N-
benzyl derivative of piperidine 6d15b,20d,25 in 98% yield (Table 1,
entry 6). The cyclisation of compound 5g at room temperature did
not give the expected product 6e. The same reaction at 60 ꢀC
afforded 1-cyclohexyl-2-vinylpiperidine 6e in 56% yield after 20 h
(Table 1, entries 7 and 8). The formation of N-tert-butyl-2-
vinylpiperidine 6f was never observed in the cyclisation of allylic
carbonate 5h (Table 1, entries 9 and 10). Finally, we studied the
Pd(0)-catalysed cyclisation of allylic carbonate 5i. Azepane 6g was
obtained in 70% yield after 24 h at 20 ꢀC (Table 1, entry 11).
The same reaction at 60 ꢀC afforded a 1:1 mixture of enantio-
mers (Table 2, entry 4). Isobutyl carbonate 5e was less reactive and
required a much longer reaction time (Table 2, entries 5e7). N-Tosyl
piperidine 6c was obtained in 10% yield after 48 h and 82% after
168 h as a 65:35 mixture, while at 60 ꢀC 6c was obtained in 92%
yield after 72 h (53:47 er). The same reaction in the presence of the
Walphosephosphines ligand derived from ferroceneeafforded
a 1:1 mixture of enantiomers (Table 2, entry 8). The trifluoromethyl
derivative of Walphos was more reactive and gave a product of
intramolecular allylic amination 6c in a higher yield (81%) and was
enantioselective (69:31). Asymmetric cyclisation of N-tosyl car-
bonate 5e was also carried out in the presence of the phosphine-
amine ligand PPM. This cyclisation gave piperidine 6c in 64%
yield and a very low er value of 53:47.
Phosphorus amidites were second class of ligands used for the
construction of heterocyclic rings (Table 2, entries 11e16). The
cyclisation of compounds 5b at room temperature in the presence
of L1(S,S,aS) gave pyrrolidine 6a (99% yield) with good selectivity
(22:78 er) (Table 2, entry 11). Piperidine 6c was obtained in 99%
yield under the same conditions with an er value of 90:10 starting
from allyl carbonate 5e (Table 2, entry 12). Lowering the temper-
ature to 0 ꢀC and ꢁ20 ꢀC improved the selectivity of the reaction,
and an er of 93:7 and 92:8, respectively (Table 2, entries 13 and 14).
We also tried to cyclise 5e in the presence of phosphorus amidite
ligand L2(R,R,R), which is different from the L1(S,S,aS) of 2,5-
Table 1
Pd0-catalysed allylic cyclisation of substrates 5aei according to Scheme 1a
Entry
Substrate
Product
T [ꢀC]
Time [h]
Yieldb [%]
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
5g
5g
5h
5h
5i
6a
6a
6b
6c
6c
6d
6e
6e
6f
20
20
20
20
20
20
20
60
20
60
20
0.5
0.5
24
0.5
0.5
48
24
24
48
48
98
99
95
97
98
99
0
56
0
0
9
10
11
6f
6g
24
70
a
[5]/[Pd2(dba)3]/[PPh3]¼40:1:4.4, THF.
b
Yield refers to isolated pure products after column chromatography.

B. Olszewska et al. / Tetrahedron 69 (2013) 9551e9556
9553
Fig. 1. Ligands used in this work.
Table 2
Cyclisation of N-benzyl carbonates 5c and 5f to pyrrolidine and
piperidine derivatives 6b and 6d, respectively, also took place in the
presence of four classes of ligands (Table 3, entries 1e22). The
phosphine ligands proved more effective for N-benzyl carbonates
than for N-tosyl derivatives 5b and 5e. When the reaction was
performed at 20 ꢀC we observed that the (S)-Binap afforded N-
benzyl pyrrolidine 6b in 88% yield and with an S/R enantiomeric
ratio20a,d of 83:17 (Table 3, entry 1). Under the same conditions N-
benzyl piperidine 6d was obtained with an er of 14:86 (S/R) but in
a 14% yield (Table 3, entry 2). Increasing the temperature to 60 ꢀC
gave the cyclised product in a 95% yield in less time, but resulted in
a decrease in enantioselectivity (Table 3, entry 3). (R,S)-Josiphos
gave good selectivity only for piperidine 6d. We obtained selectivity
S/R 65:35 for pyrrolidine 6b, and S/R 17:83 for 6d (Table 3, entries
4 and 5).
Pd0-catalysed asymmetric allylic cyclisation of N-tosyl carbonates 5b and 5ea
Entry Carbonate Product Ligand
T [ꢀC] Time [h] Yieldb [%] erc
1
2
3
4
5
6
7
8
5b
5e
5b
5b
5e
5e
5e
5e
5e
5e
5b
5e
5e
5e
5e
5e
5b
5e
5e
6a
6c
6a
6a
6c
6c
6c
6c
6c
6c
6a
6c
6c
6c
6c
6c
6a
6c
6c
(S)-Binap
(S)-Binap
20
20
20
60
20
48
48
48
48
48
97
45
87
96
10
82
92
56
81
64
99
99
99
99
0
41:59
65:35
41:59
50:50
66:34
65:35
53:47
50:50
69:31
53:47
22:78
90:10
93:7
(R,S)-Josiphos
(R,S)-Josiphos
(R,S)-Josiphos
(R,S)-Josiphos
(R,S)-Josiphos
Walphos
WalphoseCF3
PPM
L1(S,S,aS)
L1(S,S,aS)
L1(S,S,aS)
L1(S,S,aS)
L2(R,R,R)
20 168
60
20
20
20
20
20
0
ꢁ20
20
20
20
20
0
72
24
48
24
24
24
24
24
48
24
24
24
24
9
10
11
12
13
14
15
16
17
18
19
92:8
d
PipPhos
38
98
99
0
58:42
40:60
61:39
d
(R,R)-Trost
(R,R)-Trost
(R,R)-Trost
Table 3
Pd0-catalysed asymmetric allylic cyclisation of N-benzyl carbonates 5c and 5fa
a
[5]/[Pd2(dba)3]/[ligand]¼40:1:2.2 (4.4), THF; (S)-Binap: (S)-(ꢁ)-(1,10-binaph-
Entry Carbonate Product Ligand
T [ꢀC] Time [h] Yieldb [%] erc (S/R)
thalene-2,20-diyl)bis(diphenylphosphine),
(R,S)-Josiphos:
(R)-1-{(S)-2-
1
2
3
4
5
6
7
8
5c
5f
5f
5c
5f
5f
5f
5f
5c
5f
5c
5f
5f
5f
5f
5f
5f
5c
5f
5f
5f
5f
5f
6b
6d
6d
6b
6d
6d
6d
6d
6b
6d
6b
6d
6d
6d
6d
6d
6d
6b
6d
6d
6d
6d
6d
(S)-Binap
(S)-Binap
(S)-Binap
(R,S)-Josiphos 20
(R,S)-Josiphos 20
(R,S)-Josiphos 60
Walphos
Walphos-CF3
PPM
20
20
60
24
48
24
24
48
96
24
24
24
24
24
24
24
88
14
95
50
30
87
96
99
95
92
99
96
99
50
0
93
92
99
96
86
84
13
11
83:17
14:86
28:72
65:35
17:83
63:37
50:50
53:47
94:6
56:44
27:73
3:97
87:13
71:29
d
diphenylphosphanyl]ferrocenyl}ethyldicyclohexylphosphane, Walphos: (R)-1-
{(RP)-2-[2-(diphenylphosphino)phenyl]ferrocenyl}ethyldiphenylphosphine, Wal-
phoseCF3:
(R)-1-{(RP)-2-[2-(diphenylphosphino)phenyl]ferrocenyl}ethylbis[3,5-
bis-(trifluoromethyl)phenyl]phosphine, PPM: (2S,4S)-(ꢁ)-4-diphenylphosphino-2-
(diphenylphosphinomethyl)pyrrolidine,
L1(S,S,aS):
(S,S,S)-(þ)-(3,5-dioxa-4-
phosphacyclohepta[2,1-a:3,4-a0]dinaphthalen-4-yl)bis(1-phenylethyl)amine,
L2(R,R,R): (R,R,R)-1-(3,5-dioxa-4-phosphacyclohepta[2,1-a:3,4-a0]dinaphthalen-4-
yl)-2,5-diphenylpyrrolidine, PipPhos: (S)-(þ)-(3,5-dioxa-4-phosphacyclohepta[2,1-
20
20
20
20
20
20
0
a:3,4-a0]dinaphthalen-4-yl)piperidine,
(R,R)-Trost:
(1R,2R)-1,2-bis[(2-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
PPM
diphenylphosphanyl)benzoylamino]cyclohexane.
b
L1(S,S,aS)
L1(S,S,aS)
L1(S,S,aS)
L1(S,S,aS)
L2(R,R,R)
PipPhos
Monophos
(R,R)-Trost
(R,R)-Trost
(R,R)-Trost
(R,R)-Trost
(R,R)-Trost
(R,R)-Trost
Yield refers to isolated pure products after column chromatography.
Enantioselectivity (er) was measured by chiral stationary phase HPLC on a Chiral
c
IA column (25 cmꢂ4.6 mm); i-propanol/hexane (99:1), flow rate¼0.2 mL minꢁ1
,
,
tR¼23.8 min and tR¼24.8 min for 6a; methanol, flow rate¼0.2 mL minꢁ1
ꢁ20 120
20
20
20
20
60
20
0
48
24
24
24
24
48
24
tR¼23.6 min and tR¼26.4 min for 6c; the first value corresponds to the enantiomer
51:49
46:54
88:12
16:84
12:88
71:29
68:32
55:45
being eluted first.
diphenylpyrrolidine substituent [L1(S,S,aS) has a bis(1-phenylethyl)
amine substituent]. At room temperature 5e did not give the ex-
pected product 6c (Table 2, entry 15). The next phosphorus amidite
ligand with a piperidine ring (PipPhos) and carbonate 5e afforded
6c in 38% yield after 24 h but with a very low er value of 58:42
(Table 2, entry 16).
Finally, the asymmetric cyclisation of carbonates 5b and 5e was
performed in the presence of the phosphine-amide (R,R)-Trost li-
gand. Ring-closure of 5b gave 2-vinylpyrrolidine 6a as a 40:60
mixture of enantiomers in 98% overall yield (Table 2, entry 17).
Piperidine 6c was obtained in a very good yield (99%) and with
highest stereoselectivity (61:39 er) (Table 2, entry 18). Decreasing
the temperature to 0 ꢀC did not improve the selectivity of the re-
action, what is more, in these conditions cyclisation did not take
place (Table 2, entry 19).
ꢁ20 120
ꢁ40 120
a
[5]/[Pd2(dba)3]/[ligand]¼40:1:2.2 (4.4), THF; Monophos: (R)-(ꢁ)-(3,5-dioxa-4-
phosphacyclohepta[2,1-a:3,4-a0]dinaphthalen-4-yl)dimethylamine.
b
Yield refers to isolated pure products after column chromatography.
Enantioselectivity (er) was measured by chiral stationary phase HPLC on a Chiral
c
OD-H column (25 cmꢂ4.6 mm); hexane/i-propanol (99.9:0.1), flow
rate¼0.5 mL minꢁ1
tR[(S)-6b]¼8.66 min and tR[(R)-6b]¼11.31 min; hexane/i-
,
propanol (99.9:0.1), flow rate¼0.5 mL minꢁ1, tR[(S)-6d]¼7.41min and tR[(R)-6d]¼
7.95 min.
The Walphos ligands, similarly as for the tosyl derivatives,
proved to be completely unselective in this type of cyclisation and

9554
B. Olszewska et al. / Tetrahedron 69 (2013) 9551e9556
afforded practically a 1:1 mixture of enantiomers (Table 3, entries
7 and 8). The phosphine-amine ligand PPM gave products 6b and
6d in a good yield of 95% and 92%, respectively, after 24 h, but the er
value of 6d was very low (S/R 58:42) while that of 6b was 94:6
(Table 3, entries 9 and 10). Among the phosphorus amidite ligands,
the most effective proved to be L1(S,S,aS) (Table 3, entries 11e17).
Both carbonates 5c and 5f gave cyclisation products in excellent
yields (99% for 6b and 96% for 6d) and high enantioselectivity, es-
pecially for N-benzyl piperidine, 3:97 in favour of (R)-6d (Table 3,
entries 11 and 12). Additionally, lowering the temperature to 0 ꢀC
gave 6d with a reversal of configuration (S/R 87:13) (Table 3, entry
13). We observed that lowering the temperature to ꢁ20 ꢀC resulted
in a decrease in both yield and selectivity (er 71:29, 50% yield)
(Table 3, entry 14).
Finally, we tested the phosphine-amide (R,R)-Trost ligand. Cyc-
lisation of 5e at 20 ꢀC gave an 88:12 (S/R) mixture of stereoisomers
in 99% yield (Table 3, entry 18). The use of longer-chain carbonate 5f
afforded a good yield and stereoselectivity: (S)-6d/(R)-6d 16:84 and
12:88 at 60 and 20 ꢀC, respectively (Table 3, entries 19, 20). We also
examined the influence of temperature on the asymmetric allylic
amination of substrate 5f using the Trost ligand. Similarly to ligand
L1(S,S,aS), lowering the temperature resulted in a decrease in yield
and selectivity of the reaction; moreover, N-benzyl pyrrolidine 6d
showed the opposite ratio (er values of 71:29 at 0 ꢀC).
4.2.1. (E)-7-Bromohept-2-en-1-yl methyl carbonate 4c. Colourless
oil, 4.8 g, 87% yield; Rf (hexane/EtOAc, 4:1) 0.60; nmax (liquid film)
3002, 1743, 1674, 1266 cmꢁ1
; dH (200 MHz, CDCl3) 1.59 (quintet, 2H,
J 6.9, H-6),1.83 (quintet, 2H, J 6.9, H-5), 2.12 (q, 2H, J 7.1, H-4), 3.43 (t,
2H, J 6.9, H-7), 3.80 (s, 3H, CH3), 4.56 (d, 2H, J 6.3, H-1), 5.62 (dt,1H, J
15.5, 6.3, H-2), 5.80 (dt, 1H, J 15.5, 6.3, H-3); dC (50 MHz, CDCl3) 29.7
(C-4), 31.3 (C-5), 32.1 (C-6), 33.5 (C-7), 54.7 (OCH3), 68.5 (C-1), 123.9
(C-3), 136.3 (C-2), 155.5 (CO). Found: C, 42.94; H, 6.05. C9H15BrO3
requires C, 43.05; H, 6.02%.
4.2.2. (E)-8-Bromooct-2-en-1-yl methyl carbonate 4e. Colourless
oil, 4.6 g, 82% yield; Rf (hexane/EtOAc, 5:1) 0.80; nmax (liquid film)
3007, 1748,1673,1267 cmꢁ1
; dH (200 MHz, CDCl3) 1.30e1.60 (m, 4H,
H-5, H-6), 1.80e2.20 (m, 4H, H-4, H-7), 3.40 (t, 2H, J 6.6, H-8), 3.78
(s, 3H, CH3), 4.56 (d, 2H, J 6.2, H-1), 5.60 (dt,1H, J 15.2, 6.2, H-2), 5.80
(dt, 1H, J 15.2, 6.6, H-3); dC (50 MHz, CDCl3) 28.5, 29.5 (C-4 and C-5),
32.0 (C-6), 32.4 (C-7), 48.2 (C-8), 62.8 (OCH3), 63.7 (C-1),127.1 (C-3),
129.7 (C-2), 155.5 (CO). Found: C, 45.12; H, 6.48. C10H17BrO3 re-
quires C, 45.30; H, 6.46%.
4.3. Typical procedure for the synthesis of aminocarbonates
5d, 5i (5a, 5b, 5e21b
)
A solution of bromocarbonate 4 (11.0 mmol), TsNH2 (1.9 g,
11.0 mmol), and TsNHNa (2.1 g, 11.0 mmol) in DMSO (60 mL) was
stirred for 16 h at 60 ꢀC. Then the reaction mixture was diluted with
brine (60 mL) and extracted with diethyl ether (3ꢂ30 mL). The
combined organic phases were dried (Na2SO4) and evaporated
under reduced pressure. The crude product was purified by flash
column chromatography on silica gel to give allylic aminocarbonate
5.
3. Conclusion
In conclusion, we have developed a simple and efficient meth-
odology for the synthesis of chiral nitrogen-containing heterocycles
via Pd(0)-catalysed cyclisation of amino allylic carbonates. 2-
Vinylpyrrolidine and 2-vinylpiperidine were obtained in good
yields and with enantiomeric ratios of up to 3:97. The highest
enantioselectivites for both N-tosyl and N-benzyl derivatives were
obtained using the phosphorus amidite ligand L1(S,S,aS). (S)-Binap
and (R,R)-Trost ligands proved effective only in the synthesis of N-
benzyl-2-vinylpyrrolidine and piperidine.
4.3.1. (E)-(7-(4-Methylphenylsulfonamido)hept-2-en-1-yl)
carbonate 5d. Colourless oil, 2.4 g, 65% yield; Rf (hexane/EtOAc, 4:1)
0.62; nmax (liquid film) 3285, 1748, 1599, 1328, 1161, 1270 cmꢁ1
dH
methyl
;
(200 MHz, CDCl3) 1.30e1.62 (m, 4H, H-5, H-6), 2.00 (q, 2H, J 7.0, H-
4), 2.43 (s, 3H, C6H4CH3), 2.92 (q, 2H, J 6.4, H-7), 3.77 (s, 3H, OCH3),
4.53 (d, 2H, J 6.0, H-1), 5.15 (s, 1H, J 6.2, NH), 5.50 (dt, 1H, J 15.4, 6.0,
H-2), 5.70 (dt, 1H, J 15.4, 7.0, H-3), 7.30 (d, 2H, J 8.2, C6H4), 7.74 (d,
2H, J 8.2, C6H4); dC (50 MHz, CDCl3) 21.4 (CH3C6H4), 25.5 (C-5), 28.8
(C-4), 31.4 (C-6), 42.9 (C-7), 54.6 (OCH3), 68.4 (C-1), 123.9, 127.7,
129.7 (C6H4, C-2, C-3), 136.3, 143.4 (Cq), 155.7 (CO). Found: C, 56.32;
H, 6.83; N, 4.28. C16H23NO5S requires C, 56.29; H, 6.79; N, 4.10%.
4. Experimental
4.1. General
All solvents and reagents were purchased from SigmaeAldrich
and were used as supplied, without additional purification. NMR
spectra were recorded in CDCl3 on Varian Gemini 2000 (200 MHz
for 1H NMR, 50 MHz for 13C NMR) or Bruker Avance III (600 MHz for
1H NMR, 150 MHz for 13C NMR), coupling constants are reported in
hertz (Hz). Chromatographic purification of compounds was ach-
ieved with 230e400 mesh size silica gel. The progress of reactions
was monitored by silica gel thin layer chromatography plates
(Merck TLC Silicagel 60 F254). The enantiomeric ratio was de-
termined by HPLC (ProStar Varian) employing a Chiralpak IA or
Kromasil OD-H column (25 cmꢂ4.6 mm).
4.3.2. (E)-(8-(4-Methylphenylsulfonamido)oct-2-en-1-yl)
carbonate 5i. Colourless oil, 2.6 g, 67% yield; Rf (hexane/EtOAc, 2:1)
0.43; nmax (liquid film) 3285, 1746, 1598, 1328, 1160, 1269 cmꢁ1
dH
methyl
;
(200 MHz, CDCl3) 1.20e1.52 (m, 6H, H-5, H-6, H-7), 2.00 (q, 2H, J 6.7,
H-4), 2.43 (s, 3H, C6H4CH3), 2.91 (q, 2H, J 6.6, H-8), 3.77 (s, 3H,
OCH3), 4.55 (d, 2H, J 6.2, H-1), 5.47 (s, 1H, NH), 5.52 (dt, 1H, J 15.1,
6.0, H-2), 5.73 (dt, 1H, J 15.1, 6.7, H-3), 7.30 (d, 2H, J 8.0, C6H4), 7.74
(d, 2H, J 8.0, C6H4); dC (50 MHz, CDCl3) 21.5 (CH3C6H4), 25.9, 28.1,
29.3, 31.9 (C-4, C-5, C-6, C-7), 43.1 (C-8), 54.7 (OCH3), 68.5 (C-1),
123.5, 136.7 (C-2, C-3), 127.0, 129.6 (C6H4), 136.9, 143.3 (Cq), 155.6
(CO). Found: C, 57.36; H, 7.04; N, 3.82. C17H25NO5S requires C, 57.44;
H, 7.09; N, 3.94%.
4.2. Typical procedure for the synthesis of bromocarbonates
4c, 4e (4a,b,d21b
)
4.4. Typical procedure for the synthesis of aminocarbonates
A solution of alcohol 3 (22.0 mmol) in CH2Cl2 (50 mL) cooled to
5c, 5feh
0
ꢀC was treated with pyridine (2.2 mL, 27.5 mmol) and methyl
chloroformate (2.1 mL, 27.5 mmol). After 2 h at room temperature,
the reaction mixture was quenched with water (30 mL) and
extracted with CH2Cl2 (2ꢂ50 mL). The combined organic phases
were dried (Na2SO4) and evaporated under reduced pressure. The
crude product was purified by flash column chromatography on
silica gel to give allylic bromocarbonate 4.
A 1.5 M solution of i-Pr2NEt in DMF (5.2 mL i-Pr2NEt in 14.8 mL
DMF) and the corresponding amine: benzylamine, cyclohexyl-
amine, tert-butylamine (33.0 mmol) was added successively to
a 0.8 M solution of appropriate bromide 4 (11.0 mmol) in DMF
(14 mL). The reaction mixture was stirred at room temperature
until the transformation of the bromide was complete (16e24 h), as

B. Olszewska et al. / Tetrahedron 69 (2013) 9551e9556
9555
indicated by thin layer chromatography. After being diluted with
EtOAc (50 mL), the mixture was then washed with H2O (3ꢂ20 mL)
and a saturated aqueous solution of NaCl (20 mL). The organic layer
was dried on MgSO4, filtered, and concentrated under reduced
pressure. The crude product was purified by flash column chro-
matography on silica gel to give allylic aminocarbonate 5.
tube containing the unsaturated aminocarbonate 5aei (1 mmol) in
an appropriate anhydrous solvent (3 mL). The solution was stirred
at 25 ꢀC (or 60 ꢀC). After an appropriate period of time, removal of
the solvent followed by column chromatography gave the corre-
sponding product.
Compounds 6aed are known and described in the literature (6a,
6c21b and 6b, 6d20a,d).
4.4.1. (E)-6-(Benzylamino)hex-2-en-1-yl
5c. Yellow oil, 2.0 g, 60% yield; Rf (EtOAc/MeOH, 7:1) 0.63; nmax
(liquid film) 3316, 3086, 3062, 3028, 1743, 1679, 1251 cmꢁ1
dH
isobutyl
carbonate
4.5.1. 1-Cyclohexyl-2-vinylpiperidine 6e. Yellow oil; Rf (EtOAc/
MeOH/CH2Cl2, 5:3:3) 0.37; nmax (liquid film) 3076, 1643, 1329, 1160,
;
(200 MHz, CDCl3) 0.94 (d, 6H, J 6.6, CH2CH(CH3)2), 1.63 (quintet, 2H,
J 7.6, H-5), 1.85e2.20 (m, 3H, H-4, CH2CH(CH3)2), 2.64 (t, 2H, J 7.6, H-
6), 3.79 (s, 2H, CH2C6H5), 3.91(d, 2H, J 6.7, CH2CH(CH3)2), 4.55 (d, 2H,
J 6.2, H-1), 5.62 (dt, 1H, J 15.7, 6.2, H-2), 5.77 ( dt, 1H, J 15.7, 6.4, H-3),
7.21e7.41 (m, 5H, C6H5); dC (50 MHz, CDCl3) 18.8 (CH2CH(CH3)2),
27.6 (CH2CH(CH3)2), 28.7 (C-4), 29.8 (C-5), 48.4 (C-6), 53.7
(CH2C6H5), 68.3 (C-1), 74.0 (CH2CH(CH3)2), 123.8 (C-3), 127.0, 128.3,
128.4 (C6H5), 136.5 (C-2), 139.7 (Cq), 155.3 (CO). Found: C, 70.75; H,
8.89; N, 4.72. C18H27NO3 requires C, 70.79; H, 8.91; N, 34.56%.
1092 cmꢁ1
; dH (600 MHz, CDCl3) 0.95e1.90 (m, 16H, H-3, H-4, H-5,
H-20, H-30, H-40, H-50, H-60), 2.16 (dt, 1H, J 11.1, 2.5, H-6), 2.73 (dt, 1H,
J 10.8, 2.6, H-6), 2.84e3.06 (m, 2H, H-10, H-2), 5.00 (dd,1H, J 10.1,1.8,
CHCH2), 5.13 (dd, 1H, J 17.2, 1.8, CHCH2), 5.80 (dt, 1H, J 17.2, 10.2,
CHCH2); dC (150 MHz, CDCl3) 23.5 (C-30, C-50), 24.2 (C-4), 25.7 (C-40),
26.1 (C-50), 31.5 (C-3), 34.1 (C-20, C-60), 45.4 and 59.1 (C-10 and C-6),
63.8 (C-2), 114.6 (CHCH2), 142.1 (CHCH2); HRMS (EI): Mþ, found
193.18305. C13H23N requires 193.18298.
4.5.2. 1-Tosyl-2-vinylazepane 6g. Yellow oil; Rf (EtOAc/hexane, 5:1)
4.4.2. (E)-7-(Benzylamino)hept-2-en-1-yl
5f. Yellow oil, 1.7 g, 48% yield; Rf (EtOAc/MeOH, 7:1) 0.63; nmax
(liquid film) 3324, 3086, 3062, 3027, 1744, 1694, 1251 cmꢁ1
dH
isobutyl
carbonate
0.73; nmax (liquid film) 3063, 3027, 1663, 1335, 1159, 1090 cmꢁ1
; dH
(600 MHz, CDCl3) 1.08e1.60 (m, 8H, H-3, H-4, H-5, H-6), 2.42 (s, 3H,
CH3), 2.90 (dd,1H, J 13.2, 7.2, H-7), 3.68 (dd,1H, J 13.2, 6.6, H-7), 4.59
(m, 1H, H-2), 5.10 (d, 1H, J 11.6, CHCH2), 5.17 (d, 1H, J 17.0, CHCH2),
5.80 (ddd, 1H, J 17.0, 11.6, 5.2, CHCH2), 7.28 (d, 2H, J 8.2, C6H4), 7.69
(d, 2H, J 8.2, C6H4); dC (150 MHz, CDCl3) 21.4 (C6H4CH3), 24.1 (C-4),
25.9 (C-5), 29.4 (C-6), 30.1 (C-3), 43.60 (C-7), 58.9 (C-2), 115.1
(CHCH2), 127.1, 129.6 (C6H4), 136.2 (CHCH2); HRMS (EI): Mþ, found
279.12930. C15H21NO2S requires 279.12869.
;
(200 MHz, CDCl3) 0.94 (d, 6H, J 6.6, CH2CH(CH3)2), 1.34e1.60 (m, 4H,
H-5, H-6), 1.86e2.12 (m, 3H, CH2CH(CH3)2), 1.65 (s, 1H, NH), 2.06 (q,
2H, J 6.4, H-4), 2.60 (t, 2H, J 7.1, H-7), 3.80 (s, 2H, CH2C6H5), 3.92 (d,
2H, J 6.7, CH2CH(CH3)2), 4.55 (d, 2H, J 6.3, H-1), 5.62 (dt, 1H, J 12.7,
6.3, H-2), 5.77 ( dt, 1H, J 12.7, 6.4, H-3), 7.24e7.35 (m, 5H, C6H5); dC
(50 MHz, CDCl3) 18.9 (CH2CH(CH3)2), 26.5 (CH2CH(CH3)2), 27.7 (C-
4), 29.4 (C-5), 32.0 (C-2), 49.1 (C-7), 53.9 (CH2C6H5), 68.4 (C-1), 74.0
(CH2CH(CH3)2), 123.5 (C-3), 126.9, 128.1, 128.4 (C6H5), 137.0 (C-2),
140.2 (Cq), 155.2 (CO). Found: C, 71.23; H, 9.28; N, 4.42. C19H29NO3
requires C, 71.44; H, 9.15; N, 4.38%.
Acknowledgements
This work was partly financed by the European Union within the
European Regional Development Fund (POIG.01.01.02-14-102/09).
4.4.3. (E)-7-(Cyclohexylamino)hept-2-en-1-yl isobutyl carbonate
5g. Colourless oil, 2.1 g, 62% yield; Rf (EtOAc/MeOH/CH2Cl2, 5:3:3)
0.19; nmax (liquid film) 3326, 1745, 1673, 1249 cmꢁ1
; dH (200 MHz,
References and notes
CDCl3) 0.94 (d, 6H, J 6.7, CH2CH(CH3)2), 1.04e1.30 (m, 6H, C6H11),
1.36e1.60 (m, 6H, C6H11, H-6), 1.70e2.16 (m, 3H, H-5, CH2CH(CH3)2),
1.70 (s, 1H, NH), 2.08 (q, 2H, J 6.7, H-4), 2.45e2.52 (m, 1H, C6H11),
2.64 (t, 2H, J 6.8, H-7), 3.91 (d, 2H, J 6.7, CH2CH(CH3)2), 4.55 (d, 2H, J
6.3, H-1), 5.65 (dt, 1H, J 15.3, 6.3, H-2), 5.77 ( dt, 1H, J 15.3, 6.5, H-3);
dC (50 MHz, CDCl3) 18.6 (CH2CH(CH3)2), 24.7 (C6H11), 25.7 (C6H11),
26.3 (C-5), 27.4 (CH2CH(CH3)2), 29.0 (C6H11), 31.7 (C-4), 32.6 (C-6),
42.0 (C-7), 56.4 (C6H11), 68.1 (C-1), 73.6 (CH2CH(CH3)2), 123.4 (C-3),
136.6 (C-2), 155.0 (CO); EIMS (m/z): 312.3 [MþH]þ. Found: C, 69.12;
H, 10.79; N, 4.48. C18H33NO3 requires C, 69.41; H, 10.68; N, 4.50%.
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5h. Colourless oil, 2.7 g, 85% yield; Rf (EtOAc/MeOH, 7:1) 0.43; nmax
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(d, 6H, J 6.6, CH2CH(CH3)2), 1.46 (s, 9H, (CH3)3), 1.36e1.56 (m, 2H, H-
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