Intramolecular 1,5-hydride transfer in rearrangements of ammonium salts containing alkoxycarbonylmethyl and 4-penten-2-ynyl groups

Article abstract of DOI:10.1023/A:1012311824435

The Stevens 3,2 rearrangement of dialkylammonium salts containing, along with 4-penten-2-ynyl, an alkoxycarbonylmethyl group, gives mostly hydrogenated products, with simultaneous dealkylation and aldehyde formation. On acid treatment enamine amino esters

Full text of DOI:10.1023/A:1012311824435

Russian Journal of General Chemistry, Vol. 71, No. 2, 2001, pp. 265 270. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 2, 2001,
pp. 294 299.
Original Russian Text Copyright
2001 by Kocharyan, Razina, Gyul’nazaryan, Babayan.
Intramolecular 1,5-Hydride Transfer in Rearrangements
of Ammonium Salts Containing Alkoxycarbonylmethyl
and 4-Penten-2-ynyl Groups
S. T. Kocharyan, T. L. Razina, A. Kh. Gyul’nazaryan, and A. T. Babayan
Institute of Organic Chemistry, Academy of Sciences of Armenia, Erevan, Armenia
Received December 17, 1999
Abstract The Stevens 3,2 rearrangement of dialkylammonium salts containing, along with 4-penten-2-ynyl,
an alkoxycarbonylmethyl group, gives mostly hydrogenated products, with simultaneous dealkylation and
aldehyde formation. On acid treatment enamine amino esters give keto esters or their further transformation
product, 4-ethyl3-hydroxy-5-methyltetrahydrofuran-2-one.
Earlier we showed that dimethyl- and penta-
methylene(methoxycarbonylmethyl)(4-penten-2-ynyl)-
ammonium bromide under the action of ethereal
suspension of sodium alkoxide undergo Stevens 3,2
transfers [8, 9] and 1,5-hydride transfers in acyclic
compounds [10, 11].
In the present work we performed a detailed study
of hydride-transfer reactions in the products of the
Stevens 3,2 rearrangement of ammonium salts in-
corporating both 4-penten-2-ynyl and alkoxycarbonyl-
methyl groups, with various alkyl groups both at the
ammonium nitrogen and in the ester group (salts Ia
Ie) under the action of ethereal suspension of sodium
alkoxide (Table 1).
rearrangement to provide allenic
-dialkylamino
esters whose allene diene rearrangement under the
reaction conditions produces dienic amino esters [1,
2]. It is interesting that a diethyl analog Ia of the
above salts under the same conditions give hydrogena-
ted rearrangement products, with simultaneous eli-
mination of an ethyl group as acetaldehyde [2].
It is known that tertiary amines having an -hydro-
gen atom are potential donors of hydride ions and are
applied for reduction of electrophilic multiple bonds
[3, 4]. The key stage of these reactions is imonium
salt formation either via direct hydride transfer from
the amine to the multiple bond or via other routes, the
most probable of which involves charge-transfer com-
plexes. Intramolecular hydride transfers have also
been reported, viz. in isomerization of carbonium ions
[5 7], as well as transannular 1,3- and 1,5-hydride
Hydrogenated reaction products are probably
formed by a scheme, according to which rearrange-
ment products IIa IIe undergo 1,5-hydride transfer,
yielding mainly imonium salts IIIa IIIe. Under the
reaction conditions, the latter convert to enamines
IVa IVe mixed with amino esters Va Ve. Treatment
of the reaction mixture immediately after formation
of IIIa IIIe with water gives rise to hydrolysis pro-
ducts, amino esters VIa VIe and VIIa VIIe, which
can also be formed by aqueous and acid hydrolysis of
Table 1. Hydrogenated products of the Stevens rearrangement of salts Ia Ie
Found, %
Calculated, %
Starting Amino Yield,
bp,
(p, mm)
C
n2D0
Formula
salt
ester
%
C
H
N
C
H
N
Ia
Ib
Ic
Id
Ie
VIa
VIb
VIc
VId
VIea
26
11
14
12
10
70 72 (3)
1.4800 64.92 9.35 7.95 C10H17NO2
65.97 9.24 7.65
67.00 9.67 7.11
68.24 9.95 6.63
67.04 9.64 7.11
65.43 9.52 6.45
98 101 (4) 1.4762 66.67 9.29 6.92 C11H19NO2
97 98 (2)
98 99 (7)
112 118 (2)
1.4700 68.47 9.59 6.31 C12H21NO2
1.4718 66.35 9.37 6.85 C11H19NO2
64.85 9.33 6.65 C12H21NO3 (88%)
+ C11H19N (12%)
1070-3632/01/7102-0265$25.00 2001 MAIK Nauka/Interperiodica

266
KOCHARYAN et al.
Table 1. (Contd.)
Found, %
Calculated, %
Starting
salt
Yield,
%
mp,
(p, mm)
C
Keto ester
n2D0
Formula
C8H12O3
C
H
C
H
Ia
Ib
Ic
Id
Ie
VIIIa
VIIIa
VIIIa
VIIIbb
VIIIbb
17
26
27
19
14
87 89 (7)
83 85 (6)
80 82 (4)
85 89 (3)
84 89 (3)
1.4610
1.4614
1.4609
61.38
8.0
61.53
7.70
63.91
63.94
8.5
8.4
C9H14O3
C9H14O3
63.53
63.53
8.2
8.2
a
b
Contains 12% of (4-penten-2-ynyl)dipropylamine.
Contain 15 and 20% of 2-oxo-3-vinyl-3-pentenoic acid, respectively.
mixtures of IVa IVe and Va Ve. Treatment of mix-
tures of VIa VIe and VIIa VIIe with dilute hydro-
chloric acid results in formation of alkylamines and
keto esters VIIIa, VIIIb. When treated with concen-
trated hydrochloric acid, the latter convert to 4-ethyl-
3-hydroxy-5-methyltetrahydrofuran-2-one (IX).
I VII, R = R = H (a); R = CH3, R = H (b); R = C2H5, R = H (c); R = H, R = CH3 (d); R = R = CH3 (e); VIII,
R = H (a), CH3 (b); X = COOCH2R .
A detailed study of the reaction on an example of
other components, amino ester Va and diethyl(4-
salt Ia showed that the ether extract after the rearrange- penten-2-ynyl)amine, are 8 and 5%, respectively
ment has been complete contains 87% of amine pro-
ducts (titrimetric data). The major component of this
mixture is enamine IVa ( 73%). The fractions of the
(GLC data). Note that the fraction of amine Va in the
mixture increases as the reaction temperature and time,
as well as the amount of the base are increased.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

INTRAMOLECULAR 1,5-HYDRIDE TRANSFER IN REARRANGEMENTS
267
Comparison of published [3, 4] and our results led
us to conclude that the hydride transfer in the rear-
rangement products actually gives imonium salts III
which further transform by route a (see scheme). This
conclusion follows from the fact that treatment with
water of ethereal extract of the reaction mixture with
compound I sharply decreases the fraction of com-
pound IVa in the mixture and increases the fraction
of compound VIa to 65% (GLC data).
With ethoxycarbonylmethylammonium salts Id, Ie,
the yields of hydride transfer are rather low, and the
reaction mixture contains nonhydrogenated 3,2-rear-
rangement products. The latter under the reaction
conditions undergo prototropic isomerization followed
by hydrolysis to convert to ester Xc. The fractions of
keto ester VIIIb in the reaction mixtures are 15 and
20%, respectively (GLC data).
However, route b should also not be ruled out,
since treatment of anhydrous reaction residue (after
decantation of the solvent) with water, followed by
extraction with ether, too, gave compounds VIa and
VIIa, the former much prevailing. Moreover, acetal-
dehyde could be detected as 2,4-dinitrophenylhydra-
zone.
The structure of keto ester Xc was proved by spec-
tral methods and, in addition, by the independent
synthesis by rearrangement of (ethoxycarbonylmetyl)-
dimethyl(4-penten-2-ynyl)ammonium bromide (X)
followed by hydrolysis of the isomerized rearrange-
ment product Xb.
CH=CH2
CH=CH2
CH2C CCH=CH2
CH2COOC2H5
+
(C2H5)2ONa
(C2H5)2O
(CH3)2N
(CH3)2N CH C=C=CH2
(CH3)2N C=C CH=CH2
Br
COOC2H5
COOC2H5
X
Xa
Xb
HCl
CH3CH=C CO COOC2H5
CH=CH2
Xc
We also studied the effect of solvent nature and
temperature on the yields of hydrogenated reaction
products (with salt Ib as an example; Table 2). It was
found that the overall yield of the hydrogenated pro-
ducts VIb, VIIb is only slightly affected by solvent,
but in the reaction mixture in DMSO we detected
acetylene XIa ( 4%). Its formation can be explained
by the allene acetylene rearrangement of the Stevens
rearrangement product under the reaction conditions,
which is quite probable in DMSO. Steric factors
should also be neglected, since the attack of the base
on the hydrogen atom at a terminal allenic carbon
atom in this substrate is more favored sterically than
on the hydrogen atom at the carbon atom neighboring
to nitrogen.
Table 2. Effect of temperature and solvent nature on the
yield of hydrogenated rearrangement products of salt Ib
Yield, %
Solvent
Temperature,
C
VIb
VIIIa
Benzene
30 32
78 80
30 32
30 32
40 45
12
10
14
11
9
22
23
23
22
20
Ether
DMSO
Two factors are worth mentioning. First, the reac-
tion and the subsequent distillation of the reaction
products are accompanied by strong tarring, which
affects the yield of the products (Table 1). Second,
the reaction yields 5 12% of amine products of
elimination, the starting dialkyl(4-penten-2-ynyl)-
amines.
CH=CH2
C2H5ONa
Ib
(C3H7)2N CH C=C=CH2
COOCH3
DMSO
CH=CH2
(C3H7)2N CH CH C CH.
COOCH3
C2H5O
The structures of the products were proved by IR
1
and H NMR spectroscopy and mass spectrometry
(Table 3), and their purity was controlled by GLC.
XIa
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

268
KOCHARYAN et al.
Table 3. IR and 1H NMR spectra of compounds VIa VIe, VIIIa, VIIIb, IX, Xb, and Xc
Comp.
no.
1
IR spectrum, cm
1H NMR spectrum (CCl4), , ppm (J, Hz)
VIa
VIb
920, 1635, 3030, 3090 (CH=CH2), 1.02 t (3H, CH2CH3), 1.53 m (1H, NH), 1.75 d (3H, CH3C=), 2.50 q (2H,
975 (CH=CH), 1080 (C N), 1230 CH2CH3, J 7.4), 3.59 s (3H, CH3O), 4.30 s (1H, NCH), 4.7 5.4 m (2H, CH2=),
(C O), 1735 (C=O), 3340 (NH) 5.74 m (1H, CH3CH=, J 17.3), 6.10 m (1H, CH=, Jtrans 12.0, Jcis 11.5)
930, 1610, 1640, 3020, 3090 0.89 t (3H, CH2CH2CH3), 1.09 1.69 m (2H, CH2CH2CH3), 1.53 m (1H, NH),
(CH=CH2), 970 (CH=CH), 1070 1.78 d (3H, CH3C=), 2.42 q (2H, CH2C2H5, J 7.4), 3.64 s (3H, CH3O), 4.24 s
(C N), 1225 (C O), 1740 (C=O), (1H, NCH), 4.91 d (1H, CH2=CH, Jcis 10.7), 5.36 d (1H, CH2=CH, Jtrans
3345, 3465 (NH)
17.3), 5.80 m (1H, CH3CH=, J 21.3), 6.16 m (1H, CH2=CH)
VIc
VId
VIe
920, 990, 1615, 1645, 3090 0.60 1.00 m (3H, CH2CH3), 1.01 1.53 m (4H, CH2CH2CH3), 1.46 s (1H, NH),
(CH=CH2), 1080 (C N), 1740 1.69 d (3H, CH3C=, J 8.0), 2.16 2.51 m (2H, CH2C3H7), 3.55 s (3H, CH3O),
(C=O), 2130 (C C), 3340, 3470 4.17 s (1H, NCH), 4.75 d (1H, CH2=CH, Jcis 11.3), 5.17 d (1H, CH2=CH,
(NH)
Jtrans 17.3), 5.65 m (1H, CH3CH=, J 22.6), 6.06 m (1H, CH2=CH)
790, 850, 1660 (C=CH), 910, 1.07 t (3H, CH2CH3, J 8.0), 1.20 t (3H, OCH2CH3, J 8.0), 1.69 s (1H, NH),
1620, 3085 (CH=CH2), 1100 1.87 d (3H, CH3C=, J 6.6), 2.60 q (2H, CH2CH3), 4.36 s (1H, NCH), 4.98 d
(C N), 1220 (C O), 1745, 1755 (1H, CH2=CH, Jcis 12.0), 5.41 d (1H, CH2=CH, Jtrans 16.6), 5.88 q (1H,
(C=O), 1490, 3375, 3490 (NH) CH3CH=, J 22.0), 6.22 q (1H, CH2=CH)
980, 1685 (CH=CH), 1640, 3095 0.95 m (3H, CH2CH3), 1.08 1.66 m (3H, CH2CH3 and NH), 1.17 t (3H, OCH2CH3
(CH=CH2), 1730, 1740 (C=O), J 8.0), 1.75 d (3H, CH3C=, J 8.0), 2.40 m (2H, CH2C2H5), 4.17 q (2H,
1275 (C O), 1470, 3355, 3470 OCH2CH3), 4.28 s (1H, NH), 4.92 d (1H, CH2=CH, Jcis 12.0), 5.35 d (1H,
(NH)
VIIIa 820, 1635, 3060, 1675 (C=O), 0.94 t (3H, CH2CH3), 1.92 d (3H, CH3C=, J 8.0), 2.28 q (2H, CH2CH3, J 7.8),
1125, 1245, 1730 (COO) 3.77 s (3H, OCH3), 6.58 m (1H, CH=, J 6.7)
VIIIb 820, 1635, 3060, 1670 (C=O), 0.93 t and 0.95 t (3H, CH2CH3), 1.92 d (3H, CH3C=, J 8.0), 2.29 q (2H, CH2CH3
1125, 1240, 1730 (COO) J 7.8), 4.01 q (2H, OCH2), 6.60 m (1H, CH=, J 6.7)
1250 (C O), 1620 (C=C), 1730 1.17 t (3H, CH2CH3, J 8.0), 1.44 d (3H, CHCH3, J 6.7), 1.82 2.80 m (2H,
(C=O), 3100 3500 (OH) CH2CH3), 4.99 m (1H, CHCH3), 7.58 s (1H, OH)
920, 975, 1575, 1605, 3030, 3090 0.95 t (3H, CH2CH3), 2.37 s (6H, NCH3), 4.08 q (2H, OCH2, J 7.35), 4.8
1070, 1240, 1715 (COO) 5.6 m (4H, CH2=), 6.6 7.5 m (2H, CH=, Jtrans 18.0, Jcis 11.5)
CH2=CH, Jtrans 17.0), 5.90 m (1H, CH3CH=, J 22.6), 6.26 m (1H, CH2=CH)
IX
Xb
Xc
820, 920, 975, 1630, 1635, 3030, 0.97 t (3H, CH2CH3), 1.96 d (3H, CH3C=, J 8.0), 4.09 q (2H, OCH2, J 7.35),
3090, 1675 (C=O), 1120, 1240, 5.0 5.8 m (2H, CH2=), 6.0 6.95 m (2H, CH=)
1735 (COO)
EXPERIMENTAL
tional 20 min, and ether and water were then added.
The organic layer was separated, and the aqueous
layer was extracted with ether (3 10 ml). The com-
bined extract was acidified with 2.5 N HCl. Nonamine
reaction products were extracted with ether (3 10 ml),
dried with magnesium sulfate, and the solvent was
removed. In the ether extract, aldehyde was identified
as 2,4-dinitrophenylhydrazone. Vacuum distillation
gave keto esters VIII. The reaction residue was
treated with potash (0 5 C), and amine reaction pro-
ducts were extracted with ether (3 10 ml), dried with
magnesium sulfate, and the solvent was removed.
Amino esters VI were isolated by vacuum distillation.
The results are listed in Table 1. In the ether extracts
by GLC we identified dialkyl(4-penten-2-ynyl)amines.
The IR spectra were obtained in thin film on UR-
1
20 and Specord IR-75 spectrometers. The H NMR
spectra were measured on a Perkin-Elmer R-12B
spectrometer at 60 MHz (in CCl4, reference TMS).
The mass spectra were obtained on an MKh-1320
spectrometer with direct inlet, ionizing energy 70 eV.
Gas chromatography was performed on an LKhM-
8MD instrument, detector katharometer (column
2000 3 mm, 5% OV-17 on Chromaton N-Super,
carrier gas helium, rate 60 ml/min, 175 200 C).
General procedure of the rearrangement. a. To a
suspension of 0.03 mol of salt Ia Ie in 20 ml of
absolute ether we added sodium alkoxide obtained
from 0.06 mol of sodium. After heat evolution had
been complete, the mixture was refluxed for an addi-
1
The H NMR and IR spectra of compounds VI and
VIII are given in Table 3.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

INTRAMOLECULAR 1,5-HYDRIDE TRANSFER IN REARRANGEMENTS
269
b. To a suspension of 0.03 mol of salt Ia Ie in
20 ml of a solvent we added sodium alkoxide ob-
tained from 0.06 mol of sodium. After heat release
had been complete, the mixture was kept at a speci-
fied temperature for 20 30 min, cooled, the organic
layer was separated (except for DMSO which was
fully removed by distillation), and the solid residue
was washed with absolute ether (3 10 ml). The sol-
vent was removed in a vacuum, first at 40 50 mm
and then at 4 mm. The residue was examined by GLC
Reaction of (ethoxycarbonylmethyl)diethyl(4-
penten-2-ynyl)ammonium chloride (Id) with
sodium ethoxide. To a suspension of 31.3 g of salt Id
in 50 ml of ether we added sodium ethoxide obtained
from 5.5 g of sodium. The organic layer contained
four compounds, prevailing being compound IVd
(62%) whose hydrolysis yielded ethyl 2-ethylamino-3-
vinyl-3-pentenoate (VId). Further treatment according
to procedure a gave (1) 5.1 g (21%) of amino ester
VId; (2) 2.8 g of a mixture of keto esters VIIId and
Xc (85:15), bp 85 89 C (3 mm), 11% of diethyl(4-
penten-2-ynyl)amine, and 16% of ethylamine (GLC).
1
and H NMR and IR spectroscopy, after which it was
acidified with 2.5 N HCl. Further treatment was per-
formed as described in procedure a. The solid reaction
residue was treated with water, extracted with ether
(3 10 ml), dried with magnesium sulfate, and the
solvent was removed in a vacuum first at 40 50 mm
and then at 4 mm. The residue was identified by GLC,
using as reference the sample obtained by procedure a.
Reaction of (methoxycarbonylmethyl)(4-penten-
2-ynyl)dipropylammonium bromide (Ib) with
sodium methoxide in benzene. A mixture of 10.2 g
of salt Ib, sodium methoxide (obtained from 1.5 g of
sodium), and 20 ml of absolute benzene was refluxed
for 30 min. Further treatment according to procedure
b gave (1) 0.65 g (10%) of methyl 2-propylamino-3-
vinyl-3-pentenoate (VIb); (2) 1.2 g (23%) of 3-ethyl-
2-oxo-3-pentenoate (VIIIa); and (3) 0.34 g (4%) of
propionaldehyde 2,4-dinitrophenylhydrazone, mp
140 141 C (ethanol). By GLC, 7% of (4-penten-2-
ynyl)dipropylamine and 16% of propylamine were
also found.
Reaction of dibutyl(methoxycarbonylmethyl)-
(4-penten-2-ynyl)ammonium bromide (Ic) with
sodium methoxide. According to procedure a, from
11.8 g of salt Ic, 1.6 g of sodium, and 20 ml of ether
we obtained (1) 0.45 g of butyraldehyde 2,4-dinitro-
phenylhydrazone as needle-like crystals, mp 120
122 C (ethanol), mass spectrum, m/z: [M]+ 252;
(2) 2.7 g of crude methyl 3-ethyl-2-oxo-3-pentenoate
(VIIIa) contaminated with 3% of methyl 2-oxo-3-
vinyl-3-pentenoate; identified by GLC using authentic
samples [2]; distillation gave 1.4 g (26.4%) of keto
ester VIIIa; and (3) 2.4 g of crude methyl 2-butyl-
amino-3-vinyl-3-pentenoate (VIc).
Rearrangement of (ethoxycarbonylmethyl)di-
methyl(4-penten-2-ynyl)ammonium bromide (X).
To 12.4 g of salt X in 20 ml of absolute ether we
added sodium ethoxide obtained from 2.1 g of sodium.
After heat release had been complete, the mixture was
refluxed for 20 min, and then ether and water were
added. The organic layer was separated, and the re-
sidue was extracted with ether. The ether extracts
were dried with magnesium sulfate and distilled to
obtain 4.35 g (67%) of ethyl 2-dimethylamino-3-vinyl-
2,3-pentadienoate (Xb), bp 93 94 C (5 mm), nD20
1.5193. Found, %: C 68.18; H 8.97; N 6.88. C11H17
NO2. Calculated, %: C 67.77; H 8.72; N 7.18.
Repeated distillation gave 1.2 g (14%) of amino
ester VIc which, according to GLC and IR spectral
data, contained 3% of the allene acetylene rearrange-
1
ment product XIb (weak absorption at 2130 cm ),
5% of dibutyl(4-penten-2-ynyl)amine (M+ 211), and
19% of butylamine.
Reaction of (methoxycarbonylmethyl)(4-penten-
2-ynyl)dipropylammonium bromide (Ib) with
sodium methoxide. According to procedure b, from
11.3 g of salt Ib, 1.6 g of sodium, and 20 ml of ether
we obtained 7.24 g of a mixture of four compounds,
the major being IVb (85%). Hydrolysis with hydro-
chloric acid gave (1) 0.48 g (7%) of propionaldehyde
2,4-dinitrophenylhydrazone, mp 140 141 C (ethanol),
mass spectrum, m/z: [M]+ 238; (2) 1.3 g of keto ester
VIIIa; 2,4-dinitrophenylhydrazone, mp 95 96 C
(ethanol), mass spectrum, m/z: [M]+ 336; (3) 0.75 g
(11%) of methyl 2-propylamino-3-vinyl-3-pentenoate
(VIb), mass spectrum, m/z: [M]+ 197; as well as 9%
of (4-penten2-ynyl)dipropylamine and 13% of propyl-
amine (GLC). From the solid reaction residue, 0.39 g
of a mixture was isolated, containing four major com-
ponents, amino ester VIb prevailing ( 70%).
Acid hydrolysis of ethyl 2-dimethylamino-3-
vinyl-2,4-pentadienoate (Xb). To 3.9 g of amino
ester Xb in 12 ml of absolute ether we added equi-
molar amount of 1.5 N HCl. The mixture was stirred
for 45 min. The ether layer was separated, and the
aqueous layer was extracted with two portions of ether.
The ether extracts were dried with magnesium sulfate
and distilled to obtain 2.4 g (70%) of ethyl 2-oxo-3-
vinyl-3-pentenoate (Xc), bp 98 100 C (8 mm), nD20
1.4760. Found, %: C 64.67; H 7.43. C9H12O3. Cal-
culated, %: C 64.28; H 7.14.
4-Ethyl-3-hydroxy-5-methyltetrahydrofuran-2-
one (IX). To 3.2 g of methyl 3-ethyl-2-oxo-3-pente-
noate (VIIIa) was added with stirring 2.2 ml of 36%
HCl. The mixture was heated for 2.5 h at 50 60 C
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 71 No. 2 2001

270
KOCHARYAN et al.
and then extracted with three portions of ether. The
ether extracts were dried with magnesium sulfate and
distilled to obtain 1.6 g (56%) of 4-ethyl-3-hydroxy-
5-methyltetrahydrofuran-2-one (IX), bp 129 130 C
(10 mm), n2D0 1.4898 (Table 3). In a similar way, from
3.4 g of ethyl 3-ethyl-2-oxo-3-pentenoate (VIIIb) and
2.2 ml of 36% HCl we obtained 1.4 g (49%) of
butenolide IX.
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