Reaction of lactim ethers and lactim sulfides with electrophiles: Attack at nitrogen followed by ring-opening under neutral conditions

Article abstract of DOI:10.1039/a700523g

Electrophilic push-pull molecules react at the nitrogen of lactim ethers and lactim sulfides; subsequent hydrolysis gives ring-opened products in good yields.

Full text of DOI:10.1039/a700523g

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Reaction of lactim ethers and lactim sulfides with electrophiles:
attack at nitrogen followed by ring-opening under neutral conditions
Mariappan Anbazhagan, Arun N. Dixit and Srinivasachari Rajappa *
Division of Organic Chemistry (Synthesis), National Chemical Laboratory, Pune 411 008,
India
Electrophilic push-pull molecules react at the nitrogen of lactim ethers and lactim sulfides; subsequent
hydrolysis gives ring-opened products in good yields.
Introduction
followed by opening of the ring, leading to the formation of
carboxylic esters.
The reaction of lactim ethers (or sulfides) with electrophiles can
take several routes, in most of which the nitrogen atom of the
1
substrate acts as the nucleophile; but this is not always the case.
Results and discussion
There are examples in the literature where C-3 is the site of
electrophilic attack. This obviously results from the reaction
of the lactim ether as its enamine tautomer. Thus, the five-
membered γ-butyrolactim ether 1a and its six-membered homo-
logue 1b react with aryl isocyanates at C-3 to form phenylcar-
Reaction of the five-, six- or seven-membered lactim ethers 1 or
the corresponding sulfides 2 with a series of electrophilic push-
(
)n
( )n
2
bamoyl derivatives (Scheme 1). The initial nucleophilic attack
OMe
SMe
N
N
of one molecule of the lactim ether in its enamine form on
another molecule of the lactim ether at the electrophilic carbon
has been suggested to account for the products of the reaction
1
2
a n = 1
b n = 2
c n =3
3
of the lactim ether with diketene. A further variation is pro-
vided by the corresponding lactim sulfide 2. Thus, while the 5-
membered lactim sulfide 2a reacts with aryl isocyanates in the
enamine form at C-3, the higher ring homologues 2b and 2c
pull ethylenes 3–6 in methanol solution led to the ring-opened
products 7–10 in yields in the range 38–79% (Scheme 2). The
4
react at the nitrogen. Subsequent deprotonation at C-3 leads to
enaminoureas. Reaction at the nitrogen with electrophiles can
have at least two other sequels. There are several examples in
the literature in which the second step is the attack by the coun-
terion on the alkyl group of the ether leading to N-substituted
lactams via alkyl–oxygen cleavage (Scheme 1). This is the case
with alkylation, acylation and sulfonylation. Most interest-
ing in the context of the present discussion are the occasional
reports of the reaction of lactim ether with electrophiles fol-
lowed by opening of the lactam ring (Scheme 1). Thus
O2N
SMe
SMe
MeO2C(CH2)nCH2CH2NH
NO2
1
(or) 2 +
MeO
3
7
a n = 1
b n = 2
c n = 3
5
6
7
EtO
EtO
COMe
COMe
MeO2C(CH2)nCH2CH2NH
COMe
COMe
1 (or) 2 +
(
)n
( )n
4
5
6
8
a n = 1
b n = 2
c n = 3
OR + E +
+
N
OR
N
E
COMe
CO2Et
MeO2C(CH2)nCH2CH2NH
COMe
CO2R
1
1
(or) 2 +
E
9
(
)n
( )n
( )n
a n = 1, R = Et
b n = 2, R = Me
c n = 3, R = Me
CO2R
NH
OR
O
N
N
EtO
CO2Et
CO2Et
MeO2C(CH2)nCH2CH2NH
CO2Et
CO2Et
E
E
(or) 2 +
Scheme 1
10
ω-isocyano carboxylic acid esters are reported to result from the
a n = 1
b n = 2
c n = 3
8
reaction of lactim ethers with chloroform in aqueous alkali.
Similarly, the lactim ether 1c reacts with thiophosgene to form
9
an isothiocyanato carboxylic ester. There is also a recent report
Scheme 2
that 1,4-naphthoquinone reacts with 1a in methanol to form
1
0
2
-(3-methoxycarbonylpropylamino)-1,4-naphthoquinone.
The present report deals with the reaction of lactim ethers
lactim sulfides invariably gave higher yields of the product as
compared to their oxygen counterparts. Thus, treatment of the
γ-butyrolactim ether 1a with 1,1-bismethylthio-2-nitroethylene
3 in refluxing methanol for 72 h gave methyl N-(1-methoxy-2-
nitroethenyl)aminobutanoate 7a in 43% yield. The inter-
and the corresponding sulfides with a series of electrophilic
push-pull ethylenes in methanol solution. In all the examples
studied, attack took place on the nitrogen atom; this was
J. Chem. Soc., Perkin Trans. 1, 1997
2421

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Table 1 Reaction of lactim ethers with electrophiles in refluxing
methanol
yields in these and other related condensations involving ring-
opening.
The configuration around the double bond in the amino-
methyleneacetoacetic ester derivatives 9 is uncertain, although
even here, only one species was observed in the NMR spectra
Duration of
Lactim ether Electrophile reaction (h)
Product
Yield (%)
1
1
1
1
1
1
1
1
1
1
1
1
a
b
c
a
b
c
a
b
c
a
b
c
3
3
3
4
4
4
5
5
5
6
6
6
72
72
60
72
72
60
72
72
60
72
72
60
7a
7b
7c
8a
8b
8c
9a
9b
9c
43
50
56
48
53
68
38
55
57
40
60
55
in CDCl solution. Also in two of these products 9b and 9c
3
trans-esterification had taken place under the reaction condi-
tions, leading to methyl esters from ethyl ethoxymethylene-
acetoacetate 5.
One of our objectives in this area has been to utilise nitro-
ketene O,N-acetals or S,N-acetals (such as 7 and 11) for the
synthesis of peptides incorporating non-natural α-alkylated
amino acids. The route involves hydrolysis to the nitro-
acetamides and subsequent regiospecific alkylation of the
10a
10b
10c
reactive methylene group, followed by reduction of the NO to
2
1
3
NH2. Towards this end, we treated several cyclodipeptide
mono iminoethers 12 with 1,1-bismethylthio-2-nitroethylene
(Scheme 4), our hope being that the resulting nitroketene
1
4
3
Table 2 Reaction of lactim sulfides with electrophiles in refluxing
methanol for 48 h
MeS
R
H
Lactim sulfides
Electrophile
Product
Yield (%)
O
R
N
N
N
O2N
N
H
+
3
H
2a
2b
2c
2a
2b
2c
2a
2b
2c
2a
2b
2c
3
3
3
4
4
4
5
5
5
6
6
6
7a
7b
7c
8a
8b
8c
9a
9b
9c
64
65
75
71
70
79
66
64
70
68
60
67
O
OEt
CO2Et
H
1
2
13
Scheme 4
S,N-actals 13 could be hydrolysed to the corresponding nitro-
acetamides and then converted in two steps into modified
tripeptides.
Unfortunately, the initial condensation was successful only
with the cyclo (-Pro-Gly) monoiminoether 12 (R = H), leading
to 13 (R = H) (32%). The reaction failed with the analogous
derivatives of alanine, valine, leucine or phenylalanine, in each
case starting materials being recovered.
The ring-opening/N-alkylation reported above has potential
in synthesis where the lactim ethers (or lactam) are more easily
accessible than the corresponding ω-aminoalkyl carboxylic
esters. Also, some of the latter may prefer to undergo intra-
molecular cyclisation to lactams under the reaction conditions.
10a
10b
10c
mediacy of the corresponding methylthio compound was
proved by carrying out the condensation of butyrolactim ethyl
ether with 3 in dioxane–water instead of in methanol; under
these conditions, the methylthio substituted nitroenamine 11
was obtained in 65% yield (Scheme 3). Reaction of the δ-
EtO2C(CH2)3NH
MeS
NO2
Dioxane–water
+
3
OEt
N
Experimental
1
1
General
Scheme 3
Melting points were determined with a microscope hot-stage
apparatus, and are uncorrected. IR spectra were determined
1
13
valerolactim ether 1b and ε-caprolactim ether 1c with 1,1-
bismethylthio-2-nitroethylene 3 in refluxing methanol similarly
gave 7b and 7c in 50 and 56% yields, respectively. As expected
from the relative nucleophilicity of the nitrogen atom in lactim
ethers and lactim sulfides, reaction of the sulfides 2a–c with 3
under the same conditions led to higher yields of the products
on a Perkin-Elmer-Infracord spectrometer. H and C NMR
spectra were recorded on a Bruker-WH-90 (Spectrospin),
Bruker-AC-200, Bruker-MSL-300 or Varian-FT-80A instru-
ment in CDCl3 solution with tetramethylsilane as internal
standard. Coupling constants J are given in Hz. Mass spectra
were determined on a Finnigan-MAT-1020B spectrometer.
Microanalyses were performed at the Organic Chemistry
Division, NCL.
7
a–c. In all these reactions, hydrolysis of the iminium ion
11
obviously takes place by the water present in the solvent.
It has been well established earlier that nitro enamines
possessing an NH group exist almost exclusively in the intra-
molecularly hydrogen-bonded configuration, especially in non-
Typical procedure
The lactim ethers were prepared according to the literature
1
2
15
polar solvents. It is also known that the barrier to rotation
around the formal double-bond in such systems is low enough
to preclude isolation of the less energetically favoured geo-
method; thio lactams were obtained from their oxygen
1
6
counterparts using Lawesson’s reagent and etherified by
iodomethane in acetone in the presence of K CO .
2
3
1
2
metrical isomer. On this basis, the products 7a–c have been
The lactim ether or lactim sulfide (2 mmol) and the electro-
phile (2 mmol) were mixed in methanol (10 ml). The mixture
was refluxed and the progress of the reaction was monitored
by TLC. After completion of the reaction, the solvent was
removed under reduced pressure. The crude sample was puri-
fied by column chromatography over silica gel using acetone–
light petroleum.
assigned the E configuration (NH and NO cis to each other).
2
The reaction took a similar course with other electrophilic
push-pull ethylene systems as well. Thus ethoxymethylene-
acetylactone 4 reacted with γ-butyrolactim ether 1a in refluxing
methanol to give 8a (48%). The sulfide 2a gave the same prod-
uct (71%). δ-Valerolactim ether 1b and ε-caprolactim ether 1c
condensed with 4 to give 8b (53%) and 8c (68%), respectively,
while the corresponding sulfides 2b and 2c led to higher
yields of the products. Tables 1 and 2 list the products and
Methyl 4-(1-methoxy-2-nitroethenylamino)butanoate 7a. A
yellow oil (43%); νmax/cm (neat) 3360, 3260, 2960, 1740 and
Ϫ1
1520; δ (CDCl ) 1.9 (m, 2H, CH ), 2.35 (t, 2H, COCH , J 8),
H
3
2
2
2
422
J. Chem. Soc., Perkin Trans. 1, 1997

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ϩ
3
6
3
.45 (q, 2H, NCH , J 7), 3.75 (s, 3H, OCH ), 3.9 (s, 3H, OCH ),
(d, 1H, ᎐CH, J 12) and 11.10 (br s, 1H, NH); m/z 257 (M ), 242,
2
3
3
᎐
.70 (s, 1H, ᎐CH) and 9.85 (br s, 1H, NH); δ (CDCl ) 24.22,
211, 196, 182, 166, 137 (100%), 124 and 89 (Found: C, 56.18; H,
7.01; N, 5.62. C H NO requires C, 56.03; H, 7.39; N, 5.44%).
Methyl 6-(2-acetyl-2-methoxycarbonylethenylamino)hexan-
oate 9c. A colourless oil (57%); νmax/cm (neat) 3300, 2960,
1740, 1650, 1615, 1450 and 1370; δ (CDCl ) 1.55–1.85 (m, 6H,
3 CH ), 2.20 (s, 3H, COCH ), 2.30 (t, 2H, COCH , J 8), 3.35
᎐
C
3
0.42, 39.43, 51.06, 56.57, 97.32, 164.26 and 172.44; m/z 218
1
2
19
5
ϩ
(M ), 187, 172, 140, 112 (100%) and 98 (Found: C, 43.99; H,
Ϫ1
6
1
.24; N, 12.60. C H N O requires C, 44.03; H, 6.42; N,
2.84%).
Methyl 5-(1-methoxy-2-nitroethenylamino)pentanoate 7b. A
8
14
2
5
H
3
2
3
2
Ϫ1
yellow gum (50%); νmax/cm (neat) 3144, 2954, 1729, 1642,
(q, 2H, NCH , J 7), 3.65 (s, 3 H, OCH ), 3.70 (s, 3H, OCH ),
2
3
3
1
2
3
510 and 1380; δ (CDCl ) 1.55–1.70 (m, 4H, 2 CH ), 2.35 (t,
8.00 (d, 1H, ᎐CH, J 14) and 12.45 (br s, 1H, NH); m/z 257, 243,
228, 212, 184, 170, 156, 142 and 96 (100%) (Found: C, 57.27;
H
3
2
᎐
H, COCH , J 5), 3.35 (q, 2H, NCH , J 7), 3.65 (s, 3H, OMe),
2
2
.85 (s, 3H, OMe), 6.65 (s, 1H, ᎐CH) and 9.85 (br s, 1H, NH);
H, 7.46; N, 5.50. C H NO requires C, 57.56; H, 7.74; N,
᎐
13 21 5
δ (CDCl ) 21.80, 28.71, 33.11, 40.14, 51.22, 56.89, 97.57, 164.54
and 173.23; m/z 232 (M ), 201, 186, 176, 154, 140, 112, 98 and
5.16%).
C
3
ϩ
Methyl 4-(2,2-diethoxycarbonylethenylamino)butanoate 10a.
A colourless oil (40%); νmax/cm (neat) 3290, 2950, 1740, 1650,
Ϫ1
5
5 (100%) (Found: C, 46.52; H, 6.62; N, 12.08. C H N O
9
16
2
5
requires C, 46.55; H, 6.89; N, 12.06%).
1620 and 1540; δ (CDCl ) 1.15 (m, 6H, 2 CH ), 1.90 (m, 2H,
H
3
3
Methyl 6-(1-methoxy-2-nitroethenylamino)hexanoate 7c. A
brown gum (56%); νmax/cm (neat) 3250, 2960, 1745, 1630,
CH ), 2.35 (t, 2H, COCH , J 8), 3.35 (q, 2H, NCH , J 7), 3.60
(s, 3H, OCH ), 4.20 (m, 4H, 2 OCH ), 7.50 (d, 1H, ᎐CH, J 15)
3 2
2
2
2
Ϫ1
1
4
3
9
3
2
520 and 1450; δ (CDCl ) 1.40 (m, 2H, CH ), 1.50–1.70 (m,
and 9.2 (br s, 1H, NH); δ (CDCl ) 14.11, 25.74, 30.37, 50.44,
H
3
2
C 3
H, 2 CH ), 2.30 (t, 2H, COCH , J 8), 3.35 (q, 2H, NCH , J 7),
52.20, 54.70, 59.48, 60.31, 89.55, 159.81, 165.80, 169.01 and
2
2
2
ϩ
.65 (s, 3H, OCH ), 3.85 (s, 3H, OCH ), 6.65 (s, 1H, ᎐CH) and
172.68; m/z 287 (M ), 261, 218, 203, 189, 175, 161, 145, 131,
3
3
.85 (br s, 1H, NH); δ (CDCl ) 23.48, 25.26, 28.24, 32.79,
115, 89 and 75 (100%) (Found: C, 54.13; H, 7.60. C H NO
C
3
13 21
6
ϩ
9.63, 50.47, 56.26, 96.85, 163.85 and 172.83; m/z 246 (M ),
requires C, 54.35; H, 7.31%).
29, 215, 200, 173, 168, 154, 131, 126, 112, 85 (100%) and 69
Methyl 5-(2,2-diethoxycarbonylethenylamino)pentanoate 10b.
Ϫ1
(Found: C, 48.73; H, 7.48; N, 11.23. C H N O requires C,
A colourless oil (60%); νmax/cm (neat) 3287, 2952, 1736, 1656,
1
0
18
2
5
4
8.78; H, 7.31; N, 11.38%).
Methyl 4-(2,2-diacetylethenylamino)butanoate 8a. A colour-
1430 and 1220; δ (CDCl ) 1.30 (t, 6H, 2 CH , J 10), 1.70 (m,
H
3
3
4H, 2 CH ), 2.35 (t, 2H, COCH , J 8), 3.35 (q, 2H, NCH , J 8),
2
2
2
Ϫ1
less oil (48%); νmax/cm (neat) 3200, 2920, 1730, 1640, 1600 and
460; δ (CDCl ) 1.95 (m, 2H, CH ), 2.25 (s, 3H, COCH ), 2.40
3.70 (s, 3H, OCH ), 4.20 (q, 4H, 2 CH , J 10), 7.95 (d, 1H, ᎐CH,
3
2
1
J 15) and 9.2 (br s, 1H, NH); δ (CDCl ) 13.70, 13.74, 21.16,
C 3
H
3
2
3
(
t, 2H, COCH , J 8), 2.45 (s, 3H, COCH ), 3.45 (q, 2H, NCH ,
29.67, 32.63, 48.62, 50.67, 58.63, 58.78, 88.84, 159.29, 165.28,
168.41 and 172.59; m/z 301 (M ), 256, 224, 209, 154, 128, 96, 82
2
3
2
ϩ
J 7), 3.70 (s, 3H, OCH ), 7.70 (d, 1H, ᎐CH, J 14) and 11.00 (br
3
s, 1H, NH); δ (CDCl ) 24.91, 26.02, 29.59, 30.51, 48.15, 50.53,
and 55 (100%) (Found: C, 56.08; H, 7.62; N, 4.44. C H NO
requires C, 55.81; H, 7.64; N, 4.65%).
C
3
14 23
6
ϩ
1
10.22, 159.54, 171.82, 193.22 and 198.50; m/z 227 (M ), 212,
1
96, 180, 154, 138, 126 (100%), 112 and 101 (Found: C, 58.15;
Methyl 6-(2,2-diethoxycarbonylethenylamino)hexanoate 10c.
A colourless oil (55%); νmax/cm (neat) 3300, 2980, 1730, 1630,
Ϫ1
H, 7.32; N, 6.05. C H NO requires C, 58.14; H, 7.48; N,
1
1
17
4
6
.16%).
Methyl 5-(2,2-diacetylethenylamino)pentanoate 8b. A colour-
1570 and 1450; δ (CDCl ) 1.14–1.40 (m, 8H, CH , 2 CH ), 1.60
H
3
2
3
(m, 4H, 2 CH ), 2.35 (t, 2H, COCH , J 8), 3.30 (q, 2H, NHCH ,
2
2
2
Ϫ1
less oil (53%); νmax/cm (neat) 3200, 2951, 2360, 1740, 1633 and
390; δ (CDCl ) 1.65 (m, 4H, 2 CH ), 2.25 (s, 3H, COCH ), 2.35
J 7), 3.60 (s, 3H, OCH ), 4.25 (q, 4H, 2 OCH , J 8), 7.95 (d, 1H,
3
2
1
᎐CH, J 16) and 9.15 (br s, 1H, NH); δ (CDCl ) 14.06, 14.15,
᎐
C 3
H
3
2
3
(
t, 2H, COCH , J 6), 2.45 (s, 3H, COCH ), 3.35 (q, 2H,
24.12, 25.66, 30.14, 33.42, 49.21, 51.13, 59.21, 59.40, 89.28,
159.65, 165.88, 169.08 and 173.41; m/z 315 (M ), 309, 296, 270,
2
3
ϩ
NHCH , J 7), 3.65 (s, 3H, OCH ), 7.70 (d, 1H, ᎐CH, J 13) and
2
3
1
3
1.05 (br s, 1H, NH); δ (CDCl ) 20.95, 26.30, 29.30, 30.80,
238, 223, 195, 167, 154 (100%) and 128 (Found: C, 56.85; H,
7.72; N, 4.21. C H NO requires C, 57.14; H, 7.93; N, 4.44%).
C
3
2.45, 48.89, 50.60, 110.30, 156.64, 172.48, 193.37 and 198.66;
1
5
25
6
ϩ
m/z 241 (M ), 226, 210, 194, 152, 126 (100%), 112, 98 and 83
Ethyl 4-(1-methylthio-2-nitroethenylamino)butanoate 11. A
Ϫ1
(Found: C, 59.95; H, 7.91; N, 5.72. C H NO requires C,
brown gum (65%); νmax/cm (neat) 3280, 2980, 2920, 1730,
1
2
19
4
5
9.75; H, 7.88; N, 5.80%).
Methyl 6-(2,2-diacetylethenylamino)hexanoate 8c. A colour-
1580, 1460 and 1420; δ (CDCl ) 1.25 (t, 3H, CH , J 8), 2.00 (m,
H
3
3
2H, CH ), 2.40 (t, 2H, COCH , J 8), 2.45 (s, 3H, SCH ), 3.45 (q,
2
2
3
Ϫ1
less oil (68%); νmax/cm (neat) 3210, 2980, 1745, 1630, 1600,
2H, NCH , J 7), 4.10 (q, 2H, OCH , J 8), 6.55 (s, 1H, ᎐CH) and
2
2
1
2
3
405 and 1320; δ (CDCl ) 1.45 (m, 2H, CH ), 1.65 (m, 4H,
10.50 (br s, 1H, NH); δ (CDCl ) 13.72, 13.87, 24.00, 30.64,
C 3
ϩ
H
3
2
CH ), 2.25 (s, 3H, COCH ), 2.35 (t, 2H, COCH , J 8), 2.50 (s,
43.34, 60.21, 105.86, 164.67 and 171.97; m/z 248 (M ), 231, 215,
2
3
2
H, COCH ), 3.35 (q, 2H, NCH , J 7), 3.65 (s, 3H, OCH ), 7.75
202, 157, 147, 119, 115, 101, 87 (100%) and 73 (Found: C, 43.72;
3
2
3
(
d, 1H, ᎐CH, J 15) and 11.00 (br s, 1H, NH); δ (CDCl ) 23.20,
H, 6.79; N, 11.17. C H N O S requires C, 43.54; H, 6.45; N,
᎐
C
3
9 16 2 4
2
1
1
4.75, 25.92, 29.19, 30.46, 32.45, 48.73, 50.17, 109.87, 159.38,
72.42, 193.08 and 198.31; m/z 255 (M ), 240, 224, 198, 166,
54, 140, 126 (100%), 112, 96 and 69 (Found: C, 61.00; H, 8.59;
11.29%).
Ethyl 1-(1-methylthio-2-nitroethenylamino)acetylpyrrolidine-
ϩ
2-carboxylate 13 (R᎐H). A yellow solid (32%); mp 85–87 ЊC
᎐
Ϫ1
N, 5.43. C H NO requires C, 61.17; H, 8.23; N, 5.49%).
(EtOH); νmax/cm (Nujol) 3210, 2950, 1745, 1630, 1505, 1410
1
3
21
4
Methyl 4-(2-acetyl-2-ethoxycarbonylethenylamino)butanoate
a. A colourless oil (38%); νmax/cm (neat) 3490, 3280, 2940,
and 1380; δ (CDCl ) 1.30 (t, 3H, CH , J 10), 1.85–2.30 (m, 4H,
H
3
3
Ϫ1
9
2 CH ), 2.45 (s, 3H, SMe), 3.60 (q, 2H, OCH , J 9), 4.10–4.35
2
2
1
730, 1720, 1680, 1590 and 1540; δ (CDCl ) 1.25–1.45 (m, 5H,
(m, 5H, NHCH , NCH , NCHCO), 6.60 (s, 1H, ᎐CH) and
2 2
ϩ
10.70 (br s, 1H, NH); m/z 317 (M ), 299, 271, 223, 199, 125, 98,
H
3
CH , CH ), 2.40 (t, 2H, COCH , J 8), 2.50 (s, 3H, COCH ), 3.45
2
3
2
3
(
q, 2H, NCH , J 7), 3.75 (s, 3H, OCH ), 4.20 (q, 2H, OCH , J
83 and 70 (100%) (Found: C, 45.38; H, 5.59. C H N O S
2
3
2
12 19
3
5
8
2
1
1
5
), 8.00 (d, 1H, ᎐CH, J 14) and 11.00 (br s, 1H, NH); δ (CDCl )
requires C, 45.42; H, 5.99%).
᎐
C
3
5.29, 26.43, 30.04, 30.93, 48.64, 49.41, 51.09, 110.87, 159.88,
ϩ
72.36, 194.10 and 199.48; m/z 257 (M ), 243, 212, 196, 180,
64, 138 (100%), 124 and 110 (Found: C, 55.96; H, 7.15; N,
.25. C H NO requires C, 56.03; H, 7.39; N, 5.44%).
Acknowledgements
1
2
19
5
Methyl 5-(2-acetyl-2-methoxycarbonylethenylamino)pentan-
We are grateful to CSIR, New Delhi, for financial assistance
under the Emeritus Scientist scheme (to S. R.) and the award of
a research associateship (to A. N. D.). We thank the Depart-
ment of Science and Technology for funding this project and
for the award of a research assistantship (to M. A.).
Ϫ1
oate 9b. A colourless oil (55%); νmax/cm (neat) 3390, 2950,
740, 1700, 1605 and 1430; δ (CDCl ) 1.25–1.75 (m, 4H, 2
1
H
3
CH ), 1.95 (s, 3H, COCH ), 2.30 (t, 2H, COCH , J 6.5), 3.27 (q,
2
3
2
2
H, NCH , J 5), 3.60 (s, 3H, OCH ), 3.65 (s, 3H, OCH ), 8.10
2
3
3
J. Chem. Soc., Perkin Trans. 1, 1997
2423

View Article Online
1
0 J. P. Michael, P. F. Cirillo, L. Denner, G. D. Hosken, A. S. Howard
and O. S. Tinkler, Tetrahedron, 1990, 46, 7923.
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