Studies in sigmatropic rearrangement: Synthesis of 4-aryloxy-methylene-1,7-dimethyl-1,2,3-trihydropyridino-[3,2-c]pyran-5-ones

Article abstract of DOI:10.1016/S0040-4020(00)01118-2

A number of 4-[N-4′-aryloxy but-2-ynyl N-methyl amino-6-methyl pyran-2-ones (4a-g) have been prepared in excellent yields from N-(1-aryloxy-but-2-ynyl)-N-methyl amine (3) and 4-tosyloxy-6-methyl-pyran-2-one (2). Thermal rearrangement of compounds 4(a-g) gave 4-aryloxy-methyl-1,7-dimethyl-1,2-dihydropyridino-[3,2-c] pyran-5-ones (6) and/or 4-aryloxymethylene-1,7-dimethyl-1,2,3-trihydropyridino-[3,2-c] pyran-5-ones (5).

Full text of DOI:10.1016/S0040-4020(00)01118-2

TETRAHEDRON
Pergamon
Tetrahedron 57 (2001) 1589±1592
Studies in sigmatropic rearrangement: synthesis of
4-aryloxy-methylene-1,7-dimethyl-1,2,3-trihydropyridino-
[3,2-c]pyran-5-ones
K. C. Majumdarp and S. Ghosh
Department of Chemistry, University of Kalyani, Kalyani 741235, W.B., India
Received 8 September 2000; revised 9 November 2000; accepted 23 November 2000
AbstractÐA number of 4-[N-40-aryloxy but-2-ynyl N-methyl amino-6-methyl pyran-2-ones (4a±g) have been prepared in excellent yields
from N-(1-aryloxy-but-2-ynyl)-N-methyl amine (3) and 4-tosyloxy-6-methyl-pyran-2-one (2). Thermal rearrangement of compounds 4(a±g)
gave 4-aryloxy-methyl-1,7-dimethyl-1,2-dihydropyridino-[3,2-c] pyran-5-ones (6) and/or 4-aryloxymethylene-1,7-dimethyl-1,2,3-trihydro-
pyridino-[3,2-c] pyran-5-ones (5). q 2001 Published by Elsevier Science Ltd.
4-Hydroxy-6-methyl-2-pyrone (triacetic acid lactone) 1 is a
natural product of polyketide origin.1 This may also be
obtained by deacetylation of dehydroacetic acid.2 Many
natural products containing the basic structures of
4-hydroxy or (methoxy)-6-methyl-2-pyrone have been
isolated, some of them carrying biogenetically plausible
groups at C3 or C5 or both. Elasnin, isolated from
Streptomices sp., for example, is a speci®c inhibitor of
human leucocyte elastase, an enzyme involved in in¯am-
matory processes such as pulmonary emphysema.3 As a
logical extension, many more simple pyrones structurally
related to elasnin have been synthesized and evaluated as
inhibitors of several elastases.4 Some 4-hydroxy-2-pyrones
have also been tested as anticoagulant agents.5 In a con-
tinuation of our work on the synthesis of bioactive hetero-
cycles by the application of [3,3] sigmatropic rear-
rangements6±10 we became interested in incorporating the
4-hydroxy-6-methyl-2-pyrone system in the substrates in
order to achieve the synthesis of new heterocycles.
well as aryl propargyl ether moiety and it is reasonable to
expect that these may undergo a [3,3] sigmatropic rear-
rangement. With this goal, substrate 4a was re¯uxed in
chlorobenzene but the starting material was found
unchanged even after 5 h. Solvents with higher boiling
points were then tried, but 4a failed to record any change
even when it was heated in o-dichlorobenzene at 150, 160
and 1708C in an oil bath. Then 4a was re¯uxed in
o-dichlorobenzene at 178±1818C and a change was
observed on TLC within 1 h of beginning the reaction.
Complete disappearence of starting material required
almost 12 h. but the yield of the product 5a was found to
be extremely low with the formation of some untractable
mass. Then the reaction time was optimized to 2±2.5 h
when the yield of the product 5a was found to be the maxi-
mum. However, a fairly large quantity of starting material
4a (,40%) was found to remain unchanged. This was
recovered and subjected again to rearrangement in order
to obtain more of the product 5a. Product 5a was charac-
terized from its elemental analysis and spectral data. The 1H
NMR spectrum of 5a showed two triplets for two methyl-
enes each with J values of 6 Hz centered at d 2.85 and d 3.37
and a one proton singlet at d 7.99. This NMR pattern with
other data indicated this to be the exocyclic product 5a. This
was also corroborated by a proton decoupling experiment.
Unusual exocyclic products 5(a±g) were obtained in all
cases. The endocyclic product 6 was only obtained in
three cases (a,b,c) along with the exocyclic product.
When the rearrangements of 4(a,b,c) were monitored by
TLC, only spots corresponding to endocyclic products
6(a,b,c) were found up to 30 min after the commencement
of the reaction. After 30 min the spots of 5(a,b,c) began to
appear. Compounds 6(a,b,c) afforded a mixture of 5(a,b,c)
and 6(a,b,c) when re¯uxed in o-dichlorobenzene for 1 h. It
could, therefore, be concluded that both the compounds 5
The starting materials, 4-(N-40-aryloxybut-2-ynyl)-4-N-
methylamino-6-methyl-pyran-2-ones 4(a±g) were synthe-
sized from 4-hydroxy-6-methyl-pyran-2-one (1). Com-
pound 1 was converted to its tosyl derivative11 (2) which
was then allowed to react with 4-aryloxybut-2-ynylmethyl-
amine in alcohol at room temperature for 12±16 h to give
starting materials 4(a±g) in 80±90% yields (Scheme 1).
1. Results and discussion
Substrates 4(a±g) contain a vinyl propargylamine moiety as
* Corresponding author. Tel.: 133-582-8750; fax: 133-582-8282;
e-mail: kcm@klyuniv.ernet.in
0040±4020/01/$ - see front matter q 2001 Published by Elsevier Science Ltd.
PII: S0040-4020(00)01118-2

1590
K. C. Majumdar, S. Ghosh / Tetrahedron 57 (2001) 1589±1592
Scheme 1.
and 6 were formed through the same mechanistic pathway.
All the foregoing facts could be explained with the assump-
tion that the endocyclic compound 6 was converted into the
exocyclic 5 under the reaction conditions. Formation of 6
from 4 can easily be explained12 as in Scheme 2.
substrates underwent [3,3] sigmatropic rearrangement at the
vinyl amine moiety instead of the propargyl ether part.13
Exocyclic products were obtained in all cases whereas endo-
cyclic products were isolated only in cases where the
aryloxy group contained ortho-substituents.
[3,3] Sigmatropic rearrangement of 4 afforded allene 7.
Compound 7 may undergo tautomerisation to furnish 8
followed by [1,5] H shift to give 9 and 6p electrocyclic
ring closure ®nally gives 6. Compound 6 may undergo
prototropic rearrangement under the reaction conditions to
generate 5. One striking feature is that the presence of
o-substituents in the phenyl ring permits formation of endo-
cyclic product 6. This prompted us to conclude that the
o-substituent in the phenyl ring probably destabilised the
exocyclic derivatives 5(a,b,c) thereby allowing isolation
of 6(a,b,c).
2. Experimental
Melting points were measured on a sulphuric acid bath and
are uncorrected. UV absorption spectra were recorded in
EtOH on a Hitachi 200-20 Spectrophotometer. IR spectra
were run on KBr disks on a Perkin±Elmer 1330 apparatus.
1H NMR spectra were determined for solutions in CDCl3
with TMS as internal standard on a Bruker 300 (300 MHz)
instrument. Elemental analyses and recording of mass
spectra were carried out by RSIC (CDRI), Lucknow on a
JEOL D-300 (El) instrument. Silica gel (60±120 mesh),
Spectrochem, India, was used for chromatographic
The reaction is found to be of general nature. All the seven
Scheme 2.

K. C. Majumdar, S. Ghosh / Tetrahedron 57 (2001) 1589±1592
1591
separation. Petroleum ether refers to the fraction boiling
between 60 and 808C.
2.2.4.
methyl-2-pyrone (4d). Yield 86%; mp. 80±82 8C; lmax
(log e) 224 (4.02), 297 (3.48) nm; IR (KBr) nmax: 1690,
1530,1490, 1235 cm21 1H NMR (CDCl3, 300 MHz): d
2.17 (s, 3H), 2.97 (s, 3H), 4.04 (t, Jˆ1.8 Hz, 2H), 4.69 (t,
Jˆ1.8 Hz, 2H), 5.07 (s, 1H), 5.76 (s, 1H), 6.91±7.31
(m, 5H); MS m/z 283 (M1); Anal Calcd. For C17H17NO3:
C, 72.08; H, 6.00; N, 4.94. Found C, 72.20; H, 6.15; N,
4.81%.
4-[N-[4-Phenoxybut-2-ynyl)-N-methylamino-6-
:
;
2.1. Preparation of 1-(aryloxy)-4-N-methylaminobut-2-
yne
1-(Aryloxy)-4-chlorobut-2-yne (1 g) was dissolved in 20 ml
of EtOH. This solution was added dropwise at room
temperature to a well stirred solution of 23 ml of methyl-
amine (40%) for a period of 10 min. Stirring was continued
for another 2 h at room temperature. Methylamine, water
and EtOH were removed in vacuo and the residual mass
was dissolved in CHCl3 (25 ml). This was washed with
water (2£10 ml) and dried (Na2SO4). Removal of CHCl3
afforded a gummy mass. Attempt to purify this gummy
mass through column chromatography failed and so it was
directly used for the subsequent reactions.
2.2.5. 4-[N-[4-(40-Chlorophenoxy)-but-2-ynyl)-N-methyl-
amino-6-methyl-2-pyrone (4e). Yield 82%; mp. 84±85 8C;
l
max: (log e) 226 (4.47), 295 (3.90) nm; IR (KBr) nmax: 1690,
1530, 1485, 1220 cm21; 1H NMR (CDCl3, 300 MHz): d 2.18
(s, 3H), 2.98 (s, 3H), 4.04 (t, Jˆ1.8 Hz, 2H), 4.67 (t, Jˆ
1.8 Hz, 2H), 5.07 (s, 1H), 5.76 (s, 1H), 6.85±7.25 (m, 4H);
MS m/z 317, 319 (M1); Anal Calcd. For C17H16ClNO3: C,
64.25; H, 5.03; N, 4.40. Found C, 64.42; H, 5.20; N, 4.26%.
2.2.6. 4-[N-[4-(40-Methylphenoxy)-but-2-ynyl)-N-methyl-
amino-6-methyl-2-pyrone (4f). Yield 90%; mp. 129±130
2.2. General procedures for the synthesis of compounds
4(a±g)
8C; lmax: (log e) 225 (4.31), 296 (3.76) nm; IR (KBr) nmax
:
1690, 1530, 1500, 1230 cm21; 1H NMR (CDCl3, 300 MHz):
d 2.17 (s, 3H), 2.29 (s, 3H), 2.98, (s, 3H), 4.05 (t, Jˆ1.8 Hz,
2H), 4.66 (t, Jˆ1.8 Hz, 2H), 5.07 (s, 1H), 5.78 (s, 1H),
6.81±7.10 (m, 4H). MS m/z 297 (M1); Anal Calcd. For
C18H19NO3: C, 72.72; H, 6.39; N,4.71. Found C, 72.90; H,
6.50; N, 4.86%.
A
mixture of 1-(aryloxy)-4-N-methylaminobut-2-yne
(5 mmol) and 4-tosyloxy-6-methyl-2-pyrone (0.40 g,
3.3 mmol) in dehydrated EtOH was stirred for 12±16 h at
room temperature. Alcohol was removed by distillation and
the residual mass was dissolved in CHCl3 (50 ml). This was
washed with water (2£25 ml) and dried (Na2SO4). Evapo-
ration of CHCl3 afforded a gummy mass which was
subjected to column chromatography over silica gel. Elution
of the column with benzene-ethyl acetate (3:1) gave
compounds 4(a±g). All the compounds 4(a±g) were recrys-
tallised from CHCl3-petroleum ether.
2.2.7. 4-[N-[4-(40-Methoxyphenoxy)-but-2-ynyl)-N-methyl-
amino-6-methyl-2-pyrone (4g). Yield 80%; mp. 96±98 8C;
l
max: (log e) 226 (4.46), 294 (4.00) nm; IR (KBr) nmax
;
:
1700, 1535, 1490, 1235 cm21 1H NMR (CDCl3,
300 MHz): d 2.17 (s, 3H), 2.98 (s, 3H), 3.77 (s, 3H), 4.04
(t, Jˆ1.8 Hz, 2H), 4.64 (t, Jˆ1.8 Hz, 2H), 5.07 (s, 1H), 5.77
(s, 1H), 6.83±6.85 (m, 4H); MS m/z 313 (M1); Anal Calcd.
For C18H19NO4: C, 69.00; H, 6.07; N, 4.47. Found C, 69.11;
H, 6.20; N, 4.38%.
2.2.1. 4-[N-[4-(20-Chlorophenoxy)-but-2-ynyl)-N-methyl-
amino-6-methyl-2-pyrone (4a). Yield 90%; mp. 136±
1388C; lmax: (log e) 224 (4.09), 297 (3.53) nm; IR (KBr)
n
max: 1690, 1525, 1485, 1230 cm21 1H NMR (CDCl3,
;
300 MHz): d 2.17 (s, 3H), 2.97 (s, 3H), 4.03 (t, Jˆ1.8 Hz,
2H), 4.78 (t, Jˆ1.8 Hz, 2H), 5.05 (s, 1H), 5.75 (s, 1H),
6.95±7.38 (m, 4H); MS m/z 317, 319 (M1); Anal Calcd.
for C17H16ClNO3: C, 64.25; H, 5.03; N, 4.40. Found C,
64.40; H, 5.15; N, 4.48%.
2.3. General procedures for the synthesis of compounds
5(a±g) and 6(a±g)
Compounds 4a±g (300 mg) were re¯uxed in o-dichloro-
benzene (3 ml) for 2±2.5 h. The reaction mixture was then
cooled and directly subjected to column chromatography
over silica gel. o-Dichlorobenzene was eluted out with
petroleum ether. All the products 5(a±g) were obtained
when the column was eluted with benzene-ethyl acetate
(4:1). Compounds 6(a,b,c) were eluted with benzene-ethyl
acetate (3:1). Unchanged starting materials 4(a±g) were
also carefully eluted out with benzene-ethyl acetate (3:1).
Compounds 5(a±g) and 6(a,b,c) were recrystallised from
CHCl3-petroleum ether. The yields were calculated on the
basis of actual conversion of starting material.
2.2.2. 4-[N-[4-(20-Methylphenoxy)-but-2-ynyl)-N-methyl-
amino-6-methyl-2-pyrone (4b). Yield 89%; mp. 105±106
8C; lmax: (log e) 224 (3.91), 297 (3.38) nm; IR (KBr) nmax
:
1690, 1525, 1485, 1225 cm21; 1H NMR (CDCl3, 300 MHz):
d 2.18 (s, 3H), 2.22 (s, 3H), 2.98 (s, 3H), 4.04 (t, Jˆ1.8 Hz,
2H), 4.71 (t, Jˆ1.8 Hz, 2H), 5.08 (s, 1H), 5.78 (s, 1H),
6.89±7.14 (m, 4H); MS m/z 297 (M1); Anal Calcd. For
C18H19 NO3: C, 72.72; H, 6.39; N, 4.71. Found C, 72.82;
H, 6.51; N, 4.82%.
2.2.3.
4-[N-[4-(20,40-Dichlorophenoxy)-but-2-ynyl)-N-
methylamino-6-methyl-2-pyrone (4c). Yield 85%; mp.
127±129 8C; lmax: (log e) 226 (4.21), 293 (3.75) nm; IR
2.3.1. Compound (5a). Yield 58%; mp. 116±118 8C; lmax:
(log e) 238 (4.09), 351 (3.86) nm; IR (KBr) nmax: 1670,
1
(KBr) nmax: 1690, 1530, 1480, 1225 cm21
;
1H NMR
1500, 1310, 1225 cm21; H NMR (CDCl3, 300 MHz): d
(CDCl3, 300 MHz): d 2.18 (s, 3H), 2.97 (s, 3H), 4.03 (t,
Jˆ1.8 Hz, 2H), 4.76 (t, Jˆ1.8 Hz, 2H), 5.06 (s, 1H), 5.74
(s, 1H), 6.81±7.37 (m, 3H); MS m/z 351, 353, 355 (M1);
Anal Calcd. For C17H15Cl2NO3: C, 57.95; H, 4.26; N, 3.97.
Found C, 58.05; H, 4.36; N, 4.11%.
2.21 (s, 3H), 2.85 (t, Jˆ6 Hz, 2H), 3.06 (s, 3H), 3.37 (t,
Jˆ6 Hz,2H), 5.82 (s, 1H), 6.93±7.37 (m, 4H), 7.99 (s,
1H). MS m/z 317, 319 (M1); Anal Calcd. For
C17H16ClNO3: C, 64.25; H, 5.03; N, 4.40. Found C, 64.36;
H, 5.18; N, 4.49%.

1592
K. C. Majumdar, S. Ghosh / Tetrahedron 57 (2001) 1589±1592
2.3.2. Compound (5b). Yield 54%; mp. 105±106 8C; lmax:
(log e) 238 (4.29), 351 (4.02) nm; IR (KBr) nmax: 1670,
(log e) 242 (4.18), 278 (3.97) nm; IR (KBr) nmax: 1670,
1
1480, 1310, 1285 cm21; H NMR (CDCl3, 300 MHz): d
1
1500, 1315, 1210 cm21; H NMR (CDCl3, 300 MHz): d
2.19 (s, 3H), 2.27 (s, 3H), 2.90 (s, 3H), 4.20 (d, Jˆ6 Hz,
2H), 5.50 (t, Jˆ6 Hz, 1H), 5.11 (brs, 2H), 5.74 (s, 1H),
6.83±7.13 (m, 4H); MS m/z 297 (M1); Anal Calcd. For
C18H19NO3: C, 72.72; H, 6.39; N, 4.71. Found C, 72.85;
H, 6.48; N 4.87%.
2.21 (s, 3H), 2.28 (s, 3H), 2.82 (t, Jˆ6 Hz, 2H), 3.06 (s,
3H), 3.36 (t, Jˆ6 Hz, 2H), 5.82 (s, 1H), 6.90±7.17 (m, 4H),
7.97 (s, 1H). MS m/z 297 (M1); Anal Calcd. For
C18H19NO3: C, 72.72; H, 6.39; N, 4.71. Found C, 72.87;
H, 6.48; N, 4.82%.
2.3.10. Compound (6c). Yield 21%; mp. 156±158 8C; lmax
(log e) 237 (4.22), 279 (3.56) nm; IR (KBr) nmax: 1670,
:
2.3.3. Compound (5c). Yield 64%; mp. 142±143 8C; lmax:
(log e) 237 (4.06), 351 (3.93) nm; IR (KBr) nmax: 1670,
1470, 1310, 1280 cm21; H NMR (CDCl3, 300 MHz): d
1
1
1500, 1310, 1230 cm21; H NMR (CDCl3, 300 MHz): d
2.19 (s, 3H), 2.90 (s, 3H), 4.21 (d, Jˆ6 Hz, 2H), 5.55 (t,
Jˆ6 Hz, 1H), 5.13 (brs, 2H), 5.74 (s, 1H), 6.96±7.34 (m,
3H); MS m/z 351, 353, 355 (M1); Anal Calcd. For
C17H15Cl2NO3: C, 57.95; H, 4.26; N, 3.97. Found C,
58.10; H, 4.39; N 4.14%.
2.21 (s, 3H), 2.82 (t, Jˆ6 Hz, 2H), 3.07 (s, 3H), 3.37 (t,
Jˆ6 Hz, 2H), 5.82 (s, 1H), 7.11±7.37 (m, 3H), 7.94 (s,
1H). MS m/z 351, 353, 355 (M1); Anal. Calcd. For
C17H15Cl2NO3: C, 57.95; H, 4.26; N, 3.97. Found C,
58.17; H, 4.40; N, 4.11%.
2.3.4. Compound (5d). Yield 65%; mp. 164±166 8C; lmax:
(log e) 238 (4.31), 351 (4.07) nm; IR (KBr) nmax: 1670,
Acknowledgements
1
1480, 1310, 1225 cm21; H NMR (CDCl3, 300 MHz): d
We thank the CSIR (New Delhi) for ®nancial assistance and
the University of Kalyani for laboratory facilities.
2.20 (s, 3H), 2.79 (t, Jˆ6 Hz, 2H), 3.05 (s, 3H), 3.35 (t,
Jˆ6 Hz, 2H), 5.81 (s, 1H), 6.98±7.35 (m, 5H), 7.99 (s,
1H). MS m/z 283 (M1); Anal Calcd. For C17H17NO3: C,
72.08; H, 6.00; N, 4.94. Found C, 72.19; H, 6.16; N, 5.01%.
References
2.3.5. Compound (5e). Yield 56%; mp. 147±149 8C; lmax:
(log e) 238 (4.18), 350 (3.92) nm; IR (KBr) nmax: 1670,
1. (a) Bentley, R.; Zwitkowits, P. M. J. Am. Chem. Soc. 1967, 89,
676. (b) Bentley, R., Zwitkowits, P.M. J. Am. Chem. Soc.
1967, 89, 681.
1
1500, 1305, 1225 cm21; H NMR (CDCl3, 300 MHz): d
2.21 (s, 3H), 2.77 (t, Jˆ6 Hz, 2H), 3.05 (s, 3H), 3.35 (t,
Jˆ6 Hz, 2H), 5.81 (s, 1H),, 6.99±7.26 (m, 4H), 7.93
(s,1H). MS m/z 317, 319 (M1); Anal Calcd. For
C17H16ClNO3: C, 64.25; H, 5.03; N, 4.40. Found C, 64.48;
H, 5.23; N, 4.52%.
2. Collie, J. N. J. Chem. Soc. 1891, 59, 607.
3. (a) Omura, S.; Ohno, H.; Saheki, T.; Masakazu, Y.; Naka-
gawa, A. Biochem. Biophys. Res. Commun. 1978, 83, 704.
(b) Ohno, H.; Saheki, T.; Awaya, J.; Nakagawa, A.; Omura,
S. J. Antibiot. 1978, 31, 1116.
4. (a) Groutas, W. C.; Abrams, W. R.; Carrol, R. T.; Moi, M. K.;
Miller, K. E.; Margolis, M. T. Experientia. 1984, 40, 361.
(b) Groutas, W. C.; Stanga, M. A.; Brubaker, M. J.; Huang,
T. L.; Moi, M. K.; Carrol, R. T. J. Med. Chem. 1985, 28, 1106.
(c) Spencer, R. W.; Copp, L. J.; P®ster, J. R. J. Med. Chem.
1985, 28, 1828. (d) Cook, L.; Ternai, B.; Ghosh, P. J. Med.
Chem. 1987, 30, 1017. (e) Ternai, B.; Cook, M. L. Pct-Int.
Appl. WO 10, 258 [CA 1989, 110, 192652].
2.3.6. Compound (5f). Yield 60%; mp. 122±123 8C; lmax:
(log e) 237 (4.26), 351 (3.75) nm; IR (KBr) nmax: 1670,
1
1500, 1310, 1230 cm21; H NMR (CDCl3, 300 MHz): d
2.20 (s, 3H), 2.29 (s, 3H), 2.79 (t, Jˆ6 Hz, 2H), 3.05 (s,
3H), 3.35 (t, Jˆ6 Hz, 2H), 5.81 (s, 1H), 6.96±7.10 (m, 4H),
7.95 (s, 1H); MS m/z 297 (M1); Anal Calcd. For
C18H19NO3: C, 72.72; H, 6.39; N, 4.71. Found C, 72.91;
H, 6.45; N 4.84%.
5. (a) Rehse, K.; Schinkel, W.; Siemann, U. Arch. Pharm. 1980,
313, 344. (b) Rehse, K.; Schinkel, W. Arch. Pharm. 1983, 316,
845. (c) Rehse, K.; Schinkel, W. Arch. Pharm. 1983, 316, 988.
(d) Rehse, K.; Brandt, F. Arch. Pharm. 1983, 316, 1030.
(e) Rehse, K.; Ruther, D. Arch. Pharm. 1984, 317, 262.
6. Majumdar, K. C.; Biswas, P. Tetrahedron 1998, 54, 11603.
7. Majumdar, K. C.; Biswas, P. Tetrahedron 1999, 55, 1449.
8. Majumdar, K. C.; Chatterjee, P.; Saha, S. Tetrahedron Lett.
1998, 39, 7147.
2.3.7. Compound (5g). Yield 52%; mp. 101±103 8C; lmax:
(log e) 238 (4.10), 353 (3.83) nm; IR (KBr) nmax: 1670,
1
1500, 1310, 1220 cm21; H NMR (CDCl3, 300 MHz): d
2.20 (s, 3H), 2.78 (t, Jˆ6 Hz, 2H), 3.05 (s, 3H), 3.77 (s,
3H), 3.35 (t, Jˆ6 Hz, 2H), 5.81 (s, 1H), 6.82±7.01 (m, 4H),
7.91 (s, 1H); MS m/z 313 (M1); Anal Calcd. For
C18H19NO4: C, 69.00; H, 6.07; N, 4.47. Found C, 69.16;
H, 6.21; N 4.61%.
9. Majumdar, K. C.; Das, U. J. Org. Chem. 1998, 63, 9997.
10. Majumdar, K. C.; Das, U.; Jana, N. K. J. Org. Chem. 1998, 63,
3550.
2.3.8. Compound (6a). Yield 23%; mp. 146±147 8C; lmax:
(log e) 242 (4.12), 276 (3.79) nm; IR (KBr) nmax: 1670,
1
1480, 1305, 1280 cm21; H NMR (CDCl3, 300 MHz): d
11. Bittencourt, A. M.; Gottlieb, O. R.; Mors, W. B.; Taveira
Magalhaes, M.; Mageswaran, S.; Ollis, W. D.; Sutherland,
I. O. Tetrahedron 1971, 27, 1043.
2.19 (s, 3H), 2.89 (s, 3H), 4.21 (d, Jˆ6 Hz, 2H), 5.61 (t,
Jˆ6 Hz,1H), 5.16 (brs, 2H), 5.74 (s, 1H), 6.84±7.35 (m,
4H); MS m/z 317, 319 (M1); Anal Calcd. For
C17H16ClNO3: C, 64.25; H, 5.03; N, 4.40. Found C, 64.41;
H, 5.17; N 4.51%.
12. (a) Majumdar, K. C.; De, R. N. J. Chem. Soc., Perkin Trans. 1
1989, 1901. (b) Majumdar, K. C.; De, R. N.; Khan, A. T.;
Chattopadhyay, S. K.; Dey, K.; Patra, A. J. Chem. Soc.,
Chem. Commun. 1988, 777.
2.3.9. Compound (6b). Yield 18%; mp. 131±132 8C; lmax
:
13. Majumdar, K. C.; Jana, N. K. Synth. Commun. 2000, 30, 2613.