T. Ghosh, C. Bandyopadhyay / Tetrahedron Letters 45 (2004) 6169–6172
6171
R'
R'
N
O
H
O-
O
O
O
NHR'
CHO
N+
O
O
[1,5] -H -Shift
O
R
R
R
R
4
6
For 1 to 6
Path-a
O
R
R'
Et
O
a
b
c
d
e
f
H
Zn / HOAc
EtOH
O-
R'
Me Et
+
R'NO2
2
+
N
H
Me
CHO
R
Me Me
O
3
1
O
H
H
Ph
C6H4Me-p
Path-b
g
Me C6H4Me-p
H
O
O
O
O
O
OH
O
[1,5] -H -Shift
NR'
NHR'
R
NR'
R
R
O
O
5
Scheme 1.
O
O
O
O
O
PhNHNH2.HCl
EtOH, reflux, 1 h
NH2OH.HCl
EtOH, reflux, 2 h
5a-d
R
CH=NNHPh
R
for 7 and 8
a: R = H
b: R = Me
N
OH
8
7
Scheme 2.
Maiti, J. Heterocycles 1987, 26, 1623–1656; (c) Ghosh, C.
K. J. Indian Chem. Soc. 1990, 67, 5–15, 1991, 68, 21–28 and
references cited therein.
ylcoumarin. It should be mentioned that 3-(N,N-dialk-
ylaminomethylene)-4-chromanone 5 (NR2 in place of
NHR0 and CH2 in place of the C@O at the 2-position)
undergoes a similar reaction only when the enamines are
derived from 2ꢁ-amines, but fails to react when the en-
amines are derived from 1ꢁ-amines.4c Intramolecular H-
bonding in the latter compound was assumed to be
responsible for the failure.4c However, in the present
case, 5 (R0 ¼ alkyl) undergoes such reactions readily
despite the 1ꢁ-nature of the amine from which the en-
amine 5 (R0 ¼ alkyl) is formed. This may be due to the
presence of another carbonyl function at the 2-position,
which is engaged in H-bonding and keeps the other
carbonyl function free to react.
2. (a) Singh, G.; Singh, R.; Girdhar, N. K.; Ishar, M. P. S.
Tetrahedron 2002, 58, 2471–2480; (b) Singh, G.; Singh, G.;
Ishar, M. P. S. Synlett 2003, 256–258; (c) Bandyopadhyay,
C.; Sur, K. R.; Patra, R.; Banerjee, S. J. Chem. Res.
(S) 2003, 459–460; Bandyopadhyay, C.; Sur, K. R.;
Patra, R.; Banerjee, S. J. Chem. Res. (M) 2003, 847–
856.
3. Bandyopadhyay, C.; Sur, K. R.; Patra, R.; Sen, A.
Tetrahedron 2000, 56, 3583–3587.
4. (a) Smith, E. M.; Doll, R. J. Eur. Pat. Appl. EP 102,046;
Chem. Abstr. 1984, 101, 7052; (b) Chantegrel, B.; Nadi, A.
I.; Gelin, S. J. Org. Chem. 1984, 49, 4419–4424; (c)
Bellassoued-Fargeau, M. C.; Maitte, P. J. Heterocycl.
Chem. 1986, 23, 1753–1756; (d) Alberola, A.; Gonzalez-
Ortega, A.; Sadaba, M. L.; Sanudo, M. C. J. Chem. Soc.,
Perkin Trans. 1 1998, 4061–4065.
5. Ishar, M. P. S.; Kumar, K.; Singh, R. Tetrahedron Lett.
1998, 39, 6547–6550.
6. Ghosh, T.; Patra, R.; Bandyopadhyay, C. J. Chem. Res.
(S) 2004, 47–49.
In conclusion, we have synthesized 4 (R0 ¼ alkyl/aryl) in
excellent yield compared to earlier reports2c;5 by modi-
fying the solvent for the rearrangement of 3. A synthetic
route to hitherto unreported 3-(alkylaminomethyl-
ene)chroman-2,4-diones 5 (R0 ¼ alkyl) with moderate
yields has been revealed and those compounds have
been shown to be the synthetic equivalents of the ver-
satile substrate 3-formyl-4-hydroxycoumarin.
7. 5b: White solid, mmax (KBr): 3450, 3244, 2977, 1695, 1637,
1618, 1579 cmꢀ1 1H NMR (300 MHz, CDCl3): d 11.95
;
(br s, 1H, NH, Z), 10.25 (br s, 1H, NH, E), 8.57 (d,
J ¼ 14.9 Hz, 1H, –CH, E), 8.41 (d, J ¼ 14.1 Hz, 1H,
–CH, Z), 7.89 (d, J ¼ 1.9 Hz, 1H, 5H, E), 7.80 (d,
J ¼ 2:0 Hz, 1H, 5H, Z), 7.37 (dd, J ¼ 8:2, 1.9 Hz, 1H,
7H, E), 7.36 (dd, J ¼ 8:3, 2.0 Hz, 1H, 7H, Z), 7.14 (d,
J ¼ 8:2 Hz, 1H, 8H, E), 7.13 (d, J ¼ 8:3 Hz, 1H, 8H, Z),
References and notes
1. Reviews: (a) Darbarwar, M.; Sundaramurthy, V. Synthesis
1982, 337–388; (b) Ghosh, C. K.; Bandyopadhyay, C.;