Reaction of imines with 5,5-dimethyl-1,3-cyclohexandione

Article abstract of DOI:10.1080/00397910600640131

The reaction of imines 1 with 5,5-dimethyl-1,3-cyclohexandione 2 in methanol was investigated. When the reaction was carried out without a catalytic amount of molecular iodine, ring-opening derivatives of xanthenediones 3 were obtained in high yields. On

Full text of DOI:10.1080/00397910600640131

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Reaction of Imines with 5,5‐Dimethyl‐1,
3
‐cyclohexandione
a a
a
a
a
Liangce Rong , Xiaoyue Li , Haiying Wang , Daqing Shi , Shujiang Tu
&
a
Qiya Zhuang
a
Department of Chemistry , Xuzhou Normal University , Xuzhou, Jiangsu,
China
Published online: 22 Sep 2006.
To cite this article: Liangce Rong , Xiaoyue Li , Haiying Wang , Daqing Shi , Shujiang Tu & Qiya Zhuang
(
2006) Reaction of Imines with 5,5‐Dimethyl‐1, 3‐cyclohexandione, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 36:16, 2345-2353, DOI:
0.1080/00397910600640131
1
To link to this article: http://dx.doi.org/10.1080/00397910600640131
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Synthetic Communications , 36: 2345–2353, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600640131
Reaction of Imines with 5,5-Dimethyl-1,
3
-cyclohexandione
Liangce Rong, Xiaoyue Li, Haiying Wang, Daqing Shi,
Shujiang Tu, and Qiya Zhuang
Department of Chemistry, Xuzhou Normal University,
Xuzhou, Jiangsu, China
Abstract: The reaction of imines 1 with 5,5-dimethyl-1,3-cyclohexandione 2 in
methanol was investigated. When the reaction was carried out without a catalytic
amount of molecular iodine, ring-opening derivatives of xanthenediones 3 were
obtained in high yields. On the other hand, when molecular iodine and a catalytic
amount of zinc powder were employed as the catalyst, xanthenediones derivatives 4
were obtained with excellent yields.
Keywords: 5,5-Dimethyl-1,3-cyclohexandione, imine, molecular iodine, xanthene
It is well known that xanthenedione derivatives constitute structural units in a
[
number of natural products and have been used as versatile synthons
1]
[2]
because of the inherent reactivity of the in-built pyran ring. Conventional
synthesis of xanthenediones usually involves acid- or base-catalyzed conden-
[3]
sation of appropriate active methylene carbonyl compounds with aldehydes.
Recently, several reports have been put forward in which xanthenedione
derivatives were obtained through condensation of aldehyde and 5,5-
[4]
dimethyl-1,3-cyclohexanedione under various conditions. These processes
offered novel alternatives for the preparation of xanthenediones, but they
still have to be improved in terms of the yield, reaction time, practicability,
and the limitation of the instrument necessitated in corresponding procedures.
Received in Japan November 24, 2005
Address correspondence to Liangce Rong, Department of Chemistry, Xuzhou
Normal University, Xuzhou, Jiangsu, China. E-mail: lcrong2005@yahoo.com
2
345

2
346
L. Rong et al.
Therefore, developing novel and practical methods for the preparation of
xanthenedione and its derivatives is still necessary.
[5]
In recent times, the use of molecular iodine has received considerable
attention as an inexpensive, nontoxic, readily available catalyst for various
organic transformations to afford the corresponding products in excellent
yields with high selectivity. The mild Lewis acidity associated with iodine
enhanced its usage in organic synthesis to realize several organic transfor-
mations using stoichiometric levels to catalytic amounts. Owing to
numerous advantages associated with this ecofriendly element, iodine has
[6]
been explored as a powerful catalyst for various organic transformations.
Herein, we report a novel method to synthesize ring-opening derivatives
of xanthenediones and xanthenedione derivatives by the reaction of imines
with 5,5-dimethy1-1,3-cyclo-hexandione (Scheme 1). We want to synthesize
1,4-dihydropyridine derivatives 5 by the reaction of imines with 5,5-dimethly-
1,3-cyclohexandione with the catalyst iodine in methanol (Scheme 1).
However, we could not get the anticipated products (1,4-dihydropyridine
derivatives); surprisingly, we got the ring-opening derivatives of xanthene-
diones 3 and xanthenediones derivatives 4. To our knowledge, this is a
novel method to synthesize those derivatives. So, it is significant to study
the imines’ application in organic synthesis.
In a general procedure, imines 1 (1 mmol), 5,5-dimethyl-1,3-cyclo-
hexandione 2 (2 mmol), and 10 ml of methanol were added to a 50-mL
round-bottomed flask without any catalyst. Then the mixture was stirred at
708C for a certain period of time to complete the reaction (monitored by
Scheme 1.

Imines and 5,5-Dimethyl-1,3-cyclohexandione
2347
Table 1. Synthesis of compound 3
Yield
(%)
1
2
Entry
Ar
Ar
Mp (8C)
196–198
3
3
3
3
3
3
3
3
3
3
a
b
c
d
e
f
2-ClC
2,4-Cl
6
H
4
3-ClC
4-ClC
6
H
H
4
4
90
97
84
85
87
91
91
97
93
92
[
[
4c]
4c]
2
C
6
H
3
6
186–188, 188–190
143–145, 142–143
185–187
4-CH OC H
3
4-CH C H
3 6 4
6
4
4-FC H
6
C H
6
4
5
5
5
[
[
[
4c]
4c]
4c]
3,4-OCH OC
4-OH-3-CH
4-ClC H
2
6
H
3
C
C
6
H
H
165–167, 168–170
191–193, 192–194
142–144, 142–144
166–168
3 6 3
OC H
6
g
h
i
4-ClC H
6
6
4
4
4
3,4-Cl
2
C
6
H
3
6
4-ClC H
[
4c]
C
3,4-(CH ) C H
6
H
5
C
6
H
5
190–191, 188–190
[
167–169
4c]
j
4-ClC H
6
3
2
6
3
4
TLC). Then, we cound obtain ring-opening derivatives of xanthenediones 3 in
high yields. The results are shown in Table. 1. To our surprise, under similar
reaction conditions, when molecular iodine and catalytic amount of zinc
powder existed, it gave xanthenediones 4 in excellent yield instead of 3
(Table 2).
In this synthesis method, the products of imines’ reaction with 5,5-
dimethyl-1,3-cyclohexandione were the same as corresponding aromatic
aldehydes’ reaction with 5,5-dimethyl-1,3-cyclohexandione. Synthesis of
ring-opening derivatives of xanthenediones needed no catalyst. Synthesizing
xanthenediones needed the catalyst of molecular iodine; however, we found
that a catalytic amount of zinc powder is necessary, and it could promote
the reaction. In the process of reaction, and the double bonds (“s bond” and
“p bond”) of carbon and nitrogen in imines was both ruptured; this
Table 2. Synthesis of compound 4
Yield
(%)
1
Ar
2
Ar
Entry
Mp (8C)
[
[
4b]
4b]
4
4
4
4
4
4
4
4
4
4
a
b
c
d
e
f
C
6
H
5
C
6
H
5
92
93
90
90
93
91
95
89
92
94
201–203, 198–200
228–229, 230–231
181–183
4-ClC H
6
4-ClC H
6 4
4
4
3-ClC
2,4-Cl
6
H
4-CH
4-ClC
3-ClC H
3 6 3
-3-ClC H
2
C
6
H
4
6
H
4
4
252–253
225–227, 222–224
169–170
[
4b]
4-NO C H
2
6
4
6
3-NO
4-CH
4-OHC
2
C
6
H
4
6 5
C H
g
h
i
3
OC
6
H
4
4-ClC
6
H
4
4
243–245
[
[
4b]
4b]
6
H
4
C
6
H
5
245–247, 246–248
224–225, 216–218
224–226
3,4-OCH OC H
6
4-FC H
6 4
2
3
j
4-OH-3-CH
3
OC
6
H
3
6
3-ClC H

2
348
L. Rong et al.
[7]
phenomenon seldom appeared. On the basis of reported literature, we think
the possible mechanism is as follows (Scheme 2). In the mechanism, the
molecule iodine acts as a weak Lewis acid catalyst and takes part in the
reaction. At first, influenced by zinc power, the molecule iodine come about
polarization, and then forms HI by the interaction of iodine with one
hydroxy. HI combines another hydroxyl and loses a molecule of H O, and
2
finally, the derivatives of xanthenediones could be gotten. We think the HI
has an important effect during the reaction.
In conclusion, we have developed a simple, convenient, and efficient
synthetic protocol for the synthesis of xanthenediones dervatives and ring-
opening derivatives of xanthenediones. The catalyst of molecular iodine
was found to be a mild and effective catalyst for the reaction of 5,5-
dimethly-1,3-cyclohexanedione with imines to synthesize the xanthenedione
derivatives in excellent yields. The easy workup procedure and greater selec-
tivity make this protocol practical and economically attactive.
Scheme 2.

Imines and 5,5-Dimethyl-1,3-cyclohexandione
EXPERIMENTAL
2349
Melting points were determined on a XT-5 microscopic melting-point
spectrometer and are uncorrected. IR spectra were recorded on a Tensor 27
1
spectrometer in KBr. H NMR spectra were obtained from solution in
CDCl with Me Si as internal standard using a Bruker 400 spectrometer.
3
4
Synthesis of Ring-Opening Derivatives of Xanthenediones
A 50-mL round-bottomed flask was charged with imine 1 (1 mmol), 5,5-
dimethyl-1,3-cyclo-hexandione 2 (2 mmol), methanol (10 mL), and the
mixture was stirred at 708C (monitored by TLC). The mixture was poured
into water, and the product was filtered, washed, dried, and recrystallized
from 95% ethanol.
Synthesis of Xanthenediones
A 50-mL round-bottomed flask was charged with imine 1 (1 mmol), 5,5-
dimethyl-1,3-cyclo-hexandione 2 (2 mmol), methanol (10 mL), I (0.025 g),
2
and a catalytic amount (0.01 g) of zinc powder, and the mixture was stirred
at 708C (monitored by TLC). The mixture was poured into saturated
sodium thiosulfate solution, and the product was filtered, washed, dried, and
recrystallized from 95% ethanol.
SPECTRAL DATA
1
3
2
a: H NMR (CDCl ) d: 1.06(s, 6H, 2 Â CH ), 1.17 (s, 6H, 2 Â CH ), 2.25–
3
3
3
.51 (m, 8H, 4 Â CH ), 5.62 (s, 1H, CH), 7.09–7.39 (m, 4H, ArH), 9.76
2
(
s, 1H, OH), 11.88 (s, 1H, OH); IR (KBr) v. 3000–2500, 2957, 2929, 1610,
2
470, 1380, 1289, 1230, 1140, 1070, 987, 745 cm . Anal. calcd.
1
1
C H ClO : C 68.56, H 6.75; found C 68.63, H 6.59.
2
3
27
4
1
3
2
b: H NMR (CDCl ) d: 1.06 (s, 6H, 2 Â CH ), 1.28 (s, 6H, 2 Â CH ), 2.06–
2
3
3
3
.41 (m, 8H, 4 Â CH ), 5.57 (s, 1H, CH), 7.08–7.36 (m, 3H, ArH), 9.77
(
s, 1H, OH), 11.88 (s, 1H, OH); 1R (KBr) v. 3000–2500, 2956, 2872, 1608,
2
559, 1468, 1396, 1290, 1229, 1100, 987, 861, 772 cm . Anal. calcd. for
1
1
C H Cl O : C 63.16, H 5.99; found C 63.41, H 5.76.
2
3
26
2 4
1
3
2
c: H NMR (CDCl ) d: 1.06 (s, 6H, 2 Â CH ), 1.23 (s, 6H, 2 Â CH ), 2.29–
2 3
3
3
3
.48 (m, 8H, 4 Â CH ), 3.77 (s, 3H, OCH ), 5.49 (s, 1H, CH), 6.81
(
d, J ¼ 8.4 Hz, 2H, ArH), 6.99 (d, J ¼ 8.4 Hz, 2H, ArH), 9.74 (s, 1H, OH),
1
1.92 (s, 1H, OH); IR (KBr) v. 3000–2500, 2959, 2929, 1603, 1509, 1376,

2
350
L. Rong et al.
2
304, 1246, 1179, 1033, 918, 830 cm . Anal. calcd. for C H O : C 72.34,
1
1
H 7.59; found C 72.63, H 7.25.
2
4 30 5
1
3
2
d: H NMR (CDCl ) d: 1.06 (s, 6H, 2 Â CH ), 1.22 (s, 6H, 2 Â CH ), 2.29–
3
3
3
.48 (m, 8H, 4 Â CH ), 5.49 (s, 1H, CH), 6.93–7.06 (m, 4H, ArH), 9.77
2
(
s, 1H, OH), 11.88 (s, 1H, OH); IR (KBr) v. 3000–2500, 2960, 2930, 2873,
2
593, 1525, 1374, 1308, 1228, 1159, 870, 830, 800 cm . Anal. calcd. for
1
1
C H FO : C 71.48, H 7.04; found C 71.63, H 6.84.
2
3
27
4
1
3
2
e: H NMR (CDCl ) d: 1.06 (s, 6H, 2 Â CH ), 1.23 (s, 6H, 2 Â CH ), 2.37–
3
3
3
.50 (m, 8H, 4 Â CH ), 5.44 (s, 1H, CH), 5.89 (s, 2H, OCH O), 6.49–7.06
2
2
(
m, 3H, ArH), 9.70 (s, 1H, OH), 11.90 (s, 1H, OH); IR (KBr) v. 3000–
2
8
500, 2950, 2875, 1600, 1480, 1370, 1301, 1250, 1230, 1040, 940, 860,
2
10 cm . Anal. calcd. for C H O : C 69.88, H 6.84; found C 69.63, H 6.52.
1
2
4 28 6
1
3
2
f: H NMR (CDCl ) d: 1.06 (s, 6H, 2 Â CH ), 1.20 (s, 6H, 2 Â CH ), 2.37–
3
3
3
.50 (m, 8H, 4 Â CH ), 3.73 (s, 3H, OCH ), 5.45 (s, 1H, CH), 5.51 (s, 1H,
2 3
OH), 6.50–6.83 (m, 3H, ArH), 9.54 (s, 1H, OH), 11.97 (s, 1H, OH); IR
(
KBr) v. 3000–2500, 2950, 2875, 1600, 1510, 1370, 1280, 1240, 1150,
2
040, 850, 810, 780 cm . Anal. calcd. for C H O : C 69.54, H 7.30;
1
1
found C 69.32, H 7.58.
24 30 6
1
3
2
g: H NMR (CDCl ) d: 1.11 (s, 6H, 2 Â CH ), 1.19 (s, 6H, 2 Â CH ), 2.15–
3
3
3
.47 (m, 8H, 4 Â CH ), 5.47 (s, 1H, CH), 7.01–7.32 (m, 4H, ArH), 10.0
2
(
s, 1H, OH), 11.95 (s, 1H, OH); IR (KBr) v. 3000–2500, 2950, 2872, 1605,
2
518, 1360, 1260, 1230, 1110, 1060, 881, 810, 780 cm . Anal. calcd. for
1
1
C H ClO : C 68.56, H 6.75; found C 69.04, H 6.45.
2
3
27
4
1
3
(
(
h: H NMR (CDCl ) d: 0.97 (s, 6H, 2 Â CH ), 1.09 (s, 6H, 2 Â CH ), 2.06
3
3
3
s, 6H, 2 Â CH ), 2.25–2.38 (m, 8H, 4 Â CH ), 5.97 (s, 1H, CH), 7.05–7.29
3 2
m, 3H, ArH), 10.11 (s, 1H, OH), 11.93 (s, 1H, OH); IR (KBr) v. 3000–2500,
2
1
957, 2869, 1715, 1607, 1562, 1471, 1403, 1351, 1294, 1240, 1169, 1140,
21
099, 1070, 1026, 1014, 985, 935, 896, 876, 838, 810, 694 cm . Anal.
calcd. for C H Cl O : C 63.16, H 5.99; found C 63.58, H 5.47.
2
3
26
2 4
1
3
2
i: H NMR (CDCl ) d: 1.13 (s, 6H, 2 Â CH ), 1.19 (s, 6H, 2 Â CH ), 2.30–
2
3
3
3
.47 (m, 8H, 4 Â CH ), 5.53 (s, 1H, CH), 6.52–6.81 (m, 5H, ArH), 9.44
(
s, 1H, OH), 11.61 (s, 1H, OH); IR (KBr) v. 3000–2500, 2950, 2873, 1650,
2
585, 1373, 1260, 1240, 1165, 1073, 950, 829, 787 cm . Anal. calcd. for
1
1
C H O : C 74.97, H 7.66; found C 74.28, H 7.75.
2
3 28 4
1
3
2
j: H NMR (CDCl ) d: 0.92 (s, 6H, 2 Â CH ), 1.01 (s, 6H, 2 Â CH ), 2.26–
2
3
3
3
.36 (s, 8H, 4 Â CH ), 5.53 (s, 1H, CH), 6.52–6.81 (m, 3H, ArH), 9.44 (s, 1H,
OH), 11.61 (s, 1H, OH); IR (KBr) v. 3000–2500, 2958, 2889, 1584, 1501,
464, 1448, 1369, 1313, 1266, 1253, 1165, 1124, 1065, 1044, 944, 912,
1

Imines and 5,5-Dimethyl-1,3-cyclohexandione
2351
2
83, 821 cm . Anal. calcd. for C H O : C, 75.73, H, 8.13; found C, 75.28,
1
8
H, 8.01.
2
5 32 4
1
4
a: H NMR (CDCl ) d: 0.98 (s, 6H, 2 Â CH ), 1.12 (s, 6H, 2 Â CH ),
3
3
3
2.20–2.45 (m, 8H, 4 Â CH ), 4.66 (s, 1H, CH), 7.21–7.40 (m, 5H, ArH);
IR (KBr) v. 3030, 2980, 1685, 1670, 1470, 1360, 1200, 1170, 1140, 1005,
2
2
1
740, 700 cm . Anal. calcd. for C H O : C 78.83, H 7.47; found C 78.96,
23 26 3
H 7.40.
1
4
b: H NMR (CDCl ) d: 0.98 (s, 6H, 2 Â CH ), 1.10 (s, 6H, 2 Â CH ), 2.22–
3
3
3
2.50 (m, 8H, 4 Â CH ), 4.64 (s, 1H, CH), 7.26–7.42 (m, 4H, ArH); IR (KBr)
v. 3030, 2980, 1680, 1660, 1620, 1490, 1480, 1360, 1200, 1170, 1140, 1090,
2
2
1
1010, 1000, 850, 840 cm . Anal. calcd. for C H ClO : C 71.77, H 6.54;
23 25 3
found C 71.88, H 6.44.
1
4
c: H NMR (CDCl ) d: 1.02 (s, 6H, 2 Â CH ), 1.12 (s, 6H, 2 Â CH ), 2.30–
3
3
3
2.49 (m, 8H, 4 Â CH ), 4.74 (s, 1H, CH), 7.11–7.25 (m, 4H, ArH); IR (KBr)
v. 3030, 1685, 1660, 1620, 1490, 1475, 1365, 1200, 1170, 1136, 1090, 1010,
2
2
1
1
000, 850, 840 cm . Anal. calcd. for C H ClO : C 71.77, H 6.54; found C
23 25 3
7
1.92, H 6.41.
1
4
2
d: H NMR (CDCl ) d: 1.03 (s, 6H, 2 Â CH ), 1.12 (s, 6H, 2 Â CH ), 2.21–
3
3
3
.46 (m, 8H, 4 Â CH ), 4.95 (s, 1H, CH), 7.16 (s, 1H, ArH), 7.39
2
(
d, J ¼ 8.4 Hz, 2H, ArH), IR (KBr) v. 3035, 2980, 1685, 1660, 1633, 1490,
2
485, 1410, 1360, 1210, 1195, 1155, 1100, 1000, 850, 770 cm . Anal.
1
1
calcd. for C H Cl O : C 65.87, H 5.73; found C 65.94, H 5.60.
2
3
24
2 3
1
4
2
e: H NMR (CDCl ) d: 0.99 (s, 6H, 2 Â CH ), 1.12 (s, 6H, 2 Â CH ), 2.01–
2
3
3
3
.21 (m, 8H, 4 Â CH ), 4.76 (s, 1H, CH), 7.50–7.63 (m, 2H, ArH), 8.06–8.18
(
m, 2H, Ar); IR (KBr) v. 3035, 2980, 1660, 1650, 1630, 1520, 1360, 1340,
2
1
1
6
200, 1070, 1040, 1000, 870, 830 cm . Anal. calcd. for C H NO : C
23 25 5
9.85, H 6.37, N 3.54; found C 69.91, H 6.60, N 3.29.
1
4
2
7
1
f: H NMR (CDCl ) d: 1.02 (s, 6H, 2 Â CH ), 1.13 (s, 6H, 2 Â CH ),
3
3
3
.21–2.53 (m, 8H, 4 Â CH ), 4.85 (s, 1H, CH), 7.43 (s, 1H, ArH), 7.88–
2
.95 (m, 3H, ArH); IR (KBr) v. 3030, 2980, 1680, 1675, 1625,
535, 1365, 1340, 1210, 1175, 1145, 1005, 830, 765, 730, 700 cm
2
1
.
Anal. calcd. for C H NO : C 69.85, H 6.37, N 3.54; found C 69.91, H
5
2
3
25
6
.50, N 3.39.
1
4
g: H NMR (CDCl ) d: 1.01 (s, 6H, 2 Â CH ), 1.09 (s, 6H, 2 Â CH ), 2.20–
3
3
3
2.46 (m, 8H, 4 Â CH ), 4.70 (s, 1H, CH), 6.67–7.28 (m, 4H, ArH); IR (KBr)
v. 3035, 2980, 1660, 1620, 1510, 1450, 1370, 1360, 1260, 1230, 1190, 1170,
2
2
1
1140, 1030, 840 cm . Anal. calcd. for C H O : C 75.76, H 7.41; found
24 28 4
C 75.84, H 7.22.

2
352
L. Rong et al.
1
4
2
h: H NMR (CDCl ) d: 0.99 (s, 6H, 2 Â CH ), 1.10 (s, 6H, 2 Â CH ), 2.03–
3
3
3
.31 (m, 8H, 4 Â CH ), 4.62 (s, 1H, CH), 6.77 (d, J ¼ 8 Hz, 2H, ArH), 6.98
2
(
d, J ¼ 8 Hz, 2H, ArH); IR (KBr) v. 3360, 2980, 1720, 1700, 1630, 1610,
2
520, 1390, 1370, 1260, 1230, 1190, 850, 840 cm . Anal. calcd. for
1
1
C H O : C 75.38, H 7.15; found C 75.24, H 7.06.
2
3 26 4
1
4
2
i: H NMR (CDCl ) d: 1.00 (s, 6H, 2 Â CH ), 1.10 (s, 6H, 2 Â CH ), 2.06–
2 2
3
3
3
.31 (m, 8H, 4 Â CH ), 4.58 (s, 1H, CH), 5.90 (s, 2H, OCH O), 6.69–6.78
(
m, 3H, ArH); IR (KBr) v. 2980, 1720, 1630, 1565, 1510, 1490, 1440,
2
380, 1360, 1320, 1270, 1230, 1040, 940, 920, 890, 810, 790 cm . Anal.
1
1
calcd. for C H O : C 73.07, H 6.64; found C, 73.18, H, 6.76.
2
4 26 5
1
4
2
j: H NMR (CDCl ) d: 1.02 (s, 6H, 2 Â CH ), 1.12 (s, 6H, 2 Â CH ), 2.24–
2 3
3
3
3
.47 (m, 8H, 4 Â CH ), 3.90 (s, 3H, OCH ), 4.68 (s, 1H, CH), 5.49 (s, 1H,
OH), 6.60 (s, 1H, ArH), 6.74 (s, 1H, ArH), 7.03 (s, 1H, ArH); IR (KBr) v.
3
1
7
343, 3030, 2980, 2190, 1687, 1660, 1585, 1500, 1454, 1400, 1380, 1234,
2
195, 811, 743 cm . Anal. calcd. for C H O : C 77.84, H 7.57; found C
1
2
4 28 5
7.98, H, 7.46.
ACKNOWLEDGMENT
We are grateful to the Natural Science Foundation (04XLB14) of Xuzhou
Normal University for financial support.
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