Microwave-induced Monohydroxymethylation and Monoalkoxylation of 1,4-Naphthoquinones

Article abstract of DOI:10.1039/a803513j

1,4-Naphthoquinones and its derivatives have been hydroxymethylated and alkoxylated in the quinone ring using, respectively, formalin or an alcohol, in the presence of K₂CO₃ or HgO by heating or microwave irradiation.

Full text of DOI:10.1039/a803513j

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720 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 720±721$
Microwave-induced Monohydroxymethylation and
Monoalkoxylation of 1,4-Naphthoquinones$
Vandana Bansal, Jyotsana Sharma and Rajinder N. Khanna*
Department of Chemistry, University of Delhi, Delhi-110007, India
1,4-Naphthoquinones and its derivatives have been hydroxymethylated and alkoxylated in the quinone ring using,
respectively, formalin or an alcohol, in the presence of K2CO3 or HgO by heating or microwave irradiation.
Table 2 Spectral data of quinones 2a±d
Quinone dH
Several publications have described the use of commercially
available microwave ovens for microwave induced organic
reaction enhancement (MORE).1,2 The technique is energy-
and cost-ecient as well as convenient to use. The present
communication reports the synthesis of hydroxymethylated
and alkoxylated 1,4-naphthoquinones using microwave
irradiation. It dramatically reduces the reaction time and
increases the yield remarkably.
1
ꢀ/cm
2a
2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H,
CH2OH), 7.10 (s, 1 H, C3-H), 7.80±
8.10 (m, 4 H, Ar-H)
1620, 1650
2b
2c
2d
2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H,
CH2OH), 7.60±8.20 (m, 4 H, Ar-H)
2.50 (s, broad, 1 H, OH), 4.60 (s, 2 H,
CH2OH), 7.60±8.10 (m, 4 H, Ar-H)
2.10 (s, 3 H, CH3), 2.60 (s, broad, 1 H, 1625, 1655
OH), 4.70 (s, 2 H, CH2OH), 7.20±8.00
(m, 4 H, Ar-H)
1625, 1650
1625, 1650
allyl alcohol) was used for the introduction of alkoxy groups
under thermal and microwave conditions at the active qui-
nonoid position of 1,4-naphthoquinones (1a±c), to give the
corresponding alkoxy compounds (3) (Scheme 1, Table 3).
Compounds (3a±g) were identi®ed on the basis of spectral
data (Table 4).
Discussion
In the hydroxymethylation of various quinones, it was
observed that the presence of the reagent (K2CO3 or HgO)
was essential and the monohydroxymethylated products
were obtained without any polymerization or replacement of
halo group in 1b and 1c in Scheme 1. The reaction failed to
proceed with other aldehydes, e.g. acetaldehyde and benzal-
dehyde. Yields were found to be higher with K2CO3 as com-
pared to HgO. In the alkoxylation of various quinones, the
presence of reagent (HgO) was also essential and the yield
of alkoxy quinones decreased with the increase in the size of
the alkyl group in the alcohol. The yield of alkoxy quinones
is higher when halogenated quinones are alkoxylated
because the halo group is a better leaving group. Microwave
irradiation accelerates organic reactions by its high heating
eciency giving rise to a remarkable rate enhancement and
a dramatic reduction in reaction times (Tables 1 and 3).
Scheme 1
Potassium carbonate or mercury(II) oxide in aqueous
formalin were used for the introduction of hydroxymethyl
group under thermal and microwave conditions at the active
quinonoid position of 1,4-naphthoquinones 1 to give the
2-hydroxymethyl-1,4-naphthoquinones 2 (Scheme 1). Com-
pounds 2a±d were identi®ed on the basis of their spectral
data (Tables 1 and 2).
Mercury(II) oxide in various alcohols (methanol, ethanol,
isopropyl alcohol, propanol, isobutyl alcohol, butanol and
Table 1 Hydroxymethylation of 1,4-naphthoquinones (1a±d)
Yield (%)
t/min
Found (required) (%)
Quinone
Reagent
D
mꢀ
D
mꢀ
Molecular formula
C11H8O3
C
H
Lit. mp/8C
2a
K2CO3
HgO
K2CO3
HgO
K2CO3
HgO
K2CO3
HgO
92
90
95
90
94
92
85
80
90
80
95
85
92
85
82
78
30
90
30
90
30
90
60
90
5
6
5
5
5
5
5
6
70.2 (70.1)
4.25 (4.30)
1153
2b
2c
2d
C11H7O3CI
C11H7O3Br
C12H10O3
59.3 (59.1)
49.5 (49.6)
71.2 (71.0)
3.1 (3.2)
2.6 (2.4)
4.9 (4.7)
1353
1303
106
Experimental
*To receive any correspondence (e-mail: VandanaBansal@hotmail.
com).
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
Melting points are uncorrected. IR spectra were recorded on a
Shimadzu IR-435 spectrometer (Nujol, cm 1). NMR spectra were
recorded on a Perkin-Elmer R-32 (90 MHz) in CDCl3, using TMS
as internal standard. Chemical shifts were recorded on the d scale.

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J. CHEM. RESEARCH (S), 1998 721
Table 3 Alkoxylation of 1,4-naphthoquinones (1a±c)
Yield (%)
t/min
Quinone
Alcohol
CH3OH
Product
D
mꢀ
D
mꢀ
Mp/8C [lit. mp]
1a
1b
1c
1a
1b
1c
1a
1b
1c
1a
1b
1c
1a
1b
1c
1a
1b
1c
1a
1b
1c
3a
70
75
70
65
80
82
65
75
80
60
65
62
55
65
60
50
60
62
55
58
60
80
85
85
75
85
85
72
80
86
72
75
78
65
75
78
65
75
75
62
70
72
120
60
60
120
60
60
5
5
5
5
5
5
6
6
6
7
6
6
7
7
7
8
7
7
8
8
8
182 [182±183]4
CH3CH2OH
3b
3c
3d
3e
3f
116 [115±117]4
115 [115]4
90
(CH3)2CHOH
CH3(CH2)2OH
(CH3)2CHCH2OH
CH3(CH2)3OH
180
150
150
240
180
210
240
180
180
240
180
180
180
150
150
78
104 [104]5
99 [98.5]6
.
CH2 CHCH2OH
3g
®ltered. The ®ltrate was concentrated under reduced pressure,
diluted with water (100 ml) and the mixture extracted with ethyl
acetate (2Â 20 ml). The organic extract was dried (MgSO4) and
evaporated under reduced pressure to give a solid which was puri-
®ed by preparative TLC using benzene±ethyl acetate (8:2) as a
solvent to a€ord the alkoxylated product (3a±g).
Method D.ÐTo a solution of the substrate (0.1 mol, 1a±c) in
alcohol (5 ml), mercury(II) oxide (0.1 mol) was added. The mixture
was subjected to microwave irradiation at 2450 MHz for a speci®ed
time (Table 3). The reaction was worked up as described earlier to
a€ord the alkoxylated product (3a±g).
Table 4 Spectral data of quinones 3d±e
1
Quinone
dH
ꢀ/cm
3d
1.00 (t, J 7.0, 3 H, CH3), 1.50±2.10 1620, 1680
(m, 2 H, CH2CH3), 3.80 (t, J 7.0,
2 H, OCH2), 5.90 (s, 1 H, C3-H),
7.30±7.90 (m, 4 H, Ar-H)
3e
1.10 (d, J 7.0, 6 H, 2 CH3), 1.90±
2.40 (m, 1 H, OCH), 3.60 (d, J 7.0,
2 H, OCH2), 5.90 (s, 1 H, C3-H),
7.30±7.90 (m, 4 H, Ar-H)
1640, 1680
V.B. is grateful to UGC, New Delhi, for the award of
SRF.
General ProcedureÐMethod A.ÐTo a solution of the substrate
(0.1 mol, 1a±d) in 30% aqueous formaldehyde (20 ml), potassium
carbonate (0.1 mol) or yellow mercury(II) oxide (0.1 mol) was
added. The solution was re¯uxed for speci®ed time (Table 1). The
reaction mixture was ®ltered and the ®ltrate concentrated under
reduced pressure, diluted with water (100 ml) and the mixture
extracted with ethyl acetate (2Â 20 ml). The organic extract was
dried (MgSO4) and evaporated under reduced pressure to give a
solid which was puri®ed by preparative TLC (silica gel) using
benzene±ethyl acetate (9:1) as a solvent to a€ord the hydroxy-
methylated product (2a±d).
Method B.ÐTo a solution of the substrate (0.1 mol, 1a±d) in
30% aqueous formaldehyde (20 ml), potassium carbonate (0.1 mol)
or yellow mercury(II) oxide (0.1 mol) was added. The mixture was
subjected to microwave irradiation at 2450 MHz for a speci®ed time
(Table 1). The reaction mixture was worked up as described above
to a€ord the hydroxymethylated product (2a±d).
Received, 11th May 1998; Accepted, 28th July 1998
Paper E/8/03513J
References
1 G. Nagy, S. V. Filip, E. Surducan and V. Surducan, Synth.
Commun., 1997, 27, 3729.
2 D. M. P. Mingos and D. R. Baghurst, Chem. Soc. Rev., 1991,
20, 1.
3 P. C. Thapliyal, J. Sharma, K. P. Singh and R. N. Khanna, Ind.
J. Chem., 1995, 34B, 994.
4 R. N. Khanna, K. P. Singh, S. K. Yadav and S. Srinivas, Synth.
Commun., 1989, 19, 3151.
Method C.ÐTo a solution of the substrate (0.1 mol, 1a±c) in
the alcohol (20 ml), yellow mercury(II) (0.1 mol) was added. The
solution was re¯uxed for speci®ed time (Table 3), cooled and
5 L. F. Fieser, J. Am. Chem. Soc., 1926, 48, 2922.
6 L. F. Fieser, J. Am. Chem. Soc., 1926, 48, 3201.