Synthesis of novel mercury heterocycles

Article abstract of DOI:10.1016/j.poly.2010.07.010

Ortho-mercurated 4-aryloxymethylcoumarins and 1-azacoumarins have been found to undergo smooth intramolecular metalation in refluxing xylene in the presence of activated neutral alumina and anhydrous potassium carbonate. This is the first report on the synthesis of heterocycles not possessing a metal heteroatom linkage.

Full text of DOI:10.1016/j.poly.2010.07.010

Polyhedron 29 (2010) 2857–2861
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis of novel mercury heterocycles
*
Naazneen B. Yaragatti, Manohar V. Kulkarni
Post Graduate Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Ortho-mercurated 4-aryloxymethylcoumarins and 1-azacoumarins have been found to undergo smooth
intramolecular metalation in refluxing xylene in the presence of activated neutral alumina and anhy-
drous potassium carbonate. This is the first report on the synthesis of heterocycles not possessing a metal
heteroatom linkage.
Received 24 May 2010
Accepted 12 July 2010
Available online 13 August 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Dedicated to my Teacher Late Dr. (Smt.)
Geeta Manohar Kulkarni-
Naazneen Budanbaig
Keywords:
Mercuration
Metalation
Intramolecular cyclization
Neutral alumina
1. Introduction
of literature on heterocyclic systems containing mercury it was
thought to be of immense interest to study the reactivity
Organic compounds in which the aromatic hydrogens have
been replaced by main group metal substituents represent a rare
class of molecules [1]. Organomercurials have attracted much
attention from the view point of their specific reactivity, attributed
to the electropositive character of Hg.
of 4-aryloxymethylcoumarins and 1-azacoumarins possessing
o-halo/acetoxymercury substituents. The present investigation
reports probably the first intramolecular mercuration at the C-3
position on coumarins and 1-azacoumarins leading to a new class
of mercury heterocycles.
Coumarins and 1-azacoumarins are a pair of isosteric heterocy-
clic systems, the derivatives of which have exhibited wide ranging
biological properties [2]. Earlier work on chloro and acetoxy merc-
uration of coumarins has shown that mercuration was found to oc-
cur preferentially at the C-6 and C-8 positions [3]. Subsequently
mercurated 3-40-thiazolylcoumarins were reported for their fungi-
cidal activity [4]. In recent years there has been a growing interest
in the application of organomercurials in organic synthesis involv-
ing the synthesis of amino acids [5], austamide [6], oxyphenela-
tions [7] and intramolecular annulation of carboxylic acids to
triple bonds [8]. In all these reactions mercury is not retained in
the final compound but they result in a C–C bond formation via
halo/acetoxy demercuration.
4-Aryloxymethylcoumarins and 1-azacoumarins have been
of both biological [9,10] and structural interest [11]. Reactivity of
o-substituted 4-aryloxymethylcoumarins has been explored to
synthesize biologically active 4-20-benzo[b]furanylcoumarins
[12], oxygenated triheterocycles [13] and fused polycyclic
coumarins [14]. In light of the above observations and paucity
2. Experimental
2.1. Materials and methods
Reactions were performed in oven-dried glassware under nitro-
gen atmosphere containing a Teflon coated stir bar and dry sep-
tum. Butanone was dried over calcium chloride and dry distilled
before use. Xylene was dried over Na pressed wire and dry distilled
before use. Mercuric acetate was purchased from Fishers Scientific
Ltd. TLC analyses were performed on commercial Kieselgel 60 F254
silica gel plates. IR spectra were recorded on a Bruker EQUINOX 55
FTIR. NMR spectra were obtained on Bruker spectrometer using
DMSO as solvent, with proton and carbon resonances at 300, 400
and 75 MHz, respectively. Mass spectral data (ESI) were recorded
on HCT Ultra ETD II Bruker Daltonics, Germany and FAB mass data
were recorded on a JEOL SX 102/DA-6000 mass spectrometer.
2.1.1. Preparation of the 4-(2-chloromercury-phenoxymethyl)-6-
chromene-2-ones (general procedure)
To a dry 100 mL flask equipped with a stir bar was added substi-
tuted 4-bromomethylcoumarins/1-azacoumarins (0.005 mol),
* Corresponding author. Tel.: +91 836 2215286; fax: +91 836 2747884.
E-mail address: manohar274@gmail.com (M.V. Kulkarni).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.07.010

2858
N.B. Yaragatti, M.V. Kulkarni / Polyhedron 29 (2010) 2857–2861
o-chloro mercury phenol/o-acetoxy mercurated p-cresol
(0.005 mol), anhydrous K2CO3 (1.72 g, 0.0125 mol) and dry
butanone (50 mL). The solution was refluxed for 20–24 h. After
this time the reaction was cooled to room temperature, the buta-
none was concentrated and the solution was poured onto crushed
ice. The crude solid obtained was crystallized from warm acetic
acid.
2.1.1.7. 4-(2-Chloromercury-phenoxymethyl)-5,6 benzo-chromene-2-
one (3g). Yield: 2.01 g (75%). M.p. 238–240 °C. FT-IR (KBr, cmꢀ1
)
1722. 1H NMR (300 MHz, DMSO) d: 8.35–7.04 (m, 10H), 6.88 (s,
1H, C3–H of coum.), 5.83 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO)
d: 153.44, 152.16, 138.12, 132.62, 132.32, 132.09, 125.22, 125.16,
123.44, 123.26, 122.96, 122.82, 121.00, 120.90, 120.62, 119.22,
115.68, 114.92, 110.00, 67.08. MS (ESI+) m/z = 538.3. Anal. Calc.
for C20H13ClꢁHgO3: C, 44.70; H, 2.44. Found: C, 44.66; H, 2.43%.
2.1.1.1. 4-(2-Chloromercury-phenoxymethyl)-6-methyl-chromene-2-
one (3a). Yield: 2.20 g (86%). M.p. 238–240 °C. FT-IR (KBr, cmꢀ1
)
2.1.1.8. 4-(2-Chloromercury-phenoxymethyl)-7,8 benzo-chromene-2-
1722. 1H NMR (300 MHz, DMSO) d: 7.45–7.09 (m, 7H), 6.67 (s,
1H, C3–H of coum.), 5.27 (s, 2H, CH2O), 2.39 (s, 3H, CH3). 13C
NMR (75 MHz, DMSO) d: 152.66, 151.64, 132.62, 131.89, 131.09,
130.69, 125.06, 123.22, 122.10, 121.62, 121.32, 117.32, 113.82,
112.26, 109.19, 67.03, 23.00. MS (ESI+) m/z = 502.3. Anal. Calc. for
one (3h). Yield: 1.92 g (72%). M.p. 238–240 °C. FT-IR (KBr, cmꢀ1
)
1722. 1H NMR (300 MHz, DMSO) d: 8.40–7.02 (m, 10H), 6.73 (s,
1H, C3–H of coum.), 5.53 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO)
d: 153.44, 152.12, 138.10, 132.64, 132.62, 132.39, 125.62, 123.34,
123.36, 122.96, 122.68, 121.22, 120.90, 120.58, 119.22, 115.88,
114.92, 114.12, 109.00, 67.10. MS (ESI+) m/z = 538.3. Anal. Calc.
for C20H13ClHgO3: C, 44.70; H, 2.44. Found: C, 44.62; H, 2.50%.
C17H13ClHgO3: C, 40.73; H, 2.61. Found: C, 40.64; H, 2.53%.
2.1.1.2. 4-(2-Chloromercury-phenoxymethyl)-7-methyl-chromene-2-
one (3b). Yield: 2.20 g (86%). M.p. 250–252 °C. FT-IR (KBr,
cmꢀ1) 1728. 1H NMR (300 MHz, DMSO) d: 7.50–7.02 (m, 7H),
6.62 (s, 1H, C3–H of coum.), 5.32 (s, 2H, CH2O), 2.46 (s, 3H,
CH3). 13C NMR (75 MHz, DMSO) d: 152.45, 151.38, 132.82,
131.55, 130.89, 130.60, 125.08, 123.85, 122.98, 122.26, 121.64,
117.65, 113.82, 112.79, 110.00, 65.07, 22.53. MS (ESI+)
2.1.1.9. 4-(2-Acetoxymercury, 4-methyl-phenoxymethyl)-6-methyl-
chromene-2-one (3i). Yield: 0.87 g (69%). M.p. 216–218 °C. FT-IR
(KBr, cmꢀ1) 1749, 1723. 1H NMR (300 MHz, DMSO) d: 7.48–7.10
(m, 6H), 6.52 (s, 1H, C3–H of coum.), 5.86 (s, 2H, CH2O), 2.42 (s,
3H, CH3), 2.38 (s, 3H, CH3), 2.32 (s, 3H, CH3). 13C NMR (75 MHz,
DMSO) d: 169.22, 160.22, 160.02, 157.32, 157.12, 156.22, 155.88,
149.14, 147.04, 126.34, 124.58, 121.47, 118.09, 117.22, 112.10,
108.37, 67.22, 23.82, 23.12, 23.02. MS (ESI+) m/z = 539.9. Anal. Calc.
for C20H18HgO5: C, 44.57; H, 3.37. Found: C, 44.56; H, 3.39%.
m/z = 502.3. Anal. Calc. for
C17H13ClHgO3: C, 40.73; H, 2.61.
Found: C, 40.72; H, 2.65%.
2.1.1.3. 4-(2-Chloromercury-phenoxymethyl)-5,7-methyl-chromene-
2-one (3c). Yield: 2.00 g (78%). M.p. 260–262 °C. FT-IR (KBr, cmꢀ1
)
2.1.1.10. 4-(2-Acetoxymercury, 4-methyl-phenoxymethyl)-6-methoxy-
chromene-2-one (3j). Yield: 2.24 g (81%). M.p. 236–238 °C. FT-IR
(KBr, cmꢀ1) 1748, 1729. 1H NMR (300 MHz, DMSO) d: 7.36–6.92
(m, 6H), 6.49 (s, 1H, C3–H of coum.), 5.30 (s, 2H, CH2O), 3.85 (s,
1H, OCH3 of coum.), 2.43 (s, 1H, CH3), 2.30 (s, 1H, CH3). 13C NMR
(75 MHz, DMSO) d: 170.04, 160.96, 160.22, 157.88, 157.33,
156.00, 155.92, 149.88, 147.62, 126.62, 124.72, 122.36, 118.12,
117.55, 112.00, 108.44, 67.28, 48.02, 23.44, 23.00. MS (FAB+) m/
z = 555. Anal. Calc. for C20H18HgO6: C, 43.29; H, 3.27. Found: C,
43.29; H, 3.25%.
1714. 1H NMR (300 MHz, DMSO) d: 7.51–7.02 (m, 6H), 6.56 (s, 1H,
C3–H of coum.), 5.55 (s, 2H, CH2O), 2.70 (s, 3H, CH3), 2.50 (s, 3H,
CH3). 13C NMR (75 MHz, DMSO) d: 152.76, 151.24, 132.52,
131.89, 131.09, 130.22, 125.86, 123.82, 122.60, 121.66, 121.22,
117.32, 113.88, 112.32, 109.86, 67.03, 23.52, 23.02. MS (ESI+) m/
z = 516.3. Anal. Calc. for C18H15ClHgO3: C, 41.95; H, 2.93. Found:
C, 41.98; H, 2.99%.
2.1.1.4. 4-(2-Chloromercury-phenoxymethyl)-7,8-methyl-chromene-
2-one (3d). Yield: 2.05 g (80%). M.p. 264–266 °C. FT-IR (KBr, cmꢀ1
)
1704. 1H NMR (300 MHz, DMSO) d: 7.85–7.00 (m, 6H), 6.55 (s, 1H,
C3–H of coum.), 5.41(s, 2H, CH2O), 2.37 (s, 3H, CH3), 2.29 (s, 3H,
CH3). 13C NMR (75 MHz, DMSO) d: 152.76, 151.24, 131.99,
131.68, 131.14, 130.72, 130.36, 125.86, 123.88, 122.67, 121.66,
117.99, 113.57, 112.72, 109.72, 67.23, 23.02, 23.00. MS (ESI+) m/
z = 516.3. Anal. Calc. for C18H15ClHgO3: C, 41.95; H, 2.93. Found:
C, 41.98; H, 2.92%.
2.1.1.11. 4-(2-Chloromercury-phenoxymethyl)-azachromene-2-one
(8a). Yield: 1.94 g (80%). M.p. 230–232 °C. FT-IR (KBr, cmꢀ1
)
1673. 1H NMR (300 MHz, DMSO) d: 11.74 (s, 1H, NH), 7.84–7.00
(m, 8H), 6.67 (s, 1H, C3H of coum.), 5.43 (s, 2H, CH2O). 13C NMR
(75 MHz, DMSO) d: 169.48, 160.49, 160.22, 157.00, 155.86,
148.54, 147.03, 123.44, 119.05, 118.75, 115.42, 113.07, 112.61,
107.80, 106.89, 66.76. MS (ESI+) m/z = 487.3. Anal. Calc. for
C16H12ClHgNO2: C, 39.52; H, 2.49; N, 2.88. Found: C, 39.52; H,
2.1.1.5. 4-(2-Chloromercury-phenoxymethyl)-6-methoxy-chromene-
2-one (3e). Yield: 2.12 g (82%). M.p. 216–218 °C. FT-IR (KBr,
cmꢀ1) 1710. 1H NMR (400 MHz, DMSO) d: 7.48 (s, 1H, C5-H of
coum.), 7.46–7.02 (m, 6H), 6.65 (s, 1H, C3–H of coum.), 5.45 (s,
2H, CH2O), 3.85 (s, 3H, OCH3). 13C NMR (75 MHz, DMSO) d:
153.22, 152.06, 138.22, 132.92, 132.62, 132.09, 125.02, 123.44,
122.82, 121.00, 120.90, 119.22, 115.68, 114.92, 110.00, 67.02,
48.02. MS (ESI+) m/z = 518.3. Anal. Calc. for C17H13O4HgCl: C,
39.47; H, 2.53. Found: C, 39.49; H, 2.60%.
2.50; N, 2.86%.
2.1.1.12. 4-(2-Chloromercury-phenoxymethyl)-6-chloro-azachromene-
2-one (8b). Yield: 1.87 g (72%). M.p. 272–274 °C. FT-IR (KBr, cmꢀ1
)
1682. 1H NMR (300 MHz, DMSO) d: 11.78 (s, 1H, NH), 7.89–7.06
(m, 7H), 6.68 (s, 1H, C3–H of coum.), 5.72 (s, 2H, CH2O). 13C NMR
(75 MHz, DMSO) d: 170.12, 160.82, 160.00, 157.48, 150.62,
147.22, 134.24, 133.26, 129.26, 121.47, 118.88, 118.34, 117.62,
112.22, 108.12, 64.12. MS (ESI+) m/z = 521.7. Anal. Calc. for
C16H11Cl2HgNO2: C, 36.90; H, 2.13; N, 2.69. Found: C, 36.92; H,
2.1.1.6. 4-(2-Chloromercury-phenoxymethyl)-6-chloro-chromene-2-
2.11; N, 2.62%.
one (3f). Yield: 1.97 g (79%). M.p. 260–264 °C. FT-IR (KBr, cmꢀ1
)
1716. 1H NMR (300 MHz, DMSO) d: 7.99 (s, 1H, C5-H of coum.),
7.31–7.03 (m, 6H), 6.68 (s, 1H, C3–H of coum.), 5.44 (s, 2H,
CH2O). 13C NMR (75 MHz, DMSO) d: 152.49, 151.31, 137.86,
132.54, 130.03, 129.44, 125.05, 122.75, 121.42, 119.27, 119.07,
117.61, 113.80, 112.89, 109.99, 65.76. MS (ESI+) m/z = 522.7. Anal.
Calc. for C16H10Cl2HgO3: C, 36.83; H, 1.93. Found: C, 36.85; H,
1.99%.
2.1.2. Synthesis of substituted 13H-5, 12-dioxa-7-mercura-
benzo[4,5]cyclohepta[1,2-a]naphthalene 6-ones (general procedure)
Preparation of activated Al2O3/K2CO3: A mixture of neutral Al2O3
(1 g, 0.001 mol) and anhydrous K2CO3 (2.76 g, 0.002 mol) is ground
thoroughly in a glass mortar and heated on the Bunsen flame for
4 h followed by the direct usage into the reaction vessel without
allowing the mixture to attain room temperature.

N.B. Yaragatti, M.V. Kulkarni / Polyhedron 29 (2010) 2857–2861
2859
Table 1
NMR (75 MHz, DMSO) d: 152.63, 151.76, 137.22, 130.23, 129.22,
124.09, 123.65, 122.32, 119.06, 119.02, 117.27, 113.44, 112.07,
112.05, 109.14, 57.02, 48.03. MS (FAB+) m/z = 481. Anal. Calc. for
Synthesis of substituted 13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta[1,2-
a]naphthalene 6-ones.
S. no.
Entry
Product R
R1
Reaction time (h)
% Yield
C17H12HgO4: C, 42.46; H, 2.52. Found: C, 42.48; H, 2.50%.
1
2
3
4
5
6
7
8
6a
6b
6c
6d
6e
6f
6g
6h
6i
6-CH3
7-CH3
5,7-CH3
7,8-CH3
6-OCH3
6-Cl
5,6-benzo
7,8-benzo
6-CH3
6-OCH3
H
H
H
H
H
H
H
H
H
24
20
24
23
22
27
23
23
21
19
18
20
80
73
77
79
76
62
72
71
71
72
76
60
2.1.2.6. 2-Chloro-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6f). Yield: 0.41 g (62%). FT-IR (KBr,
cmꢀ1) 1685. 1H NMR (300 MHz, DMSO) d: 7.93–7.02 (m, 7H),
4.09 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO) d: 152.66, 151.42,
148.21, 130.62, 130.09, 123.62, 123.12, 121.00, 119.99, 119.82,
117.06, 113.98, 113.00, 112.89, 109.82, 57.02. MS (ESI+) m/
z = 486.2. Anal. Calc. for C16H9ClHgO3: C, 39.60; H, 1.87. Found:
C, 39.64; H, 1.81%.
9
–CH3
–CH3
H
10
11
12
6j
9a
9b
6-Cl
H
2.1.2.7. 1,2-Benzo-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6g). Yield: 0.50 g (72%). FT-IR (KBr,
cmꢀ1) 1672. 1H NMR (300 MHz, DMSO) d: 8.20–7.22 (m, 10H),
4.12 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO) d: 153.48, 152.58,
138.20, 132.68, 130.68, 130.72, 124.66, 123.62, 121.82, 121.65,
120.98, 120.22, 119.72, 119.12, 117.42, 114.32, 113.82, 113.10,
110.10, 57.06. MS (ESI+) m/z = 501.9. Anal. Calc. for C20H12HgO3:
C, 47.96; H, 2.41. Found: C, 47.95; H, 2.46%.
To a dry 100 mL round bottom flask equipped with a stir bar,
was added substituted o-chloromercury phenoxy methylcouma-
rins/o-chloromercury phenoxy 1-azacoumarins (13 mmol), acti-
vated Al2O3:K2CO3 (1.41g) and dry xylene (25 mL). The solution
was refluxed for 24–28 h under nitrogen atmosphere. After this
time the solution was filtered hot and cooled to room temperature.
The separated crude solid was filtered and washed with minimum
amount of xylene. All the compounds were recrystallised from dry
xylene (Table 1).
2.1.2.8. 3,4-Benzo-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6h). Yield: 0.51 g (71%). FT-IR (KBr,
cmꢀ1) 1673. 1H NMR (300 MHz, DMSO) d: 8.40–7.10 (m, 10H),
4.10 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO) d: 153.42, 152.62,
138.08, 132.22, 130.24, 130.02, 124.82, 123.44, 121.82, 121.66,
120.58, 120.22, 119.22, 118.12, 117.19, 114.54, 113.66, 113.22,
110.66, 57.10. MS (ESI+) m/z = 501.9. Anal. Calc. for C20H12HgO3:
C, 47.96; H, 2.41. Found: C, 47.98; H, 2.42%.
2.1.2.1. 2-Methyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6a). Yield: 0.51 g (80%). FT-IR (KBr,
cmꢀ1) 1685. 1H NMR (300 MHz, DMSO) d: 7.61 (s, 1H, C5-H),
6.71–7.41 (m, 6H), 4.08 (s, 2H, CH2O), 2.48 (s, 3H, CH3). 13C NMR
(75 MHz, DMSO) d: 153.24, 152.62, 138.02, 132.22, 130.62,
130.02, 124.62, 123.10, 121.82, 119.62, 119.09, 117.22, 114.27,
113.06, 110.01, 57.07, 23.00. MS (ESI+) m/z = 465.8. Anal. Calc.
for C17H12HgO3: C, 43.92; H, 2.60. Found: C, 43.90; H, 2.60%.
2.1.2.9. 2,9-Dimethyl-13sH-5,12-dioxa-7-mercura-benzo[4,5]cyclohe-
pta[1,2-a]naphthalene-6-one (6i). Yield: 0.44 g (71%). FT-IR (KBr,
cmꢀ1) 1662. 1H NMR (300 MHz, DMSO) d: 8.28–7.28 (m, 6H),
4.08 (s, 2H, CH2O), 2.30 (s, 3H, CH3), 2.36 (s, 3H, CH3). 13C NMR
(75 MHz, DMSO) d: 152.72, 151.33, 138.17, 130.88, 130.09,
123.82, 123.12, 121.12, 119.92, 119.82, 117.06, 113.98, 113.00,
112.89, 109.82, 57.12, 23.22, 23.02. MS (ESI+) m/z = 479.9. Anal.
Calc. for C18H14HgO3: C, 45.14; H, 2.95. Found: C, 45.21; H, 2.94%.
2.1.2.2. 3-Methyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6b). Yield 0.47 g (73%). FT-IR (KBr)
1686. 1H NMR (300 MHz, DMSO) d: 7.68 (s, 1H, C5-H), 6.65–7.38
(m, 6H), 4.08 (s, 2H, CH2O), 2.42 (s, 3H, CH3). 13C NMR (75 MHz,
DMSO) d: 153.28, 152.66, 138.22, 132.68, 130.88, 130.62,
124.88, 123.62, 121.96, 119.62, 119.09, 117.32, 114.27, 113.26,
110.10, 57.10, 23.08. MS (ESI+) m/z = 465.8. Anal. Calc. for
2.1.2.10.2-Methoxy-9-methyl-13H-5,12-dioxa-7-mercura-benzo[4,5]-
cyclohepta[1,2-a]naphthalene-6-one (6j). Yield: 0.44 g (72%). FT-IR
(KBr, cmꢀ1) 1682. 1H NMR (300 MHz, DMSO) d: 8.40–7.35 (m,
6H), 4.08 (s, 2H, CH2O), 3.85 (s, 1H, OCH3 of coum.), 2.36 (s, 1H,
CH3). 13C NMR (75 MHz, DMSO) d: 153.72, 152.55, 138.17,
132.46, 130.77, 130.32, 124.65, 123.09, 121.78, 119.92, 119.57,
117.22, 114.66, 113.20, 109.88, 57.13, 48.00, 23.00. MS (ESI+) m/
z = 495.9. Anal. Calc. for C18H14HgO4: C, 43.68; H, 2.85. Found: C,
43.62; H, 2.87%.
C
17H12HgO3: C, 43.92; H, 2.60. Found: C, 43.88; H, 2.65%.
2.1.2.3. 1,3-Dimethyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohep-
ta[1,2-a]naphthalene 6-one (6c). Yield: 0.49 g (77%). FT-IR (KBr,
cmꢀ1) 1690. 1H NMR (300 MHz, DMSO) d: 8.00–6.64 (m, 6H),
4.03 (s, 2H, CH2O), 2.52 (s, 3H, CH3), 2.32 (s, 3H, CH3). 13C NMR
(75 MHz, DMSO) d: 153.22, 152.44, 138.02, 132.40, 130.72,
130.23, 124.66, 123.09, 121.88, 119.84, 119.66, 117.32, 114.33,
113.12, 109.92, 57.22, 23.00, 22.95. MS (ESI+) m/z = 479.9. Anal.
Calc. for C18H14HgO3: C, 45.14; H, 2.95. Found: 45.10; H, 2.93%.
2.1.2.11. 5H,13H-12-Oxa-5-aza-7-mercura-benzo[4,5]cyclohepta[1,2-
a]naphthalene-6-one (9a). Yield: 0.48 g (76%). FT-IR (KBr, cmꢀ1
)
1650. 1H NMR (300 MHz, DMSO) d: 11.79 (s, 1H, NH), 7.88–7.06
(m, 8H), 4.08 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO) d: 152.32,
151.16, 137.26, 131.12, 130.42, 127.45, 126.82, 125.36, 119.23,
118.95, 117.45, 112.86, 112.26, 111.26, 110.26, 57.36. MS (ESI+)
m/z = 450.8. Anal. Calc. for C16H11HgNO2: C, 42.72; H, 2.46; N,
3.11. Found: C, 42.73; H, 2.42; N, 3.15%.
2.1.2.4. 3,4-Dimethyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohep-
ta[1,2-a]naphthalene 6-one (6d). Yield: 0.50 g (79%). FT-IR (KBr,
cmꢀ1) 1687. 1H NMR (300 MHz, DMSO) d: 8.20–6.72 (m, 6H),
4.09 (s, 2H, CH2O), 2.48 (s, 3H, CH3), 2.30 (s, 3H, CH3). 13C NMR
(75 MHz, DMSO) d: 153.27, 152.64, 138.22, 132.46, 130.62,
130.32, 124.72, 123.29, 121.78, 119.92, 119.57, 117.82, 114.82,
113.19, 109.97, 57.09, 23.00, 22.96. MS (ESI+) m/z = 479.9. Anal.
Calc. for C18H14HgO3: C, 45.14; H, 2.95. Found: 45.18; H, 2.93%.
2.1.2.12. 2-Chloro-5H,13H-12-Oxa-5-aza-7-mercura-benzo[4,5]cyclo-
hepta[1,2-a]naphthalene-6-one (9b). Yield: 0.39 g (60%). FT-IR (KBr,
cmꢀ1) 1652. 1H NMR (300 MHz, DMSO) d: 11.82 (s, 1H, NH), 7.86–
7.04 (m, 7H), 4.07 (s, 2H, CH2O). 13C NMR (75 MHz, DMSO) d:
153.74, 152.22, 149.22, 130.86, 130.22, 125.22, 125.02, 122.86,
120.24, 119.32, 117.26, 116.62, 115.24, 111.14, 109.00, 57.24. MS
2.1.2.5. 2-Methoxy-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta-
[1,2-a]naphthalene 6-one (6e). Yield: 0.51 g (76%). FT-IR (KBr,
cmꢀ1) 1663. 1H NMR (300 MHz, DMSO) d: 7.93 (s, 1H, C5-H),
7.69–6.96 (m, 6H), 4.08 (s, 2H, CH2O), 3.89 (s, 3H, OCH3). 13C

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N.B. Yaragatti, M.V. Kulkarni / Polyhedron 29 (2010) 2857–2861
(ESI+) m/z = 485.3. Anal. Calc. for C16H10ClHgNO2: C, 39.68; H, 2.08;
N, 2.89. Found: C, 39.64; H, 2.10; N, 2.83%.
acteristic of 4-aryloxymethylcoumarins [17]. The ESI mass
spectrum exhibited a peak at m/z 502. The carbon mercury bond
formation, envisaged in terms of an intramolecular Friedel–Crafts
reaction lead to chlorodemercuration resulting in the formation
of 4-o-chlorophenoxymethylcoumarins 4a which was identical
with compound obtained by the reaction of 1a with o-chlorophe-
nol according to our earlier work [17]. Use of pyridine and acetic
anhydride resulted in acetoxy mercurated compound 5a
(Scheme 1). Literature survey revealed that basic alumina has been
employed to form carbon mercury bond at the alpha position in p-
benzoquinones [18]. Due to the vulnerability of coumarins under
basic conditions especially at higher temperatures we thought of
3. Results and discussion
Initially the reaction of 6-methyl-4-bromomethylcoumarin [15]
1a with o-chloro mercury phenol [16] 2a in butanone was carried
out at reflux temperature to obtain 2-o-chloromercurated 4-aryl-
oxymethylcoumarin 3a by the allylic nucleophilic displacement.
The formation of intermediate 3a was supported by the appear-
ance of –CH2 protons at 5.27 ppm, C3–H at 6.67 ppm which is char-
Scheme 1. Synthesis of 2-methyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta[1,2-a]naphthalene 6-one (6a).
Scheme 2. Synthesis of 2-methoxy-9-methyl-13H-5,12-dioxa-7-mercura-benzo[4,5]cyclohepta[1,2-a]naphthalene-6-one (6j).

N.B. Yaragatti, M.V. Kulkarni / Polyhedron 29 (2010) 2857–2861
2861
Scheme 3. Synthesis of 5H,13H-12-oxa-5-aza-7-mercura-benzo[4,5]cyclohepta[1,2-a]naphthalene-6-one (9a).
using neutral alumina impregnated with anhydrous potassium car-
Acknowledgments
bonate in xylene and the reaction occurred only under reflux con-
ditions. Under these conditions 2-o-chloromercurated 4-
aryloxymethylcoumarin 3a yielded the cyclized compound 6a
which exhibited significant changes in its spectral features. The
lactone carbonyl exhibited lower stretching frequency at
1685 cmꢀ1. The 1H NMR spectrum, apart from showing the ab-
sence of C3–H, indicated an unusual up field shift of the CH2 pro-
tons which appeared at 3.42 ppm and were clearly identified by
protonation (DMSO + TFA) when they appeared at 4.08. 13C NMR
shift of the CH2 carbons in the ether 3a and 6a were observed at
67.03 ppm and 57.07 ppm, respectively.
N.B. Yaragatti is grateful to UGC (New Delhi) for the financial
assistance in the form of Research Fellowship in Science for Meri-
torious Students. We thank University Scientific Instrumentation
Center (USIC), Karnatak University Dharwad, Indian Institute of
Science Bangalore for the spectral analysis.
References
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To determine the effect of groups on mercury on this two step
sequence, o-acetoxy mercurated p-cresol 2b was reacted with 1e
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intramolecular cyclization under the aforementioned experimental
conditions (Scheme 2) which indicated the robustness of this reac-
tion to different leaving groups on o-mercurated phenols.
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