Convenient method for synthesis of 6-(N,N-diethylamino)-9-(2-carboxyphenyl) -1,2,3,4-tetrahydroxanthylium perchlorate [2]

Full text of DOI:10.1023/B:COHC.0000023779.81485.9f

Chemistry of Heterocyclic Compounds, Vol. 40, No. 1, 2004
CONVENIENT METHOD FOR
SYNTHESIS OF 6-(N,N-DIETHYLAMINO)-
9-(2-CARBOXYPHENYL)-1,2,3,4-TETRA-
HYDROXANTHYLIUM PERCHLORATE
Ya. A. Prostota
Keywords: tetrahydroxanthylium salts, cyclocondensation, polymethine dyes.
Goal-directed search for new dyes absorbing in the near IR range of the spectrum is an important
problem in polymethine dye chemistry [1]. A major method for solving this problem is to search for new
heterocyclic rings for assembling polymethine dyes.
Some 6-(N,N-dialkylamino)-1,2,3,4-tetrahydroxanthylium salts are used as starting materials for
synthesis of fluorescent polymethine dyes absorbing in the near IR region [2]. Generally synthesis of such
compounds is a multistep and labor-intensive process, while the yields of the target products are insignificant
[2]. At the same time, derivatives of 6-(N,N-dialkylamino)-1,2,3,4-tetrahydroxanthylium derivatives substituted
at the position 9 have not been described in the literature.
With the aim of obtaining new derivatives of this heterocyclic system, we have studied
cyclocondensation of the easily prepared 2-hydroxy-4-(N,N-diethylamino)-(2-carboxy)benzophenone (1) and
cyclohexanone. We found that carrying out the reaction in concentrated H2SO4 makes it possible to obtain the
target compound 2 in rather high yield, and the isolation and purification processes are significantly simplified.
Benzophenone 1 is obtained from phthalic anhydride and 3-(N,N-diethylamino)phenol according to the
procedure in [3].
The proposed synthesis method allows us to obtain compound 2 in good yield. Furthermore, this method
is based on using accessible and inexpensive starting materials, which makes it promising for further application.
CO2H
CO2H
1. H2SO4 / ∆
O
+
O
+
O
2. 70% HClO4
N
N
OH
_
ClO4
2
1
__________________________________________________________________________________________
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev 02094; e-mail:
yprostota@bpci.kiev.ua, yprostota@ukr.net. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1,
pp. 123-124, January, 2004. Original article submitted April 7, 2003; revised November 20, 2003.
116
0009-3122/04/4001-0116©2004 Plenum Publishing Corporation

Freshly distilled cyclohexanone (6.6 ml, 63.7 mmol) was added dropwise to concentrated H2SO4 (70 ml)
cooled down to 0°C. Then compound 1 (10 g, 32 mmol) was added in portions with vigorous stirring. The
reaction mixture was held for 1-1.5 h at 90°C, cooled down, and poured onto ice (300 g). 70% perchloric acid
(7 ml) was added to the solution formed. The precipitate was filtered off, washed with cold water (100 ml), and
recrystallized from acetic acid (25 ml). Yield 9.7 g (67%); mp 214-216°C (decomp.). 1H NMR spectrum (Bruker
AC-250, 250 MHz, acetone-d6/TMS), δ, ppm (J, Hz): 1.36 (6H, t, J = 7.14, N–CH2CH3); 1.81 (2H, m, CH2); 2.0
(2H, m, CH2); 2.31 (2H, m, CH2); 3.2 (2H, m, CH2); 3.78-3.87 (4H, q, J = 7.14, N–CH2CH3); 7.19-7.22 (1H, m,
HPh); 7.26 (1H, s, 5-H); 7.39-7.46 (2H, m, HAr); 7.81-7.97 (3H, td, J = 7.6, J = 1.34, HPh); 8.35-8.38 (1H, d,
J = 8.8, 7-H). Found, %: C 60.8; H 5.7; N 3.1. C24H26ClNO7. Calculated, %: C 60.6; H 5.5; N 2.9.
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