Pyridyl sulfobetaines as phase-transfer catalysts for reactions involving dichlorocarbene [4]

Full text of DOI:10.1023/A:1011942102377

Chemistry of Heterocyclic Compounds, Vol. 37, No. 6, 2001
PYRIDYL SULFOBETAINES
AS PHASE-TRANSFER CATALYSTS
FOR REACTIONS INVOLVING
DICHLOROCARBENE
G.-K. Kupyatis, G. Shaduikis, O. Nivinskene, and O. Eicher-Lorka
Keywords: dichlorocarbene, pyridyl sulfobetaines, phase transfer catalysis.
Not much information is available about the use of sulfobetaines in phase-transfer catalysis. It has been
–
established [1,2] that the presence of the zwitterionic salt C12H25N+(CH3)2CH2CH2SO3 in the reaction of
chloromethylation of acenaphthene increases the yield of 5-chloromethylacenaphthene up to 79%, i.e., by more
than a factor of two. According to the patent [3], carboxybetaines or sulfobetaines are used in the synthesis of
glycidyl ethers. These data inspired us to synthesize some pyridyl sulfobetaines in order to study the feasibility
of using them as phase transfer catalysts.
We synthesized the pyridyl sulfobetaines 2a-e by quaternization of 4-amino-, 4-dimethylamino-, and
4-morpholinopyridines 1a-c with an equimolar amount of sodium bromoethanesulfonate or 1,3-propanesultone
in DMF, and we showed (1H NMR spectra) that quaternization proceeds only at the pyridinium nitrogen:
NR2
NR2
+
N
N
_
1a–c
(CH2)n–SO3
2a–e
1a, 2a,c R = H; 1b, 2b,d CH3; 1c, 2e NR2 = 4-morpholyl;
2a,b n = 2; 2c-e n = 3
We tested the pyridyl sulfobetaines 2a-e as phase-transfer catalysts in reactions involving
dichlorocarbene, generated by the Makosza method [4,5]: dehydration of benzamide and N-formylation of
diphenylamine (reactions (1) and (2), respectively):
PhCONH2 → PhC N
(1)
(2)
≡
PhNH Ph2N–CHO
→
__________________________________________________________________________________________
Institute of Chemistry, Vilnius LT-2600, Lithuania; e-mail: lorka@takas.lt. Translated from Khimiya
Geterotsiklicheskikh Soedinenii, No. 6, pp. 845-847, June, 2001. Original article submitted February 28, 2001.
0009-3122/01/3706-0781$25.00©2001 Plenum Publishing Corporation
781

Reaction (1): benzamide (0.05 mol), CHCl3 (35 ml), 40% NaOH (0.2 mol, 12 ml), catalyst (5 mol %),
50°C, 3 h; reaction (2): diphenylamine (0.05 mol), CHCl3 (44 ml), 45% NaOH (0.2 mol, 10 ml), catalyst
(5 mol %), 55°C, 5-6 h.
Dehydration of benzamide to benzonitrile at 50°C in the absence of catalyst occurs with 7% yield; in the
presence of catalysts 2a-e, the yield of benzonitrile in 3 h is respectively 15%, 38%, 16%, 44%, and 38%
(monitored by GC-MS). The use of catalyst 2d accelerates the course of reaction (1) by a factor of 6; at 30°C in
the presence of 2d, the yield of benzonitrile in 6 h was 36% (without the catalyst, only traces). In reaction (2),
including an additional step of dehydration of the N-dichloromethyl derivative formed, these compounds exhibit
an insignificant catalytic effect. The yield of diphenylformamide when using 2b, 2d, and 2e is respectively 4%,
7%, and 5% (without a catalyst, about 1%).
We also tested the catalysts we synthesized, along with other quaternary compounds in the pyridine
series, in other phase transfer catalysis reactions.
2-(4-Amino-1-pyridinium)-1-ethanesulfonate (2a). Yield 62%; mp > 331°C (decomp.). IR spectrum
(KBr), , cm-1: 1050, 1190 (SO2); 1660 (C=N+). 1H NMR spectrum (80 MHz, D2O), , ppm: 3.42 (2H, t, –CH2SO3);
ν
δ
4.55 (2H, t, –CH2N); 6.85 (2H, d, 3-PyH): 8.04 (2H, d, 2-PyH). Found, %: C 48.95; H 6.76; N 11.32.
C7H12N2O3S. Calculated, %: C 49.16; H 6.60; N 11.46.
2-(4-Dimethylamino-1-pyridinium)-1-ethanesulfonate (2b). Yield 72%; mp > 335°C (decomp.). IR
1
spectrum (KBr), , cm-1: 1050, 1201 (SO2); 1653 (C=N+). H NMR spectrum (D2O), , ppm: 3.14 (6H, s,
ν
δ
(CH3)2N); 3.36 (2H, t, –CH2SO3); 4.47 (2H, t, –CH2N); 6.82 (2H, d, 3-PyH); 7.98 (2H, d, 2-PyH). Found, %:
C 46.71; H 6.25; N 12.23. C9H14N2O3S. Calculated, %: C 46.94; H 6.13; N 12.16.
3-(4-Amino-1-pyridinium)-1-propanesulfonate (2c). Yield 94%; mp 284-286°C. IR spectrum (KBr),
, cm-1: 1032, 1188 (SO2); 1669 (C=N+). 1H NMR spectrum (D2O), , ppm: 2.22 (2H, m, –CH2–); 2.87 (2H, t,
ν
δ
–CH2SO3); 4.22 (2H, t, –CH2N); 6.79 (2H, d, 3-PyH); 7.95 (2H, d, 2-PyH). Found, %: C 44.21; H 5.71; N 12.83.
C8H12N2O3S. Calculated, %: C 44.43; H 5.59; N 12.95.
3-(4-Dimethylamino-1-pyridinium)-1-propanesulfonate (2d). Yield 92%; mp 226-228°C. IR
1
spectrum (KBr), , cm-1: 1034, 1209 (SO2); 1655 (C=N+). H NMR spectrum (D2O), , ppm: 2.19 (2H, dd,
ν
δ
–CH2–); 2.83 (2H, t, –CH2SO3); 3.11 (6H, s, (CH3)2N); 4.19 (2H, t, –CH2N+); 6.80 (2H, d, 3-PyH); 7.93 (2H, d,
2-PyH). Found, %: C 48.95; H 6.76; N 11.32. C10H16N2O3S. Calculated, %: C 49.16; H 6.60; N 11.46.
3-(4-Morpholino-1-pyridinium)-1-propanesulfonate (2e). Yield 84%; mp > 305°C (decomp.). IR
1
spectrum (KBr), , cm-1: 1045, 1193 (SO2); 1652 (C=N+). H NMR spectrum (D2O), , ppm; 2.23 (2H, dd,
ν
δ
–CH2–); 2.86 (2H, t, –CH2SO3); 3.67 (4H, t, CH2NCH2); 3.76 (4H, t, CH2OCH2); 4.25 (2H, t, –CH2N); 7.00 (2H,
d, 3-PyH); 8.04 (2H, d, 2-PyH). Found, %: C 50.22; H 6.45; N 9.70. C12H18N2O4S. Calculated, %; C 50.33;
H 6.33; N 9.78.
We would like to thank Doctor R. Rekertas for technical cooperation in performing the GC-MS
analysis.
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