Synthesis of 1,3-thiazetidin-2-imines from 3H-1,2-dithiol-3-imines

Full text of DOI:10.1007/s11172-012-0103-9

Russian Chemical Bulletin, International Edition, Vol. 61, No. 3, pp. 680—681, March, 2012
680
Letters to the Editor
Synthesis of 1,3ꢀthiazetidinꢀ2ꢀimines from 3Hꢀ1,2ꢀdithiolꢀ3ꢀimines
V. A. Ogurtsov, Yu. V. Karpychev, and O. A. Rakitin
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: vao@ioc.ac.ru
Earlier,1,2 we have shown that the reaction of 3Hꢀ1,2ꢀdiꢀ
Scheme 1
thioleꢀ3ꢀthiones with isonitriles at room temperature leads
to iminoꢀ1,3ꢀdithietanes. The reaction was found to be
reversible, and at elevated temperatures the equilibrium
favors starting compounds.2 At the same time, 3Hꢀ1,2ꢀdiꢀ
thiolꢀ3ꢀones in the reaction with these reactants unexꢀ
pectedly are converted to 2ꢀiminothiophenꢀ3(2H)ꢀones.3
This fact can be explained by addition of the isonitrile
molecule to the 1,2ꢀdithiole ring with the formation of
1,3ꢀoxothietane, which easily loses the isothiocyanate
molecule, that afterwards leads to the final thiophenone.
In continuation of our research on reactions of 1,2ꢀdiꢀ
thioles with isonitriles, we studied a reaction of 3Hꢀ1,2ꢀdiꢀ
thiolꢀ3ꢀimines 1 with isonitriles 2. Before we started our
work, it was impossible to predict whether the reaction
would stop in the stage of formation of 1,3ꢀthiazetidinꢀ2ꢀ
imines 3 or the compounds formed would undergo further
transformations.
We studied a reaction of Nꢀ[(3Z)ꢀ3Hꢀ1,2ꢀdithiolꢀ3ꢀylꢀ
idene]anilines 1 containing an electronꢀdonating (methyl)
or electronꢀwithdrawing (nitro) groups on the aromatic
ring. Arylimines 1 containing a nitro group on the aromatic
ring have proved reactive. We for the first time have shown
that 1,2ꢀdithiolꢀ3ꢀimines 1 react with 4ꢀmethoxyphenylꢀ
isocyanide 2 upon reflux in benzene for 18—20 h to form
1,3ꢀthiazetidines 3 in moderate yields (Scheme 1).
R = Cl (a), PhO (b)
The structure of the unreported in the literature
1,3ꢀthiazetidinꢀ2ꢀimines 3 was confirmed by elemental
1
analysis, H and 13C NMR spectroscopy, IR spectroscoꢀ
py, and mass spectrometry. Thus, the elemental analysis
data correspond to the 1 : 1 addition product of isonitrile 2
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 677—678, March, 2012.
1066ꢀ5285/12/6103ꢀ680 © 2012 Springer Science+Business Media, Inc.

1,3ꢀThiazetidinꢀ2ꢀimines
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 3, March, 2012
681
157.3, 160.3 (7 C (sp2)); 201.6 (C=S). MS (EI, 70 eV), m/z (Irel (%)):
310 [M + 4ꢀCNC6H4OMe]+ (12), 308 [M + 2ꢀCNC6H4OMe]+
(62), 306 [M – CNC6H4OMe]+ (100), 133 [CNC6H4OMe]+
(4). IR, /cm–1: 3069, 2934, 2842 (CH); 1586; 1564; 1533
(C=N); 1501; 1344; 1261; 1160 (C=S); 1108; 1028; 963; 834;
752. Found (%): C, 46.51; H, 2.60; Cl, 16.15; N, 9.49; S, 14.47.
C17H11Cl2N3O3S2. Calculated (%): C, 46.37; H, 2.52; Cl, 16.10;
N, 9.54; S, 14.56.
to dithiolimine 1. We suppose that the addition proceeds
similarly to the reaction with 1,2ꢀdithioleꢀ3ꢀthiones2 to
form a fourꢀmembered ring, in this case thiazetidine one.
1
The H and 13C NMR spectroscopic data are consistent
with such a structure, and a signal in the region  200
characteristic of the fragment C=S is observed in the
13C NMR spectrum. At the same time, no absorption bands
characteristic of an isonitrile group (2150—2110 cm–1
are found in the IR spectrum.4
)
OꢀPhenyl (2E)ꢀchloro[(4Z)ꢀ4ꢀ[(4ꢀmethoxyphenyl)imino]ꢀ3ꢀ
(4ꢀnitrophenyl)ꢀ1,3ꢀthiazetidinꢀ2ꢀylidene]ethanethioate (3b). The
yield was 47%, yellow crystals, m.p. 133—134 C, Rf 0.77
(CH2Cl2). 1H NMR (300 MHz CDCl3), : 3.80 (s, 3 H, Me);
6.89, 7.03, 7.63, 8.35 (all d, 2 H each, 2 C6H4, J = 8.8 Hz);
7.06—7.12 (m, 2 H, Ph); 7.28—7.37 (m, 1 H, Ph); 7.41—7.49
(m, 2 H, Ph). 13C NMR (75 MHz, CDCl3), : 55.6 (OMe);
114.9, 122.2, 123.2, 124.1, 127.7, 129.8 (12 CH, Ar); 126.9
(CH, Ph); 102.2, 136.8, 139.6, 146.9, 149.0, 153.9, 154.3, 158.2
(8 C (sp2)); 200.7 (C=S). MS (EI, 70 eV), m/z (Irel (%)): 364
[M + 2ꢀCNC6H4OMe]+ (4), 364 [M – CNC6H4OMe]+ (11),
Elevation of the reaction temperature (reflux in toluꢀ
ene or xylene) causes decomposition of thiazetidines, and
isolation of individual compounds from the reaction mixꢀ
tures becomes impossible. Less reactive aromatic isonitriles
containing no donor substituents on the benzene ring
(phenylisocyanide and its 4ꢀnitro derivative) or containing
nonaromatic substituents at the isonitrile group (CH2Tos,
CH2CO2Et, and Bn) do not react with 1,2ꢀdithiolꢀ3ꢀimiꢀ
nes 1 neither at room temperature, nor upon reflux in
benzene; the starting compounds were recovered from the
reaction mixture almost quantitatively.
Only several methods are described in the literature
concerning synthesis of such 4ꢀylideneꢀ1,3ꢀthiazetidinꢀ2ꢀ
imines, they use poorly available starting compounds such
as ketene imines,5 thioketenes,6 and dimethyl dithiono
oxalate.7 The known method are successfully complementꢀ
ed by the approach suggested by us.
223 (72), 133 [CNC6H4OMe]+ (84), 77 [Ph]+ (100). IR, /cm–1
:
3036, 2920, 2836 (CH); 1700; 1604; 1580 (C=N); 1520; 1504;
1488; 1344; 1260; 1252; 1228 (C=S); 1080; 932; 824; 748; 684.
Found (%): C, 55.59; H, 3.48; Cl, 7.23; N, 8.16; S, 12.73.
C23H16ClN3O4S2. Calculated (%): C, 55.47; H, 3.24; Cl, 7.12;
N, 8.44; S, 12.88.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 11ꢀ03ꢀ00004ꢀa).
1
H and 13C NMR spectra (CDCl3) were recorded on a Bruker
References
AMꢀ300 spectrometer, using signals for the residual protons of
the solvent as a reference. Melting points were determined on
a Kofler heating stage and were not corrected. Mass spectra
were recorded on a Finnigan MAT INCOS 50 instrument (EI),
IR spectra were recorded on a Specord M80ꢀ2 spectrometer in
KBr pellets. Reaction mixtures were monitored by TLC on Sorbfil
plates, using UV light and iodine vapors for visualization.
Synthesis of 1,3ꢀthiazetidines 3 (general procedure). A mixꢀ
ture of 1,3ꢀdithiolꢀ3ꢀimines 1a,b (1 mmol) and isonitrile 2
(1 mmol) in benzene (10 mL) was refluxed with stirring until
either 1,2ꢀdithiolꢀ3ꢀimine or isonitrile disappeared (TLC moꢀ
nitoring). The reaction mixture was concentrated and subjected
to chromatography on a column with silica gel (Silicagel Merck
60, eluent light petroleum—CH2Cl2).
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: 3.80 (s, 3 H, OMe); 6.65—7.03 (m, 6 H, Ar); 8.21 (d, 2 H, Ar,
J = 9.2 Hz). 13C NMR (75 MHz, CDCl3), : 55.6 (OMe); 114.9,
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Received November 1, 2011;
in revised form February 3, 2012