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Unexpected formation of 5,5-diethoxy-5H-1,2,3-dithiazoles from 5H-1,2,3-dithiazole-5-thiones
Abstract
5H-1,2,3-Dithiazole-5-thiones undergo an unexpected transformation into 5,5-diethoxy-5H-1,2,3-dithiazoles upon treatment with sodium ethoxide; the structure of the products was confirmed by Raman and IR spectra.
... Their chemistry also involves the transformation of their ring system into other systems such as pyrazolo [3,4-d]thiazoles [22], pyridothiazoles [23], pyrido [2,3-d]pyrimidines [24] and the rare pyrazolo [3,4-e] [1,2,4]dithiazines and benzo[e] [1,2,4]dithiazines [25]. 1,2,3-Dithiazoles have also been used as starting materials or appeared as intermediates in various reactions [26][27][28][29][30][31][32][33][34][35][36]. Table 1. ...
The crystal structure and solid-state packing of 4-chloro-5H-1,2,3-dithiazol-5-one and two polymorphs of 4-chloro-5H-1,2,3-dithiazole-5-thione were analyzed and compared to structural data of similar systems. These five-membered S,N-rich heterocycles are planar with considerable bond localization. All three structures demonstrate tight solid-state packing without voids which is attributed to a rich network of short intermolecular electrostatic contacts. These include S δ+ … N δ-, S δ+ … O δ-, S δ+ … Cl δ-and S δ+ … S δ-interactions that are well within the sum of their van der Waals radii (∑VDW). B3LYP, BLYP, M06, mPW1PW, PBE and MP2 were employed to calculate their intramolecular geometrical parameters, the Fukui condensed functions to probe their reactivity, the bond order , Bird Index and NICS(1) to establish their aromaticity.
... The unexpected formation of 5,5-diethoxy-5H-1,2,3-dithiazoles 289 from 5H-1,2,3-dithiazole-5-thiones 66 upon treatment with sodium ethoxide (Scheme 93) was reported. 230 Rakitin and co-workers showed that reaction of 4-substituted 5-ylidene-1,2,3-dithiazoles 290 with two equivalents of n-butylamine yields monoamidines 291 as the addition product of the amine to the nitrile group (Scheme 94). 231 3-Chloro and 3-bromoisothiazole-5-carbonitriles 298 were obtained from (4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitriles through intermediate 2-chloro 295 and 2-bromo(dithiazolylidene)acetonitriles 296. ...
In this article, the chemistry of 1,2,3-dithiazoles and 1,2,3-oxathiazoles is covered from 2009 to 2018 inclusive. The 1,2,3-dithiazoles studied are: 1,2,3-dithiazolium cations, 1,2,3-dithiazolyl radicals, 1,2,3-dithiazole-5-ones and related thiones, imines and ylidene compounds, their 5,5-disubstituted derivatives, and their 2-oxides. 1,2,3-Oxathiazoles have been investigated in the form of their S-oxides and are also referred to as cyclic sulfamidites, sulfonimidates, sulfimidates and sulfamidates.
Three aryl and three naphthylmethylene derivatives containing thiadiazole ring have been synthesized. The structures of target compounds were characterized on the basis of spectral (FT-IR,1H NMR, and MS). The optical properties were detected using UV-vis absorption spectroscopy and fluorescence spectroscopy. The absorption spectra of 1a, 2a and 3a substituted by naphthylmethylene are primarily characterized by a peak around 284 nm originating from naphthalene, which is different from that of compounds 1b, 2b and 3b. Compared to 1a and 2a (separated by a saturable atomic cluster -CH2-), the maximum absorption wavelength of 1b and 2b takes on obvious red-shifted, which is from thiadiazole and benzene with more large conjugated system. The fluorescence intensity of 2-(4-aminobenzoyl) amide-5-naphthylmethylene-1,3,4-thiadiazole (3a) was significantly higher than that of 5-(4-aminobenzoyl)-1,3,4-thiadiazole (3b) due to the presence of naphthalene.
A chemical genomic screen of an in-house library of small molecule heterocycles was carried out using Xenopus laevis embryos. This led to the identification of N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-4-methoxyaniline (1c), which elicits loss of pigmentation in melanophores and the retinal pigment epithelium (RPE) of developing embryos, independent of the developmental stage of initial exposure. The phenotype was reversible, since pigmentation returned upon compound removal while analysis of neural crest cell
markers (Pax7) and melanophore markers (Dct/Xtrp2) revealed that both neural crest precursors and fully differentiated melanophores were present in the dithiazole 1c treated embryos. A subsequent focused structure–activity relationship (SAR) study identified the more active dithiazole 4-benzyloxy-N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-aniline (1l) and the need for a chlorine substituent at the dithiazole C-4 position. Both the initial chemical genomic screen and the focused SAR study highlighted the toxicity of
(dithiazolylidene)aminoazines, and also of methoxyaniline (anisidine) analogues that hosted strong electron-withdrawing or electronegative substituents or acidic hydroxyl groups on the anisidine moiety. This study suggests that 1,2,3-dithiazoles can act as reversible melanin synthesis inhibitors, revealing a new biological activity for this class of compounds. The inhibition of melanin synthesis is medically relevant as a potential treatment for pigmentation disorders such as melasma.
Kinetics and mechanism of desulfurization reaction of 1-methyl-2-(substituted phenyl)-quinazoline-4(1 H )-thiones in sodium methoxide solutions have been studied, giving the corresponding 1-methyl-2-(substituted phenyl)quinazolin-4(1 H )-ones. The reaction proceeds in two steps. The first step involves splitting off of sulfur in the form of SH<sup>-</sup> and is much faster than the second step, whose rate is almost independent of the concentration of water in methanol. At lowest concentrations of methoxide, the rate of the first step increases linearly, but at higher concentrations a gradual decrease in the rate takes place. The rate of the second step, i.e. the transformation of the intermediate formed In into 1-methyl-2-(substituted phenyl)quinazolin-4(1 H )-one ( 2a - 2e ), is independent of the methoxide concentration but increases with increasing concentration of water in methanol. On the basis of the kinetic dependences, the mechanism for both steps of desulfurization and the structure of intermediate In were proposed.
A contracted Gaussian basis set (6‐311G∗∗) is developed by optimizing exponents and coefficients at the Møller–Plesset (MP) second‐order level for the ground states of first‐row atoms. This has a triple split in the valence s and p shells together with a single set of uncontracted polarization functions on each atom. The basis is tested by computing structures and energies for some simple molecules at various levels of MP theory and comparing with experiment.
Treatment of
5-arylimino-4-chloro-5H-1,2,3-dithiazoles with in situ
generated (chloro)phenylketene in CH2Cl2 at rt gave
azetidin-2-one-4-spiro-5′-(1′,2′,3′-dithiazoles) as
major products, which reacted with primary and secondary alkylamines in
CH2Cl2 at rt to afford bis(2-oxo-azetidin-4-yl)
trisulfides in good to excellent yields.
5H-1,2,3-Dithiazole-5-thiones and 5H-1,2,3-dithiazol-5-ones undergo a new transformation into 1,2,5-thiadiazole-3(2H)-thiones and 1,2,5-thiadiazol-3(2H)-ones, respectively, upon treatment with primary amines; the structure of thiadiazolethione was confirmed by X-ray diffraction.
The classical spectral problem is analyzed on the level of the harmonic force field approximation to determine the vector describing the mean atomic displacements from the equilibrium positions, <&> =Σk <&> =— B(O)−1 Σ kΔBk, where B(O) is the transformation matrix between the internal and Cartesian coordinates defined for the equilibrium configuration, ΔBk is the variation in the transformation matrix caused by molecular motion along the kth eigenvector and the summation is over all molecular modes. A simple procedure for determining the ΔBk quantities without explicitly calculating the ΔBk matrices is described. The vectors <and < enter nto the expressions for the shrinkage corrections and the mean square vibrational amplitudes. The harmonic amplitudes calculated for the C3O2 molecule using the present theory agree well with the observed quantities.
Conversion of N-arylimino-4-chloro-5H-1,2,3-dithiazole 11 into the 4-alkoxyquinazoline-2-carbonitriles 13a-i and of the aryl isothiocyanates 15 into aryl thiocarbamates 16a-j with sodium alkoxides in the corresponding alcohol, either by conventional thermolysis or by microwave irradiation are described and directly compared. Microwave irradiation of the solutions in open vessels in a monomode system with focused irradiation and continuous temperature control (Synthewave S402 reactor) usually gave cleaner, faster and higher yielding reactions. These reactions could be safely and beneficially scaled up to multigram quantities in a larger reactor (Synthewave S1000).
Treatment of 5-(arylimino)-4-(dialkylamino)-5H-1,2,3-dithiazoles (2) with NaOH in aqueous EtOH at room temperature gave N′-arylthiocarbamoyl-N,N-dialkylamidines (3) in good to excellent yields. The reaction of 3 with sulfur monochloride, thiophosgene, thionyl chloride, sulfuryl chloride, N-phenylimidoyl dichloride, and phthaloyl chloride in CH2Cl2 gave 2, 5-(arylimino)-4-(dialkylamino)-Δ3-thiazoline-2-thiones (5), 5-(arylimino)-4-(dialkylamino)-5H-2-oxo-1,2,3-dithiazoles (6), 5-(arylimino)-4-(dialkylamino)-5H-2,2-dioxo-1,2,3-dithiazoles (7), 5-(arylimino)-4-(dialkylamino)-2-(phenylimino)-Δ3-thiazolines (8), and 3-(arylimino)-4-(dialkylamino)-2,5-benzothiazocine-1,6-diones (10) as major products, respectively.
Data on the methods for the synthesis and properties of 1,2,3-dithiazoles published over the last 15 years are reviewed and described systematically.
Treatment of 1,2-bis(4-chloro-5H-1,2,3-dithiazol-5-ylidene)hydrazine 4 with benzyltriethylammonium io-dide (1 equiv) affords dicyano-1,3,4-thiadiazole 3 and 5-cyano-1,3,4-thiadiazole-2-carboxamide 5 in 79 and 21% yields, respectively. By using polymer bound triphenylphosphine instead of benzyltriethylammonium iodide the dicyano-1,3,4-thiadiazole 3 can be isolated in 70% yield without chromatography. The reaction of DAMN with Appel salt 8 gave 2-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)-2-(4-chloro-5H-1,2,3-dithia-zol-5-ylidene)acetonitrile 7 (14%), 2,3-bis-(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)fumaronitrile 10 (14%), and 2,3-bis(4-chloro-5H-1,2,3-dithiazol-5-ylideneamino)maleonitrile 11 (24%) together with other products. The maleonitrile 11 isomerizes into the fumaronitrile 10 on irradiation at 365 nm. Reaction of aminoacetonitrile with Appel salt 8 gives the (dithiazolylidene)acetonitrile 7 in 33% yield. Treatment of (dithiazolylidene)acetonitrile 7 with polymer bound triphenylphosphine gives tricyanothiazole 6 in 76% yield. A rational general mechanism for the transformation of bisdithiazoles to percyanoheteroles is proposed.
2-(4-Chloro-5H-1,2,3-dithiazolylideneamino)benzonitrile 1a reacts with triphenylphosphine (4 equiv) in the presence of water (2 equiv) to afford anthranilonitrile 2a, 3-aminoindole-2-carbonitrile 3a and (2-cyanoindol-3-yl)iminotriphenylphosphorane 4a, together with triphenylphosphine sulfide and oxide. The use of polymer bound triphenylphosphine provides cleaner reaction mixtures. 2-(4-Chloro-5H-1,2,3-di-thiazolylideneamino)-4,5-dimethoxybenzonitrile 1h does not give the corresponding indole on treatment with triphenylphosphine but gives 6,7-dimethoxyquinazoline-2-carbonitrile 5 (15%) and 2-cyano-4,5-dimethoxy cyanothioformanilide 6 (36%). A total of seven new 3-aminoindole-2-carbonitriles 3a–g are prepared and fully characterised.
Generalized gradient approximations (GGA{close_quote}s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. {copyright} {ital 1996 The American Physical Society.}
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Received: 19th February 2010; Com. 10/3471