The synthesis of new thiosubstituted butadienes, butenynes and butatrienes

By treatment of the pentachlorobutadiene 1 and of the tetrachlorobromobutadiene 9 with thiolates in ethanol, a very fast and extensive replacement of chlorine was observed even at room temperature. The reaction of 1 with three molar equivalents of thiolates lead to butadienes with two, three, four and five organylthio groups. Tris(thio)-substituted butadienes 3a-c tetrakis (thio)-substituted butadiene 4a were treated with potassium tert -butoxide to form tris(thio)- substituted butatrienyl halide compounds 12a-c and tetrakis(thio)-substituted butatriene 14a , respectively. The butatrienyl halides 12a-c obtained partly isomerizes to give butenynes 13a-c at room temperature and without catalyst.


Introduction
Polyhalogenobutadienes have been used as model substrates for studying of the process of vinylic substitution (SNVin).There are various possibilities of the use of these compounds for the sythesis of numerous polyfunctional products.][3][4][5][6][7] It is known that some thiosubstituted butadienes exhibit high biological activity.Industrial research has long focused on biological applications of thiosubstituted compounds as insectisides, herbicides, fungicides, and bactericides. 85-lipoxygenase inhibition effect of 1-thiosubstituted butadienes also reported. 9Butenynes and butatrienes are very valuable compounds for their use in polymer chemistry.1][12]  electronic conductors, ferromagnets, electron-accepting supramolecules, optical materials in material chemistry and as stabilizers in polimer chemistry. 13chmidt et al. have synthesised thiosubstituted butatrienes and 1,3-butadienes from the reaction of a tetrakis(pyridinium)-substituted butadiene with some thiolates. 14In an earlier study, Block et al. have used perchalcogenohydrocarbons as starting material to obtain perthio-1,3butadienes, -1-buten-3-ynes and -1,2,3-butatrienes. 15In this work, we report another efficient method for the synthesis of novel thiosubstituted butadiene, butenyne and butatriene compounds.
Compounds 3a, 4a and 5a were obtained from the reaction of 2H-pentachlorobutadiene with three molar equivalents of thiol a.In the possible reaction mechanism of 5a, it is thought that perchlorobutenyne formed by HCl elimination from 2H-pentachlorobutadiene firstly and then tetrakis(thio)-substituted butenyne and tetrakis(thio)-substituted butatriene intermediates were occurred via addition of four molar of thiol a to perchlorobutenyne.These intermediates both were stabilized by mesomery.In the last step of the mechanism, 5a was obtained by addition of one molar of thiol a to tetrakis(thio)-substituted butenyne or tetrakis(thio)-substituted butatriene. 1 H-NMR spectra of 2d, 3a-c, 4a and 5a exhibited the presence of vinyl proton as a singlet at approximately 6.50 ppm.The mass spectrum of 3a confirmed the estimated structure; two main peaks were observed at m/z 683.62 and 648.77corresponding to [M] + and [M-Cl] + , respectively.The IR spectra of butenyne derivatives 6d, 7a, 7c, 7e-i and 10e-i showed the characteristic strong band at 2147 and 2152 cm -1 for C≡C group.In the 13 C-NMR spectra of these compounds, two alkyne carbons provide chemical shift values around 85.11 and 92.07 ppm.In the ESI-MS spectrum of 10h showed a molecular ion peak at m/z 455.93 and the fragmentation of molecular ion peak at m/z 375 corresponding to the loss of a bromine atom.New thiosubstituted polyhalobutadiene compounds 8a, 8c, 8e-i and 11e-i were formed by the electrophilic addition of Br2 to butenynes.It is evidence for succesful bromination reaction that the IR spectra of these compounds showed no absorbtion band around 2147 or 2152 cm -1 .

ISSN 1551-7012
Page 246  ARKAT USA, Inc. Tris(thio)-substituted butatriene compounds 12a-c were formed by HCl elimination in the presence of potassium tert-butoxide from tris(thio)-substituted butadienes 3a-c.These butatriene compounds 12a-c partly isomerize to the tris(thio)-substituted butenynes 13a-c even at room temperature, in a solvent medium.Tetrakis(thio)-substituted butatriene 14a, obtained from 4a by HCl elimination, is more stable than 12a-c.This stability was proved by IR spectrum of 14a that there was no typical absorption band at 2142-2157 cm -1 region corresponding to C≡C group.Addition of I2 to butatriene compounds 12a and 14a were performed in apolar solvent at room temperature to give 15a and 16a.Electrophilic addition reaction mechanism proceeds via an iodonium cation (Scheme 2).
Scheme 2. The synthesis and iodination of butatriene compounds.
The solvolysis of butatrienyl halides gives the ambident vinyl cation which has positive charge on a disubstituted carbon in both mesomeric structures (x and y).The possible isomerization mechanism of 1-chloro-1,4,4-tris(4-methylphenylthio)butatriene have been explained in the previous study by our group (Scheme 3). 5

Cl -Cl +Cl Cl
x y Scheme 3. The possible isomerization mechanism of butatrienyl halides to butenynes.
12a and 12c obtained under the action of potassium tert-butoxide, are stable solid compounds.The peaks at 2037 and 2043 cm -1 in the IR spectra of 12a and 12c was assigned to C=C=C=C stretching vibration, respectively.12b, yellow oily compound, easily isomerizes to 1-buten-3ynes 13b at room temperature without catalyst.IR spectrum of 12b showed C≡C stretching band at 2143 cm -1 next to butatriene band at 2043 cm -1 .However, in the solvent medium, stable butatrienyl halides 12a and 12c are solvolyzed to give the ambident allenyl cation which isomerizes to butenyne compounds 13a and 13c.12a-c cannot be isolated from the isomeric mixture by the chromatographic techniques.IR, Mass spectra and elemental analyses results confirmed that these compounds are the isomeric mixture Thiosubstituted butadiene and butenyne compounds showed maximum absorption of the range 244-266 nm in CHCl3, the maximum absorption wavelenghts of butatriene compounds were observed between 367-392 nm.

Experimental Section
General.Melting points were measured on Buchi B-540 capillary apparatus and are uncorrected.IR-spectras were recorded on Shimadzu FTIR-8101.NMR spectra were recorded on Varian Unity Inova 500 MHz.Mass spectra were obtained on a Thermo Finnigan LCQ Advantage MAX LC/MS/MS Spectrometer using ion-trap mass analyzer for both APCI or ESI source.UV spectra were recorded on UV-VIS Spectrophotometer TU-1901.Microanalyses were obtained by using a Carlo-Erba 1110 element analyser.Thin-layer chromatography (TLC) : E. Merck silica gel 60 F254 foils.Column chromatography: Silica gel 60 ( particle size 0.063-0.20 mm, E. Merck ).
General procedure 1 2H-pentachlorobutadiene 1 (1 g, 4.4 mmol) and thiols (13.2 mmol) were stirred in a mixture of EtOH (30 mL) and aqueous solution of NaOH (1.2 g and 8 ml water) for 30 min.at room temperature.Ether was added to the reaction mixture and the organic layer was separated, washed with water (4x30 mL), and dried with MgSO4.The solvent was evaporated and the residue was purified by column chromatography over silica gel (petroleum ether/chloroform or petroleum ether).

General procedure 3
Tris-or tetrakis-thiosubstituted butadiene compound (0.9 mmol) in 50 mL Petroleum ether (30-50 °C) was mixed with potassium tert-butoxide (0.2 g, 1.8 mmol) for 4h at room temperature.For 12-13c, Tetrahydofuran was used as solvent instead of Petroleum ether.Ether and water added to the reaction mixture and then organic layer was separated, dried with anhydrous MgSO4.The solvent was evaporated and the residue was purified by column chromatography over silica gel (petroleum ether/chloroform).

General procedure 4
Monothiosubstituted butenyne compound (1.5 mmol) and bromine (0.25 g, 1.5 mmol) were stirred in CCl4 (30mL) for 3h at room temperature.Ether was added to the reaction mixture and extracted with 100 ml of 3% aqueous solution of Na2S2O5 twice.The organic layer was separated, washed with water (4x30 mL), dried with anhydrous MgSO4.The solvent was evaporated and the residue was purified by column chromatography over silica gel (petroleum ether).

General procedure 5
Arylthiosubstituted butatriene compound (1.5 mmol) and iodine (0.38 g, 1.5 mmol) were stirred in CCl4 (30 mL) for 3h at room temperature.Ether was added to the reaction mixture and extracted with 100 ml of 3% aqueous solution of Na2S2O5 twice.The organic layer was separated, washed with water (4x30 mL), dried with anhydrous MgSO4.The solvent was evaporated and the residue was purified by column chromatography over silica gel (petroleum ether/chloroform).
Thiosubstituted compounds are used as  ARKAT USA, Inc.