2- -ethane thiol synthesis

Perfluoroalkyl)ethane thiols have been used as precursors to fluorinated surfactants and products for hydro- and oligophobic finishing of substrates such as textiles and leather (1). The synthesis of 2-(perfluoroalkyl)ethane thiol and a byproduct bis-(-2-perfluoroalkylethane)-disulfide (5-10%) has been practiced via the reaction of 2-(perfluoroalkyl)ethane iodide with thiourea to form an isothiuronium salt which is cleaved with alkali or high molecular weight amine as shown in Equation 1 for 2-(perfluorohexyl)ethane iodide (1). 

It is apparent that a new synthetic methodology, preferably catalytic, is needed for the synthesis of this important class of 2-(perfinoroalkyl)ethane thiols. In this context, a variety of catalysts was examined to determine if they wonld catalyze the hydrogenolysis of 2-(perfinorohexyl)ethane thiocyanate. In the conrse of this study, much to our surprise, it was discovered that a carbon supported Pd-Sn would catalyze the reaction. It is known that palladium and other group Vtll metal catalysts are poisoned by the product thiol, traces of hydrogen sulfide byproduct, and the hydrogen cyanide co-prodnct (6), but our observations are that this catalyst is surprisingly robust in the reaction medium. 

Scheme 4. Synthesis of 1-(2-methy1-3 - thienylthio)-ethanethiol H3 and 1-(2-methy1-3-furylthio)-ethane-thiol 19...

The described synthesis of l,4-thiazino[3,2-6][l,4]thiazine (305) <87JA4308> starts with the reaction of aqueous glyoxal (302) with iV-methylguanidinium chloride (303) in water (pH 8). The resulting 2-amino-4,5-dihydro-4,5-dihydroxy-l-methylimidazolium chloride (304) is treated with 2-amino-ethane thiol in H20 (pH 8-9) to give either (305) or (306). The NMR spectrum of the product supports both of the structures (305) and (306) there is only one diastereomer <87JA4308>. 

For sensitive substrates, transace talisation using ethane thiol in the presence of a mild Lewis acid such as zinc(Il) triflate is especially advantageous. Scheme 3.52. taken from a synthesis of Zaragozic Add, illustrates the method for the removal of a benzylidene acetal in a densely functionalised substrate whilst pre-... 

Esterification, 86,107,110 Ester synthesis, 191 Ethanedithiol, 330 Ethane thiol, 33 Ethoxyacetylene, 103 Ethoxyaoetylene-Magnesium bromide, 145... 

The subjects of this chapter are the exploration of the scope and hmitations of the new Pd-Sn catalyzed hydrogenolysis route for the synthesis of thiols via 2-(perfluoroalkyl)ethane thiocyanate, the characterization of the surprisingly active and robust Pd-Sn catalysts, and the attempted correlation of the characterization of the catalysts with observed onset of hydrogenolysis reactivity and snrprisingly long lifetime in the presence of known catalyst poisons. ... 

Dithiocarbene 159 is obtained when a trifluoromethyl group is reacted with a thiol (Equation (28)). Yields are high and the solution resonance of the carbon bonded to platinum is reported as 306 ppm. On the NMR timescale, the two SMe groups adopt different orientations relative to the Pt-G bond, indicating that there must be significant 7r-bonding between the sulfurs and the carbene carbon. This work was expanded to include the synthesis of 3 -heterocylic carbenes with the use of ethane-1,2-dithiol in place of methane thiol. ... 

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