Aluminum chloride with ethanethiol

Several methods are employed for the reductive defluorination of 2-fluoro-l-phenyl-ethanones. Electrolytic reduction at a mercury cathode selectively replaces fluorine in 2-fluoro-l -phenylethanone by hydrogen.94 The hydrodefluorination of fluoroacetophenones, e.g. 7, to dithioacetals of the corresponding defluorinated ketones with aluminum chloride and ethanethiol take place readily by stirring the mixture in dichloromethane at 0°C under nitro-... 

Double bonds activated by the presence of electron withdrawing groups (NO , COjEt, COMe, CN) can be cleaved by use of ethanethiol and a hard Lewis acid such as AICI3, AlBra, FeCh or ZnCl2 to give dithioacetals in good yields.For example, dicyanostyrene (12) can be converted into the corresponding dithioacetal (13) in quantitative yields when treated with aluminum chloride and ethanethiol (equation 39). 

Under a nitrogen blanket, a mixture of 3 g of 4-(2-piperidinoethoxy)benzoic acid hydrochloride, 2 drops of dimethylformamide, 2.5 ml of thionyl chloride and 40 ml of chlorobenzene was heated at 70°-75°C for about one hour. The excess thionyl chloride and 15-20 ml of solvent were then distilled off. The remaining suspension was cooled to ambient temperature, and to it were added 100 ml of dichloromethane, 2.7 g of 6-methoxy-2-(4-methoxyphenyl) benzo[b]thiophene and 10 g of aluminum chloride. The solution was stirred for about one hour, 7.5 ml of ethanethiol was added, and the mixture was stirred for 45 minutes more. Then 40 ml of tetrahydrofuran was added, followed by 15 ml of 20% hydrochloric acid, with an exotherm to reflux. Fifty ml of water and 25 ml of saturated aqueous sodium chloride was added. The mixture was stirred and allowed to cool to ambient temperature. The precipitate was collected by filtration and washed successively with 30 ml of water, 40 ml of 25% aqueous tetrahydrofuran, and 35 ml of water. The solids were then dried at 40°C under vacuum to obtain 5.05 g of product, which was identified by NMR as 6-hydroxy-2-(4-hydroxyphenyl)-3-[4-(2-piperidinoethoxy)benzoyl] benzo[b]thiophene hydrochloride melting point 217°C. 

Removal of fluorine from 1-fIuoronaphthalene is accomplished by treatment with ethanethiol and aluminum chloride at room temperature (equation 40). ... 

Isopropyl alcohol under UV irradiation converts bromobenzene to benzene in 72% yield (Table 4). Similar replacement of bromine by hydrogen is accomplished by treatment of aryl bromides dissolved in dichloromethane with a mixture of ethanethiol and anhydrous aluminum chloride. This hard acid-soft base combination reacts with polycyclic aromatic halides and halogenated phenols by an addition-elimination mechanism, leading to an aryl ethyl sulfide through a radical anion intermediate. This is converted by another molecule of ethanethiol to the debrominated arene and diethyl disulfide. 1-Bro-monaphthalene is thus transformed into naphthalene (equation 59), 2,4,6-tribromophenol into phenol (equation 60), and bromochlorophenols into chlorophenols in 61-91% yields. ... 

Naphthyl phenyl sulfide is desulfurized to naphthalene on refluxing with lithium aluminum hydride and titanium tetrachloride, and 1-naphthyl ethyl sulfide and 1-naphthyl isopropyl sulfide are converted to naphthalene on treatment with ethanethiol and anhydrous aluminum chloride (equation 83). ... 

A rather special procedure for the preparation of 21-hydroxy-20-ketopreg-nanes starts with the 17a-ethoxyethynyl-17 -hydroxy steroids described earlier. Free radical addition of ethanethiol to the triple bond, followed by acid-catalyzed hydrolysis and dehydration gives the 20-thioenol ether 21-aldehyde. This can be reduced with lithium aluminum hydride to the C-21 alcohol and then hydrolyzed to the C-20 ketone in the presence of mercuric chloride. The overall yield, without isolation of intermediates, is in the order of 50% ... 

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