Hydrogen sulfide thietanes

Both anhydrous and hydrated sodium or potassium sulfide in ethanol have been used in the synthesis of thietanes. A common procedure is to use a solution of sodium or potassium hydroxide saturated with hydrogen sulfide. Liquid ammonia has been used as a solvent for the preparation of thietane (32%) from sodium sulfide and 1,3-dibromopropane. Phase-transfer catalysis has been used to good effect.A variation in which l,3-dichloro-3-methylbutane 3 is treated with aluminium chloride and hydrogen sulfide followed by aqueous sodium hydroxide gave 2,2-dimethylthietane 4 in 90% yield. An intermediate aluminium chloride-alkene complex, 5 or 6, was proposed. 

Heating several thietanes with sulfur or selenium yields 1,2-dithiolanes and a 2-selenathiolane, for example, 107 from 19, respectively. The reaction of 108 with sulfur provides a synthesis of thioctic acid. ° A somewhat similar reaction involves heating thietane with aluminum oxide whereby 1,2-dithiolane and hydrogen sulfide are produced, but the dithiolane yield is very low. A photochemical ring-expansion of 99 has been described in Section 11.5.1. ° Treatment of thietane with hexafluoroacetone gives a six-membered cyclic sulfenate. ... 

Thietane 1-oxides may be reduced to thietanes by iodide ion in acidic mediaby hydrogen sulfide, and by zinc-hydrochloric acid. Thietane 1-oxide is reduced by iodide about four times more rapidly than dimethyl sulfoxide the rate of reduction as a function of ring-size decreases as follows 5 > 4 > 6. The mechanism of reduction by iodide involves slow formation of an iodosulfonium salt 120. The thietane product is unstable in the aeidic medium and was not identified. 

The mechanism proposed for the reduction of thietane 1-oxide by hydrogen sulfide is complex the order of reactivity is ethyl methyl sulfoxide > thiolane 1-oxide > diethyl sulfoxide > dimethyl sulfoxide > thietane l-oxide. ... 

Flash-vacuum thermolysis of thietane 1-oxide affords the reactive intermediate, sulfine, CH2=S=0. Field-ionization mass spectrometry of the thermolysis products also indicates the formation of thietane, propenal, ethylene, CaHsO, CaHg, and hydrogen sulfide. A 1,2-oxathiolane intermediate was suggested. The exo sulfoxide 118 is thermally stable, but the endo derivative 115 decomposes around 200°C, probably because of the ease of -elimination ... 

Additions of the Michael type of nucleophiles to the carbon-carbon double bond of thiete 1,1-dioxides to give 3-substituted thietane 1,1-dioxides occur readily. The addition of hydrogen has been discussed in Section A. Nucleophiles include cyanide, the anion of nitroethane, the lithium salt of r-butyl o-tolyl sulfone, dimethylamine, cyclohexylamine, ethoxide, and hydrogen sulfide. The reaction is exemplified by the synthesis of 278. Additions to 3-chloro-2H-thiete 1,1-dioxide most likely proceed by an addition-elimination mechanism an example is shown for the addition of the anion of dimethylmalonate to give 279. The replacement of a 3-morpholinyl group by a 3-A methyl-A-phenylamino group in thiete 1,1-dioxide is another example of addition-elimination. An addition of ethoxide with elimination of p-nitrophenyl anion may occur with 268 (Ar = / -N02C6H4). " Addition of bromine via N-bromo-succinimide to the double bond of 4-phenyl-2H-thiete 1,1-dioxide occurs only in 1.5% yield. ... 

Sulfunes. A recent preparation of thietane 1,1-dioxide1 emphasizes the advantage of tungstic acid catalysis2 in the hydrogen peroxide oxidation of sulfides to sulfones an induction period is eliminated and the yield improved. 

Oxidation of thietane 1-oxides to thietane 1,1-dioxides is easy, but not particularly important except as a structure proof, since most sulfones can be made directly from the sulfides. Oxidation reagents that have been used on the sulfoxides are hydrogen peroxide-acetic acid, hydrogen peroxide-formic acid, perbenzoic acid, peroxydodecanoic acid, " and perlauric acid. The relative rates of oxidation of four-, five, and six-membered sulfoxides with perbenzoic acid in 40% dioxane at 25° were similar. Oxidations were more rapid at high pH. 

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