Monothioketals, cyclic

Cyclic hve-membered monothioketals are desulfurized by Raney nickel mainly to their parent ketones (53-55% yields) and several by-products [935]. After stirring for 2 hours at 25° in benzene with W-2 Raney nickel, 4-tert-butylcyclohexanone ethylene monothioketal afforded 53-55% of 4-/err-bu-tylcyclohexanone, 12-14% of cw-4-/ert-butylcyclohexyl ethyl ether, 6-11% of 4-rert-butylcyclohexanone diethyl ketal, 16% of 4-rert-butylcyclohex-l-enyl ethyl ether, and 7-12% of 4-terr-butylcyclohexene [935]. 

Alone formed by the reaction of lithium aluminum hydride and aluminum chloride in ether cleaves exclusively the carbon-oxygen bond in cyclic monothioketals derived from ketones and mercaptoethanol, and on refluxing in 100% excess for 2 hours produces -hydroxyethyl sulfides (yields 66-91%) on prolonged heating with the reagent these -hydroxyethyl sulfides are further reduced to the corresponding ethyl sulfides (thioethers) (yields 28-81%) [936]. 

Reduction of cyclic five-membered ethylene monothioketals with calcium in liquid ammonia cleaves the bond- between carbon and sulfur and yields alkyl -mercaptoethyl ethers (7-88%) [795]. Cyclic five-membered ethylene dithioketals (ethylenemercaptoles) afford, analogously, alkyl -mercaptoethyl thioethers (yields 85%) [795]. 

Potassium hydroxideltert-butanol co-(l,3-Dithianyl)carboxylic acids from cyclic a-diketone monothioketals... 

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