Ethylene dithioketals

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]. 

In the discussion on 1,1,4,4-tetrafluorocyclooctane the argument was made that substitution of a methylene group in cyclooctane by a difluoro-methylene group increases the barrier to pseudorotation by about 1.2 kcal/ mole, owing to the presence of additional non-bonded repulsions in the transition state for the boat-chair to twist-boat-chair interconversion. Supporting evidence for this view comes from proton nmr studies on 1,1-dimethylcyclooctane (VIII) and on the ethylene ketal (IX) and the ethylene dithioketal (X) of specifically deuterated cyclooctanone. 

The Y labelled isomer XII is actually a racemate, but it is sufficient to consider one of the enantiomers as was done with the ethylene dithioketal of XII, which was discussed in Section VII. A. There are then four conformations BC-3,6a, BC-7,2e, BC-3,8a, and BC-7,4e, as shown below. 

Oxidative hydrolysis of an ethylene dithioketal. Cain and Welling report that the method of Corey and Erickson (4,216) for oxidative hydrolysis of... 

Oxidative hydrolysis of an ethylene dithioketal. Cain and Welling report that the method of Corey and Erickson (4,216) for oxidative hydrolysis of 2-acyl-1,3-dithianes is also useful for unmasking of ethylene dithioketals. Thus treatment of the bisethylene dithioketal (1) with 4 eq. of NBS in 10% aqueous acetone at 0° for 20 min. selectively removes the less hindered ethylene dithioketal group at C to give (2) in 80% yield. Removal of the ethylene dithioketal group at C2 with Raney nickel requires reflux in ethanol and is accompanied by reduction of the carbonyl group. 

Oxidative cleavage of ethylene dithioketals. This reagent can be used for regeneration of ketones and aldehydes from 1, .3-dilhiolanc derivatives at room... 

Excellent yields are obtained for dimethyl acetals and ketals. Table VI, or ethylene dithioketals (Table VII) (23). The... 

A mixture of mercaptal, 3-5 parts hydrazine hydrate, 1.5-2.5 parts KOH, and 8-20 parts di- or tri-ethylene glycol heated until gas evolution starts at 90-135°, then heating continued until the gas evolution is complete after 0.5-3 hrs. whereby the temp, may be raised to 155-190°. Y 60-95%.—E 4-Phenylcyclo-hexanone ethylene dithioketal phenylcyclohexane.—This method is free of... 

Small pieces of lithium added to a suspension of l,4,4aa,5,8,8ay5,9aa,10a)5-octa-hydroanthraquinone bis (ethylene dithioketal) in ethylamine, the flask stopper-... 

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