Mercaptoles preparation

Sulfonal — Diethylsulfondimethylmetliane — qh / vIo c h . —is obtained by the oxidation of ethyl-mercaptol, prepared as above described, by potassium permanganate. It crystallizes in thick, colorless prisms, dilBcultly soluble in cold water or alcohol, readily soluble in hot water or alcohol, and in ether, benzene and chloroform. It fuses at 130"-131 (366°-267°.8 P.), and boils at 300° (572° F.), suffering partial decomposition. It dissolves in concentrated HjSOi, and is decomposed by the acid when heated, but may be precipitated from the cold solution unchanged bydilution with HjO. Nitric acid does not affect it, even when heated. It is not attacked bj Br, by caustic alkalies or by nascent H. 

Bis(3,5-di-tert-butyl-4-hydroxyphenyl) acetone mercaptole, melting at 125°C to 126°C is prepared by employing 2,6-di-tert-butyl-4-mercaptophenol and acetone as starting materials. In one representative procedure, the 2,6-di-tert-butyl-4-mercaptophenol (47.5 g, 0.2 mol) is dissolved in methanol (50 ml) heated at a temperature of 50°C. A catalytic amount of concentrated hydrochloric acid (1 ml) is added, followed by acetone (5S g,0.1 mol). The temperature of the mixture rises to about 60°C, and is maintained at about 60°C to 65°C for 1.5 hours. The mixture is cooled, diluted with water and about 10 ml of aqueous sodium bicarbonate and extracted with ether. The ether extract is evaporated, and the product is obtained as a residue, which is recrystallized from ethanol and then from isopropanol to obtain the bis(3,5-di-tert-butyl-4-hydroxyphenyl) acetone mercaptole as a crystalline solid melting at about 125°Cto 126°C. 

The cis-2,3-diaryl-2,3-dihydro-l,4-benzoxathiin is a very unique structural motif. Other than scattered reports in the literature on the formation of this scaffold, there was no effective asymmetric synthesis for it [6]. We explored two major synthetic approaches to realize the key chiral as-diaryl dihydrobenzoxathiin scaffold, as shown in Scheme 5.3. One was the quinone ketal route in which the quinone ketal 13 and the chiral mercaptol alcohol 14 were the key intermediates. The other approach was the stereo- and enantioselective reduction of the diaryl benzoxathiin 16. The key mercaptol alcohol 14 and the diaryl benzoxathiin 16 were both envisioned to be prepared from the key, common iodoketone intermediate 15. 

The mercaptol alcohol rac-14 undergoes facile Michael addition reaction with quinone ketal 13 which is commercially available or can be readily prepared. 

Two 4-amino-3-mercaptol,2,4-triazole residues linked by a two-carbon bridge have been prepared by the reaction of thiocarbohydrazide with succinic acid 157a or malic acid 157b to give l,2-bis-(4-amino-5-mercapto-477-l,2,4-triazol-3-yl)ethan-l-ol 158a or l,2-bis-(4-amino-5-mercapto-477-l,2,4-triazol-3-yl)ethane 158b in yields of 56% and 60%, respectively (Equation 49) <2006PS(181)2361>. 

Nickel prepared by reduction of nickel chloride with sodium borohydride was used for desulfurization of diethyl mercaptole of benzil. Partial desulfurization using 2 mol of nickel per mol of the mercaptole gave 71% yield of ethylthiodesoxybenzoin while treatment with a 10-fold molar excess of nickel over the mercaptole gave 61% yield of desoxybenzoin (benzyl phenyl ketone) 937. ... 

Mercaptoles of ketones are best prepared by treatment of ketones with ethanedithiol or 1,3-propanedithiol in the presence of anhydrous zinc chloride or boron trifluoride etherate. Many desulfurizations have been carried out with these cyclic mercaptoles, especially in steroids. Yields of the hydrocarbons range from 50 to 95% [797]. 

Acetone Ethyl Mercaptol.—50 gms. ethyl mercaptan (see Preparation 306) are added to 20 gms. acetone aqd 6 gms. anhydrous calcium chloride. Dry hydrochloric acid gas is passed in, the temperature being kept below 25° by external cooling. When saturated with acid the mixture is allowed to stand overnight, and washed with water. The layer of mercaptol is separated and dried over calcium chloride, and fractionally distilled. Unchanged ethyl mercaptan passes over first, and then the mercaptol at 190°. 

Fridinger and co-workers (1971) found that, with 1,2-dithiols, pyruvic aldehyde yields, instead of the expected mercaptal ketones, mercaptol aldehydes (e.g. 50). Using this reaction, the oximes of the mercaptol aldehydes prepared by these... 

Dithioles of mercaptol type can be prepared from w-dithiols and a-halo ketones. The l,3-dithiolan-4-ols first formed are dehydrated to 1,3-di-thioles in the presence of acid 330... 

A general prescription for the preparation of dibutyl mercaptols and mercaptals has been given by Whitner and Reid.419... 

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