Mercaptoles

Mercaptans form hemimercaptols by addition and mercaptols, (CH2)2C(SR)2, by substitution following the addition. 

Chemical Name Bis(35-di-tert-butyl-4-hydroxyphenyl) acetone mercaptole Common Name —... 

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. 

In another representative procedure about 2.3 mols of 2,6-di-tert-butyl-4-mercaptophenol is dissolved in about 1,700 ml of methanol under a nitrogen atmosphere about 100 ml of concentrated hydrochloric acid and 1B0 ml of acetone are added, and the mixture is stirred and maintainedat a temperature of about 35°C to 50°C, for 1.5 hours. The mixture is then cooled to room temperature and filtered, and the bis(3,5-di-tert-butyl-4-hydroxyphenyl) acetone mercaptole product is collected as a colorless crystalline solid filter cake. The product is washed with water and aqueous sodium bicarbonate and purified by recrystallization from ethanol. 

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 reduction of a-sulfur substituted ketone 27 and its analogues usually gives the anti-mercaptol alcohol like roc-14 which can be elaborated into cis-dihydrobenzoxathiin 30. 

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

The above sequence was demonstrated on racemic onti-mercaptol alcohol 14 as well on a small amount of optically pure 14 (separated by chiral HPLC separation) and the chiral centers of 14 were completely retained, as expected (Scheme 5.6) [8]. With proof of concept for the ring formation strategy, some efforts were put into developing a chiral synthesis of 14, as shown in Scheme 5.7. 

Scheme 5.7 Synthetic approach to chiral mercaptol alcohol 14.

The dynamic kinetic resolution (DKR) of a-sulfur-substituted ketones such as 31 and 33 was investigated. When the MOM protected mercaptol ketone 31 was treated with the BINOL-LiAlH4 complex, a moderate diastereoselectivity of 5 1 favoring the desired anti isomer was observed. The major diastereomer had 70%... 

Self-forming microspheres polymercaptol 0.8 Oral and hemoperfusion for treatment of heavy metal poisioning Mercaptol... 

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>. 

Acetone Ethyl Mercaptan. 50 g of ethyl mercaptan are added to 20 g of acetone and 6 g of anhydrous calcium chloride. Dry hydrochloric acid gas is passed into the reaction, while the temp is controlled to 25°, by external cooling. When saturated with acid, the mixture is allowed to stand for 12 hours, and is then washed with water. The resulting mercaptol is separated, dried with calcium chloride, and fractionally distilled. Unreacted ethyl mercaptan passes over first and is saved for a second run. Next, the mercaptol passes over at about 190°. 

Most frequently mercaptoles (dithioketals) are desulfurized to hydrocarbons... 

Raney nickel in ethanol or other solvents. If reducible functions are present in the molecule of the mercaptole, Raney nickel must be stripped of hydrogen by refluxing with acetone for a few hours before use [46. ... 

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]. 

Alternative desulfurizations can be achieved using tributylstannane or hydrazine. Reaction with the former reagent is carried out by heating the mercaptole for 1.5 hours at 80° with 3-4 equivalents of tributylstannane and azobis(isobutyronitrile) as a catalyst and distilling the product and the byproduct, bis(tributyltin) sulfide, in vacuo. Yields are 74-95% [798],... 

The reaction with hydrazine consists of heating the mercaptole with 3-5... 

Probucol Probucol, (nX3,5-tert-butyl-4-hydroxyphenyl)mercaptol acetone (20.2.6), is synthesized by thioketalizing acetone with 2,6-di-tert-butyM-mercaptophenol in the presence of hydrogen chloride [12-16]. 

The photochemistry of certain cyclic mercaptoles has been investigated,43 and the two major pathways can be interpreted in terms of initial carbon-sulfur bond cleavage [Eq. (11)]. 

Die Mercaptanolyse von 14 in HBr/Eisessig liefert in guten Ausbeuten oc-Ketosaure-mercaptole (oder a-Alkylmercapto-acrylsauren) und 2.2.2-Trifluor-l-alkylmercapto-athylamin-hydrobromide (51) i 5,20i> ... 

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