Mercaptals ketones

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... 

Several kinds of products can be obtained by reaction of thioglycolic acid and its esters with aldehydes to form mercaptals, RCH(SCH2COOH)2, or with ketones to form thiolketals, RR C(SCH2COOH)2. Reaction with formaldehyde (qv) yields di- -butyhnethylene-bisthioglycolate [1433882-0] (MET ester) ... 

Two techniques, electrochemical reduction (section IIl-C) and Clem-mensen reduction (section ITI-D), have previously been recommended for the direct reduction of isolated ketones to hydrocarbons. Since the applicability of these methods is limited to compounds which can withstand strongly acidic reaction conditions or to cases where isotope scrambling is not a problem, it is desirable to provide milder alternative procedures. Two of the methods discussed in this section, desulfurization of mercaptal derivatives with deuterated Raney nickel (section IV-A) and metal deuteride reduction of tosylhydrazone derivatives (section IV-B), permit the replacement of a carbonyl oxygen by deuterium under neutral or alkaline conditions. 

Thioketals are readily formed by acid-catalyzed reaction with ethane-dithiol. Selective thioketal formation is achieved at C-3 in the presence of a 6-ketone by carrying out the boron trifluoride catalyzed reaction in diluted medium. Selective protection of the 3-carbonyl group as a thioketal has been effected in high yield with A" -3,17-diketones, A" -3,20-diketones and A" -3,l 1,17-triones in acetic acid at room temperature in the presence of p-toluenesulfonic acid. In the case of thioketals the double bond remains in the 4,5-position. This result is attributed to the greater nucleophilicity of sulfur as compared to oxygen, which promotes closure of intermediate (66) to the protonated cyclic mercaptal (67) rather than elimination to the 3,5-diene [cf. ketal (70) via intermediates (68) and (69)]." " ... 

This ester is converted in high yield to the y -ketosulfoxide by means of the dimethyl sulfoxide anion. Heating in acetic acid then produces a hemi-mercaptal acetate, which on treatment with Raney nickel gives the desired 21-acetoxy-20-ketone in a 50-70% overall yield from the -ketosulfoxide. A 17a-hydroxyl may also be present during the sequence. 

Thiols add to aldehydes and ketones to give hemimercaptals and dithioacetals. Hemi-mercaptals are ordinarily unstable,127 though they are more stable than the corresponding... 

Such a di-thio-ether is known as a mercaptal and this particular one is known as di-thio acetal (p. 117). Analogous compounds obtained from ketones, e.g., from acetone, are called mercaptols. 

Carbanions of type (2) or (4) react readily with ketones to give mercaptals of a-hydroxy aldehydes and a-hydroxy ketones, respectively ... 

Ketone mercaptals can be desulfurized by NaBH4 (in excess) and nickel chloride in ethanol, the reaction proceding stepwise.567... 

Mercaptals (dithioacetals)327 or mercaptols (ketone dithioacetals)328 329 are obtained by reaction of geminal dihalogen compounds with thioiates, usually in a smooth reaction when hydrogen halide cannot be split off from the halogen compound ... 

Reaction of thiols with aldehydes or ketones leads to formation of water and geminal bis(alkylthio) compounds, which, when derived from aldehydes, are known as mercaptals or, when derived from ketones, as mercaptols ... 

When acetals of aldehydes or ketones are heated with thiols in a bomb tube at 100-130° the OR groups are replaced by SR, this process having been used to provide acetaldehyde diethyl mercaptal (84% yield), acetone diethyl mercaptol (81%), and triethyl trithioorthoformate (87%).425... 

Baumann was the first to report the reaction of a mercaptan with either an aldehyde or a ketone to give a high yield of the corresponding mercaptal or mecaptol [83],... 

Mercuric acetate Ketones from cyclic mercaptals... 

To an ice cold solution of 20.0 g D-glucose diethyl mercaptal pentaacetate in 200 mL dry ether was added 35.21 g monoperphthalic acid in ether (4.8 eq.). The solution was cooled in ice for 1 h and then allowed to stand at room temperature for an additional 16 h. The ether was removed under reduced pressure, and the residue was extracted with CHCI3 (4 X 75 mL). The chloroform was washed with saturated aqueous NaHCOs and then with water and was dried over Na2S04. Then CHCI3 was removed under reduced pressure to give 19.9 g D-arabo-3,4,5,6-tetraacetoxy-l,l-bis-(ethanesulfonyl)-hexene-l as a crystalline material, m.p., 134-146°C. Two recrystallizations from diisobutyl ketone followed by one from isopropyl alcohol and one from methyl ethyl ketone by addition of petroleum ether (b.p. 35-60°C), gave 12.9 g pure product with a constant melting point of 160-162°C, in a yield of 64%. 

A mixture of allyltrimethylsilane and bis(phenylthio)methane in toluene added slowly to a soln. of AICI3 in same solvent at room temp., the mixture cooled to 0°, and worked-up when reaction complete by t.l.c. ca. 1-5 h) product. Y 60%. Ketone mercaptals gave a mixture of products. F.e., also thioenolethers using excess of the silane, s. A. Mann et al.. Tetrahedron Letters 29, 6175-6 (1988). 

Lithio-l,3-dithianes add to the carbonyl group of aldehydes and ketones to provide mercaptal derivatives of a-hydroxy aldehydes or ketones (equation 55). The yields are normally quite high. Reaction with a,j8-unsaturated ketones has been observed to give only 1,2-addition however, Seebach and Lietz have reported 1,4-addition to occur in reactions with a,]8-unsaturated nitro derivatives (equation 56). In the case... 

Hydrocarbons from alcohols via bromides s. 18, 125 Replacement of hydroxyl by hydrogen via mesylates and iodides s. 19, 114 via mesylates and benzyl thioethers s. 16, 107 via ketones and cyclic mercaptals s. 16, 138 OH H... 

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