Sulfides, p-keto

Many 3-substituted indoles have also been prepared with the use of a-alkyl or a-aryl-p-keto sulfides. Thus indolization of aniline 5 with 3-methylthio-2-butanone 27 furnished indolenine 28, presumably via the same mechanism discussed earlier. The indolenine 28 was relatively unstable and reduced to the indole 29 without purification. Tetrahydrocarbazole 32 was prepared in 58% overall yield. Smith et al. made excellent use of the Gassman process in the total synthesis of (-i-)-paspalicine and (+)-paspalinine. ... 

As with the dithiane derivatives, the reaction of a-stannyl sulfides 20-22 with various carbon nucleophiles also proceeded smoothly and P-keto sulfides 23-25 were obtained in excellent yield (Table 4). ... 

In the presence of chiral diamine 1, the sulfurization of tin(II) enolates of ketones or 3-acetylthiazolidine-2-thiones by use of thiosulfonates proceeds smoothly to give the corresponding p-keto sulfides with high enantioselectivities (eq 8 and eq 9). ... 

Asynunetric Synthesis of P-Keto Sulfides. C inine can be used to catalyze asymmetrically the addition of thiols to cyclo-hexenone, thus forming p-keto sulfides (eq 12). The absolute stereochemistry of the products has not been determined. 

Oxidations. Sulfides including P-keto sulfides give optically active sulfoxides by the Sharpless system with modification in using furylhydroperoxides. Alternatively, the tartrate ester may be replaced by (R.R)- or (S,51-diphenylethane-l,2-diol. ... 

Some methyl vinyl ketones behave similarly to acetophenones in aldol condensations, a primary requirement being that the vinyl ketone not be particularly susceptible to Michael addition or base-catalyzed polymerization processes. A recent example utilizes the vinylogous p-keto sulfide (15), which undergoes smooth condensation with benzaldehyde and its derivatives (equation 87). The product of this aldol condensation, enone (16), may be converted by a straightforward sequence of steps into the dienal (17), which is obtained as a 4 1 mixture of ( )- and (Z)-isomers at the C(2>=C(3) double bond. A number of other examples of this useful process are reported in the primary publication. 

Dithia-isotwistan-lO-one 344) actually represent a combination of the two P-keto-sulfides 336 and 341. Its UV-spectrum indeed reflects this situation quite well exhibiting four absorption maxima. 

Capitta F, Frongia A, Piras PP, Pitzanti P, Seed F. Enantioselective organocatal)Tic rearrangement of a-acyloxy-P-keto sulfides to a-acyloxy thioesters. Adv. Synth. Catal. 2010 352 2955-2960. 

B. Asymmetric Reduction of p-Keto Esters and a p-Keto Sulfide... 

A series of l,2-dithiole-3-thiones substituted with nitrogen-containing heterocyclic groups has been prepared for pharmaceutical studies. Groups include pyrazinyl, pyrimidinyl, pyridazinyl, piperidinyl, morpholinyl, and pyrolidinyl.57-60 The dimer of p-methoxyphenylthionophosphine sulfide (29) has been shown to be a versatile reagent for the sulfuration of /3-ketoesters.61 High yields of l,2-dithiole-3-thiones are obtained. However, the method seems to be most suitable for small scale preparations (0.1 mol).62 Keto-... 

The foregoing conditions were applied successfully in the synthesis of diplodialide A (175 Scheme 37). Since earlier studies had demonstrated that the sulfide-contraction conditions were not compatible with a,3-unsaturated thioamides, the 3-acetoxy precursor (173) was used instead. The intramolecular sulfide-contraction reaction successfully accomplished the cyclization to generate the P-keto lactone (174) in modest yields. Elimination of the acetoxy group yielded diplodialide A (175). 

Thiobenzylation. Benzyl sulfides are dehydrogenated to give benzalsulfonium salts on heating with o-chloranil at 80°. These can be used to react with p-keto esters. If a larger excess of o-chloranil is present (3 equiv.) the initial products are converted into the benzyhdene derivatives. ... 

Other sulfur-containing ketones such as keto sulfones and keto sulfides are also reduced by aluminum isopropoxide. Bachmann and Carlson333 prepared 1 - [ p-(methylsulfonyl)phenyl]ethanol and 1 - [p-(methylthio)phenyl]ethanol in good yield by this method ... 

Thiol is converted to a nucleophilic thiolate anion, which reacts with an epoxide to give a ring-opened sulfide, in the presence of TMG (1) [74]. A carbapenem antibiotic carrying a sulfide function was synthesized practically by the addition-ehmination reactions of a thiol to the enol phosphate of p-keto ester in the presence of TMG (1) as a key step [75] (Scheme 4.27). 

Isopropyl 2-iodoxybenzoate is a useful reagent for the clean, selective oxidation of organic sulfides to sulfoxides [1127]. This reaction proceeds without overoxidation to sulfones and is compatible with the presence of the hydroxy group, double bond, phenol ether, benzylic carbon and various substituted phenyl rings in the molecule of organic sulfide. Duschek and Kirsch have reported that isopropyl 2-iodoxybenzoate in the presence of trifiuoroacetic anhydride can be used for the a-hydroxylation of p-keto esters at room temperature in THF [1128]. 

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