Dithioacetal oxides

In addition to the application of malonic esters, four-membered ring compounds can also be realized by using methyl methylsulfanylmethyl sulfoxide (14) as the active methylene component.25 27 As demonstrated in the following scheme, when the potassium salt of methyl methylsulfanylmethyl sulfoxide is allowed to react with 1,3-dibromopropane, cyclobutanone dimethyl dithioacetal 5-oxide (16) is isolated in 97% yield.8,10 Of particular interest is that the... 

Formaldehyde dimethyl dithioacetal 5-oxide (FAMSO 113) and its ethyl analog are widely used as synthetic carbonyl equivalents. - Addition of the lithio derivative of (113) to aldehydes and ketones followed by acidic hydrolysis is a preparative method for a-hydroxy aldehyde derivatives (equation 27). A chiral analog of (113), (5)-formaldehyde di-p-tolyl dithioacetal 5-oxide (114), can be synthesized from (-)-mentyl (/ )-p-toluenesulfinate. °° The reaction of the lithio derivative of (5)-(114)... 

The anion of an aldehyde dithioacetal 5-oxide is well known to add to a,3-unsaturated carbonyl compounds. " Conjugate addition of formaldehyde di-p-tolyl dithioacetal 5-oxide (114) to open-chain and cyclic enones is achieved by using HMPA as a polar cosolvent in THF (-78 C)." The lithio derivative of (5)-(114) was found to add to 2-cyclopentenone with asymmetric induction. Transformation of the dithioacetal part into a formyl group gives 3-formylcyclopentanone in 39% enantiomeric excess (equation 28)." Interestingly, highly asymmetric induction is observed in the conjugate addition of the... 

When the dithioacetal 5-oxide (29.1) is stirred in dichloromethane containing hydrogen sulphide and hydrochloric acid, it is efficiently cyclized to a 1-arylsul-phonyl-2-methylthioindole. 

Ogura [296, 297] has proposed other interesting uses of MMTS (also known as FAMSO, for formaldehyde dimethyl dithioacetal 5-oxide) and also of the two following dithioacetal monosulfones ... 

Closely related to the Iwao indole synthesis (Chapter 33) is the discovery by Hewson and colleagues, who found that ortfto-sulfonamide ketene dithioacetal 5-oxides 1 readily cyclize to the corresponding 2-thiomethylindoles 2 upon treatment with hydrochloric acid in the presence of hydrogen sulfide (Scheme 1) [1]. The hydrogen sulfide prevents the... 

An unexpected thermal rearrangement of a 2-pyridylaldehyde dimethyl-dithioacetal 5-oxide to a sulphinate has been encountered during the exploration... 

Dithioacetal monoxide anions react with carbonyl compounds in a similar way affording the corresponding a-hydroxy aldehyde dithioacetal oxides 428. Ogura and Tsuchihashi, who performed this reaction for the first time using the anion of methyl methylthiomethyl sulphoxide 324, obtained in this way a series of a-hydroxyaldehydes 429504 (equation 257). 

A general way to achieve thiophilic addition is to use sulfines [149]. The sulfur atom of thiocarbonyl oxides is selectively attacked by carbanions. We have applied this property to aliphatic dithioester oxides and shown [150] that, despite the probably high acidity of the a-protons, thiophilic addition of alkyllithiums is observed, leading to stabilised carbanions. After treatment with electrophiles, dithioacetal oxides were obtained. From a synthetic point of view, it is worthy of note that these adducts are much more easily... 

Cycloaddition reactions of thioaldehydes and sulfines are most probably encountered in plants, as elegantly and soundly shown by the group of Eric Block during their investigation of sulfur products occurring in the Allium species (for a review see [91]). They were able [92, 93] to isolate bicyclic dithioacetal oxides, called zwiebelanes, and also to synthesise them from a thioxosulfine, already described in this review (Sect. 2.6, Scheme 18). An extremely rich stereochemical and analytical study has resulted. 

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