Dithioacetal S-oxides

From the synthetic point of view the most important a-sulphinyl carbanions are the anions derived from dithioacetal S-oxides which may be considered as synthons of acyl... 

From the synthetic point of view, the most important a-sulfinyl carbanions appear to be those derived from dithioacetal S-oxides which are a synthon for acyl anions65. However, the yields of the alkylation reaction were found to be low. In spite of the fact that dithiane S-oxides have been intensively studied66 63, their synthetic applications are limited,... 

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

Scheme 21). Some important a-sulfinyl carbanions (42) are derived from dithioacetal S-oxides (43), and on subsequent alkylation and hydrolysis they yield the aldehydes (40) (Scheme 22).

Im Gegensatzzu den Dithioacetalen 1,1,1-Disulfonen IV und den Dithioacetal-bis-S-oxi-den III sind die Dithioacetal-S-oxide II saurempfindliche Verbindungen359. 

Dithioacetal-S-oxide entstehen als Zwischenprodukte bei der hydrolytischen Spaltung von Dithioacetalen nach vorangehender Oxidation (s.S. 376). 

Schlecht lassen sich auf diese Weise die beiden folgenden Dithioacetal-S-oxide spalten364. 

Das Verhaltnis 1,2- 1,4-Addition ist abhangig vom Enon, dem Dithioacetal-S-oxid und der Temperatur374. 

Zur Herstellung von Aldehyden iiber Keten-dithioacetale und -dithioacetal-S-oxide s. 

FAMSO formaldehyde dimethyl dithioacetal S-oxide (=MMTS)... 

Cyclobutanones. Reaction of methyl methylthiomethyl sulfoxide with 1,3-dibromopropane in the presence of 2 eq. of potassium hydride leads to cyclo-butanone dimethyl dithioacetal S-oxide (2) in high yield. Intermediates (a)... 

I, 4, 341-342) with Triton B as catalyst. The product (2) is reduced to (3). Oxidation of (3) with hydrogen peroxide gives the dimethyl dithioacetal S-oxide (4), which is hydrolyzed by acid to (5). 

Formaldehyde dimediyl preparative method for a-hydroxy aldehyde derivatives (equation 27). A chiral analog of (113), (S formaldehyde di-p-tolyl dithioacetal S-oxide (114), can be synthesized from (-)-mentyl (/ )-p-toluenesulfinate. - The reaction of the lithio derivative of (S)-(114)... 

A new route to dicyclopropylidenemethane (142) involving initial condensation makes the allene now readily available. The dithioacetal S-oxide (143) can also be obtained in high yield, but it is not clear whether the acid-catalysed hydrolysis examined led to cyclopropanone or its decomposition products. ... 

An alternative approach to benzo[Z ]thiophene derivatives includes treatment of an aryl-substituted ketene dithioacetal monoxide 188 with trifluoromethanesulfonic anhydride [99] (TfjO) in the presence of K2CO3 in toluene at 25 °C, followed by addition of ethanolamine to the reaction mixture, provided benzo[fc]thiophenes, including 3-trifluoromethylbenzo[Z ]thiophene 189, in good yields. The cyclization proceeded through formation of reactive sulfonium electrophile [1(X)]. The synthesis of the starting material 188 was also facile and scalable, starting from aryl ketone 186 and formaldehyde dimethyl dithioacetal S-oxide (FAMSO) [101]. 

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