Formaldehyde dithioacetals, synthesis

The synthesis of formaldehyde dithioacetals may be achieved through a reaction with thiols and dichloromethane in the presence of Wilkinson s catalyst and triethylamine (eq 83). The reaction is simple and takes place under very mUd reaction conditions. 

Synthesis from o-xylose A construction of the AB ring has also been achieved from D-xylose (Scheme 5). D-Xylose was reacted with ethanethiol followed by treatment with formaldehyde to afford the dithioacetal 35, which underwent partial acetolysis of the... 

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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