Thionium salts

Addition of methyl iodide to a solution of the aminodithioacrylate 1 in acetone resulted in the rapid formation of the corresponding thionium salt in high yield. Treatment of a solution of 1 in... 

A Pummerer-type rearrangement has also been utilized to prepare a number of 1-acyloxy-l-phenylsulfanylcyclopropanes and 1-alkoxycarbonyloxy-l-phenylsulfanylcyclopropanes 10 from a single compound, 1-phenylsulfinyl-l-tributylstannylcyclopropane (7). The reaction proceeds via an a-stannyl acylsulfoxonium salt 8, which affords the thionium salt 9 which is subsequently attacked by the carboxylate anion. 

Thioacylium salts Thioaldehydes Thioketones Thionium salts... 

Two reports [93,94] have shown that allyl vinyl sulfonium salts rearranged readily to form thionium salts, which were subsequently transformed into a thioacetal (Scheme9.16). It is noteworthy that the initial investigation was made in the context of a possible path for an indole alkaloid biosynthesis [93]. The rearrangement of an allyl aryl dithiacation was also shown to proceed by an analogous route [95]. 

Lactam sulfonium salts bearing a dihydrothiopyran skeleton with a sulfonio bridgehead have been synthesized. Tricyclic benzothiazinium salts 87 were prepared by [4+2+]-polar cycloaddition of a thionium intermediate 99, generated from the corresponding a-chloro sulfide 98, in the presence of silver perchlorate in moderate to good yields (see Equation (28) and Table 17) <1997J(P1)309>. Cycloaddition with isoprene 41b gave adducts 87b and 87c as a... 

The additive Pummerer reaction is a reaction in which displacement of the acyloxy group in the initially formed acyloxysulfonium salt by an internal nucleophile occurs to give a new positively charged sulfur species (Scheme 33). A number of pathways are open for the subsequent reaction of intermediate (138), including elimination of the proton a to the sulfur to give a thionium ion (pathway a), displacement of the sulfur from the a -carbon by an external nucleophile (pathway b), elimination of a 3-proton with formation of an alkene and (139) (pathway c) and loss of a proton fimm the carbon atom a to Nu with formation of (140 pathway d). 

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