5- Aminosulfoxonium salts reactions with

The ready deprotonation of the vinyl aminosulfoxonium salts 46 with a strong base at the a-position prompted a study of their reactions with weaker bases. It was speculated that in this case a vinyl-allyl isomerization of 46 might occur, followed by an intramolecular substitution of the allyl aminosulfoxonium salt... 

The methylation of sulfoximines 45 with Me30BF4 proceeded readily and gave the corresponding cyclic aminosulfoxonium salts 46 in quantitative yields. Upon treatment with LiN(H)t-Bu first at-78 °C and then at room temperature, salts 46 delivered the enantio- and diastereomerically pure bicyclic 2,3-dihydrofurans 50 cleanly in high overall yields. It is proposed that the reactions of the aminosulfoxonium salts 40 and 46 with the lithium amide at low temperatures afford the vinyl aminosulfoxonium ylides 41 and 47, respectively. These alkylidene carbenoids eliminate sulfinamide 35 at higher temperatures with formation of the alkylidene carbenes 42 and 48, respectively. Subsequently, the alkylidene... 

When acyclic and cyclicl-alkenyl aminosulfoxonium salts were allowed to react with a base, p-silyloxy alkylidene carbenes were generated, which underwent a l,5-0,Si-bond insertion and 1,2-silyl migration to form 2,3-dihydrofurans <04JA485ft>. As can be seen in the scheme below, 2,3-dihydrofurans could also be formed from various 2,2-dimethyl-5-methoxy-carbonyloxy-3-pentyn-l-ols in the presence of p-methoxyphenol via a palladium-catalyzed cyclization reaction <04TL1861>. 

Reactions with S-aminosulfoxonium salts via their ylids Ring closures... 

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