Sulfonium salts, acetylenic

Sulfonium, cyclopropyldiphenyl tetrafluoroborate, 54, 28 Sulfonium salts, acetylenic, furans from, 53, 3 Sulfonium ylides, 54, 32 Sulfur, reaction with organo-lithium compounds, 50, 105 Sulfuryl chloride, with 1,1-cyclobutanedicarboxylic acid to give 3-chloro-l,1-cyclobutanedicarboxylic acid, 51, 73... 

The method described has some features in common with the well-known, but apparently little-used, Feist-Benary furan synthesis,1 which uses an a-haloketone in place of the sulfonium salt. Acetylenic bromides suitable for preparing the sulfonium salts are readily available by well-documented procedures involving acetylenic organometallic compounds. 

Ylides 2 can be prepared in situ from the sulfonium salts 1 with sodium hydride. These ylides 2 react with electrophiles, for example, acetylenes, to give the new stable ylides 3, for R1 =R2 = Me as a mixture of the cis- and trans-isomer, otherwise as the trans-isomer only. Compounds 3 are stable in refluxing tetrahydrofuran for 1 hour, but heating without solvent at 170-200r C for 3 to 5 minutes results in a 1,4-rearrangement to give thiaazulenes 4 quantitatively, with the exception of R1 = R2 = Et, where the yield is 25%.98... 

Acetylenedicarboxylic acid, dimethyl ester, 50, 25, 36 Acetylenes, reaction with tri-methylsilyl azide, 50, 109 Acetylenic sulfonium salts, furans from, 53, 3 2-Acetylindane-l,3-dione, 52, 4 2-ACETYL-6-METHOXYNAPHTHALENE, 53, 5... 

Scheme 4 [2,3]Sigmatropic rearrangement of acetylenic and allenic sulfonium ylides via copper salt catalyzed thermal decomposition of diazomalonates...

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