Sila-Pummerer Rearrangement of Cyclic Sulfoxides:  Computational Study of the Mechanism

Abstract

The sila-Pummerer rearrangement of organosilicon cyclic sulfoxides proceeds via the two transition states, the first one with pentacoordinated Si that connects the reagent and the intermediate ylide and the second one that connects the ylide and the product of rearrangement.

Computational study of conformations and of sulfinyl oxygen-induced pentacoordination at silicon in 4-chloro-4-silathiacyclohexane 1-oxide and 4,4-dichloro-4-silathiacyclohexane 1-oxide

“…Interestingly, the electrostatic and natural charges on the sulfinyl oxygen decrease upon pentacoordination, whereas the Mulliken charges increase [7b,23]. As was discussed recently, the best agreement with chemical reasoning for nonclassical partial bonding formed by silicon is obtained with electrostatic atomic charges [24].…”

Guanidinium Nitrate/Silica Sulfuric Acid/Ammonium Bromide as an Effective, Viable and Metal-free Catalytic Media for the Selective Oxidation of Sulfides to the Sulfoxides

“…Chemicals were purchased on Fluka, Merck and Aldrich chemical companies. The oxidation products were characterized by comparison of their spectral (IR, 1 H NMR, or 13 C NMR) and physical data with authentic samples. Oxidation of 4-chlorophenyl methyl sulfide to 4-chlorophenyl methyl sulfoxide by guanidinium nitrate and silica …”

“…[6][7][8] Sulfoxides are also valuable in C-C bond-forming 9,10 and molecular rearrangements. [11][12][13] Even though various approaches have been reported for the oxidation of sulfides to sulfoxides such as H2O2/ iron(III)-salen, 14 tert-butyl hydroperoxide/Ti(iPrO) 4 /1,2-diphenylethane-1,2-diol, 15 TaCl5/H2O2, 16 sodium perborate or sodium percarbonate/silica sulfuric acid/KBr, 17 3-carboxypyridinium chlorochromate/AlCl3, 18 ZrCl4/H2O2, 19 ceric ammonium nitrate (CAN) supported on silica/NaBrO3, 20 H2O2/ N-hydroxysuccinimide, 21 these methods suffer from some disadvantages like long reaction times, expensive reagents and catalysts, contamination of metallic reagents, difficulties in isolation of products, and formation of over-oxidation products.…”

Metal-free catalytic oxidation of sulfides to sulfoxides with ammonium nitrate, ammonium hydrogen sulfate and ammonium bromide as catalyst

“…[1][2][3] Sulfoxides are also valuable materials in C-C bond-forming 4,5 and molecular rearrangements. [6][7][8] Additionally some of biologically active sulfoxides play an important role as therapeutic agents such as anti-ulcer, [9][10][11] antibacterial, 12 anti-atherosclerotic, 13,14 among others. Although a wide variety of oxidizing systems has been applied for the oxidation of sulfides to the sulfoxides such as H 2 O 2 /silica sulfuric acid, 15 urea hydrogen peroxide (UHP)/Mn(III), 16 Me-IBX, 17 24 some of these methods still suffer from some drawbacks like overoxidation to sulfones, low selectivity, low yields of products, tedious work-up, toxicity, and expensive reagents or catalysts.…”