Reactions of Wittig Reagents with Episulfides or Elemental Sulfur

Abstract

The reactions of Wittig reagents with episulfides gave symmetrical olefins and triphenylphosphine sulfide in moderate yields. The same olefins were obtained by reactions of Wittig reagents with elemental sulfur. These reactions might proceed through thiocarbonyl intermediates, the existence of which was confirmed by Diels–Alder reactions with dienes.

Structure-Based Design, Synthesis, and Biological Evaluation of Irreversible Human Rhinovirus 3C Protease Inhibitors. 8. Pharmacological Optimization of Orally Bioavailable 2-Pyridone-Containing Peptidomimetics

“…25 The remainder of the 3CP inhibitors described in this work were prepared by utilization of synthetic Method B to couple either carboxylic acid 27 (compounds 3 and 4 as well as 8-12) or 38 (compounds 14-20) to appropriately derivatized P 1 fragments. The phosphorus ylides required to effect these syntheses, along with those illustrated in Schemes 1, 2, and 3, were either commercially available (compounds 3, 5, 11-13, 15, and 20), known in the literature (compounds 4, 29 and 14 29 ) or were prepared by slight modifications of known syntheses 29 (compounds 6-10, and 16-19; see Experimental Section).…”

Structure-Based Design, Synthesis, and Biological Evaluation of Irreversible Human Rhinovirus 3C Protease Inhibitors. 6. Structure−Activity Studies of Orally Bioavailable, 2-Pyridone-Containing Peptidomimetics

“…The ester present in 43 was converted to the corresponding carboxylic acid (44) under nearneutral conditions, and the crude material thus obtained was coupled with γ-lactam 45 43 to give alcohol 46 in moderate overall yield. Oxidation of alcohol 46 and olefination of the resulting aldehyde (not shown) using (triphenyl-λ 5 -phosphanylidene)acetic acid isopropyl ester 44 afforded compound 21 in reasonable yield.…”

“…The residue was then dissolved in THF (10 mL). (Triphenyl-λ 5 -phosphanylidene)acetic acid isopropyl ester 44 (0.226 g, 0.624 mmol, 1.15 equiv) was added, and the reaction mixture was refluxed for 30 min, then cooled to 23 °C, and concentrated under reduced pressure. The resulting residue was purified by flash column chromatography (2% CH 3OH in CHCl3) to afford 21 contaminated with several impurities.…”

An Efficient Combined Electrochemical and Ultrasound Assisted Synthesis of Imidazole‐2‐Thiones

“…[15] When reacting with elemental sulfur, it acts as nucleophile, opening the eight-membered ring of sulfur and probably giving a linear intermediate (Scheme 2) (an analogous mechanism has been reported in the case of the reaction between elemental sulfur and phosphonium ylides). [16] As at the end of the reaction all eight atoms of sulfur have been used, S 7 can re-enter the reaction and go on till all sulfur atoms are used.…”