56399-99-6Relevant articles and documents
Acid-Catalyzed O-Glycosylation with Stable Thioglycoside Donors
Lacey, Kristina D.,Quarels, Rashanique D.,Du, Shaofu,Fulton, Ashley,Reid, Nicholas J.,Firesheets, Austin,Ragains, Justin R.
, p. 5181 - 5185 (2018)
Two classes of thioglycoside, 4-(4-methoxyphenyl)-3-butenylthioglycosides (MBTGs) and 4-(4-methoxyphenyl)-4-pentenylthioglycosides (MPTGs), undergo acid-catalyzed O-glycosylations with a range of sugar and nonsugar alcohols at 25 °C. Electron density at t
Regiochemical and Stereochemical Studies on Halocyclization Reactions of Unsaturated Sulfides
Ren, Xiao-Feng,Turos, Edward,Lake, Charles H.,Churchill, Melvyn Rowen
, p. 6468 - 6483 (2007/10/03)
The regiochemistry and stereochemistry for the halocyclization reactions of unsaturated benzyl sulfides have been examined as a function of tether length, type of unsaturation (carbon-carbon double bond versus carbon-carbon triple bond), substituents, and halogenating agent.Alkenyl sulfides were found to react with iodine or bromine at room temperature to give five-membered ring cycloadducts exclusively over those having four-membered rings, while for larger systems, six-membered ring products are formed preferentially over their five-membered ring isomers and exclusively over the seven-membered ring adducts.The endo- versus exo-regioselectivity of these alkenyl sulfide ring closure most likely reflects the difference in thermodynamic stabilities of the β-halo sulfide cycloadducts, which are able to equilibrate via a common episulfonium intermediate.The efficiency of cyclization process markedly drops off for these alkenyl sulfides as the tether length increases beyond four intervening carbon centers.Thus, while the halogenations of 3-butenyl sulfides and 4-pentenyl sulfides give high yields of cycloadducts, those of 5-hexenyl sulfides afford only small amounts of cyclized products and large quantities of acyclic dibromides.Conversely, the reactions of acetylenic sulfides with iodine give uniformly high yields and regiochemical control regardless of the tether length.Thus, 3-butynyl and 4-pentynyl sulfides cyclize cleanly to the five-membered ring while 5-hexynyl sulfides give exclusively the six-membered ring.The products arising from these alkynyl sulfide ring closures are believed to be formed under kinetic control.The methodology has been applied to the synthesis of unusual bicyclic β-lactams related to the penicillin family of antibiotics.
Mechanistic Evidence regarding the Magnesium Halide Transformation of Cyclopropylmethanols into Homoallylic Halides
McCormick, J. P.,Fitterman, Alan S.,Barton, Donald L.
, p. 4708 - 4712 (2007/10/02)
Cyclopropylmethanols are converted into homoallylic halides in high yield by treatment with magnesium bromide or iodide in refluxing, anhydrous diethyl ether.For uncovering of the details of the reaction mechanism, (cyclopropylphenylmethoxy)magnesium bromide (3a) was prepared by treatment of cyclopropylphenylmethanol (1) with hydridomagnesium bromide.Alkoyoxymagnesium bromide 3a was stable in refluxing diethyl ether and was not changed when treated with tetrabutylammonium bromide but was transformed into 4-bromo-1-phenyl-1-butene by treatment with hydrogen bromide or magnesium bromide.These results, together with first-order kinetics for the reaction of magnesium halide with 1, suggest a mechanism involving rapid formation of an intermediate ion pair (4), a magnesium oxonium bromide, which undergoes rate-determining ring opening to give homoallylic halide.A Hammett study of the reaction of substituted cyclopropylphenylmethanols with magnesium iodide provides a p value of -1.82, revealing substantial positive charge development on the carbinol carbon in the latter step.This investigation provides one of only a very few reported examples of Hammett studies used to probe positive charge development for a reaction carried out in anhydrous diethyl ether.
