164594-44-9Relevant academic research and scientific papers
Carbocation-forming reactions in dimethyl sulfoxide
Creary, Xavier,Burtch, Elizabeth A.,Jiang, Ziqi
, p. 1117 - 1127 (2007/10/03)
Mesylate derivatives of 3-aryl-3-hydroxy-β-lactams and thiolactams react in DMSO-d6 by first-order processes to give alcohol products. Substituent effect studies implicate carbocation intermediates (ion-pairs) that are captured by DMSO-d6 to give transient oxosulfonium ions. Rapid reaction of the oxosulfonium ions with trace amounts of water leads to the alcohol product and regenerates DMSO-d6. H217O labeling studies show that 17O is incorporated into the DMSO. The mesylate derivatives of endo- and exo-2-hydroxy-2-phenylbicyclo[2.2.1]heptan-3-one also react in DMSO-d6 to give the alcohol products. Ion-pair intermediates that capture DMSO giving unstable oxosulfonium ions are again proposed. Exo-2-phenyl-endo-bicyclo[2.2.1]heptyl trifluoroacetate readily eliminates trifluoroacetic acid in DMSO-d6 via a cationic mechanism involving loss of the endotrifluoroacetate leaving group as well as an exo-hydrogen. The O-methyl oxime derivative of α-chloroα,α-diphenylacetophenone reacts in DMSO-d6 to give 1-methoxy-2,3-diphenylindole, a product derived from cyclization of a cationic intermediate. A common ion rate suppression provides further evidence for a cationic mechanism. The triflate derivative of pivaloin reacts by a cationic mechanism in DMSO-d6 to give rearranged products. The rate is even faster than in highly ionizing solvents such as trifluoroethanol or trifluoroacetic acid. 1-Adamantyl mesylate reacts in DMSO-d6 by a first-order process (YOMs = -4.00) to give a long-lived oxosulfonium ion, 1-Ad-OS(CD3)2+, which can be characterized spectroscopically. This oxosulfonium ion reacts only slowly with water at elevated temperatures to give 1-adamantanol. DMSO is therefore a viable solvent for ks, kC, and kΔ cationic processes.
