7282-09-9Relevant articles and documents
Silica-supported phosphorus pentoxide: A reusable catalyst for S,S-acetalization of carbonyl groups under ambient conditions
Shaterian, Hamid Reza,Azizi, Kobra,Fahimi, Nafiseh
experimental part, p. 85 - 91 (2012/01/06)
Phosphorus pentoxide supported on silica gel (P2O 5/SiO2) efficiently acts as a highly active and reusable catalyst for cyclic and non-cyclic S,S-acetalization of a variety of carbonyl compounds under mild, solvent-free an
Reactions of Triplet Carbenes with Sulfides and Disulfides: Ylide vs. Radical Formation
Alberti, A.,Griller, D.,Nazran, A. S.,Pedulli, G. F.
, p. 3024 - 3028 (2007/10/02)
The reactions between triplet diphenylcarbene and fluorenylidene with a variety of sulfides and disulfides were investigated with use of electron paramagnetic resonance (EPR) spectroscopy, laser flash photolysis, and product studies.Diphenylcarbene reacted with these substrates by a radical-like displacement mechanism.Rate constants were ca. 1E6 M-1 s-1, and the resulting thio-substituted diphenylmethyl radicals were identified by their EPR and optical spectra.By contrast, the analogous reactions of fluorenylidene had rate constants of 1E8-1E9 M-1 s-1 and proceeded by an ylide mechanism.Product studies were consistent with these results but were not sufficient in themselves to reveal these mechanistic differences.
A Kinetic Study of the Soft Metal Ion-promoted Hydrolyses of Some S-Acetals
Satchell, Derek P. N.,Weil, Thomas J.
, p. 1191 - 1200 (2007/10/02)
The S-acetals (III)-(VII) hydrolyse readily in aqueous ethanol or in aqueous dioxan solutions containing an excess of Tl3+ or Ag+ ions to give benzophenone and the appropriate sulphide.The hydrogen-ion catalysed hydrolyses are very slow by comparison and the supposedly soft ions Cd2+ and Cu2+ have even less effect than H3O+.Kinetic and spectroscopic studies of the hydrolyses, mainly at 25 deg C, show that the Tl3+-promoted reactions occur via the rapid formation of a 1 Tl3+ : 1-S-acetal adduct.This adduct is formed stoicheiometrically with (IV), (V), and(VII), but in small amounts with (III) and (VI).The tripositive adduct probably reacts with water in the slow step of the overall hydrolysis.This adduct can also lose charge by proton dissociation from hydroxy groups in the bound S-acetal, or from thallium-bound water.The resulting dipositive adducts, however formed, hydrolyse much less rapidly than the tripositive adducts.The (chelated) dipositive adduct from (V) is sufficiently stable for contributions to hydrolysis from a 4+ adduct to be detected.The Ag+-promoted hydrolyses proceed principally via small amounts of rapidly formed dipositive 2 Ag+ : 1-S-acetal adducts.For (V), where loss of a carboxy proton can occur, the formation constant of the monopositive + adduct is very large (K ca. 107 l mol-1) but that of the dipositive adduct is small, as for the other S-acetals.With (V) and (VI) the 1 Ag+ : 1-S-acetal adduct is formed stoicheiometrically and with (IV) its formation constant is large (K ca, 900 l mol-1).For (III), (IV), (VI), and (VII) these 1:1 adducts contribute significantly to the hydrolysis at low silver ion concentrations.For both the Tl3+-and the Ag+-promoted reactions the effects of ionic strength are consistent: where more charged adduct can form an increase in ionic strength increases the reaction rate; where adduct formation is complete, changes in ionic strength have little effect on the rate.The S-acetals display wide (up to 105-fold) differences in reactivity towards hydrolysis and their sequence of reactivity alters markedly with the promoting ion.With both ions (VI) hydrolyses relatively slowly.For all the substrates Tl3+ is a better promoter than Ag+.Exact comparisons of reactivity are impossible owing to the differences in mechanistic detail and in solvent.In view of its soft acid character Tl3+ is surprisingly more acidic towards the O-containing acetals than towards those having just two S atoms.For (IV) and Ag+ the establishment of the pre-equilibrium giving the 1 Ag+ : 1-S-acetal adduct is slow enough at 25 deg C to be followed by stopped-flow spectroscopy.
