Sequential Knoevenagel Reaction/Mislow-Evans Rearrangement Catalyzed by Heterogeneous Amine Grafted on Silica in Water, Leading to γ-Hydroxy-α,β-unsaturated Nitrile
selective oxidation of sulfides to sulfoxides under mild and environmentally safe conditions is achieved using hydrogen peroxide in the presence of Amberlyst 15 and Amberlite IR-400 at room temperature. This procedure can be applied for dialkyl and diaryl sulfides with a variety of functional groups. Functional groups such as hydroxyl, methoxy, amino, aldehyde, and olefinic double bonds remain intact
optically active cyanomethyl aryl sulfoxides with aceticanhydride gave the corresponding α-acetoxy sulfides which were induced with a partial asymmetry nearly 30% at α-carbon, while the 18O-label of the original sulfoxides was retained in more than 85% in the resulting ester, the Pummerer reaction product. Kinetic experiments with cyanomethyl (p-substituted phenyl) sulfoxides and α,α-dideuterated cyanomethyl
HIO<sub>3</sub>in the Presence of Wet SiO<sub>2</sub>: A Mild and Efficient Reagent for Selective Oxidation of Sulfides to Sulfoxides under Solvent‐Free Conditions
作者:M. M. Lakouraj、M. Tajbakhsh、F. Shirini、M. V. Asady Tamami
DOI:10.1081/scc-200050940
日期:2005.3
In the presence of wet SiO2, HIO3 is highly efficient for the selective oxidation of sulfides to sulfoxides. It may be applied to any type of dialkyl and alkyl aryl sulfides. It develops under solvent-free conditions, and gives high yield in the presence of different functional groups on the sulfide at room temperature.
作者:Barry M. Trost、Timothy A. Grese、Dominic M. T. Chan
DOI:10.1021/ja00019a036
日期:1991.9
The potential application of [3 + 2] cycloadditions to polycarbocycle construction is considerably enhanced by the ability to perform such reactions intramolecularly. The feasibility of such processes is explored in the context of Pd-catalyzed cycloadditions of 2-[(trimethylsilyl)methyl]allyl carboxylates, wherein trimethylenemethane (TMM) precursor fragment (donor) and the electron-deficient olefin (acceptor) is joined by a tether of simple methylene groups of 3, 4, 5, and 8 members. Several versatile synthetic routes to these substrates were developed. 2-Bromo-3-(trimethylsilyl)propene proves to be a key reagent for construction of the donor portion. Acceptors bearing esters, cyano groups, and especially sulfones have been examined. The diastereoselectivity of the reaction has been explored both in terms of ring juncture and the diastereofacial selectivity with respect to an oxygen substituent at the allylic position of the acceptor. Excellent cycloadditions to give the bicyclo[3.3.0] octyl and bicyclo[4.3.0]nonyl systems are observed, whereas larger rings cannot be obtained in this series. The choice of catalyst proves critical, the most useful being either tetrakis(triphenylphosphine)palladium and DPPE or, more generally, triisopropyl phosphite and palladium acetate. The first cycloaddition of a 1,1-dialkylated TMM precursor, which fails in intermolecular cases, has been observed in this intramolecular series to give a bridgehead-substituted bicycle. A rationale for the observed diastereoselectivity is presented.
Rudorf, Wolf-Dieter; Uhlig, Gabriele; Dargatz, Manfred, Liebigs Annalen der Chemie, 1992, # 4, p. 395 - 398