5138-90-9Relevant academic research and scientific papers
Synthesis of 3-chloro-Δ3-cephem-4-carboxylate by addition/cyclization of allenecarboxylate. Copper(II)-promoted aerobic oxidation of arenesulfinic acids
Tanaka, Hideo,Kikuchi, Ryo,Torii, Sigeru
, p. 1391 - 1396 (2007/10/03)
The selective transformation of allenecarboxylate derived from penicillin into 3-chloro-Δ3-cephem-4-carboxylate was successfully achieved by an addition/cyclization reaction with chloride salts in aerobic media containing a copper(II) catalyst, in which copper(II)-catalyzed aerobic oxidation of in situ generated benzenesulfinate ion into less nucleophilic sulfonate ion prior to the nucleophilic addition of the former ion to the allenecarboxylate would completely eliminate the formation of undesired 3-phenylsulfonyl-Δ3-cephem-4-carboxylate. Under similar aerobic conditions, arenesulfinates salts and arenesulfinic acids were smoothly oxidized to the corresponding sulfonate salts and sulfonic acids, respectively.
Synthesis of Aromatic and Olefinic Sodium Sulfonates by Electrophilic Destannylation with Trimethylsilyl Chlorosulfonate
Niestroj, Michael,Lube, Andreas,Neumann, Wilhelm P.
, p. 575 - 580 (2007/10/02)
A mild and effective method for the preparation of a variety of aromatic, olefinic, and acetylenic sodium sulfonates is described.The reaction of trialkylaryl- (2a-k) and -heteroarylstannanes (4a-d), bis-(1-alkenyl)dibutylstannanes (6a-f), or trialkylakynylstannanes with trimethylsilyl chlorosulfonate (1) followed by hydrolysis with aqueous NaHCO3 provides the sodium sulfonates in an ipso-specific and in the case of vinylic stannanes stereospecific manner.A comparision of the reactivity of stannylated and silylated olefinic compounds 13 and 14 underlines the greater leaving ability of the stannyl moiety.The in situ preparation of the stannanes makes it possible to apply the synthetic method to natural products such as N-substituted apocodeine (17). - Key Words: Electrophilic aromatic substitution/ Electrophilic vinylic substitution/ Trialkylstannanes, application of/ Arylsulfonates, sodium salts of/ Vinylsulfonates, sodium salts of
Enolate Structures Contributing to the Transition State for Nucleophilic Substitution on α-Substituted Carbonyl Compounds
Yousaf, T. I.,Lewis, E. S.
, p. 6137 - 6142 (2007/10/02)
The high SN2 reactivity of α-halocarbonyl compounds is explained by the lowering of the intrinsic barrier by a major contribution of enolate structure to the transition state.This theoretical conclusion is now shown experimentally.The evidence is as follows: (1) Change in structure of a leaving arenesulfonate ion does not change the rates of attack of benzenesulfonate ion by nearly as much as it changes the equilibrium constants.A charge on the transferring phenacyl group of -0.48 is deduced. (2) The ρ value (-3.9) for attack of substituted thiophenoxides on phenacyl bromide is much more negative than that for attack on methyl iodide (-1.8). (3) A related ρ value is found for reaction of 2,4,6-trimethylphenacyl bromide with thiophenoxides (-2.2), showing a lesser, but still large sensitivity to nucleophile structure where addition to the carbonyl is sterically forbidden.The enolate structure leaves the attacking or leaving nucleophiles with a single electron each instead of the unshared pairs.Thus, the enolate structure is emphesized if the leaving group and the nucleophile readily lose an electron.
Micellar Effects on the Reaction of (Arylsulfonyl)alkyl Arenesulfonates with Hydroxide Ion. Microenvironmental and Substituent Effects in the Stern Layer of Cationic Micelles
van de Langkruis, Gerard B.,Engberts, Jan B. F. N.
, p. 4152 - 4157 (2007/10/02)
The reaction of the sulfonates p-XC6H4SO2CH(R)OSO2C6H4Y-p 1a-g with hydroxide ion (involving nucleophilic attack at sulfonate sulfur) is accelerated (7-25 times) in the presence of CTAB micelles (32.1 deg C).The kinetic data are analyzed in detail by using the pseudophase ion-exchange (PPIE) model, taking into account partitioning of the reactants between the micellar and aqueous pseudophases and competition between hydroxide ions and detergent counterions for binding to the micelles.Binding constants obtained from the kinetic analysis are compared with those from ultrafiltration experiments.Generally, the PPIE model reproduces the experimental rate constants quite well, except at low detergent concentration (around the cmc).The second-order rate constants for reaction in the micellar pseudophase are 4-12 times smaller than those for reaction in bulk water.Therefore the observed catalysis is purely the result of the high local concentration of both reactants in the micellar pseudophase.The substituent effects for the reaction in the micelles reveal an increased susceptibility for variation of Y.No evidence for orientational effects was found.It is shown that the binding of the sulfonates with the micelles is mainly determined by the presence of the aryl groups.Based on a comparison with kinetic solvent effects on the reaction in 1,4-dioxane-water, it is suggested that the rates in the micellar pseudophase reflect a decrease in micropolarity at the binding sites of the substrate molecules.
