Ionic liquids as novel media for electrophilic/onium ion chemistry and metal-mediated reactions: A progress summary

The account presented here summarizes progress from the author\u27s laboratory during the past 15 years on the application of room temperature ionic liquids (RTILs) as solvents and catalysts in electrophilic/onium ion chemistry as well as in metal-mediated bond forming reactions

Reaction of allene esters with Selectfluor/TMSX (X = I, Br, Cl) and Selectfluor/NH4SCN: Competing oxidative/electrophilic dihalogenation and nucleophilic/conjugate addition

Reaction of benzyl and ethyl allenoates with TMSX (X = I, Br, Cl) and with NH4SCN were investigated in MeCN, DMF, and in imidazolium ionic liquids [BMIM][NTf2] and [BMIM][PF6] as solvent, in the presence and absence of Selectfluor. Comparative product analysis studies demonstrate that the ability of Selectflour to promote oxidative/electrophilic dihalogenation/dithiocyanation with TMSX/NH4SCN (as observed previously for 1-arylallenes) is diminished in allenoates, most significantly in reactions with TMSCl, and essentially disappearing in reactions with NH4SCN, in favor of nucleophilic/conjugate addition. The study underscores the contrasting reactivity patterns in 1-arylallenes and allenoates toward electrophilic and nucleophilic additions in halofunctionalization with TMSX/Selectfluor and thiocyanation reactions with NH4SCN/Selectfluor. These competing pathways are influenced by the nature of the anion, allene structure, and the choice of solvent

Mono- and dinitration of pentafluorosulfanylbenzenes with [NO 2][BF4], and substrate selectivity (PhSF5 vs PhCF3 and PhSF5 vs PhNO2) in competitive nitration

PhSF5 1 reacts with NO2+BF 4-/TfOH in CH2Cl2 (DCM) at room temperature to give 1-nitro-3-(pentafluorosulfanyl)benzene 2 in near quantitative yield. The dinitro derivative 4 is synthesized from 2 by reaction with NO2+BF4-/TfOH at 70 °C. The p-MeC6H4SF5 is mononitrated at room temperature with NO2+BF4-/DCM and dinitrated with NO2+BF4-/TfOH. Substrate selectivity (kPhSF5kRPh) in competitive nitration for PhSF5/PhCF3 and PhSF5/PhNO 2 with NO2+BF4- in DCM at room temperature was determined at 21.3 and ∼1 respectively. Relative stability of the corresponding benzenium ions were gauged by DFT from the isodesmic proton transfer reaction SF5-C6H 6+ + R-C6H5 → SF 5-C6H5 + R-C6H6+ (R = CF3 and NO2). These studies indicate that reactivity of ArSF5 in SEAr is similar to ArNO 2. © 2014 Elsevier B.V

Ionic Liquids as Novel Media and Catalysts for Electrophilic/Onium Ion Chemistry and Metal-Mediated Reactions

This chapter summarizes recent progress in the application of room temperature ionic liquids as solvents and catalysts in electrophilic/onium ion chemistry, in metal-mediated bond-forming reactions, and in selected other key reactions

Ionic liquids as novel media and catalysts for diels-alder chemistry

Background: The Diels-Alder reaction has played a fundamental role in advancing synthetic chemistry over the years and continues to greatly impact modern synthetic methodology. Ever increasing interest in the application of ionic liquids (ILs) as catalyst and solvents in organic synthesis has provided the impetus to explore their application in Diels-Alder chemistry with the goal to improve efficiency as well as chemo-, regio- and enantio-selectivity. Objective: The review focuses on recent progress in the area of IL-mediated Diels-Alder reactions through illustrative examples that demonstrate their efficacy as solvent and catalysts. Conclusion: It is clear from the review of the topic that a vast amount of work has been done in this area, employing diverse types of ILs which were employed either alone or in conjunction with Lewis-acids, metal ions, chiral additives, organocatalysts, and/or other additives. The results in comparison to conventional solvents have demonstrated improved yields, faster rates, as well as improved regio- and enantioselectivity. These attributes along with the advantages associated with recycling/reuse clearly point to ILs as superior media for Diels-Alder chemistry. Much of the emphasis has been on synthesis but some fundamental mechanistic work aimed at understanding rate enhancement and endo-selectivity have also been reported

Metallophosphaalkenes and Metalloarsaalkenes as Synthons in Organometallic Chemistry

Weber L. Metallophosphaalkenes and Metalloarsaalkenes as Synthons in Organometallic Chemistry. In: Laali KK, ed. Advances in Strained and Interesting Organic Molecules. Vol Supplement 1. Stamford, Conn.: JAI Press; 1999: 269-298